Thermodynamics of a Bose-Einstein condensate with weak disorder

International Nuclear Information System (INIS)

Falco, G. M.; Pelster, A.; Graham, R.

2007-01-01

We consider the thermodynamics of a homogeneous superfluid dilute Bose gas in the presence of weak quenched disorder. Following the zero-temperature approach of Huang and Meng, we diagonalize the Hamiltonian of a dilute Bose gas in an external random δ-correlated potential by means of a Bogoliubov transformation. We extend this approach to finite temperature by combining the Popov and the many-body T-matrix approximations. This approach permits us to include the quasiparticle interactions within this temperature range. We derive the disorder-induced shifts of the Bose-Einstein critical temperature and of the temperature for the onset of superfluidity by approaching the transition points from below, i.e., from the superfluid phase. Our results lead to a phase diagram consistent with that of the finite-temperature theory of Lopatin and Vinokur which was based on the replica method, and in which the transition points were approached from above

Faraday waves in quasi-one-dimensional superfluid Fermi-Bose mixtures

DEFF Research Database (Denmark)

Abdullaev, F. Kh.; Ögren, Magnus; Sørensen, Mads Peter

2013-01-01

The generation of Faraday waves in superfluid Fermi-Bose mixtures in elongated traps is investigated. The generation of waves is achieved by periodically changing a parameter of the system in time. Two types of modulations of parameters are considered: a variation of the fermion-boson scattering...... length and the boson-boson scattering length. We predict the properties of the generated Faraday patterns and study the parameter regions where they can be excited....

Ultracold Fermi and Bose gases and Spinless Bose Charged Sound Particles

Directory of Open Access Journals (Sweden)

Minasyan V.

2011-10-01

Full Text Available We propose a novel approach for investigation of the motion of Bose or Fermi liquid (or gas which consists of decoupled electrons and ions in the uppermost hyperfine state. Hence, we use such a concept as the fluctuation motion of “charged fluid particles” or “charged fluid points” representing a charged longitudinal elastic wave. In turn, this elastic wave is quantized by spinless longitudinal Bose charged sound particles with the rest mass m and charge e 0 . The existence of spinless Bose charged sound particles allows us to present a new model for description of Bose or Fermi liquid via a non-ideal Bose gas of charged sound particles . In this respect, we introduce a new postulation for the superfluid component of Bose or Fermi liquid determined by means of charged sound particles in the condensate, which may explain the results of experiments connected with ultra-cold Fermi gases of spin-polarized hydrogen, 6 Li and 40 K, and such a Bose gas as 87 Rb in the uppermost hyperfine state, where the Bose- Einstein condensation of charged sound particles is realized by tuning the magnetic field.

Single-particle density matrix and superfluidity in the two-dimensional Bose Coulomb fluid

International Nuclear Information System (INIS)

Minguzzi, A.; Tosi, M.P.; Davoudi, B.

2002-01-01

A study by Magro and Ceperley [Phys. Rev. Lett. 73, 826 (1994)] has shown that the ground state of the two-dimensional fluid of charged bosons with logarithmic interactions is not Bose condensed, but exhibits algebraic off-diagonal order in the single-particle density matrix ρ(r). We use a hydrodynamic Hamiltonian expressed in terms of density and phase operators, in combination with an f-sum rule on the superfluid fraction, to reproduce these results and to extend the evaluation of the density matrix to finite temperature T. This approach allows us to treat the liquid as a superfluid in the absence of a condensate. The algebraic decay of the one-body density matrix is due to correlations between phase fluctuations, and we find that the exponent in the power law is determined by the superfluid density n s (T). We also find that the plasmon gap in the single-particle energy spectrum at long wavelengths decreases with increasing T and closes at the critical temperature for the onset of superfluidity

Localization of weakly interacting Bose gas in quasiperiodic potential

International Nuclear Information System (INIS)

Ray, Sayak; Pandey, Mohit; Ghosh, Anandamohan; Sinha, Subhasis

2016-01-01

We study the localization properties of weakly interacting Bose gas in a quasiperiodic potential. The Hamiltonian of the non-interacting system reduces to the well known ‘Aubry–André model’, which shows the localization transition at a critical strength of the potential. In the presence of repulsive interaction we observe multi-site localization and obtain a phase diagram of the dilute Bose gas by computing the superfluid fraction and the inverse participation ratio. We construct a low-dimensional classical Hamiltonian map and show that the onset of localization is manifested by the chaotic phase space dynamics. The level spacing statistics also identify the transition to localized states resembling a Poisson distribution that are ubiquitous for both non-interacting and interacting systems. We also study the quantum fluctuations within the Bogoliubov approximation and compute the quasiparticle energy spectrum. Enhanced quantum fluctuation and multi-site localization phenomenon of non-condensate density are observed above the critical coupling of the potential. We briefly discuss the effect of the trapping potential on the localization of matter wave. (paper)

Superfluidity, Bose-Einstein condensation, and structure in one-dimensional Luttinger liquids

Science.gov (United States)

Vranješ Markić, L.; Vrcan, H.; Zuhrianda, Z.; Glyde, H. R.

2018-01-01

We report diffusion Monte Carlo (DMC) and path integral Monte Carlo (PIMC) calculations of the properties of a one-dimensional (1D) Bose quantum fluid. The equation of state, the superfluid fraction ρS/ρ0 , the one-body density matrix n (x ) , the pair distribution function g (x ) , and the static structure factor S (q ) are evaluated. The aim is to test Luttinger liquid (LL) predictions for 1D fluids over a wide range of fluid density and LL parameter K . The 1D Bose fluid examined is a single chain of 4He atoms confined to a line in the center of a narrow nanopore. The atoms cannot exchange positions in the nanopore, the criterion for 1D. The fluid density is varied from the spinodal density where the 1D liquid is unstable to droplet formation to the density of bulk liquid 4He. In this range, K varies from K >2 at low density, where a robust superfluid is predicted, to K theory. The n (x ) and g (x ) show long range oscillations and decay with x as predicted by LL theory. The amplitude of the oscillations is large at high density (small K ) and small at low density (large K ). The K values obtained from different properties agree well verifying the internal structure of LL theory. In the presence of disorder, the ρS/ρ0 does not scale as predicted by LL theory. A single vJ parameter in the LL theory that recovers LL scaling was not found. The one body density matrix (OBDM) in disorder is well predicted by LL theory. The "dynamical" superfluid fraction, ρSD/ρ0 , is determined. The physics of the deviation from LL theory in disorder and the "dynamical" ρSD/ρ0 are discussed.

Magnon Bose-Einstein condensation and spin superfluidity.

Science.gov (United States)

Bunkov, Yuriy M; Volovik, Grigory E

2010-04-28

Bose-Einstein condensation (BEC) is a quantum phenomenon of formation of a collective quantum state in which a macroscopic number of particles occupy the lowest energy state and thus is governed by a single wavefunction. Here we highlight the BEC in a magnetic subsystem--the BEC of magnons, elementary magnetic excitations. The magnon BEC is manifested as the spontaneously emerging state of the precessing spins, in which all spins precess with the same frequency and phase even in an inhomogeneous magnetic field. The coherent spin precession was observed first in superfluid (3)He-B and this domain was called the homogeneously precessing domain (HPD). The main feature of the HPD is the induction decay signal, which ranges over many orders of magnitude longer than is prescribed by the inhomogeneity of magnetic field. This means that spins precess not with a local Larmor frequency, but coherently with a common frequency and phase. This BEC can also be created and stabilized by continuous NMR pumping. In this case the NMR frequency plays the role of a magnon chemical potential, which determines the density of the magnon condensate. The interference between two condensates has also been demonstrated. It was shown that HPD exhibits all the properties of spin superfluidity. The main property is the existence of a spin supercurrent. This spin supercurrent flows separately from the mass current. Transfer of magnetization by the spin supercurrent by a distance of more than 1 cm has been observed. Also related phenomena have been observed: the spin current Josephson effect; the phase-slip processes at the critical current; and the spin current vortex--a topological defect which is the analog of a quantized vortex in superfluids and of an Abrikosov vortex in superconductors; and so on. It is important to mention that the spin supercurrent is a magnetic phenomenon, which is not directly related to the mass superfluidity of (3)He: it is the consequence of a specific

Collective excitations in unconventional superconductors and superfluids

CERN Document Server

Brusov, Peter

2009-01-01

This is the first monograph that strives to give a complete and detailed description of the collective modes (CMs) in unconventional superfluids and superconductors (UCSF&SC). Using the most powerful method of modern theoretical physics - the path (functional) integral technique - authors build the three- and two-dimensional models for s -, p - and d -wave pairing in neutral as well as in charged Fermi-systems, models of superfluid Bose-systems and Fermi-Bose-mixtures. Within these models they study the collective properties of such systems as superfluid 3 He, superfluid 4 He, superfluid 3 He-

Off-equilibrium infrared structure of self-interacting scalar fields: Universal scaling, vortex-antivortex superfluid dynamics, and Bose-Einstein condensation

Science.gov (United States)

Deng, Jian; Schlichting, Soeren; Venugopalan, Raju; Wang, Qun

2018-05-01

We map the infrared dynamics of a relativistic single-component (N =1 ) interacting scalar field theory to that of nonrelativistic complex scalar fields. The Gross-Pitaevskii (GP) equation, describing the real-time dynamics of single-component ultracold Bose gases, is obtained at first nontrivial order in an expansion proportional to the powers of λ ϕ2/m2 where λ , ϕ , and m are the coupling constant, the scalar field, and the particle mass respectively. Our analytical studies are corroborated by numerical simulations of the spatial and momentum structure of overoccupied scalar fields in (2+1)-dimensions. Universal scaling of infrared modes, vortex-antivortex superfluid dynamics, and the off-equilibrium formation of a Bose-Einstein condensate are observed. Our results for the universal scaling exponents are in agreement with those extracted in the numerical simulations of the GP equation. As in these simulations, we observe coarsening phase kinetics in the Bose superfluid with strongly anomalous scaling exponents relative to that of vertex resummed kinetic theory. Our relativistic field theory framework further allows one to study more closely the coupling between superfluid and normal fluid modes, specifically the turbulent momentum and spatial structure of the coupling between a quasiparticle cascade to the infrared and an energy cascade to the ultraviolet. We outline possible applications of the formalism to the dynamics of vortex-antivortex formation and to the off-equilibrium dynamics of the strongly interacting matter formed in heavy-ion collisions.

Effective interactions in a quantum Bose-Bose mixture

Science.gov (United States)

Utesov, O. I.; Baglay, M. I.; Andreev, S. V.

2018-05-01

We generalize the Beliaev diagrammatic theory of an interacting spinless Bose-Einstein condensate to the case of a binary mixture. We derive a set of coupled Dyson equations and find analytically the Green's functions of the system. The elementary excitation spectrum consists of two branches, one of which takes the characteristic parabolic form ω ∝p2 in the limit of a spin-independent interaction. We observe renormalization of the magnon mass and the spin-wave velocity due to the Andreev-Bashkin entrainment effect. For a three-dimensional weakly interacting gas the spectrum can be obtained by applying the Bogoliubov transformation to a second-quantized Hamiltonian in which the microscopic two-body potentials in each channel are replaced by the corresponding off-shell scattering amplitudes. The superfluid drag density can be calculated by considering a mixture of phonons and magnons interacting via the effective potentials. We show that this problem is identical to the second-order perturbative treatment of a Bose polaron. In two dimensions the drag contributes to the magnon dispersion already in the first approximation. Our consideration provides a basis for systematic study of emergent phases in quantum degenerate Bose-Bose mixtures.

Scenario of strongly nonequilibrated Bose-Einstein condensation

International Nuclear Information System (INIS)

Berloff, Natalia G.; Svistunov, Boris V.

2002-01-01

Large scale numerical simulations of the Gross-Pitaevskii equation are used to elucidate the self-evolution of a Bose gas from a strongly nonequilibrium initial state. The stages of the process confirm and refine the theoretical scenario of Bose-Einstein condensation developed by Svistunov and co-workers [J. Mosc. Phys. Soc. 1, 373 (1991); Sov. Phys. JETP 75, 387 (1992); 78, 187 (1994)]: the system evolves from the regime of weak turbulence to superfluid turbulence via states of strong turbulence in the long-wavelength region of energy space

High temperature superconductors and other superfluids

CERN Document Server

Alexandrov, A S

2017-01-01

Written by eminent researchers in the field, this text describes the theory of superconductivity and superfluidity starting from liquid helium and a charged Bose-gas. It also discusses the modern bipolaron theory of strongly coupled superconductors, which explains the basic physical properties of high-temperature superconductors. This book will be of interest to fourth year graduate and postgraduate students, specialist libraries, information centres and chemists working in high-temperature superconductivity.

Thermodynamic Properties of a Trapped Interacting Bose Gas

OpenAIRE

Shi, Hualin; Zheng, Wei-Mou

1996-01-01

A Bose gas in an external potential is studied by means of the local density approximation. Analytical results are derived for the thermodynamic properties of an ideal Bose gas in a generic power-law trapping potential, and their dependence on the mutual interaction of atoms in the case of a non-ideal Bose gas.

Guiding-center dynamics of vortex dipoles in Bose-Einstein condensates

International Nuclear Information System (INIS)

Middelkamp, S.; Schmelcher, P.; Torres, P. J.; Kevrekidis, P. G.; Frantzeskakis, D. J.; Carretero-Gonzalez, R.; Freilich, D. V.; Hall, D. S.

2011-01-01

A quantized vortex dipole is the simplest vortex molecule, comprising two countercirculating vortex lines in a superfluid. Although vortex dipoles are endemic in two-dimensional superfluids, the precise details of their dynamics have remained largely unexplored. We present here several striking observations of vortex dipoles in dilute-gas Bose-Einstein condensates, and develop a vortex-particle model that generates vortex line trajectories that are in good agreement with the experimental data. Interestingly, these diverse trajectories exhibit essentially identical quasiperiodic behavior, in which the vortex lines undergo stable epicyclic orbits.

Bose condensation in 4He and neutron scattering

International Nuclear Information System (INIS)

Silver, R.N.

1997-01-01

The discovery of superfluidity in liquid 4 He below T λ = 2.17 K, and its phenomenological characterization since then, has been one of the great success stories of condensed matter physics. The relation of superfluidity to the behavior of atoms was conjectured by F. London in 1938. Superfluidity is a manifestation of the Bose condensation of helium atoms, the extensive occupation of the zero momentum state. Ever since 4 He has been the paradigm in the search for Bose condensates in other systems. At the Pune meeting scientists have heard exciting new evidence for Bose condensates of laser cooled alkali atoms in magnetic traps, of excitons in Cu 2 O, and possibly pre-formed Cooper pairs of electrons in the high T c perovskite superconductors. There remains the holy-grail of forming a Bose condensate in spin-polarized hydrogen. In the current excitement for new types of Bose condensates, and new phenomena such as atom lasers, it may be useful to recall the older story of the experimental verification of a relation between superfluidity and Bose condensation in 4 He. This topic has been investigated over many years by neutron scattering experiments and quantum many-body theory. The authors goal is to illustrate the difficulties of establishing the existence of a Bose condensate in a strongly interacting system, even though its macroscopic effects are manifest. The author assumes readers have access to a review by Silver and Sokol which emphasizes the neutron scattering theory through 1990 and a review by Snow and Sokol of the deep inelastic neutron scattering (DINS) experiments through 1995

Anisotropic and long-range vortex interactions in two-dimensional dipolar bose gases

NARCIS (Netherlands)

Mulkerin, B.C.; Bijnen, van R.M.W.; O'Dell, D.H.J.; Martin, A.M.; Parker, N.G.

2013-01-01

We perform a theoretical study into how dipole-dipole interactions modify the properties of superfluid vortices within the context of a two-dimensional atomic Bose gas of co-oriented dipoles. The reduced density at a vortex acts like a giant antidipole, changing the density profile and generating an

Classical region of a trapped Bose gas

Energy Technology Data Exchange (ETDEWEB)

Blakie, P Blair [Jack Dodd Centre for Photonics and Ultra-Cold Atoms, University of Otago, Dunedin (New Zealand); Davis, Matthew J [ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, QLD 4072 (Australia)

2007-06-14

The classical region of a Bose gas consists of all single particle modes that have a high average occupation and are well described by a classical field. Highly occupied modes only occur in massive Bose gases at ultra-cold temperatures, in contrast to the photon case where there are highly occupied modes at all temperatures. For the Bose gas the number of these modes is dependent on the temperature, the total number of particles and their interaction strength. In this paper, we characterize the classical region of a harmonically trapped Bose gas over a wide parameter regime. We use a Hartree-Fock approach to account for the effects of interactions, which we observe to significantly change the classical region as compared to the idealized case. We compare our results to full classical field calculations and show that the Hartree-Fock approach provides a qualitatively accurate description of a classical region for the interacting gas.

Destruction of superfluidity by disorder in one dimension

International Nuclear Information System (INIS)

Zhang, L.; Ma, M.

1988-01-01

We study the effect of disorder on the superfluidity of the hard-sphere Bose gas in one dimension. This system is equivalent to the spin-(1/2 XY model with a random transverse field, which in turn can be mapped onto a disordered spinless-fermion model. We show that the localization of all fermionic states implies an exponential decay in the spin-spin correlation function and hence the instability of the superfluid against any amount of disorder. We point out a fundamental difference in the characteristics of the Jordan-Wigner transformation between the pure and disordered systems. Generalization of our results beyond the present model and implications to disordered superconductivity are discussed

Goldstone mode and pair-breaking excitations in atomic Fermi superfluids

Science.gov (United States)

Hoinka, Sascha; Dyke, Paul; Lingham, Marcus G.; Kinnunen, Jami J.; Bruun, Georg M.; Vale, Chris J.

2017-10-01

Spontaneous symmetry breaking is a central paradigm of elementary particle physics, magnetism, superfluidity and superconductivity. According to Goldstone's theorem, phase transitions that break continuous symmetries lead to the existence of gapless excitations in the long-wavelength limit. These Goldstone modes can become the dominant low-energy excitation, showing that symmetry breaking has a profound impact on the physical properties of matter. Here, we present a comprehensive study of the elementary excitations in a homogeneous strongly interacting Fermi gas through the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a Bose-Einstein condensate (BEC) of molecules using two-photon Bragg spectroscopy. The spectra exhibit a discrete Goldstone mode, associated with the broken-symmetry superfluid phase, as well as pair-breaking single-particle excitations. Our techniques yield a direct determination of the superfluid pairing gap and speed of sound in close agreement with strong-coupling theories.

Relativistic charged Bose gas

International Nuclear Information System (INIS)

Hines, D.F.; Frankel, N.E.

1979-01-01

The charged Bose has been previously studied as a many body problem of great intrinsic interest which can also serve as a model of some real physical systems, for example, superconductors, white dwarf stars and neutron stars. In this article the excitation spectrum of a relativistic spin-zero charged Bose gas is obtained in a dielectric response formulation. Relativity introduces a dip in the spectrum and consequences of this dip for the thermodynamic functions are discussed

Bose-Einstein condensation in the relativistic ideal Bose gas.

Science.gov (United States)

Grether, M; de Llano, M; Baker, George A

2007-11-16

The Bose-Einstein condensation (BEC) critical temperature in a relativistic ideal Bose gas of identical bosons, with and without the antibosons expected to be pair-produced abundantly at sufficiently hot temperatures, is exactly calculated for all boson number densities, all boson point rest masses, and all temperatures. The Helmholtz free energy at the critical BEC temperature is lower with antibosons, thus implying that omitting antibosons always leads to the computation of a metastable state.

Bose-Einstein Condensation in the Relativistic Ideal Bose Gas

International Nuclear Information System (INIS)

Grether, M.; Llano, M. de; Baker, George A. Jr.

2007-01-01

The Bose-Einstein condensation (BEC) critical temperature in a relativistic ideal Bose gas of identical bosons, with and without the antibosons expected to be pair-produced abundantly at sufficiently hot temperatures, is exactly calculated for all boson number densities, all boson point rest masses, and all temperatures. The Helmholtz free energy at the critical BEC temperature is lower with antibosons, thus implying that omitting antibosons always leads to the computation of a metastable state

Vortex mass in a superfluid

Science.gov (United States)

Simula, Tapio

2018-02-01

We consider the inertial mass of a vortex in a superfluid. We obtain a vortex mass that is well defined and is determined microscopically and self-consistently by the elementary excitation energy of the kelvon quasiparticle localized within the vortex core. The obtained result for the vortex mass is found to be consistent with experimental observations on superfluid quantum gases and vortex rings in water. We propose a method to measure the inertial rest mass and Berry phase of a vortex in superfluid Bose and Fermi gases.

Bose-Einstein condensation and superfluidity

CERN Document Server

Pitaevskii, Lev

2016-01-01

This volume introduces the basic concepts of Bose–Einstein condensation and superfluidity. It makes special reference to the physics of ultracold atomic gases; an area in which enormous experimental and theoretical progress has been achieved in the last twenty years. Various theoretical approaches to describing the physics of interacting bosons and of interacting Fermi gases, giving rise to bosonic pairs and hence to condensation, are discussed in detail, both in uniform and harmonically trapped configurations. Special focus is given to the comparison between theory and experiment, concerning various equilibrium, dynamic, thermodynamic, and superfluid properties of these novel systems. The volume also includes discussions of ultracold gases in dimensions, quantum mixtures, and long-range dipolar interactions.

Vortices in trapped Bose-Einstein condensates

International Nuclear Information System (INIS)

Jackson, B.

2000-09-01

In this thesis we solve the Gross-Pitaevskii equation numerically in order to model the response of trapped Bose-Einstein condensed gases to perturbations by electromagnetic fields. First, we simulate output coupling of pulses from the condensate and compare our results to experiments. The excitation and separation of eigenmodes on flow through a constriction is also studied. We then move on to the main theme of this thesis: the important subject of quantised vortices in Bose condensates, and the relation between Bose-Einstein condensation and superfluidity. We propose methods of producing vortex pairs and rings by controlled motion of objects. Full three-dimensional simulations under realistic experimental conditions are performed in order to test the validity of these ideas. We link vortex formation to drag forces on the object, which in turn is connected with energy transfer to the condensate. We therefore argue that vortex formation by moving objects is intimately related to the onset of dissipation in superfluids. We discuss this idea in the context of a recent experiment, using simulations to provide evidence of vortex formation in the experimental scenario. Superfluidity is also manifest in the property of persistent currents, which is linked to vortex stability and dynamics. We simulate vortex line and ring motion, and find in both cases precessional motion and thermodynamic instability to dissipation. Strictly speaking, the Gross-Pitaevskii equation is valid only for temperatures far below the BEC transition. We end the thesis by describing a simple finite-temperature model to describe mean-field coupling between condensed and non-condensed components of the gas. We show that our hybrid Monte-Carlo/FFT technique can describe damping of the lowest energy excitations of the system. Extensions to this model and future research directions are discussed in the conclusion. (author)

Sound propagation in elongated superfluid fermionic clouds

International Nuclear Information System (INIS)

Capuzzi, P.; Vignolo, P.; Federici, F.; Tosi, M. P.

2006-01-01

We use hydrodynamic equations to study sound propagation in a superfluid Fermi gas at zero temperature inside a strongly elongated cigar-shaped trap, with main attention to the transition from the BCS to the unitary regime. First, we treat the role of the radial density profile in the limit of a cylindrical geometry and then evaluate numerically the effect of the axial confinement in a configuration in which a hole is present in the gas density at the center of the trap. We find that in a strongly elongated trap the speed of sound in both the BCS and the unitary regime differs by a factor √(3/5) from that in a homogeneous three-dimensional superfluid. The predictions of the theory could be tested by measurements of sound-wave propagation in a setup such as that exploited by Andrews et al. [Phys. Rev. Lett. 79, 553 (1997)] for an atomic Bose-Einstein condensate

Superfluidity of bosons on a deformable lattice

International Nuclear Information System (INIS)

Jackeli, G.; Ranninger, J.

2001-01-01

We study the superfluid properties of a system of interacting bosons on a lattice, which, moreover, are coupled to the vibrational modes of this lattice, treated here in terms of Einstein phonon modes. The ground state corresponds to two correlated condensates: that of the bosons and that of the phonons. Two competing effects determine the common collective sound-wave-like mode with sound velocity v, arising from gauge symmetry breaking. (i) The sound velocity v 0 (corresponding to a weakly interacting Bose system on a rigid lattice) in the lowest-order approximation is reduced due to reduction of the repulsive boson-boson interaction, arising from the attractive part of the phonon-mediated interaction in the static limit. (ii) The second-order correction to the sound velocity is enhanced as compared to that of bosons on a rigid lattice when the boson-phonon interaction is switched on due to the retarded nature of the phonon-mediated interaction. The overall effect is that the sound velocity is essentially unaffected by the coupling with phonons, indicating the robustness of the superfluid state. The induction of a coherent state in the phonon system driven by the condensation of the bosons could be of experimental significance, permitting spectroscopic detection of superfluid properties of bosons. Our results are based on an extension of the Beliaev-Popov formalism for a weakly interacting Bose gas on a rigid lattice to one on a deformable lattice with which it interacts

Bose-Einstein condensation of a relativistic Bose gas trapped in a general external potential

International Nuclear Information System (INIS)

Su Guozhen; Chen Jincan; Chen Lixuan

2006-01-01

Bose-Einstein condensation of an ideal relativistic Bose gas trapped in a generic power-law potential is investigated. The analytical expressions for some important parameters such as the critical temperature, ground-state fraction and heat capacity are derived. The general criteria on the occurrence of Bose-Einstein condensation and the discontinuity of heat capacity at the critical temperature are obtained. The results obtained here present a unified description for the Bose-Einstein condensation of a class of ideal Bose systems so that many important conclusions in the literature are included in this paper

Study related to the generation of the conditional intensities of ideal Bose-gas

International Nuclear Information System (INIS)

Al-Oklah, H.

2007-01-01

In this paper, we will answer on the following question: Are there any conditions on the chemical potential and temperature of an ideal BOSE gas when generating the conditional intensities of ideal Bose-gas, and will the position distribution of the ideal Bose-gas be a Gibbs-process. The study shows that there should be no conditions on the chemical potential and thermodynamical temperature of an ideal BOSE gas when we generate the conditional intensities of ideal Bose-gas except that the fundamental conditions, the chemical potential is negative and the inverse temperature is positive. Thus the position distribution of the ideal Bose-gas may only be a Gibbs-process, in the special case when the thermodynamical temperature of the ideal BOSE gas tends to the absolute zero. (author)

Spin Superfluidity and Magnone BEC in He-3

Science.gov (United States)

Bunkov, Yury

2011-03-01

The spin superfluidity -- superfluidity in the magnetic subsystem of a condensed matter -- is manifested as the spontaneous phase-coherent precession of spins first discovered in 1984 in 3 He-B. This superfluid current of spins -- spin supercurrent -- is one more representative of superfluid currents known or discussed in other systems, such as the superfluid current of mass and atoms in superfluid 4 He; superfluid current of electric charge in superconductors; superfluid current of hypercharge in Standard Model of particle physics; superfluid baryonic current and current of chiral charge in quark matter; etc. Spin superfluidity can be described in terms of the Bose condensation of spin waves -- magnons. We discuss different states of magnon superfluidity with different types of spin-orbit coupling: in bulk 3 He-B; magnetically traped `` Q -balls'' at very low temperatures; in 3 He-A and 3 He-B immerged in deformed aerogel; etc. Some effects in normal 3 He can also be treated as a magnetic BEC of fermi liquid. A very similar phenomena can be observed also in a magnetic systems with dinamical frequensy shift, like MnC03 . We will discuss the main experimental signatures of magnons superfluidity: (i) spin supercurrent, which transports the magnetization on a macroscopic distance more than 1 cm long; (ii) spin current Josephson effect which shows interference between two condensates; (iii) spin current vortex -- a topological defect which is an analog of a quantized vortex in superfluids, of an Abrikosov vortex in superconductors, and cosmic strings in relativistic theories; (iv) Goldstone modes related to the broken U (1) symmetry -- phonons in the spin-superfluid magnon gas; etc. For recent review see Yu. M. Bunkov and G. E. Volovik J. Phys. Cond. Matter. 22, 164210 (2010) This work is partly supported by the Ministry of Education and Science of the Russian Federation (contract N 02.740.11.5217).

Spinor bose gases in cubic optical lattice

International Nuclear Information System (INIS)

Mobarak, Mohamed Saidan Sayed Mohamed

2014-01-01

In recent years the quantum simulation of condensed-matter physics problems has resulted from exciting experimental progress in the realm of ultracold atoms and molecules in optical lattices. In this thesis we analyze theoretically a spinor Bose gas loaded into a three-dimensional cubic optical lattice. In order to account for different superfluid phases of spin-1 bosons with a linear Zeeman effect, we work out a Ginzburg-Landau theory for the underlying spin-1 Bose-Hubbard model. To this end we add artificial symmetry-breaking currents to the spin-1 Bose-Hubbard Hamiltonian in order to break the global U (1) symmetry. With this we determine a diagrammatic expansion of the grand-canonical free energy up to fourth order in the symmetry-breaking currents and up to the leading non-trivial order in the hopping strength which is of first order. As a cross-check we demonstrate that the resulting grand-canonical free energy allows to recover the mean-field theory. Applying a Legendre transformation to the grand-canonical free energy, where the symmetry-breaking currents are transformed to order parameters, we obtain the effective Ginzburg-Landau action. With this we calculate in detail at zero temperature the Mott insulator-superfluid quantum phase boundary as well as condensate and particle number density in the superfluid phase. We find that both mean-field and Ginzburg-Landau theory yield the same quantum phase transition between the Mott insulator and superfluid phases, but the range of validity of the mean-field theory turns out to be smaller than that of the Ginzburg-Landau theory. Due to this finding we expect that the Ginzburg-Landau theory gives better results for the superfluid phase and, thus, we restrict ourselves to extremize only the effective Ginzburg-Landau action with respect to the order parameters. Without external magnetic field the superfluid phase is a polar (ferromagnetic) state for anti-ferromagnetic (ferromagnetic) interactions, i.e. only the

Observations of density fluctuations in an elongated Bose gas: ideal gas and quasicondensate regimes.

Science.gov (United States)

Esteve, J; Trebbia, J-B; Schumm, T; Aspect, A; Westbrook, C I; Bouchoule, I

2006-04-07

We report in situ measurements of density fluctuations in a quasi-one-dimensional 87Rb Bose gas at thermal equilibrium in an elongated harmonic trap. We observe an excess of fluctuations compared to the shot-noise level expected for uncorrelated atoms. At low atomic density, the measured excess is in good agreement with the expected "bunching" for an ideal Bose gas. At high density, the measured fluctuations are strongly reduced compared to the ideal gas case. We attribute this reduction to repulsive interatomic interactions. The data are compared with a calculation for an interacting Bose gas in the quasicondensate regime.

Novel superfluids

CERN Document Server

Ketterson, John B

This book reports on the latest developments in the field of Superfluidity. The phenomenon has had a tremendous impact on the fundamental sciences as well as a host of technologies. It began with the discovery of superconductivity in mercury in 1911, which was ultimately described theoretically by the theory of Bardeen Cooper and Schriever (BCS) in 1957. The analogous phenomena, superfluidity, was discovered in helium in 1938 and tentatively explained shortly thereafter as arising from a Bose-Einstein Condensation (BEC) by London. But the importance of superfluidity, and the range of systems in which it occurs, has grown enormously. In addition to metals and the helium liquids the phenomena has now been observed for photons in cavities, excitons in semiconductors, magnons in certain materials, and cold gasses trapped in high vacuum. It very likely exist for neutrons in a neutron star and, possibly, in a conjectured quark state at their center. Even the Universe itself can be regarded as being in a kind of sup...

Quasiparticle scattering by quantum phase slips in one-dimensional superfluids

International Nuclear Information System (INIS)

Khlebnikov, S.

2004-01-01

Quantum phase slips (QPS) in narrow superfluid channels generate momentum by unwinding the supercurrent. In a uniform Bose gas, this momentum needs to be absorbed by quasiparticles (phonons). We show that this requirement results in an additional exponential suppression of the QPS rate (compared to the rate of QPS induced by a sharply localized perturbation). In BCS-paired fluids, momentum can be transferred to fermionic quasiparticles, and we find an interesting interplay between quasiparticle scattering on QPS and on disorder

Faraday instability and Faraday patterns in a superfluid Fermi gas

International Nuclear Information System (INIS)

Tang Rongan; Xue Jukui; Li Haocai

2011-01-01

With the consideration of the coupling between the transverse width and the longitudinal density, the parametric excitations related to Faraday waves in a cigar-shaped superfluid Fermi gas are studied. A Mathieu equation is obtained, and it is demonstrated firstly that the excited actual 3D Faraday pattern is the combination of the longitudinal Faraday density wave and the corresponding transverse width fluctuation in the longitudinal direction. The Faraday instability growth index and the kinematic equations of the Faraday density wave and the width fluctuation along the Bose-Einstein condensate (BEC)-Bardeen-Cooper-Schrieffer (BCS) crossover are also given for the first time. It is found that the 3D Faraday pattern presents quite different behaviours (such as the excitations and the motions) when the system crosses from the BEC side to the BCS side. The coupling not only plays an important role in the parametric excitation, but also determines the dominant wavelength of the spatial structure. Along the crossover, the coupling effects are more significant in the BCS side. The final numerical investigation verifies these results and gives a detailed study of the parametric excitations (i.e. Faraday instability) and the 3D pattern formation.

Path-integral computation of superfluid densities

International Nuclear Information System (INIS)

Pollock, E.L.; Ceperley, D.M.

1987-01-01

The normal and superfluid densities are defined by the response of a liquid to sample boundary motion. The free-energy change due to uniform boundary motion can be calculated by path-integral methods from the distribution of the winding number of the paths around a periodic cell. This provides a conceptually and computationally simple way of calculating the superfluid density for any Bose system. The linear-response formulation relates the superfluid density to the momentum-density correlation function, which has a short-ranged part related to the normal density and, in the case of a superfluid, a long-ranged part whose strength is proportional to the superfluid density. These facts are discussed in the context of path-integral computations and demonstrated for liquid 4 He along the saturated vapor-pressure curve. Below the experimental superfluid transition temperature the computed superfluid fractions agree with the experimental values to within the statistical uncertainties of a few percent in the computations. The computed transition is broadened by finite-sample-size effects

Lenr:. Superfluids, Self-Trapping and Non-Self States

Science.gov (United States)

Chubb, Talbot A.

2005-12-01

LENR ion band state models involve deuteron many-body systems resembling superfluids. The physics of atom Bose-Einstein condensates in optical lattices teaches that superfluid behavior occurs when the potential barriers between adjacent potential wells permit high tunneling rates and the well potentials are shallow. These superfluids have fractional occupation of individual wells. Well periodic symmetry is not affected by the presence of the atoms. This behavior suggests that deuterons in a lattice should be in non-self-trapping sites, which may indicate that D+Bloch occupies the Pd tetrahedral sites.

On the theory of point vortices in two-dimensional Bose liquids

International Nuclear Information System (INIS)

Speliotopoulos, A.D.

1991-01-01

The physics and structure of the Kosterlitz-Thouless phase transition, as it is applied to superfluidity in two dimensions, will be studied by looking at the origins and properties of point vortices in a Bose Liquid. A lagrangian for the two-dimensional vortex gas is derived from a general microscopic lagrangian for 4 He atoms on an arbitrary compact Riemann Surface without boundary. In the contrast density limit the vortex hamiltonian obtained from this lagrangian is found to be the same as the Kosterlitz and Thouless coulombic interaction hamiltonian. The dynamics and symmetries of the vortex gas on compact Riemann Surfaces are analyzed using lagrangian dynamics and Dirac's theory of constraints is used to formulate the hamiltonian dynamics for the system. The superfluid phase transition of the general vortex gas, in which the circulations may be any non-zero integer, is studied. When the net circulation of the system is not zero the absence of a superfluid phase is shown. When the net circulation of the vortices vanishes, presence of off-diagonal long range order is demonstrated and the existence of an order parameter is proposed. The transition temperature for general vortex gas is shown to be the Kosterlitz-Thouless temperature. An upper bound for the average vortex number density is established for the general vortex gas and an exact expression is derived for the Kosterlitz-Thouless ensemble

Response of the Higgs amplitude mode of superfluid Bose gases in a three-dimensional optical lattice

Science.gov (United States)

Nagao, Kazuma; Takahashi, Yoshiro; Danshita, Ippei

2018-04-01

We study the Higgs mode of superfluid Bose gases in a three-dimensional optical lattice, which emerges near the quantum phase transition to the Mott insulator at commensurate fillings. Specifically, we consider responses of the Higgs mode to temporal modulations of the onsite interaction and the hopping energy. In order to calculate the response functions including the effects of quantum and thermal fluctuations, we map the Bose-Hubbard model onto an effective pseudospin-1 model and use a perturbative expansion based on the imaginary-time Green's function theory. We also include the effects of an inhomogeneous trapping potential by means of a local density approximation. We find that the response function for the hopping modulation is equal to that for the interaction modulation within our approximation. At the unit filling rate and in the absence of a trapping potential, we show that the Higgs mode can exist as a sharp resonance peak in the dynamical susceptibilities at typical temperatures. However, the resonance peak is significantly broadened due to the trapping potential when the modulations are applied globally to the entire system. We suggest that the Higgs mode can be detected as a sharp resonance peak by partial modulations around the trap center.

Effective action for superfluid Fermi systems in the strong-coupling limit

Science.gov (United States)

Dupuis, N.

2005-07-01

We derive the low-energy effective action for three-dimensional superfluid Fermi systems in the strong-coupling limit, where superfluidity originates from Bose-Einstein condensation of composite bosons. Taking into account density and pairing fluctuations on the same footing, we show that the effective action involves only the fermion density ρr and its conjugate variable, the phase θr of the pairing order parameter Δr . We recover the standard action of a Bose superfluid of density ρr/2 , where the bosons have a mass mB=2m and interact via a repulsive contact potential with amplitude gB=4πaB/mB,aB=2a ( a the s -wave scattering length associated to the fermion-fermion interaction in vacuum). For lattice models, the derivation of the effective action is based on the mapping of the attractive Hubbard model onto the Heisenberg model in a uniform magnetic field, and a coherent state path integral representation of the partition function. The effective description of the Fermi superfluid in the strong-coupling limit is a Bose-Hubbard model with an intersite hopping amplitude tB=J/2 and an on-site repulsive interaction UB=2Jz , where J=4t2/U ( t and -U are the intersite hopping amplitude and the on-site attraction in the (fermionic) Hubbard model, z the number of nearest-neighbor sites).

Optical absorption in a degenerate Bose-Einstein gas

International Nuclear Information System (INIS)

Yip, S.K.

2002-01-01

We develop a theory on optical absorption in a dilute Bose-Einstein gas at low temperatures. This theory is motivated by the Bogoliubov theory of elementary excitations for this system, and takes into account explicitly the modification of the nature and dispersion of elementary excitations due to Bose-Einstein condensation. Our results show important differences from existing theories

The canonical ensemble redefined - 3. Ideal Bose gas

International Nuclear Information System (INIS)

Venkataraman, R.

1984-12-01

The ideal Bose gas solved in the redefined ensemble formalism exhibits a discontinuity in the specific heat suggesting that Bose-Einstein condensation is a second order phase transition. The deviations from the classical ideal gas behaviour are larger than those predicted by Gibbs ensemble. Below Tsub(c) the pressure is not independent of the volume. For a certain range of values of VT 3 , the peak in black body radiation shows a shift in the frequency scale and this could be detected, at least in principle, experimentally. (author)

Low-temperature behaviour of an ideal Bose gas and some forbidden thermodynamic cycles

International Nuclear Information System (INIS)

Chen Jincan; Lin Bihong

2003-01-01

Based on the equation of state of an ideal Bose gas, the heat capacities at constant volume and constant pressure of the Bose system are derived and used to analyse the low-temperature behaviour of the Bose system. It is expounded that some important thermodynamic processes such as a constant pressure and an adiabatic process cannot be carried out from the region of T > T c to that of T c , where T c is the critical temperature of Bose-Einstein condensation of the Bose system. Consequently, some typical thermodynamic cycles such as the Carnot cycle, Brayton cycle, Otto cycle, Ericsson cycle, Diesel cycle and Atkinson cycle cannot be operated across the critical temperature T c of Bose-Einstein condensation of an ideal Bose gas

Universal Themes of Bose-Einstein Condensation

Science.gov (United States)

Proukakis, Nick P.; Snoke, David W.; Littlewood, Peter B.

2017-04-01

Foreword; List of contributors; Preface; Part I. Introduction: 1. Universality and Bose-Einstein condensation: perspectives on recent work D. W. Snoke, N. P. Proukakis, T. Giamarchi and P. B. Littlewood; 2. A history of Bose-Einstein condensation of atomic hydrogen T. Greytak and D. Kleppner; 3. Twenty years of atomic quantum gases: 1995-2015 W. Ketterle; 4. Introduction to polariton condensation P. B. Littlewood and A. Edelman; Part II. General Topics: Editorial notes; 5. The question of spontaneous symmetry breaking in condensates D. W. Snoke and A. J. Daley; 6. Effects of interactions on Bose-Einstein condensation R. P. Smith; 7. Formation of Bose-Einstein condensates M. J. Davis, T. M. Wright, T. Gasenzer, S. A. Gardiner and N. P. Proukakis; 8. Quenches, relaxation and pre-thermalization in an isolated quantum system T. Langen and J. Schmiedmayer; 9. Ultracold gases with intrinsic scale invariance C. Chin; 10. Berezinskii-Kosterlitz-Thouless phase of a driven-dissipative condensate N. Y. Kim, W. H. Nitsche and Y. Yamamoto; 11. Superfluidity and phase correlations of driven dissipative condensates J. Keeling, L. M. Sieberer, E. Altman, L. Chen, S. Diehl and J. Toner; 12. BEC to BCS crossover from superconductors to polaritons A. Edelman and P. B. Littlewood; Part III. Condensates in Atomic Physics: Editorial notes; 13. Probing and controlling strongly correlated quantum many-body systems using ultracold quantum gases I. Bloch; 14. Preparing and probing chern bands with cold atoms N. Goldman, N. R. Cooper and J. Dalibard; 15. Bose-Einstein condensates in artificial gauge fields L. J. LeBlanc and I. B. Spielman; 16. Second sound in ultracold atomic gases L. Pitaevskii and S. Stringari; 17. Quantum turbulence in atomic Bose-Einstein condensates N. G. Parker, A. J. Allen, C. F. Barenghi and N. P. Proukakis; 18. Spinor-dipolar aspects of Bose-Einstein condensation M. Ueda; Part IV. Condensates in Condensed Matter Physics: Editorial notes; 19. Bose

Effective action for superfluid Fermi systems in the strong-coupling limit

International Nuclear Information System (INIS)

Dupuis, N.

2005-01-01

We derive the low-energy effective action for three-dimensional superfluid Fermi systems in the strong-coupling limit, where superfluidity originates from Bose-Einstein condensation of composite bosons. Taking into account density and pairing fluctuations on the same footing, we show that the effective action involves only the fermion density ρ r and its conjugate variable, the phase θ r of the pairing order parameter Δ r . We recover the standard action of a Bose superfluid of density ρ r /2, where the bosons have a mass m B =2m and interact via a repulsive contact potential with amplitude g B =4πa B /m B ,a B =2a (a the s-wave scattering length associated to the fermion-fermion interaction in vacuum). For lattice models, the derivation of the effective action is based on the mapping of the attractive Hubbard model onto the Heisenberg model in a uniform magnetic field, and a coherent state path integral representation of the partition function. The effective description of the Fermi superfluid in the strong-coupling limit is a Bose-Hubbard model with an intersite hopping amplitude t B =J/2 and an on-site repulsive interaction U B =2Jz, where J=4t 2 /U (t and -U are the intersite hopping amplitude and the on-site attraction in the (fermionic) Hubbard model, z the number of nearest-neighbor sites)

Extended Bose Hubbard model of interacting bosonic atoms in optical lattices: From superfluidity to density waves

International Nuclear Information System (INIS)

Mazzarella, G.; Giampaolo, S. M.; Illuminati, F.

2006-01-01

For systems of interacting, ultracold spin-zero neutral bosonic atoms, harmonically trapped and subject to an optical lattice potential, we derive an Extended Bose Hubbard (EBH) model by developing a systematic expansion for the Hamiltonian of the system in powers of the lattice parameters and of a scale parameter, the lattice attenuation factor. We identify the dominant terms that need to be retained in realistic experimental conditions, up to nearest-neighbor interactions and nearest-neighbor hoppings conditioned by the on-site occupation numbers. In the mean field approximation, we determine the free energy of the system and study the phase diagram both at zero and at finite temperature. At variance with the standard on site Bose Hubbard model, the zero-temperature phase diagram of the EBH model possesses a dual structure in the Mott insulating regime. Namely, for specific ranges of the lattice parameters, a density wave phase characterizes the system at integer fillings, with domains of alternating mean occupation numbers that are the atomic counterparts of the domains of staggered magnetizations in an antiferromagnetic phase. We show as well that in the EBH model, a zero-temperature quantum phase transition to pair superfluidity is, in principle, possible, but completely suppressed at the lowest order in the lattice attenuation factor. Finally, we determine the possible occurrence of the different phases as a function of the experimentally controllable lattice parameters

Cooper pairs versus Bose condensed molecules: The ground-state current in superfluid 3He-A

International Nuclear Information System (INIS)

Mermin, N.D.; Muzikar, P.

1980-01-01

We present a new calculation of the current g flowing in a ground state of the Bardeen-Cooper-Schrieffer (BCS) form for a weakly inhomogeneous superfluid with the symmetry of 3 He-A. When the structure of the order parameter not determined by symmetry is appropriate to 3 He-A and when the mass density rho of the helium is essentially uniform, our current reduces to that calculated by Cross. If the mass density is allowed to vary, we find a generalization of the Cross current which shows that when v/sub s/=0 and the anisotropy axis l is uniform, then the current is simply (h/4M) del-arrow-rightrho x l. We show that this property of the BCS ground state, which taken with the Cross definition leads to an ''intrinsic angular momentum density'' of rhoh/2M at zero temperature, also follows directly from the Gor'kov equations. If the range of the order parameter is taken to be small compared with the interatomic separation, then the ground state does not describe 3 He-A, but a Bose-Einstein condensate of tightly bound diatomic molecules. In this limit our current reduces to the form calculated by Ishikawa et al. We indicate why their analysis is only valid in this limit, and offer some rather more general remarks on the differences between Cooper pairing and the Bose-Einstein condensation of diatomic molecules

Magnetized pair Bose gas: relativistic superconductor

International Nuclear Information System (INIS)

Daicic, J.; Frankel, N.E.; Kowalenko, V.

1993-01-01

The magnetized Bose gas at temperatures above pair threshold is investigated. New magnetization laws are obtained for a wide range of field strengths, and the gas is shown to exhibit the Meissner effect. Some related results for the Fermi gas, a relativistic paramagnet, are also discussed. It is concluded that the pair gases, through the interplay between pair creation, temperature, field strength, statistics and/in the case of fermions/spin, have remarkable magnetic properties. 14 refs

Phase diagram of the disordered Bose-Hubbard model

International Nuclear Information System (INIS)

Gurarie, V.; Pollet, L.; Prokof'ev, N. V.; Svistunov, B. V.; Troyer, M.

2009-01-01

We establish the phase diagram of the disordered three-dimensional Bose-Hubbard model at unity filling which has been controversial for many years. The theorem of inclusions, proven by Pollet et al. [Phys. Rev. Lett. 103, 140402 (2009)] states that the Bose-glass phase always intervenes between the Mott insulating and superfluid phases. Here, we note that assumptions on which the theorem is based exclude phase transitions between gapped (Mott insulator) and gapless phases (Bose glass). The apparent paradox is resolved through a unique mechanism: such transitions have to be of the Griffiths type when the vanishing of the gap at the critical point is due to a zero concentration of rare regions where extreme fluctuations of disorder mimic a regular gapless system. An exactly solvable random transverse field Ising model in one dimension is used to illustrate the point. A highly nontrivial overall shape of the phase diagram is revealed with the worm algorithm. The phase diagram features a long superfluid finger at strong disorder and on-site interaction. Moreover, bosonic superfluidity is extremely robust against disorder in a broad range of interaction parameters; it persists in random potentials nearly 50 (!) times larger than the particle half-bandwidth. Finally, we comment on the feasibility of obtaining this phase diagram in cold-atom experiments, which work with trapped systems at finite temperature.

Superfluid/Bose-glass transition in one dimension

Science.gov (United States)

Ristivojevic, Zoran; Petković, Aleksandra; Le Doussal, Pierre; Giamarchi, Thierry

2014-09-01

We consider a one-dimensional system of interacting bosons in a random potential. At zero temperature, it can be either in the superfluid or in the insulating phase. We study the transition at weak disorder and moderate interaction. Using a systematic approach, we derive the renormalization group equations at two-loop order and discuss the phase diagram. We find the universal form of the correlation functions at the transitions and compute the logarithmic corrections to the main universal power-law behavior. In order to mimic large density fluctuations on a single site, we study a simplified model of disordered two-leg bosonic ladders with correlated disorder across the rung. Contrarily to the single-chain case, the latter system exhibits a transition between a superfluid and a localized phase where the exponents of the correlation functions at the transition do not take universal values.

Higher first Chern numbers in one-dimensional Bose-Fermi mixtures

Science.gov (United States)

Knakkergaard Nielsen, Kristian; Wu, Zhigang; Bruun, G. M.

2018-02-01

We propose to use a one-dimensional system consisting of identical fermions in a periodically driven lattice immersed in a Bose gas, to realise topological superfluid phases with Chern numbers larger than 1. The bosons mediate an attractive induced interaction between the fermions, and we derive a simple formula to analyse the topological properties of the resulting pairing. When the coherence length of the bosons is large compared to the lattice spacing and there is a significant next-nearest neighbour hopping for the fermions, the system can realise a superfluid with Chern number ±2. We show that this phase is stable in a large region of the phase diagram as a function of the filling fraction of the fermions and the coherence length of the bosons. Cold atomic gases offer the possibility to realise the proposed system using well-known experimental techniques.

Superfluid quenching of the moment of inertia in a strongly interacting Fermi gas

Science.gov (United States)

Riedl, S.; Sánchez Guajardo, E. R.; Kohstall, C.; Hecker Denschlag, J.; Grimm, R.

2011-03-01

We report on the observation of a quenched moment of inertia resulting from superfluidity in a strongly interacting Fermi gas. Our method is based on setting the hydrodynamic gas in slow rotation and determining its angular momentum by detecting the precession of a radial quadrupole excitation. The measurements distinguish between the superfluid and collisional origins of hydrodynamic behavior, and show the phase transition.

Bose-Einstein Condensation of Long-Lifetime Polaritons in Thermal Equilibrium.

Science.gov (United States)

Sun, Yongbao; Wen, Patrick; Yoon, Yoseob; Liu, Gangqiang; Steger, Mark; Pfeiffer, Loren N; West, Ken; Snoke, David W; Nelson, Keith A

2017-01-06

The experimental realization of Bose-Einstein condensation (BEC) with atoms and quasiparticles has triggered wide exploration of macroscopic quantum effects. Microcavity polaritons are of particular interest because quantum phenomena such as BEC and superfluidity can be observed at elevated temperatures. However, polariton lifetimes are typically too short to permit thermal equilibration. This has led to debate about whether polariton condensation is intrinsically a nonequilibrium effect. Here we report the first unambiguous observation of BEC of optically trapped polaritons in thermal equilibrium in a high-Q microcavity, evidenced by equilibrium Bose-Einstein distributions over broad ranges of polariton densities and bath temperatures. With thermal equilibrium established, we verify that polariton condensation is a phase transition with a well-defined density-temperature phase diagram. The measured phase boundary agrees well with the predictions of basic quantum gas theory.

Topological Coherent Modes in Trapped Bose Gas

International Nuclear Information System (INIS)

Yukalov, V.I.; Marzlin, K.-P.; Yukalova, E.P.; Bagnato, V.S.

2005-01-01

The report reviews the problem of topological coherent modes, which are nonlinear collective states of Bose-condensed atoms. Such modes can be generated by means of alternating external fields, whose frequencies are in resonance with the transition frequencies between the related modes. The Bose gas with generated topological coherent modes is a collective nonlinear analog of a resonant atom. Such systems exhibit a variety of nontrivial effects, e.g. interference fringes, interference current, mode locking, dynamic transitions, critical phenomena, chaotic motion, harmonic generation, parametric conversion, atomic squeezing, and entanglement production

The shear viscosity of a trapped Bose-condensed gas

International Nuclear Information System (INIS)

Shahzamanian, M.A.; Yavary, H.

2006-01-01

By obtaining Kubo formula type and using nonequilibrium Green's functions, we calculate the shear viscosity of a trapped Bose-condensed gas below and above the Bose-Einstein condensation temperature (T BEC ). The contributions of the interactions between condensate and noncondensate atoms and between noncondensate atoms take into account to the viscous relaxation time, by evaluating second order self-energies in Beliaev approximation

Numerical calculation of spectral functions of the Bose-Hubbard model using bosonic dynamical mean-field theory

Czech Academy of Sciences Publication Activity Database

Panas, J.; Kauch, Anna; Kuneš, Jan; Vollhardt, D.; Byczuk, K.

2015-01-01

Roč. 92, č. 4 (2015), "045102-1"-"045102-9" ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : Bose-Hubbard model * Bose-Einstein condensation * superfluidity Subject RIV: BE - Theoretical Physics Impact factor: 3.736, year: 2014

Coulomb-gas scaling, superfluid films, and the XY model

International Nuclear Information System (INIS)

Minnhagen, P.; Nylen, M.

1985-01-01

Coulomb-gas-scaling ideas are invoked as a link between the superfluid density of two-dimensional 4 He films and the XY model; the Coulomb-gas-scaling function epsilon(X) is extracted from experiments and is compared with Monte Carlo simulations of the XY model. The agreement is found to be excellent

Nucleation and creep of vortices in superfluids and clean superconductors

International Nuclear Information System (INIS)

Sonin, E.B.

1995-01-01

The paper is devoted to vortex nucleation in uniform and nonuniform superflows in superfluids, and to creep of vortices trapped by twin boundaries and columnar defects in isotropic and anisotropic superconductors. The shape of a nuclated loop which yields the maximal nucleation rate is defined from the balance of the Lorentz and the line-tension forces. If the trapping energy is small, the contact angle at which the vortex line meets the plane of the twin-boundary or the axis of the columnar defect is also small. This may strongly enhance the rate of thermal nucleation and especially of quantum nucleation. In the analysis of quantum tunnelling it was assumed that the vortex has no mass and its motion is governed by the Magnus force, as expected for superfluids and very pure superconductors. Quantum nucleation rate from the traditional quasiclassical theory of macroscopic tunnelling is compared with the nucleation rate derived from the Gross-Pitaevskii theory of a weakly nonideal Bose-gas. (orig.)

Resonance superfluidity in a quantum degenerate Fermi gas

NARCIS (Netherlands)

Kokkelmans, S.J.J.M.F.; Holland, M.; Walser, R.; Chiofalo, M.L.; Chu, S.; Vuletic, V.; Kerman, A.J.; Chin, C.

2002-01-01

We consider the superfluid phase transition that arises when a Feshbach resonance pairing occurs in a dilute Fermi gas. This is related to the phenomenon of superconductivity described by the seminal Bardeen-Cooper-Schrieffer (BCS) theory. In superconductivity, the phase transition is caused by a

On the infimum of the energy-momentum spectrum of a homogeneous Bose gas

DEFF Research Database (Denmark)

Cornean, Horia; Derezinski, J.; Zin, P.

2009-01-01

We consider second-quantized homogeneous Bose gas in a large cubic box with periodic boundary conditions at zero temperature. We discuss the energy-momentum spectrum of the Bose gas and its physical significance. We review various rigorous and heuristic results as well as open conjectures about its...

Anisotropic superfluidity in the two-species polar Fermi gas

International Nuclear Information System (INIS)

Liao Renyuan; Brand, Joachim

2010-01-01

We study the superfluid pairing in a two-species gas of heteronuclear fermionic molecules with equal density. The interplay of the isotropic s-wave interaction and anisotropic long-range dipolar interaction reveals rich physics. We find that the single-particle momentum distribution has a characteristic ellipsoidal shape that can be reasonably represented by a deformation parameter α defined similarly to the normal phase. Interesting momentum-dependent features of the order parameter are identified. We calculate the critical temperatures of both the singlet and triplet superfluids, suggesting a possible pairing symmetry transition by tuning the s-wave or dipolar interaction strength.

Bose-Einstein Condensation

International Nuclear Information System (INIS)

Jaksch, D

2003-01-01

The Gross-Pitaevskii equation, named after one of the authors of the book, and its large number of applications for describing the properties of Bose-Einstein condensation (BEC) in trapped weakly interacting atomic gases, is the main topic of this book. In total the monograph comprises 18 chapters and is divided into two parts. Part I introduces the notion of BEC and superfluidity in general terms. The most important properties of the ideal and the weakly interacting Bose gas are described and the effects of nonuniformity due to an external potential at zero temperature are studied. The first part is then concluded with a summary of the properties of superfluid He. In Part II the authors describe the theoretical aspects of BEC in harmonically trapped weakly interacting atomic gases. A short and rather rudimentary chapter on collisions and trapping of atomic gases which seems to be included for completeness only is followed by a detailed analysis of the ground state, collective excitations, thermodynamics, and vortices as well as mixtures of BECs and the Josephson effect in BEC. Finally, the last three chapters deal with topics of more recent interest like BEC in optical lattices, low dimensional systems, and cold Fermi gases. The book is well written and in fact it provides numerous useful and important relations between the different properties of a BEC and covers most of the aspects of ultracold weakly interacting atomic gases from the point of view of condensed matter physics. The book contains a comprehensive introduction to BEC for physicists new to the field as well as a lot of detail and insight for those already familiar with this area. I therefore recommend it to everyone who is interested in BEC. Very clearly however, the intention of the book is not to provide prospects for applications of BEC in atomic physics, quantum optics or quantum state engineering and therefore the more practically oriented reader might sometimes wonder why exactly an equation is

Non-equilibrium coherence dynamics in one-dimensional Bose gases.

Science.gov (United States)

Hofferberth, S; Lesanovsky, I; Fischer, B; Schumm, T; Schmiedmayer, J

2007-09-20

Low-dimensional systems provide beautiful examples of many-body quantum physics. For one-dimensional (1D) systems, the Luttinger liquid approach provides insight into universal properties. Much is known of the equilibrium state, both in the weakly and strongly interacting regimes. However, it remains a challenge to probe the dynamics by which this equilibrium state is reached. Here we present a direct experimental study of the coherence dynamics in both isolated and coupled degenerate 1D Bose gases. Dynamic splitting is used to create two 1D systems in a phase coherent state. The time evolution of the coherence is revealed through local phase shifts of the subsequently observed interference patterns. Completely isolated 1D Bose gases are observed to exhibit universal sub-exponential coherence decay, in excellent agreement with recent predictions. For two coupled 1D Bose gases, the coherence factor is observed to approach a non-zero equilibrium value, as predicted by a Bogoliubov approach. This coupled-system decay to finite coherence is the matter wave equivalent of phase-locking two lasers by injection. The non-equilibrium dynamics of superfluids has an important role in a wide range of physical systems, such as superconductors, quantum Hall systems, superfluid helium and spin systems. Our experiments studying coherence dynamics show that 1D Bose gases are ideally suited for investigating this class of phenomena.

Transport of a Bose gas in 1D disordered lattices at the fluid-insulator transition.

Science.gov (United States)

Tanzi, Luca; Lucioni, Eleonora; Chaudhuri, Saptarishi; Gori, Lorenzo; Kumar, Avinash; D'Errico, Chiara; Inguscio, Massimo; Modugno, Giovanni

2013-09-13

We investigate the momentum-dependent transport of 1D quasicondensates in quasiperiodic optical lattices. We observe a sharp crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. In the limit of nondisordered lattices the observations suggest a contribution of quantum phase slips to the dissipation. We identify a set of critical disorder and interaction strengths for which such critical momentum vanishes, separating a fluid regime from an insulating one. We relate our observation to the predicted zero-temperature superfluid-Bose glass transition.

Ferroelectricity by Bose-Einstein condensation in a quantum magnet.

Science.gov (United States)

Kimura, S; Kakihata, K; Sawada, Y; Watanabe, K; Matsumoto, M; Hagiwara, M; Tanaka, H

2016-09-26

The Bose-Einstein condensation is a fascinating phenomenon, which results from quantum statistics for identical particles with an integer spin. Surprising properties, such as superfluidity, vortex quantization or Josephson effect, appear owing to the macroscopic quantum coherence, which spontaneously develops in Bose-Einstein condensates. Realization of Bose-Einstein condensation is not restricted in fluids like liquid helium, a superconducting phase of paired electrons in a metal and laser-cooled dilute alkali atoms. Bosonic quasi-particles like exciton-polariton and magnon in solids-state systems can also undergo Bose-Einstein condensation in certain conditions. Here, we report that the quantum coherence in Bose-Einstein condensate of the magnon quasi particles yields spontaneous electric polarization in the quantum magnet TlCuCl 3 , leading to remarkable magnetoelectric effect. Very soft ferroelectricity is realized as a consequence of the O(2) symmetry breaking by magnon Bose-Einstein condensation. The finding of this ferroelectricity will open a new window to explore multi-functionality of quantum magnets.

Hybrid Optical-Magnetic Traps for Studies of 2D Quantum Turbulence in Bose-Einstein Condensates

Science.gov (United States)

Myers, Jessica Ann

Turbulence appears in most natural and man-made flows. However, the analysis of turbulence is particularly difficult. Links between microscopic fluid dynamics and statistical signatures of turbulence appear unobtainable from the postulates of fluid dynamics making turbulence one of the most important unsolved theoretical problems in physics. Two-dimensional quantum turbulence (2DQT), an emerging field of study, involves turbulence in two-dimensional (2D) flows in superfluids, such as Bose-Einstein condensates (BECs). In 2D superfluids, a turbulent state can be characterized by a disordered distribution of numerous vortex cores. The question of how to effectively and efficiently generate turbulent states in superfluids is a fundamental question in the field of quantum turbulence. Therefore, experimental studies of vortex nucleation and the onset of turbulence in a superfluid are important for achieving a deeper understanding of the overall problem of turbulence. My PhD dissertation involves the study of vortex nucleation and the onset of turbulence in quasi-2D BECs. First, I discuss experimental apparatus advancements that now enable BECs to be created in a hybrid optical-magnetic trap, an atom trapping configuration conducive to 2DQT experiments. Next, I discuss the design and construction of a quantum vortex microscope and initial vortex detection tests. Finally, I present the first experiments aimed at studying 2DQT carried out in the updated apparatus. Thermal counterflow in superfluid helium, in which the normal and superfluid components flow in opposite directions, is known to create turbulence in the superfluid. However, this phenomenon has not been simulated or studied in dilute-gas BECs as a possible vortex nucleation method. In this dissertation, I present preliminary data from the first experiments aimed at understanding thermal counterflow turbulence in dilute-gas BECs.

Boson localization and the superfluid-insulator transition

International Nuclear Information System (INIS)

Fisher, M.P.A.; Weichman, P.B.; Grinstein, G.; Fisher, D.S.; Condensed Matter Physics 114-36, California Institute of Technology, Pasadena, California 91125; IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, New York 10598; Joseph Henry Laboratory of Physics, Jadwin Hall, Princeton University, Princeton, New Jersey 08544)

1989-01-01

The phase diagrams and phase transitions of bosons with short-ranged repulsive interactions moving in periodic and/or random external potentials at zero temperature are investigated with emphasis on the superfluid-insulator transition induced by varying a parameter such as the density. Bosons in periodic potentials (e.g., on a lattice) at T=0 exhibit two types of phases: a superfluid phase and Mott insulating phases characterized by integer (or commensurate) boson densities, by the existence of a gap for particle-hole excitations, and by zero compressibility. Generically, the superfluid onset transition in d dimensions from a Mott insulator to superfluidity is ''ideal,'' or mean field in character, but at special multicritical points with particle-hole symmetry it is in the universality class of the (d+1)-dimensional XY model. In the presence of disorder, a third, ''Bose glass'' phase exists. This phase is insulating because of the localization effects of the randomness and analogous to the Fermi glass phase of interacting fermions in a strongly disordered potential

BCS-BEC crossover at finite temperature for superfluid trapped Fermi atoms

International Nuclear Information System (INIS)

Perali, A.; Pieri, P.; Pisani, L.; Strinati, G.C.

2004-01-01

We consider the BCS-BEC (Bose-Einstein-condensate) crossover for a system of trapped Fermi atoms at finite temperature, both below and above the superfluid critical temperature, by including fluctuations beyond mean field. We determine the superfluid critical temperature and the pair-breaking temperature as functions of the attractive interaction between Fermi atoms, from the weak- to the strong-coupling limit (where bosonic molecules form as bound-fermion pairs). Density profiles in the trap are also obtained for all temperatures and couplings

Two-step condensation of the ideal Bose gas in highly anisotropic traps

NARCIS (Netherlands)

van Druten, N.J.; Ketterle, W.

1997-01-01

The ideal Bose gas in a highly anisotropic harmonic potential is studied. It is found that Bose-Einstein condensation occurs in two distinct steps as the temperature is lowered. In the first step the specific heat shows a sharp feature, but the system still occupies many one-dimensional quantum

Quantum degeneracy effect on performance of irreversible Otto cycle with ideal Bose gas

International Nuclear Information System (INIS)

Wu Feng; Chen Lingen; Sun Fengrui; Wu Chih; Guo Fangzhong; Li Qing

2006-01-01

An Otto cycle working with an ideal Bose gas is called a Bose Otto cycle. The internal irreversibility of the cycle is included in the factors of internal irreversibility degree. The quantum degeneracy effect on the performance of the cycle is investigated based on quantum statistical mechanics and thermodynamics. Variations of the maximum work output ratio R W and the efficiency ratio y with temperature ratio τ are examined, which reveal the influence of the quantum degeneracy of the working substance on the performance of a Bose Otto cycle. It is shown that the results obtained herein are valid under both classical and quantum ideal gas conditions

Investigation of Bose Condensation in Ideal Bose Gas Trapped under Generic Power Law Potential in d Dimension

Science.gov (United States)

Mehedi Faruk, Mir; Sazzad Hossain, Md.; Muktadir Rahman, Md.

2016-02-01

The changes in characteristics of Bose condensation of ideal Bose gas due to an external generic power law potential U=\\sumi=1dci\\vert xi/ai\\vertni are studied carefully. Detailed calculation of Kim et al. (J. Phys. Condens. Matter 11 (1999) 10269) yielded the hierarchy of condensation transitions with changing fractional dimensionality. In this manuscript, some theorems regarding specific heat at constant volume CV are presented. Careful examination of these theorems reveal the existence of hidden hierarchy of the condensation transition in trapped systems as well.

Quantum Monte Carlo studies of superfluid Fermi gases

International Nuclear Information System (INIS)

Chang, S.Y.; Pandharipande, V.R.; Carlson, J.; Schmidt, K.E.

2004-01-01

We report results of quantum Monte Carlo calculations of the ground state of dilute Fermi gases with attractive short-range two-body interactions. The strength of the interaction is varied to study different pairing regimes which are characterized by the product of the s-wave scattering length and the Fermi wave vector, ak F . We report results for the ground-state energy, the pairing gap Δ, and the quasiparticle spectrum. In the weak-coupling regime, 1/ak F FG . When a>0, the interaction is strong enough to form bound molecules with energy E mol . For 1/ak F > or approx. 0.5, we find that weakly interacting composite bosons are formed in the superfluid gas with Δ and gas energy per particle approaching E mol /2. In this region, we seem to have Bose-Einstein condensation (BEC) of molecules. The behavior of the energy and the gap in the BCS-to-BEC transition region, -0.5 F <0.5, is discussed

Transport of an interacting Bose gas in 1D disordered lattices

Energy Technology Data Exchange (ETDEWEB)

D' Errico, C.; Chaudhuri, S.; Gori, L.; Kumar, A.; Lucioni, E.; Tanzi, L.; Inguscio, M.; Modugno, G. [LENS and Dipartimento di Fisica e Astronomia, Università di Firenze, and CNR-INO, 50019 Sesto Fiorentino (Italy)

2014-08-20

We use ultracold atoms in a quasiperiodic lattice to study two outstanding problems in the physics of disordered systems: a) the anomalous diffusion of a wavepacket in the presence of disorder, interactions and noise; b) the transport of a disordered superfluid. a) Our results show that the subdiffusion, observed when interaction alone is present, can be modelled with a nonlinear diffusion equation and the peculiar shape of the expanding density profiles can be connected to the microscopic nonlinear diffusion coefficients. Also when noise alone is present we can describe the observed normal diffusion dynamics by existing microscopic models. In the unexplored regime in which noise and interaction are combined, instead, we observe an anomalous diffusion, that we model with a generalized diffusion equation, where noise- and interaction-induced contributions add each other. b) We find that an instability appearing at relatively large momenta can be employed to locate the fluid-insulator crossover driven by disorder. By investigating the momentum-dependent transport, we observe a sharp crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. The set of critical disorder and interaction strengths for which such critical momentum vanishes, can be identified with the separation between a fluid regime and an insulating one and can be related to the predicted zero-temperature superfluid-Bose glass transition.

Transport of an interacting Bose gas in 1D disordered lattices

International Nuclear Information System (INIS)

D'Errico, C.; Chaudhuri, S.; Gori, L.; Kumar, A.; Lucioni, E.; Tanzi, L.; Inguscio, M.; Modugno, G.

2014-01-01

We use ultracold atoms in a quasiperiodic lattice to study two outstanding problems in the physics of disordered systems: a) the anomalous diffusion of a wavepacket in the presence of disorder, interactions and noise; b) the transport of a disordered superfluid. a) Our results show that the subdiffusion, observed when interaction alone is present, can be modelled with a nonlinear diffusion equation and the peculiar shape of the expanding density profiles can be connected to the microscopic nonlinear diffusion coefficients. Also when noise alone is present we can describe the observed normal diffusion dynamics by existing microscopic models. In the unexplored regime in which noise and interaction are combined, instead, we observe an anomalous diffusion, that we model with a generalized diffusion equation, where noise- and interaction-induced contributions add each other. b) We find that an instability appearing at relatively large momenta can be employed to locate the fluid-insulator crossover driven by disorder. By investigating the momentum-dependent transport, we observe a sharp crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. The set of critical disorder and interaction strengths for which such critical momentum vanishes, can be identified with the separation between a fluid regime and an insulating one and can be related to the predicted zero-temperature superfluid-Bose glass transition

Conserving gapless mean-field theory for weakly interacting Bose gases

International Nuclear Information System (INIS)

Kita, Takafumi

2006-01-01

This paper presents a conserving gapless mean-field theory for weakly interacting Bose gases. We first construct a mean-field Luttinger-Ward thermodynamic functional in terms of the condensate wave function Ψ and the Nambu Green's function G for the quasiparticle field. Imposing its stationarity respect to Ψ and G yields a set of equations to determine the equilibrium for general non-uniform systems. They have a plausible property of satisfying the Hugenholtz-Pines theorem to provide a gapless excitation spectrum. Also, the corresponding dynamical equations of motion obey various conservation laws. Thus, the present mean-field theory shares two important properties with the exact theory: 'conserving' and 'gapless'. The theory is then applied to a homogeneous weakly interacting Bose gas with s-wave scattering length a and particle mass m to clarify its basic thermodynamic properties under two complementary conditions of constant density n and constant pressure p. The superfluid transition is predicted to be first-order because of the non-analytic nature of the order-parameter expansion near T c inherent in Bose systems, i.e., the Landau-Ginzburg expansion is not possible here. The transition temperature T c shows quite a different interaction dependence between the n-fixed and p-fixed cases. In the former case T c increases from the ideal gas value T 0 as T c /T 0 =1+2.33an 1/3 , whereas it decreases in the latter as T c /T 0 =1-3.84a(mp/2πℎ 2 ) 1/5 . Temperature dependences of basic thermodynamic quantities are clarified explicitly. (author)

High-temperature electron-hole superfluidity with strong anisotropic gaps in double phosphorene monolayers

Science.gov (United States)

Saberi-Pouya, S.; Zarenia, M.; Perali, A.; Vazifehshenas, T.; Peeters, F. M.

2018-05-01

Excitonic superfluidity in double phosphorene monolayers is investigated using the BCS mean-field equations. Highly anisotropic superfluidity is predicted where we found that the maximum superfluid gap is in the Bose-Einstein condensate (BEC) regime along the armchair direction and in the BCS-BEC crossover regime along the zigzag direction. We estimate the highest Kosterlitz-Thouless transition temperature with maximum value up to ˜90 K with onset carrier densities as high as 4 ×1012cm-2 . This transition temperature is significantly larger than what is found in double electron-hole few-layers graphene. Our results can guide experimental research toward the realization of anisotropic condensate states in electron-hole phosphorene monolayers.

Bose-Einstein condensation in an ultra-hot gas of pumped magnons.

Science.gov (United States)

Serga, Alexander A; Tiberkevich, Vasil S; Sandweg, Christian W; Vasyuchka, Vitaliy I; Bozhko, Dmytro A; Chumak, Andrii V; Neumann, Timo; Obry, Björn; Melkov, Gennadii A; Slavin, Andrei N; Hillebrands, Burkard

2014-03-11

Bose-Einstein condensation of quasi-particles such as excitons, polaritons, magnons and photons is a fascinating quantum mechanical phenomenon. Unlike the Bose-Einstein condensation of real particles (like atoms), these processes do not require low temperatures, since the high densities of low-energy quasi-particles needed for the condensate to form can be produced via external pumping. Here we demonstrate that such a pumping can create remarkably high effective temperatures in a narrow spectral region of the lowest energy states in a magnon gas, resulting in strikingly unexpected transitional dynamics of Bose-Einstein magnon condensate: the density of the condensate increases immediately after the external magnon flow is switched off and initially decreases if it is switched on again. This behaviour finds explanation in a nonlinear 'evaporative supercooling' mechanism that couples the low-energy magnons overheated by pumping with all the other thermal magnons, removing the excess heat, and allowing Bose-Einstein condensate formation.

Singular f-sum rule for superfluid 4He

International Nuclear Information System (INIS)

Wong, V.K.

1979-01-01

The validity and applicability to inelastic neutron scattering of a singular f-sum rule for superfluid helium, proposed by Griffin to explain the rhosub(s) dependence in S(k, ω) as observed by Woods and Svensson, are examined in the light of similar sum rules rigorously derived for anharmonic crystals and Bose liquids. It is concluded that the singular f-sum rules are only of microscopic interest. (Auth,)

Simple point vortex model for the relaxation of 2D superfluid turbulence in a Bose-Einstein condensate

Science.gov (United States)

Kim, Joon Hyun; Kwon, Woo Jin; Shin, Yong-Il

2016-05-01

In a recent experiment, it was found that the dissipative evolution of a corotating vortex pair in a trapped Bose-Einstein condensate is well described by a point vortex model with longitudinal friction on the vortex motion and the thermal friction coefficient was determined as a function of sample temperature. In this poster, we present a numerical study on the relaxation of 2D superfluid turbulence based on the dissipative point vortex model. We consider a homogeneous system in a cylindrical trap having randomly distributed vortices and implement the vortex-antivortex pair annihilation by removing a pair when its separation becomes smaller than a certain threshold value. We characterize the relaxation of the turbulent vortex states with the decay time required for the vortex number to be reduced to a quarter of initial number. We find the vortex decay time is inversely proportional to the thermal friction coefficient. In particular, we observe the decay times obtained from this work show good quantitative agreement with the experimental results in, indicating that in spite of its simplicity, the point vortex model reasonably captures the physics in the relaxation dynamics of the real system.

Linear spin waves in a trapped Bose gas

International Nuclear Information System (INIS)

Nikuni, T.; Williams, J.E.; Clark, C.W.

2002-01-01

An ultracold Bose gas of two-level atoms can be thought of as a spin-1/2 Bose gas. It supports spin-wave collective modes due to the exchange mean field. Such collective spin oscillations have been observed in recent experiments at JILA with 87 Rb atoms confined in a harmonic trap. We present a theory of the spin-wave collective modes based on the moment method for trapped gases. In the collisionless and hydrodynamic limits, we derive analytic expressions for the frequencies and damping rates of modes with dipole and quadrupole symmetry. We find that the frequency for a given mode is given by a temperature-independent function of the peak density n, and falls off as 1/n. We also find that, to a very good approximation, excitations in the radial and axial directions are decoupled. We compare our model to the numerical integration of a one-dimensional version of the kinetic equation and find very good qualitative agreement. The damping rates, however, show the largest deviation for intermediate densities, where one expects Landau damping--which is unaccounted for in our moment approach--to play a significant role

Kohn's theorem in a superfluid Fermi gas with a Feshbach resonance

International Nuclear Information System (INIS)

Ohashi, Y.

2004-01-01

We investigate the dipole mode in a superfluid gas of Fermi atoms trapped in a harmonic potential. According to Kohn's theorem, the frequency of this collective mode is not affected by an interaction between the atoms and is always equal to the trap frequency. This remarkable property, however, does not necessarily hold in an approximate theory. We explicitly prove that the Hartree-Fock-Bogoliubov generalized random phase approximation (HFB-GRPA), including a coupling between fluctuations in the density and Cooper channels, is consistent with both Kohn's theorem as well as Goldstone's theorem. This proof can be immediately extended to the strong-coupling superfluid theory developed by Nozieres and Schmitt-Rink (NSR), where the effect of superfluid fluctuations is included within the Gaussian level. As a result, the NSR-GRPA formalism can be used to study collective modes in the BCS-BEC crossover region in a manner which is consistent with Kohn's theorem. We also include the effect of a Feshbach resonance and a condensate of the associated molecular bound states. A detailed discussion is given of the unusual nature of the Kohn mode eigenfunctions in a Fermi superfluid, in the presence and absence of a Feshbach resonance. When the molecular bosons feel a different trap frequency from the Fermi atoms, the dipole frequency is shown to depend on the strength of effective interaction associated with the Feshbach resonance

Simultaneous diagonal and off-diagonal order in the Bose-Hubbard Hamiltonian

International Nuclear Information System (INIS)

Scalettar, R.T.; Batrouni, G.G.; Kampf, A.P.; Zimanyi, G.T.

1995-01-01

The Bose-Hubbard model exhibits a rich phase diagram consisting both of insulating regimes where diagonal long-range (solid) order dominates as well as conducting regimes where off-diagonal long-range order (superfluidity) is present. In this paper we describe the results of quantum Monte Carlo calculations of the phase diagram, both for the hard- and soft-core cases, with a particular focus on the possibility of simultaneous superfluid and solid order. We also discuss the appearance of phase separation in the model. The simulations are compared with analytic calculations of the phase diagram and spin-wave dispersion

Spontaneous symmetry breaking of Bose-Fermi mixtures in double-well potentials

International Nuclear Information System (INIS)

Adhikari, S. K.; Malomed, B. A.; Salasnich, L.; Toigo, F.

2010-01-01

We study the spontaneous symmetry breaking (SSB) of a superfluid Bose-Fermi (BF) mixture in a double-well potential (DWP). The mixture is described by the Gross-Pitaevskii equation (GPE) for the bosons, coupled to an equation for the order parameter of the Fermi superfluid, which is derived from the respective density functional in the unitarity limit (a similar model applies to the BCS regime, too). Straightforward SSB in the degenerate Fermi gas loaded into a DWP is impossible, as it requires an attractive self-interaction, and the intrinsic nonlinearity in the Fermi gas is repulsive. Nonetheless, we demonstrate that the symmetry breaking is possible in the mixture with attraction between fermions and bosons, like 40 K and 87 Rb. Numerical results are represented by dependencies of asymmetry parameters for both components on particle numbers of the mixture, N F and N B , and by phase diagrams in the (N F ,N B ) plane, which displays regions of symmetric and asymmetric ground states. The dynamical picture of the SSB, induced by a gradual transformation of the single-well potential into the DWP, is reported too. An analytical approximation is proposed for the case when the GPE for the boson wave function may be treated by means of the Thomas-Fermi (TF) approximation. Under a special linear relationship between N F and N B , the TF approximation allows us to reduce the model to a single equation for the fermionic function, which includes competing repulsive and attractive nonlinear terms. The latter one directly displays the mechanism of the generation of the effective attraction in the Fermi superfluid, mediated by the bosonic component of the mixture.

Quantum quenches to the attractive one-dimensional Bose gas: exact results

Directory of Open Access Journals (Sweden)

Lorenzo Piroli, Pasquale Calabrese, Fabian H. L. Essler

2016-09-01

Full Text Available We study quantum quenches to the one-dimensional Bose gas with attractive interactions in the case when the initial state is an ideal one-dimensional Bose condensate. We focus on properties of the stationary state reached at late times after the quench. This displays a finite density of multi-particle bound states, whose rapidity distribution is determined exactly by means of the quench action method. We discuss the relevance of the multi-particle bound states for the physical properties of the system, computing in particular the stationary value of the local pair correlation function $g_2$.

Fractional statistics of the vortex in two-dimensional superfluids

International Nuclear Information System (INIS)

Chiao, R.Y.; Hansen, A.; Moulthrop, A.A.

1985-01-01

The quantum behavior of two identical point vortices (e.g., in a superfluid 4 He thin film) is studied. It is argued that this system obeys neither Bose nor Fermi statistics, but intermediate or theta statistics: We find that a single vortex in this system possesses quarter-fractional statistics (i.e., theta = π/2 or 3π/2). The source of the theta statistics is identified in the relative zero-point motion of the vortices

Correlation Functions of the One-Dimensional Attractive Bose Gas

International Nuclear Information System (INIS)

Calabrese, Pasquale; Caux, Jean-Sebastien

2007-01-01

The zero-temperature correlation functions of the one-dimensional attractive Bose gas with a delta-function interaction are calculated analytically for any value of the interaction parameter and number of particles, directly from the integrability of the model. We point out a number of interesting features, including zero recoil energy for a large number of particles, analogous to the Moessbauer effect

Off-diagonal long-range order, cycle probabilities, and condensate fraction in the ideal Bose gas.

Science.gov (United States)

Chevallier, Maguelonne; Krauth, Werner

2007-11-01

We discuss the relationship between the cycle probabilities in the path-integral representation of the ideal Bose gas, off-diagonal long-range order, and Bose-Einstein condensation. Starting from the Landsberg recursion relation for the canonic partition function, we use elementary considerations to show that in a box of size L3 the sum of the cycle probabilities of length k>L2 equals the off-diagonal long-range order parameter in the thermodynamic limit. For arbitrary systems of ideal bosons, the integer derivative of the cycle probabilities is related to the probability of condensing k bosons. We use this relation to derive the precise form of the pik in the thermodynamic limit. We also determine the function pik for arbitrary systems. Furthermore, we use the cycle probabilities to compute the probability distribution of the maximum-length cycles both at T=0, where the ideal Bose gas reduces to the study of random permutations, and at finite temperature. We close with comments on the cycle probabilities in interacting Bose gases.

Disordered ultracold atomic gases in optical lattices: A case study of Fermi-Bose mixtures

International Nuclear Information System (INIS)

Ahufinger, V.; Sanchez-Palencia, L.; Kantian, A.; Sanpera, A.; Lewenstein, M.

2005-01-01

We present a review of properties of ultracold atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. In the strong interacting limit and at very low temperatures, fermions form, together with bosons or bosonic holes, composite fermions. Composite fermions behave as a spinless interacting Fermi gas, and in the presence of local disorder they interact via random couplings and feel effective random local potential. This opens a wide variety of possibilities of realizing various kinds of ultracold quantum disordered systems. In this paper we review these possibilities, discuss the accessible quantum disordered phases, and methods for their detection. The discussed quantum phases include Fermi glasses, quantum spin glasses, 'dirty' superfluids, disordered metallic phases, and phases involving quantum percolation

Magnon condensation and spin superfluidity

Science.gov (United States)

Bunkov, Yury M.; Safonov, Vladimir L.

2018-04-01

We consider the Bose-Einstein condensation (BEC) of quasi-equilibrium magnons which leads to spin superfluidity, the coherent quantum transfer of magnetization in magnetic material. The critical conditions for excited magnon density in ferro- and antiferromagnets, bulk and thin films, are estimated and discussed. It was demonstrated that only the highly populated region of the spectrum is responsible for the emergence of any BEC. This finding substantially simplifies the BEC theoretical analysis and is surely to be used for simulations. It is shown that the conditions of magnon BEC in the perpendicular magnetized YIG thin film is fulfillied at small angle, when signals are treated as excited spin waves. We also predict that the magnon BEC should occur in the antiferromagnetic hematite at room temperature at much lower excited magnon density compared to that of ferromagnetic YIG. Bogoliubov's theory of Bose-Einstein condensate is generalized to the case of multi-particle interactions. The six-magnon repulsive interaction may be responsible for the BEC stability in ferro- and antiferromagnets where the four-magnon interaction is attractive.

Rotons, Superfluidity, and Helium Crystals

Science.gov (United States)

Balibar, Sébastien

2006-09-01

Fritz London understood that quantum mechanics could show up at the macroscopic level, and, in 1938, he proposed that superfluidity was a consequence of Bose-Einstein condensation. However, Lev Landau never believed in London's ideas; instead, he introduced quasiparticles to explain the thermodynamics of superfluid 4He and a possible mechanism for its critical velocity. One of these quasiparticles, a crucial one, was his famous "roton" which he considered as an elementary vortex. At the LT0 conference (Cambridge, 1946), London criticized Landau and his "theory based on the shaky grounds of imaginary rotons". Despite their rather strong disagreement, Landau was awarded the London prize in 1960, six years after London's death. Today, we know that London and Landau had both found part of the truth: BEC takes place in 4He, and rotons exist. In my early experiments on quantum evaporation, I found direct evidence for the existence of rotons and for evaporation processes in which they play the role of photons in the photoelectric effect. But rotons are now considered as particular phonons which are nearly soft, due to some local order in superfluid 4He. Later we studied helium crystals which are model systems for the general study of crystal surfaces, but also exceptional systems with unique quantum properties. In our recent studies of nucleation, rotons show their importance again: by using acoustic techniques, we have extended the study of liquid 4He up to very high pressures where the liquid state is metastable, and we wish to demonstrate that the vanishing of the roton gap may destroy superfluidity and trigger an instability towards the crystalline state.

On the Bose-Einstein condensation of an ideal gas

International Nuclear Information System (INIS)

Landau, L.J.; Wilde, I.F.

1979-01-01

A mathematically precise treatment is given of the well-known Bose-Einstein condensation of an ideal gas in the grand canonical ensemble at fixed density. The method works equally well for any of the standard boundary conditions and it is shown that the finite volume activity converges and that in three dimensions condensation occurs for Dirichlet, Neumann, periodic, and repulsive walls. (orig.) 891 HJ/orig. 892 CKA

Superfluidity breakdown of periodic matter waves in quasi-one-dimensional annular traps via resonant scattering with moving defects

Czech Academy of Sciences Publication Activity Database

Yulin, A.V.; Bludov, Yu.V.; Konotop, V. V.; Kuzmiak, Vladimír; Salerno, M.

2013-01-01

Roč. 87, č. 3 (2013) ISSN 1050-2947 R&D Projects: GA MŠk LH12009 Institutional support: RVO:67985882 Keywords : Superfluidity * Bose-Einstein condensates * Matter Waves Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.991, year: 2013

Non-equilibrium coherence dynamics in one-dimensional Bose gases

DEFF Research Database (Denmark)

Hofferberth, S.; Lesanovsky, Igor; Fischer, B.

2007-01-01

Low-dimensional systems provide beautiful examples of many-body quantum physics. For one-dimensional (1D) systems, the Luttinger liquid approach provides insight into universal properties. Much is known of the equilibrium state, both in the weakly and strongly interacting regimes. However......, the coherence factor is observed to approach a non-zero equilibrium value, as predicted by a Bogoliubov approach. This coupled-system decay to finite coherence is the matter wave equivalent of phase-locking two lasers by injection. The non-equilibrium dynamics of superfluids has an important role in a wide...... range of physical systems, such as superconductors, quantum Hall systems, superfluid helium and spin systems. Our experiments studying coherence dynamics show that 1D Bose gases are ideally suited for investigating this class of phenomena....

Bose condensation in (random traps

Directory of Open Access Journals (Sweden)

V.A. Zagrebnov

2009-01-01

Full Text Available We study a non-interacting (perfect Bose-gas in random external potentials (traps. It is shown that a generalized Bose-Einstein condensation in the random eigenstates manifests if and only if the same occurs in the one-particle kinetic-energy eigenstates, which corresponds to the generalized condensation of the free Bose-gas. Moreover, we prove that the amounts of both condensate densities are equal. This statement is relevant for justification of the Bogoliubov approximation} in the theory of disordered boson systems.

Two-Step Condensation of the Ideal Bose Gas in Highly Anisotropic Traps

International Nuclear Information System (INIS)

van Druten, N.J.; Ketterle, W.

1997-01-01

The ideal Bose gas in a highly anisotropic harmonic potential is studied. It is found that Bose-Einstein condensation occurs in two distinct steps as the temperature is lowered. In the first step the specific heat shows a sharp feature, but the system still occupies many one-dimensional quantum states. In the second step, at a significantly lower temperature, the ground state becomes macroscopically occupied. It should be possible to verify these predictions using present-day atom traps. The two-step behavior can occur in a rather general class of anisotropic traps, including the box potential. copyright 1997 The American Physical Society

On the ground state of the two-dimensional non-ideal Bose gas

International Nuclear Information System (INIS)

Lozovik, Yu.E.; Yudson, V.I.

1978-01-01

The theory of the ground state of the two-dimensional non-ideal Bose gas is presented. The conditions for the validity of the ladder and the Bogolubov approximations are derived. These conditions ensure the existence of a Bose condensate in the ground state of two-dimensional systems. These conditions are different from the corresponding conditions for the three-dimensional case. The connection between the effective interaction and the two-dimensional scattering amplitude at some characteristic energy kappa 2 /2m (not equal to 0) is obtained (f(kappa = 0) = infinity in the two-dimensional case). (Auth.)

Collective excitation frequencies and vortices of a Bose-Einstein condensed state with gravitylike interatomic attraction

International Nuclear Information System (INIS)

Ghosh, Tarun Kanti

2002-01-01

We study the collective excitations of a neutral atomic Bose-Einstein condensate with gravitylike 1/r interatomic attraction induced by an electromagnetic wave. Using the time-dependent variational approach, we derive an analytical spectrum for monopole and quadrupole mode frequencies of a gravitylike self-bound Bose condensed state at zero temperature. We also analyze the excitation frequencies of the Thomas-Fermi-gravity (TF-G) and gravity (G) regimes. Our result agrees excellently with that of Giovanazzi et al. [Europhysics Lett., 56, 1 (2001)], which is obtained within the sum-rule approach. We also consider the vortex state. We estimate the superfluid coherence length and the critical angular frequencies to create a vortex around the z axis. We find that the TF-G regime can exhibit the superfluid properties more prominently than the G regime. We find that the monopole mode frequency of the condensate decreases due to the presence of a vortex

Bose-Einstein condensation of paraxial light

Science.gov (United States)

Klaers, J.; Schmitt, J.; Damm, T.; Vewinger, F.; Weitz, M.

2011-10-01

Photons, due to the virtually vanishing photon-photon interaction, constitute to very good approximation an ideal Bose gas, but owing to the vanishing chemical potential a (free) photon gas does not show Bose-Einstein condensation. However, this is not necessarily true for a lower-dimensional photon gas. By means of a fluorescence induced thermalization process in an optical microcavity one can achieve a thermal photon gas with freely adjustable chemical potential. Experimentally, we have observed thermalization and subsequently Bose-Einstein condensation of the photon gas at room temperature. In this paper, we give a detailed description of the experiment, which is based on a dye-filled optical microcavity, acting as a white-wall box for photons. Thermalization is achieved in a photon number-conserving way by photon scattering off the dye molecules, and the cavity mirrors both provide an effective photon mass and a confining potential-key prerequisites for the Bose-Einstein condensation of photons. The experimental results are in good agreement with both a statistical and a simple rate equation model, describing the properties of the thermalized photon gas.

Bose-Einstein condensation of atomic gases

International Nuclear Information System (INIS)

Anglin, J. R.; Ketterle, W.

2003-01-01

The early experiments on Bose-Einstein condensation in dilute atomic gases accomplished three longstanding goals. First, cooling of neutral atoms into their motional state, thus subjecting them to ultimate control, limited only by Heisenberg uncertainty relation. Second, creation of a coherent sample of atoms, in which all occupy the same quantum states, and the realization of atom lasers - devices that output coherent matter waves. And third, creation of gaseous quantum fluid, with properties that are different from the quantum liquids helium-3 and helium-4. The field of Bose-Einstein condensation of atomic gases has continued to progress rapidly, driven by the combination of new experimental techniques and theoretical advances. The family of quantum degenerate gases has grown, and now includes metastable and fermionic atoms. condensates have become an ultralow-temperature laboratory for atom optics, collisional physics and many-body physics, encompassing phonons, superfluidity, quantized vortices, Josephson junctions and quantum phase transitions. (author)

Variational cluster perturbation theory for Bose-Hubbard models

International Nuclear Information System (INIS)

Koller, W; Dupuis, N

2006-01-01

We discuss the application of the variational cluster perturbation theory (VCPT) to the Mott-insulator-to-superfluid transition in the Bose-Hubbard model. We show how the VCPT can be formulated in such a way that it gives a translation invariant excitation spectrum-free of spurious gaps-despite the fact that it formally breaks translation invariance. The phase diagram and the single-particle Green function in the insulating phase are obtained for one-dimensional systems. When the chemical potential of the cluster is taken as a variational parameter, the VCPT reproduces the dimensional dependence of the phase diagram even for one-site clusters. We find a good quantitative agreement with the results of the density-matrix renormalization group when the number of sites in the cluster becomes of order 10. The extension of the method to the superfluid phase is discussed

Bose-Hubbard lattice as a controllable environment for open quantum systems

Science.gov (United States)

Cosco, Francesco; Borrelli, Massimo; Mendoza-Arenas, Juan José; Plastina, Francesco; Jaksch, Dieter; Maniscalco, Sabrina

2018-04-01

We investigate the open dynamics of an atomic impurity embedded in a one-dimensional Bose-Hubbard lattice. We derive the reduced evolution equation for the impurity and show that the Bose-Hubbard lattice behaves as a tunable engineered environment allowing one to simulate both Markovian and non-Markovian dynamics in a controlled and experimentally realizable way. We demonstrate that the presence or absence of memory effects is a signature of the nature of the excitations induced by the impurity, being delocalized or localized in the two limiting cases of a superfluid and Mott insulator, respectively. Furthermore, our findings show how the excitations supported in the two phases can be characterized as information carriers.

Existence of a critical point in the phase diagram of the ideal relativistic neutral Bose gas

International Nuclear Information System (INIS)

Park, Jeong-Hyuck; Kim, Sang-Woo

2011-01-01

We explore the phase transitions of the ideal relativistic neutral Bose gas confined in a cubic box, without assuming the thermodynamic limit nor continuous approximation. While the corresponding non-relativistic canonical partition function is essentially a one-variable function depending on a particular combination of temperature and volume, the relativistic canonical partition function is genuinely a two-variable function of them. Based on an exact expression for the canonical partition function, we performed numerical computations for up to 10 5 particles. We report that if the number of particles is equal to or greater than a critical value, which amounts to 7616, the ideal relativistic neutral Bose gas features a spinodal curve with a critical point. This enables us to depict the phase diagram of the ideal Bose gas. The consequent phase transition is first order below the critical pressure or second order at the critical pressure. The exponents corresponding to the singularities are 1/2 and 2/3, respectively. We also verify the recently observed 'Widom line' in the supercritical region.

Mean-Field Scaling of the Superfluid to Mott Insulator Transition in a 2D Optical Superlattice.

Science.gov (United States)

Thomas, Claire K; Barter, Thomas H; Leung, Tsz-Him; Okano, Masayuki; Jo, Gyu-Boong; Guzman, Jennie; Kimchi, Itamar; Vishwanath, Ashvin; Stamper-Kurn, Dan M

2017-09-08

The mean-field treatment of the Bose-Hubbard model predicts properties of lattice-trapped gases to be insensitive to the specific lattice geometry once system energies are scaled by the lattice coordination number z. We test this scaling directly by comparing coherence properties of ^{87}Rb gases that are driven across the superfluid to Mott insulator transition within optical lattices of either the kagome (z=4) or the triangular (z=6) geometries. The coherent fraction measured for atoms in the kagome lattice is lower than for those in a triangular lattice with the same interaction and tunneling energies. A comparison of measurements from both lattices agrees quantitatively with the scaling prediction. We also study the response of the gas to a change in lattice geometry, and observe the dynamics as a strongly interacting kagome-lattice gas is suddenly "hole doped" by introducing the additional sites of the triangular lattice.

Cooperative ring exchange and quantum melting of vortex lattices in atomic Bose-Einstein condensates

International Nuclear Information System (INIS)

Ghosh, Tarun Kanti; Baskaran, G.

2004-01-01

Cooperative ring exchange is suggested as a mechanism of quantum melting of vortex lattices in a rapidly rotating quasi-two-dimensional atomic Bose-Einstein condensate (BEC). Using an approach pioneered by Kivelson et al. [Phys. Rev. Lett. 56, 873 (1986)] for the fractional quantized Hall effect, we calculate the condition for quantum melting instability by considering large-correlated ring exchanges in a two-dimensional Wigner crystal of vortices in a strong 'pseudomagnetic field' generated by the background superfluid Bose particles. BEC may be profitably used to address issues of quantum melting of a pristine Wigner solid devoid of complications of real solids

Phases of a polar spin-1 Bose gas in a magnetic field

International Nuclear Information System (INIS)

Kis-Szabo, Krisztian; Szepfalusy, Peter; Szirmai, Gergely

2007-01-01

The two Bose-Einstein condensed phases of a polar spin-1 gas at nonzero magnetizations and temperatures are investigated. The Hugenholtz-Pines theorem is generalized to this system. Crossover to a quantum phase transition is also studied. Results are discussed in a mean field approximation

Effects of interaction imbalance in a strongly repulsive one-dimensional Bose gas

DEFF Research Database (Denmark)

Barfknecht, Rafael Emilio; Zinner, Nikolaj Thomas; Foerster, Angela

2018-01-01

We calculate the spatial distributions and the dynamics of a few-body two-component strongly interacting Bose gas confined to an effectively one-dimensional trapping potential. We describe the densities for each component in the trap for different interaction and population imbalances. We calculate...

Energetic and dynamical instability of spin-orbit coupled Bose-Einstein condensate in a deep optical lattice

Science.gov (United States)

Yu, Zi-Fa; Chai, Xu-Dan; Xue, Ju-Kui

2018-05-01

We investigate the energetic and dynamical instability of spin-orbit coupled Bose-Einstein condensate in a deep optical lattice via a tight-binding model. The stability phase diagram is completely revealed in full parameter space, while the dependence of superfluidity on the dispersion relation is illustrated explicitly. In the absence of spin-orbit coupling, the superfluidity only exists in the center of the Brillouin zone. However, the combination of spin-orbit coupling, Zeeman field, nonlinearity and optical lattice potential can modify the dispersion relation of the system, and change the position of Brillouin zone for generating the superfluidity. Thus, the superfluidity can appear in either the center or the other position of the Brillouin zone. Namely, in the center of the Brillouin zone, the system is either superfluid or Landau unstable, which depends on the momentum of the lowest energy. Therefore, the superfluidity can occur at optional position of the Brillouin zone by elaborating spin-orbit coupling, Zeeman splitting, nonlinearity and optical lattice potential. For the linear case, the system is always dynamically stable, however, the nonlinearity can induce the dynamical instability, and also expand the superfluid region. These predicted results can provide a theoretical evidence for exploring the superfluidity of the system experimentally.

Isobars of an ideal Bose gas within the grand canonical ensemble

International Nuclear Information System (INIS)

Jeon, Imtak; Park, Jeong-Hyuck; Kim, Sang-Woo

2011-01-01

We investigate the isobar of an ideal Bose gas confined in a cubic box within the grand canonical ensemble for a large yet finite number of particles, N. After solving the equation of the spinodal curve, we derive precise formulas for the supercooling and the superheating temperatures that reveal an N -1/3 or N -1/4 power correction to the known Bose-Einstein condensation temperature in the thermodynamic limit. Numerical computations confirm the accuracy of our analytical approximation, and further show that the isobar zigzags on the temperature-volume plane if N≥14 393. In particular, for the Avogadro's number of particles, the volume expands discretely about 10 5 times. Our results quantitatively agree with a previous study on the canonical ensemble within 0.1% error.

Bose-Einstein condensation of paraxial light

OpenAIRE

Klaers, J.; Schmitt, J.; Damm, T.; Vewinger, F.; Weitz, M.

2011-01-01

Photons, due to the virtually vanishing photon-photon interaction, constitute to very good approximation an ideal Bose gas, but owing to the vanishing chemical potential a (free) photon gas does not show Bose-Einstein condensation. However, this is not necessarily true for a lower-dimensional photon gas. By means of a fluorescence induced thermalization process in an optical microcavity one can achieve a thermal photon gas with freely adjustable chemical potential. Experimentally, we have obs...

Renormalization group analysis of order parameter fluctuations in fermionic superfluids

International Nuclear Information System (INIS)

Obert, Benjamin

2014-01-01

In this work fluctuation effects in two interacting fermion systems exhibiting fermionic s-wave superfluidity are analyzed with a modern renormalization group method. A description in terms of a fermion-boson theory allows an investigation of order parameter fluctuations already on the one-loop level. In the first project a quantum phase transition between a semimetal and a s-wave superfluid in a Dirac cone model is studied. The interplay between fermions and quantum critical fluctuations close to and at the quantum critical point at zero and finite temperatures are studied within a coupled fermion-boson theory. At the quantum critical point non-Fermi liquid and non-Gaussian behaviour emerge. Close to criticality several quantities as the susceptibility show a power law behaviour with critical exponents. We find an infinite correlation length in the entire semimetallic ground state also away from the quantum critical point. In the second project, the ground state of an s-wave fermionic superfluid is investigated. Here, the mutual interplay between fermions and order parameter fluctuations is studied, especially the impact of massless Goldstone fluctuations, which occur due to spontaneous breaking of the continuous U(1)-symmetry. Fermionic gap and bosonic order parameter are distinguished. Furthermore, the bosonic order parameter is decomposed in transverse and longitudinal fluctuations. The mixing between transverse and longitudinal fluctuations is included in our description. Within a simple truncation of the fermion-boson RG flow, we describe the fermion-boson theory for the first time in a consistent manner. Several singularities appear due the Goldstone fluctuations, which partially cancel due to symmetry. Our RG flow captures the correct infrared asymptotics of the system, where the collective excitations act as an interacting Bose gas. Lowest order Ward identities and the massless Goldstone mode are fulfilled in our truncation.

Phase transitions in the hard-core Bose-Fermi-Hubbard model at non-zero temperatures in the heavy-fermion limit

Energy Technology Data Exchange (ETDEWEB)

Stasyuk, I.V.; Krasnov, V.O., E-mail: krasnoff@icmp.lviv.ua

2017-04-15

Phase transitions at non-zero temperatures in ultracold Bose- and Fermi-particles mixture in optical lattices using the Bose-Fermi-Hubbard model in the mean field and hard-core boson approximations are investigated. The case of infinitely small fermion transfer and the repulsive on-site boson-fermion interaction is considered. The possibility of change of order (from the 2nd to the 1st one) of the phase transition to the superfluid phase in the regime of fixed values of the chemical potentials of Bose- and Fermi-particles is established. The relevant phase diagrams determining the conditions at which such a change takes place, are built.

Dimension effect in impuriton gas of 3He -4He superfluid mixture

International Nuclear Information System (INIS)

Adamenko, I.N.; Bortnik, L.N.; Chervanev, A.I.

1999-01-01

The flow of quasiparticle gas forced by the gradients of thermodynamical values in the volume filled with a powder is considered. The exact solution of the kinetic equation is obtained. It is expressed in terms of matrix elements of the collision integral and partial scattering cross-sections of quasiparticles at the powder. The condition describing the steady non-equilibrium state of the quasiparticles gas in the volume filled with a porous material is obtained. The results obtained are valid for arbitrary relations of frequencies of quasiparticle-quasiparticle and quasiparticle-powder collisions. The transitions from the Knudsen regime of quasiparticle gas flow to the hydrodynamic one is investigated. The Knudsen effect in degenerated quantum gas is studied. The steady non-equilibrium state of 3 He- 4 He superfluid mixture impuriton gas is studied in confined geometry

Macroscopic angular-momentum stages of Bose-Einstein condensates in toroidal traps

International Nuclear Information System (INIS)

Benakli, M.; Raghavan, S.; Smerzi, A.; Fantoni, S.; Shenoy, S.R.

2001-03-01

We study the stability of a rotating repulsive-atom Bose-Einstein condensate in a toroidal trap. The resulting macroscopic angular-momentum states with integer vorticity l spread radially, lowering rotational energies. These states are robust against vorticity-lowering decays, with estimated metastability barriers capable of sustaining large angular momenta (1 < or ∼ 10) for typical parameters. We identify the centrifugally squashed l-dependent density profile as a possible signature of condensate rotation and superfluidity. (author)

Satyendranath Bose: Co-Founder of Quantum Statistics

Science.gov (United States)

Blanpied, William A.

1972-01-01

Satyendranath Bose was first to prove Planck's Law by using ideal quantum gas. Einstein credited Bose for this first step in the development of quantum statistical mechanics. Bose did not realize the importance of his work, perhaps because of peculiar academic settings in India under British rule. (PS)

Quantum versus classical statistical dynamics of an ultracold Bose gas

International Nuclear Information System (INIS)

Berges, Juergen; Gasenzer, Thomas

2007-01-01

We investigate the conditions under which quantum fluctuations are relevant for the quantitative interpretation of experiments with ultracold Bose gases. This requires to go beyond the description in terms of the Gross-Pitaevskii and Hartree-Fock-Bogoliubov mean-field theories, which can be obtained as classical (statistical) field-theory approximations of the quantum many-body problem. We employ functional-integral techniques based on the two-particle irreducible (2PI) effective action. The role of quantum fluctuations is studied within the nonperturbative 2PI 1/N expansion to next-to-leading order. At this accuracy level memory integrals enter the dynamic equations, which differ for quantum and classical statistical descriptions. This can be used to obtain a classicality condition for the many-body dynamics. We exemplify this condition by studying the nonequilibrium evolution of a one-dimensional Bose gas of sodium atoms, and discuss some distinctive properties of quantum versus classical statistical dynamics

Quench dynamics of the interacting Bose gas in one dimension.

Science.gov (United States)

Iyer, Deepak; Andrei, Natan

2012-09-14

We obtain an exact expression for the time evolution of the interacting Bose gas following a quench from a generic initial state using the Yudson representation for integrable systems. We study the time evolution of the density and noise correlation for a small number of bosons and their asymptotic behavior for any number. We show that for any value of the coupling, as long as it is repulsive, the system asymptotes towards a strongly repulsive gas, while for any value of an attractive coupling the long time behavior is dominated by the maximal bound state. This occurs independently of the initial state and can be viewed as an emerging "dynamic universality."

On the infimum of the energy-momentum spectrum of a homogeneous Bose gas

DEFF Research Database (Denmark)

Cornean, Horia; Derezinski, J.; Zin, P.

We consider second quantized homogeneous Bose gas in a large cubic box with periodic boundary conditions, at zero temperature, and in the grand canonical setting (the chemical potential μ is fixed, the number of particles can vary). We investigate upper bounds on the infimum of the energy...

Quantum mechanics of the fractional-statistics gas: Random-phase approximation

International Nuclear Information System (INIS)

Dai, Q.; Levy, J.L.; Fetter, A.L.; Hanna, C.B.; Laughlin, R.B.

1992-01-01

A description of the fractional-statistics gas based on the complete summation of Hartree, Fock, ladder and bubble diagrams is presented. The superfluid properties identified previously in the random-phase-approximation (RPA) calculation of Fetter, Hanna, and Laughlin [Phys. Rev. B 39, 9679 (1989)] are substantially confirmed. The discrepancy between the RPA sound speed and the Hartree-Fock bulk modulus is found to be eliminated. The unusual Hall-effect behavior is found to vanish for the Bose gas test case but not for the fractional-statistics gas, implying that it is physically correct. Excellent agreement is obtained with the collective-mode dispersion obtained numerically by Xie, He, and Das Sarma [Phys. Rev. Lett. 65, 649 (1990)

Dipolar oscillations in a quantum degenerate Fermi-Bose atomic mixture

International Nuclear Information System (INIS)

Ferlaino, F; Brecha, R J; Hannaford, P; Riboli, F; Roati, G; Modugno, G; Inguscio, M

2003-01-01

We study the dynamics of coupled dipolar oscillations in a Fermi-Bose mixture of 40 K and 87 Rb atoms. This low-energy collective mode is strongly affected by the interspecies interactions. Measurements are performed in the classical and quantum degenerate regimes and reveal the crucial role of the statistical properties of the mixture. At the onset of quantum degeneracy, we investigate the role of Pauli blocking and superfluidity for K and Rb atoms, respectively, resulting in a change in the collisional interactions

Bose-Einstein condensates in atomic gases: simple theoretical results

International Nuclear Information System (INIS)

Castin, Y.

2001-01-01

The author presents the theory of the Bose-Einstein condensation along with a discussion of experimental tests. The author deals successively with the following topics: - the ideal Bose gas in a trap (first in a harmonic trap and then in a more general trap), - a model for the atomic interaction, - interacting Bose gas in the Hartree-Fock approximation, - properties of the condensate wavefunction, - the Gross-Pitaevskii equation, - Bogoliubov approach and thermodynamical stability, - phase coherence properties at the Bose-Einstein condensate, and - symmetry-breaking description of condensates. (A.C.)

Quantized vortices in the ideal bose gas: a physical realization of random polynomials.

Science.gov (United States)

Castin, Yvan; Hadzibabic, Zoran; Stock, Sabine; Dalibard, Jean; Stringari, Sandro

2006-02-03

We propose a physical system allowing one to experimentally observe the distribution of the complex zeros of a random polynomial. We consider a degenerate, rotating, quasi-ideal atomic Bose gas prepared in the lowest Landau level. Thermal fluctuations provide the randomness of the bosonic field and of the locations of the vortex cores. These vortices can be mapped to zeros of random polynomials, and observed in the density profile of the gas.

Magnon edge states in the hardcore- Bose-Hubbard model.

Science.gov (United States)

Owerre, S A

2016-11-02

Quantum Monte Carlo (QMC) simulation has uncovered nonzero Berry curvature and bosonic edge states in the hardcore-Bose-Hubbard model on the gapped honeycomb lattice. The competition between the chemical potential and staggered onsite potential leads to an interesting quantum phase diagram comprising the superfluid phase, Mott insulator, and charge density wave insulator. In this paper, we present a semiclassical perspective of this system by mapping to a spin-1/2 quantum XY model. We give an explicit analytical origin of the quantum phase diagram, the Berry curvatures, and the edge states using semiclassical approximations. We find very good agreement between the semiclassical analyses and the QMC results. Our results show that the topological properties of the hardcore-Bose-Hubbard model are the same as those of magnon in the corresponding quantum spin system. Our results are applicable to systems of ultracold bosonic atoms trapped in honeycomb optical lattices.

Dipole oscillations of a Bose-Einstein condensate in the presence of defects and disorder.

Science.gov (United States)

Albert, M; Paul, T; Pavloff, N; Leboeuf, P

2008-06-27

We consider dipole oscillations of a trapped dilute Bose-Einstein condensate in the presence of a scattering potential consisting either in a localized defect or in an extended disordered potential. In both cases the breaking of superfluidity and the damping of the oscillations are shown to be related to the appearance of a nonlinear dissipative flow. At supersonic velocities the flow becomes asymptotically dissipationless.

Perron-Frobenius theorem on the superfluid transition of an ultracold Fermi gas

Science.gov (United States)

Sakumichi, Naoyuki; Kawakami, Norio; Ueda, Masahito

2014-05-01

The Perron-Frobenius theorem is applied to identify the superfluid transition of the BCS-BEC crossover based on a cluster expansion method of Lee and Yang. Here, the cluster expansion is a systematic expansion of the equation of state (EOS) in terms of the fugacity z = exp (βμ) as βpλ3 = 2 z +b2z2 +b3z3 + ⋯ , with inverse temperature β =(kB T) - 1 , chemical potential μ, pressure p, and thermal de Broglie length λ =(2 πℏβ / m) 1 / 2 . According to the method of Lee and Yang, EOS is expressed by the Lee-Yang graphs. A singularity of an infinite series of ladder-type Lee-Yang graphs is analyzed. We point out that the singularity is governed by the Perron-Frobenius eigenvalue of a certain primitive matrix which is defined in terms of the two-body cluster functions and the Fermi distribution functions. As a consequence, it is found that there exists a unique fugacity at the phase transition point, which implies that there is no fragmentation of Bose-Einstein condensates of dimers and Cooper pairs at the ladder-approximation level of Lee-Yang graphs. An application to a BEC of strongly bounded dimers is also made.

On the number of Bose-selected modes in driven-dissipative ideal Bose gases

Science.gov (United States)

Schnell, Alexander; Ketzmerick, Roland; Eckardt, André

2018-03-01

In an ideal Bose gas that is driven into a steady state far from thermal equilibrium, a generalized form of Bose condensation can occur. Namely, the single-particle states unambiguously separate into two groups: the group of Bose-selected states, whose occupations increase linearly with the total particle number, and the group of all other states whose occupations saturate [Phys. Rev. Lett. 111, 240405 (2013), 10.1103/PhysRevLett.111.240405]. However, so far very little is known about how the number of Bose-selected states depends on the properties of the system and its coupling to the environment. The answer to this question is crucial since systems hosting a single, a few, or an extensive number of Bose-selected states will show rather different behavior. While in the former two scenarios each selected mode acquires a macroscopic occupation, corresponding to (fragmented) Bose condensation, the latter case rather bears resemblance to a high-temperature state of matter. In this paper, we systematically investigate the number of Bose-selected states, considering different classes of the rate matrices that characterize the driven-dissipative ideal Bose gases in the limit of weak system-bath coupling. These include rate matrices with continuum limit, rate matrices of chaotic driven systems, random rate matrices, and rate matrices resulting from thermal baths that couple to a few observables only.

Minimally destructive, Doppler measurement of a quantized flow in a ring-shaped Bose-Einstein condensate

Science.gov (United States)

Kumar, A.; Anderson, N.; Phillips, W. D.; Eckel, S.; Campbell, G. K.; Stringari, S.

2016-02-01

The Doppler effect, the shift in the frequency of sound due to motion, is present in both classical gases and quantum superfluids. Here, we perform an in situ, minimally destructive measurement, of the persistent current in a ring-shaped, superfluid Bose-Einstein condensate using the Doppler effect. Phonon modes generated in this condensate have their frequencies Doppler shifted by a persistent current. This frequency shift will cause a standing-wave phonon mode to be ‘dragged’ along with the persistent current. By measuring this precession, one can extract the background flow velocity. This technique will find utility in experiments where the winding number is important, such as in emerging ‘atomtronic’ devices.

Observation of a Time Quasicrystal and Its Transition to a Superfluid Time Crystal

Science.gov (United States)

Autti, S.; Eltsov, V. B.; Volovik, G. E.

2018-05-01

We report experimental realization of a quantum time quasicrystal and its transformation to a quantum time crystal. We study Bose-Einstein condensation of magnons, associated with coherent spin precession, created in a flexible trap in superfluid 3He-B . Under a periodic drive with an oscillating magnetic field, the coherent spin precession is stabilized at a frequency smaller than that of the drive, demonstrating spontaneous breaking of discrete time translation symmetry. The induced precession frequency is incommensurate with the drive, and hence, the obtained state is a time quasicrystal. When the drive is turned off, the self-sustained coherent precession lives a macroscopically long time, now representing a time crystal with broken symmetry with respect to continuous time translations. Additionally, the magnon condensate manifests spin superfluidity, justifying calling the obtained state a time supersolid or a time supercrystal.

Real-Time Dynamics of an Impurity in an Ideal Bose Gas in a Trap

DEFF Research Database (Denmark)

Volosniev, A. G.; Hammer, H. -W.; Zinner, N. T.

2015-01-01

We investigate the behavior of a harmonically trapped system consisting of an impurity in a dilute ideal Bose gas after the boson-impurity interaction is suddenly switched on. As theoretical framework, we use a field theory approach in the space-time domain within the T-matrix approximation. We...

Thermalization and Prethermalization in an ultracold Bose Gas

International Nuclear Information System (INIS)

Kuhnert, M.

2013-01-01

Atom chips consist of microscopic current carrying structures that generate magnetic trapping potentials for ultracold neutral atoms. These atom chips provide a high design flexibility of possible trap geometries, making the creation of highly anisotropic trapping potentials feasible. The resulting magnetic traps are characterized by a high isolation from the environment and are used to create degenerate, one-dimensional (1d) Bose gases. On typical experimental time scales, these 1d Bose gases can be described as practically closed quantum many-body systems. By applying a rapid quantum quench, the many-body system is brought out of thermal equilibrium and the resulting dynamics are studied via the statistical properties of matter-wave interference measurements. These measured quantum statistical distributions reveal that thermalization of this effectively integrable 1d Bose gas happens in a two-step process. First, the system rapidly dephases to a prethermalized state, characterized by thermal-like correlation properties, which are still distinctly different from the true thermal equilibrium state. Second, on a much longer time scale, the measured distribution functions indicate a further decay to the true thermal equilibrium state. Furthermore, by studying a highly non-equilibrium system via matter-wave interferometry, the underlying multimode dynamics, characterizing one-dimensional quantum systems, are revealed. This thesis shows that these dynamics are essential in establishing the prethermalized state and that its properties are defined by the quantum shot noise of the splitting process. In conclusion, this work aims at improving the understanding of quantum thermalization processes in integrable and nearly-integrable systems in the 1d and 1d/3d crossover regimes. Apparently, the general paths to thermal equilibrium in nearly-integrable systems are indirect and complex. This work provides an in depth experimental study of the relaxation dynamics of a highly

Discrete Bose-Einstein spectra

International Nuclear Information System (INIS)

Vlad, Valentin I.; Ionescu-Pallas, Nicholas

2001-03-01

The Bose-Einstein energy spectrum of a quantum gas, confined in a rigid cubic box, is shown to become discrete and strongly dependent on the box geometry (size L), temperature, T and atomic mass number, A at , in the region of small γ=A at TV 1/3 . This behavior is the consequence of the random state degeneracy in the box. Furthermore, we demonstrate that the total energy does not obey the conventional law any longer, but a new law, which depends on γ and on the quantum gas fugacity. This energy law imposes a faster decrease to zero than it is classically expected, for γ→0. The lighter the gas atoms, the higher the temperatures or the box size, for the same effects in the discrete Bose-Einstein regime. (author)

Effects of Interaction Imbalance in a Strongly Repulsive One-Dimensional Bose Gas

Science.gov (United States)

Barfknecht, R. E.; Foerster, A.; Zinner, N. T.

2018-05-01

We calculate the spatial distributions and the dynamics of a few-body two-component strongly interacting Bose gas confined to an effectively one-dimensional trapping potential. We describe the densities for each component in the trap for different interaction and population imbalances. We calculate the time evolution of the system and show that, for a certain ratio of interactions, the minority population travels through the system as an effective wave packet.

Quantitative study of quasi-one-dimensional Bose gas experiments via the stochastic Gross-Pitaevskii equation

International Nuclear Information System (INIS)

Cockburn, S. P.; Gallucci, D.; Proukakis, N. P.

2011-01-01

The stochastic Gross-Pitaevskii equation is shown to be an excellent model for quasi-one-dimensional Bose gas experiments, accurately reproducing the in situ density profiles recently obtained in the experiments of Trebbia et al.[Phys. Rev. Lett. 97, 250403 (2006)] and van Amerongen et al.[Phys. Rev. Lett. 100, 090402 (2008)] and the density fluctuation data reported by Armijo et al.[Phys. Rev. Lett. 105, 230402 (2010)]. To facilitate such agreement, we propose and implement a quasi-one-dimensional extension to the one-dimensional stochastic Gross-Pitaevskii equation for the low-energy, axial modes, while atoms in excited transverse modes are treated as independent ideal Bose gases.

Gravitational wave as probe of superfluid dark matter

Science.gov (United States)

Cai, Rong-Gen; Liu, Tong-Bo; Wang, Shao-Jiang

2018-02-01

In recent years, superfluid dark matter (SfDM) has become a competitive model of emergent modified Newtonian dynamics (MOND) scenario: MOND phenomenons naturally emerge as a derived concept due to an extra force mediated between baryons by phonons as a result of axionlike particles condensed as superfluid at galactic scales; Beyond galactic scales, these axionlike particles behave as normal fluid without phonon-mediated MOND-like force between baryons, therefore SfDM also maintains the usual success of Λ CDM at cosmological scales. In this paper, we use gravitational waves (GWs) to probe the relevant parameter space of SfDM. GWs through Bose-Einstein condensate (BEC) could propagate with a speed slightly deviation from the speed-of-light due to the change in the effective refractive index, which depends on the SfDM parameters and GW-source properties. We find that Five hundred meter Aperture Spherical Telescope (FAST), Square Kilometre Array (SKA) and International Pulsar Timing Array (IPTA) are the most promising means as GW probe of relevant parameter space of SfDM. Future space-based GW detectors are also capable of probing SfDM if a multimessenger approach is adopted.

Equilibrium and Non-Equilibrium Condensation Phenomena in Tuneable 3D and 2D Bose Gases

Science.gov (United States)

2016-04-01

on Atomic Physics (ICAP), the biennial BEC Conference (“Frontiers in Quantum Gases ”) in Sant Feliu, DAMOP and the APS March Meeting. Our results can...turbulence have been studied in a wide variety of physical systems (from classical gases and water to superfluid helium) for many years. However, a system...112.040403 Featured in Physics Today [6] Observing properties of an interacting homogeneous Bose-Einstein condensate: Heisenberg-limited momentum

Bose condensates make quantum leaps and bounds

International Nuclear Information System (INIS)

Castin, Y.; Dum, R.; Sinatra, A.

1999-01-01

Since the first observation in 1995 of Bose-Einstein condensation in dilute atomic gases, atomic physicists have made extraordinary progress in understanding this unusual quantum state of matter. BOSE-EINSTEIN condensation is a macroscopic quantum phenomenon that was first predicted by Albert Einstein in the 1920s, at a time when quantum theory was still developing and was being applied to microscopic systems, such as individual particles and atoms. Einstein applied the new concept of Bose statistics to an ideal gas of identical atoms that were at thermal equilibrium and trapped in a box. He predicted that at sufficiently low temperatures the particles would accumulate in the lowest quantum state in the box, giving rise to a new state of matter with many unusual properties. The crucial point of Einstein's model is the absence of interactions between the particles in the box. However, this makes his prediction difficult to test in practice. In most real systems the complicating effect of particle interactions causes the gas to solidify well before the temperature for Bose-Einstein condensation is reached. But techniques developed in the past four years have allowed physicists to form Bose-Einstein condensates for a wide range of elements. In this article the authors describe the latest advances in Bose-Einstein condensation. (UK)

Competition between Bose-Einstein Condensation and Spin Dynamics.

Science.gov (United States)

Naylor, B; Brewczyk, M; Gajda, M; Gorceix, O; Maréchal, E; Vernac, L; Laburthe-Tolra, B

2016-10-28

We study the impact of spin-exchange collisions on the dynamics of Bose-Einstein condensation by rapidly cooling a chromium multicomponent Bose gas. Despite relatively strong spin-dependent interactions, the critical temperature for Bose-Einstein condensation is reached before the spin degrees of freedom fully thermalize. The increase in density due to Bose-Einstein condensation then triggers spin dynamics, hampering the formation of condensates in spin-excited states. Small metastable spinor condensates are, nevertheless, produced, and they manifest in strong spin fluctuations.

Dynamics of vortex assisted metal condensation in superfluid helium.

Science.gov (United States)

Popov, Evgeny; Mammetkuliyev, Muhammet; Eloranta, Jussi

2013-05-28

Laser ablation of copper and silver targets immersed in bulk normal and superfluid (4)He was studied through time-resolved shadowgraph photography. In normal fluid, only a sub-millimeter cavitation bubble is created and immediate formation of metal clusters is observed within a few hundred microseconds. The metal clusters remain spatially tightly focused up to 15 ms, and it is proposed that this observation may find applications in particle image velocimetry. In superfluid helium, the cavitation bubble formation process is distinctly different from the normal fluid. Due to the high thermal conductivity and an apparent lag in the breakdown of superfluidity, about 20% of the laser pulse energy was transferred directly into the liquid and a large gas bubble, up to several millimeters depending on laser pulse energy, is created. The internal temperature of the gas bubble is estimated to exceed 9 K and the following bubble cool down period therefore includes two separate phase transitions: gas-normal liquid and normal liquid-superfluid. The last stage of the cool down process was assigned to the superfluid lambda transition where a sudden formation of large metal clusters is observed. This is attributed to high vorticity created in the volume where the gas bubble previously resided. As shown by theoretical bosonic density functional theory calculations, quantized vortices can trap atoms and dimers efficiently, exhibiting static binding energies up to 22 K. This, combined with hydrodynamic Bernoulli attraction, yields total binding energies as high as 35 K. For larger clusters, the static binding energy increases as a function of the volume occupied in the liquid to minimize the surface tension energy. For heliophobic species an energy barrier develops as a function of the cluster size, whereas heliophilics show barrierless entry into vortices. The present theoretical and experimental observations are used to rationalize the previously reported metal nanowire assembly in

Bose and his statistics

International Nuclear Information System (INIS)

Venkataraman, G.

1992-01-01

Treating radiation gas as a classical gas, Einstein derived Planck's law of radiation by considering the dynamic equilibrium between atoms and radiation. Dissatisfied with this treatment, S.N. Bose derived Plank's law by another original way. He treated the problem in generality: he counted how many cells were available for the photon gas in phase space and distributed the photons into these cells. In this manner of distribution, there were three radically new ideas: The indistinguishability of particles, the spin of the photon (with only two possible orientations) and the nonconservation of photon number. This gave rise to a new discipline of quantum statistical mechanics. Physics underlying Bose's discovery, its significance and its role in development of the concept of ideal gas, spin-statistics theorem and spin particles are described. The book has been written in a simple and direct language in an informal style aiming to stimulate the curiosity of a reader. (M.G.B.)

The performance evaluation of a micro/nano-scaled cooler working with an ideal Bose gas

International Nuclear Information System (INIS)

Guo, Juncheng; Su, Guozhen; Chen, Jincan

2012-01-01

Based on the size effect of a confined ideal Bose gas, the design concept of a quantum cooler is originally put forward. The cooler consists of two long tubes with the same length but different sizes of cross section, which are filled up with the ideal Bose gas, and is operated between two heat reservoirs. Expressions for the refrigeration rate and coefficient of performance (COP) of the cooler are derived. The effects of the size effect on the refrigeration rate and COP are discussed. The general performance characteristics of the cooler are revealed. -- Highlights: ► The design concept of a quantum cooler is originally put forward. ► Expressions for the refrigeration rate and coefficient of performance (COP) of the cooler are derived. ► The effects of the size effect on the refrigeration rate and COP are discussed. ► The general performance characteristics of the cooler are revealed. ► The results obtained are more general and significant than those in the current literature.

ν-Dimensional ideal quantum q-gas: Bose-Einstein condensation and λ-point transition

International Nuclear Information System (INIS)

R-Monteiro, M.; Roditi, I.; Rodrigues, L.M.C.S.

1994-01-01

The authors consider an ideal quantum q-gas in ν spatial dimensions and energy spectrum ω i αp α . Departing from the Hamiltonian H = ω[N], the authors study the effect of the deformation on thermodynamic functions and equation of state of that system. The virial expansion is obtained for the high temperature (or low density) regime. The critical temperature is higher than in non-deformed ideal gases. They show that Bose-Einstein condensation always exists (unless when ν/α = 1) for finite q but not for q = ∞. Employing numerical calculations and selecting for ν/α the values 3/2, 2 and 3, the authors show the critical temperature as a function of q, the specific heat C V and the chemical potential μ as functions of T/T c q for q = 1.05 and q= 4.5. C V exhibits a λ-point discontinuity in all cases, instead of the cusp singularity found in the usual ideal gas. The results indicate that physical systems which have quantum symmetries can exhibit Bose-Einstein condensation phenomenon, the critical temperature being favored by the deformation parameter

Superfluidity

International Nuclear Information System (INIS)

Seyfert, P.; Claudet, G.

1988-01-01

The paper reviews the understanding of superfluid helium with regard to its use as coolant for superconducting devices. The topics to be addressed include heat transfer properties of the stagnant fluid, cooling by forced flow superfluid helium, design principles for superfluid helium cryogenic systems and, finally, an illustration of these principles by a few practical examples. 18 refs

Bose-Einstein-condensed gases with arbitrary strong interactions

International Nuclear Information System (INIS)

Yukalov, V. I.; Yukalova, E. P.

2006-01-01

Bose-condensed gases are considered with an effective interaction strength varying in the whole range of the values between zero and infinity. The consideration is based on the usage of a representative statistical ensemble for Bose systems with broken global gauge symmetry. Practical calculations are illustrated for a uniform Bose gas at zero temperature, employing a self-consistent mean-field theory, which is both conserving and gapless

Functional renormalization group approach to the two dimensional Bose gas

Energy Technology Data Exchange (ETDEWEB)

Sinner, A; Kopietz, P [Institut fuer Theoretische Physik, Universitaet Frankfurt, Max-von-Laue Strasse 1, 60438 Frankfurt (Germany); Hasselmann, N [International Center for Condensed Matter Physics, Universidade de BrasIlia, Caixa Postal 04667, 70910-900 BrasIlia, DF (Brazil)], E-mail: hasselma@itp.uni-frankfurt.de, E-mail: sinner@itp.uni-frankfurt.de

2009-02-01

We investigate the small frequency and momentum structure of the weakly interacting Bose gas in two dimensions using a functional renormalization group approach. The flow equations are derived within a derivative approximation of the effective action up to second order in spatial and temporal variables and investigated numerically. The truncation we employ is based on the perturbative structure of the theory and is well described as a renormalization group enhanced perturbation theory. It allows to calculate corrections to the Bogoliubov spectrum and to investigate the damping of quasiparticles. Our approach allows to circumvent the divergences which plague the usual perturbative approach.

Upper limit on the transition temperature for non-ideal Bose gases

International Nuclear Information System (INIS)

Dai Wusheng; Xie Mi

2007-01-01

In this paper, we show that for a non-ideal Bose gas there exists an upper limit on the transition temperature above which Bose-Einstein condensation cannot occur regardless of the pressure applied. Such upper limits for some realistic Bose gases are estimated

Renormalisation group approach to the ideal Bose gas in d dimensions

International Nuclear Information System (INIS)

Singh, K.K.

1981-01-01

Critical behaviour of a d-dimensional ideal Bose gas is investigated from the point of view of the renormalisation-group approach. Rescaling of quantum-field amplitudes is avoided by introducing a scaling variable inversely proportional to the thermal momentum of the particles. The scaling properties of various thermodynamic quantities are seen to emerge as a consequence of the irrelevant nature of this variable. Critical behaviour is discussed at fixed particle density as well as at fixed pressure. Connection between susceptibility and correlation function of the order-parameter for a quantum system is elucidated. (author)

Effects of a delta-attractive impurity in the thermodynamics properties of an one-dimensional ideal Bose gas

International Nuclear Information System (INIS)

Ioriatti Junior, L.C.

1976-01-01

The thermodynamic behavior of the one-dimensional bose gas-attractive delta impurity system is studied. The system is shown to undergo the Bose-Einstein condensation and the cause of the phase transition is attributed to the bound state introduced by the impurity in the free particle energy spectrum. The condensed phase is composed by particles captured by the impurity, forming a drop of particles well localized in space. This gives to the Bose-Einstein condensation in this system the appearance of the ordinary vapor-liquid phase transition. The order of the phase transition is analized with the aid of the Clausius-Clayperon equation, leading to the conclusion that the transition is a first order one. This reinforces the interpretation of a vapor-liquid transition. The evaluation of the heat capacity at constant length shows the existence of a finite discontinuity at the transition temperature [pt

Resummation of Infrared Divergencies in the Theory of Atomic Bose Gases

NARCIS (Netherlands)

Stoof, H.T.C.; van Heugten, J. J. R. M.

2014-01-01

We present a general strong-coupling approach for the description of an atomic Bose gas beyond the Bogoliubov approximation, when infrared divergences start to occur that need to be resummed exactly. We consider the determination of several important physical properties of the Bose gas, namely the

Matter-wave interference, Josephson oscillation and its disruption in a Bose-Einstein condensate on an optical lattice

International Nuclear Information System (INIS)

Adhikari, Sadhan K.

2004-01-01

Using the axially-symmetric time-dependent mean-field Gross-Pitaevskii equation we study the Josephson oscillation in a repulsive Bose-Einstein condensate trapped by a harmonic plus an one-dimensional optical-lattice potential to describe the experiments by Cataliotti et al. [Science 293 (2001) 843, New J. Phys. 5 (2003) 71.1]. After a study of the formation of matter-wave interference upon releasing the condensate from the optical trap, we directly investigate the alternating atomic superfluid Josephson current upon displacing the harmonic trap along the optical axis. The Josephson current is found to be disrupted upon displacing the harmonic trap through a distance greater than a critical distance signaling a superfluid to a classical insulator transition in the condensate

Bose-condensate temperature dependence and new liquid 4He measurements on the DIN-2PR spectrometer

International Nuclear Information System (INIS)

Blagoveshchenskij, N.M.; Bogoyavlenskij, I.V.; Karnatsevich, L.V.; Kozlov, Zh.A.; Puchkov, A.V.

1992-01-01

Experimental estimates of the bose-condensate density n 0 in the superfluid liquid helium obtained by a method of inelastic neutron scattering during the last 20 years are analysed. It should be noted that different groups of researches have used two basically different approaches to analyse the neutron-scattering data for n 0 determination. Recently the development and improvement of the both methods have shown the results being in agreement. 18 refs.; 3 figs

Vortices in atomic Bose-Einstein condensates in the large-gas-parameter region

International Nuclear Information System (INIS)

Nilsen, J.K.; Mur-Petit, J.; Guilleumas, M.; Polls, A.; Hjorth-Jensen, M.

2005-01-01

In this work we compare the results of the Gross-Pitaevskii and modified Gross-Pitaevskii equations with ab initio variational Monte Carlo calculations for Bose-Einstein condensates of atoms in axially symmetric traps. We examine both the ground state and excited states having a vortex line along the z axis at high values of the gas parameter and demonstrate an excellent agreement between the modified Gross-Pitaevskii and ab initio Monte Carlo methods, both for the ground and vortex states

Novel sound phenomena in superfluid helium in aerogel and other impure superfluids

International Nuclear Information System (INIS)

Brusov, Peter; Brusov, Paul; Lawes, Gavin; Lee, Chong; Matsubara, Akira; Ishikawa, Osamu; Majumdar, Pinaki

2003-01-01

During the last decade new techniques for producing impure superfluids with unique properties have been developed. This new class of systems includes superfluid helium confined to aerogel, HeII with different impurities (D 2 , N 2 , Ne, Kr), superfluids in Vycor glasses, and watergel. These systems exhibit very unusual properties including unexpected acoustic features. We discuss the sound properties of these systems and show that sound phenomena in impure superfluids are modified from those in pure superfluids. We calculate the coupling between temperature and pressure oscillations for impure superfluids and for superfluid He in aerogel. We show that the coupling between these two sound modes is governed either by c∂ρ/∂c or σρ a ρ s (for aerogel) rather than thermal expansion coefficient ∂ρ/∂T, which is enormously small in pure superfluids. This replacement plays a fundamental role in all sound phenomena in impure superfluids. It enhances the coupling between the two sound modes that leads to the existence of such phenomena as the slow mode and heat pulse propagation with the velocity of first sound observed in superfluids in aerogel. This means that it is possible to observe in impure superfluids such unusual sound phenomena as slow pressure (density) waves and fast temperature (entropy) waves. The enhancement of the coupling between the two sound modes decreases the threshold values for nonlinear processes as compared to pure superfluids. Sound conversion, which has been observed in pure superfluids only by shock waves should be observed at moderate sound amplitude in impure superfluids. Cerenkov emission of second sound by first sound (which never been observed in pure superfluids) could be observed in impure superfluids

Thermodynamics of two-parameter quantum group Bose and Fermi gases

International Nuclear Information System (INIS)

Algin, A.

2005-01-01

The high and low temperature thermodynamic properties of the two-parameter deformed quantum group Bose and Fermi gases with SU p/q (2) symmetry are studied. Starting with a SU p/q (2)-invariant bosonic as well as fermionic Hamiltonian, several thermodynamic functions of the system such as the average number of particles, internal energy and equation of state are derived. The effects of two real independent deformation parameters p and q on the properties of the systems are discussed. Particular emphasis is given to a discussion of the Bose-Einstein condensation phenomenon for the two-parameter deformed quantum group Bose gas. The results are also compared with earlier undeformed and one-parameter deformed versions of Bose and Fermi gas models. (author)

Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas

International Nuclear Information System (INIS)

Perali, A.; Palestini, F.; Pieri, P.; Strinati, G. C.; Stewart, J. T.; Gaebler, J. P.; Drake, T. E.; Jin, D. S.

2011-01-01

Wave-vector resolved radio frequency spectroscopy data for an ultracold trapped Fermi gas are reported for several couplings at T c , and extensively analyzed in terms of a pairing-fluctuation theory. We map the evolution of a strongly interacting Fermi gas from the pseudogap phase into a fully gapped molecular Bose gas as a function of the interaction strength, which is marked by a rapid disappearance of a remnant Fermi surface in the single-particle dispersion. We also show that our theory of a pseudogap phase is consistent with a recent experimental observation as well as with quantum Monte Carlo data of thermodynamic quantities of a unitary Fermi gas above T c .

Theory of a Nearly Two-Dimensional Dipolar Bose Gas

Science.gov (United States)

2016-05-11

order to be published, he sent the paper to Einstein to translate it. The other contributing scientist is world famous physicist Albert Einstein , maybe...mechanical state, a Bose- Einstein condensate (BEC), where the atoms cease to behave like distinguishable entities, and instead form a single macroscopic...model in both three- and two-dimensional geometries. 15. SUBJECT TERMS Bose Einstein condensation, ultracold physics, condensed matter, dipoles 16

Bose-Einstein condensation in a decorated lattice: an application to the problem of supersolid He

International Nuclear Information System (INIS)

Fil, D.V.; Shevchenko, S.I.

2008-01-01

The Bose-Einstein condensation of vacancies in a three-dimensional decorated lattice is considered. The model describes possible scenario of superfluidity of solid helium, caused by the presence of zero-point vacancies in a dislocation network. It is shown that the temperature of Bose-Einstein condensation decreases under increase of the length of the network segments, and the law of decrease depends essentially on the properties of the vertices of the network. If the vertices correspond to barriers with a small transparency, the critical temperature varies inversely as the square of the length of the segment. On the contrary, if the vertices correspond to traps for the vacancies (it is energetically preferable for the vacancies to be localized at the vertices), an exponential lowering of the temperature of transition takes place. The highest temperature of Bose-Einstein condensation is reached in the intermediate case of vertices with large transparency, but in the absence of tendency of localization at them. In the latter case the critical temperature is inversely as the length of the segment

Spatial chaos of trapped Bose-Einstein condensate in one-dimensional weak optical lattice potential

International Nuclear Information System (INIS)

Chong Guishu; Hai Wenhua; Xie Qiongtao

2004-01-01

The spatially chaotic attractor in an elongated cloud of Bose-Einstein condensed atoms perturbed by a weak optical lattice potential is studied. The analytical insolvability and numerical incomputability of the atomic number density are revealed by a perturbed solution that illustrates the unpredictability of the deterministic chaos. Although this could lead the nonphysical explosion and unboundedness to the numerical solution, the theoretical analysis offers a criterion to avoid them. Moreover, the velocity field is investigated that exhibits the superfluid property of the chaotic system

Long-distance behavior of temperature correlation functions in the one-dimensional Bose gas

Energy Technology Data Exchange (ETDEWEB)

Kozlowski, K.K. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Maillet, J.M. [UMR 5672 du CNRS, ENS Lyon (France). Lab. de Physique; Slavnov, N.A. [Steklov Mathematical Institute, Moscow (Russian Federation)

2010-12-15

We describe a Bethe ansatz based method to derive, starting from a multiple integral representation, the long-distance asymptotic behavior at finite temperature of the density-density correlation function in the interacting onedimensional Bose gas. We compute the correlation lengths in terms of solutions of non-linear integral equations of the thermodynamic Bethe ansatz type. Finally, we establish a connection between the results obtained in our approach with the correlation lengths stemming from the quantum transfer matrix method. (orig.)

Bose gas with two- and three-particle interaction: evolution of soliton-like bubbles

International Nuclear Information System (INIS)

Barashenkov, I.V.; Kholmurodov, Kh.T.

1988-01-01

Solutions of the non-linear Schroedinger equation (NSE) for the Bose gas with two- and three-particle interaction are considered. Problems of soliton-like bubble existence, stability and evolution of the moving soliton are studied. It is shown that at D=2.3 for low-amplitude waves propagating at the transonic velocity the NSE is reduced to a two- and three-dimensional Kadomtsev-Petviashvili (KP) equation and the NSE bubble soliton transfers to the KP one

Resonant amplification of quantum fluctuations in a spinor gas

DEFF Research Database (Denmark)

Topic, O.; Scherer, M.; Gebreyesus, G.

2010-01-01

Bose-Einstein condensates of atoms with non-zero spin are known to constitute an ideal system to investigate fundamental properties of magnetic superfluids. More recently it was realized that they also provide the fascinating opportunity to investigate the macroscopic amplification of quantum...

The free Bose gas with flowing condensate in algebraic quantum field theory

International Nuclear Information System (INIS)

Hein, S.

1979-01-01

After the definition of the Weyl-algebra as a universal C* algebra of the canonical commutation relations the author classifies the equilibrium states of the free dynamics of a Bose gas in a representation independent way starting from the Kubo-Martin-Schwinger boundary conditions. The role of the Laplace equation is studied in this connection. It is shown that states with a two-point function can be described by simple natural hydrodynamics using a precise definition of the term vortex. The transition to these states is considered regarding the thermodynamic limit. (HSI)

Rotational states of Bose gases with attractive interactions in anharmonic traps

International Nuclear Information System (INIS)

Lundh, Emil; Collin, Anssi; Suominen, Kalle-Antti

2004-01-01

A rotated and harmonically trapped Bose gas with attractive interactions is expected to either remain stationary or escape from the trap. Here we report that, on the contrary, in an anharmonic trapping potential the Bose gas with attractive interactions responds to external rotation very differently, namely, through center-of-mass motion or by formation of vortices

Quantum particle-number fluctuations in a two-component Bose gas in a double-well potential

International Nuclear Information System (INIS)

Zin, Pawel; Oles, Bartlomiej; Sacha, Krzysztof

2011-01-01

A two-component Bose gas in a double-well potential with repulsive interactions may undergo a phase separation transition if the interspecies interactions outweigh the intraspecies ones. We analyze the transition in the strong interaction limit within the two-mode approximation. Numbers of particles in each potential well are equal and constant. However, at the transition point, the ground state of the system reveals huge fluctuations of numbers of particles belonging to the different gas components; that is, the probability for observation of any mixture of particles in each potential well becomes uniform.

Bose-Einstein condensation and long-range phase coherence in the many-particle Schroedinger wave function

International Nuclear Information System (INIS)

Mayers, J.

2001-01-01

The properties of the many-particle Schroedinger wave function Ψ are examined in the presence of Bose-Einstein condensation (BEC). It is shown that it is possible to define, in terms of Ψ, a function ψ(r-vector vertical bar s-vector), which can be regarded as the single-particle wave function of an arbitrary particle for a fixed configuration s-vector of all other particles. It is shown that ψ(r-vector|s-vector) plays an analogous role to the field operator of standard field-theoretical treatments of superfluidity. It is shown that in the presence of a Bose-Einstein condensate fraction f, ψ(r-vector|s-vector) must be nonzero and phase coherent within at least a fraction f of the total volume of the N-particle system for essentially all s-vector. Examination of the form of variational many-particle wave functions shows that in liquid 4 He, ψ(r-vector|s-vector) extends throughout the spaces left between the hard cores of the other atoms at s-vector. By contrast, in the absence of BEC, ψ(r-vector|s-vector) in the ground state must be nonzero only over a localized region of space. It is shown that in order for long-range phase coherence in ψ(r-vector|s-vector) to be maintained in the presence of velocity fields, any circulation must be quantized over macroscopic length scales. Some numerical calculations of the properties and fluctuations of liquid helium are presented. These suggest that the approach outlined in this paper may have significant advantages for the numerical calculations of the properties of Bose-Einstein condensed systems. The properties of ψ(r-vector|s-vector) are used to show that there is no general connection between the static structure factor and the size of the Bose-Einstein condensate fraction in a Bose fluid. It is suggested that the observed connection in liquid 4 He is due to the creation of vacancies in the liquid structure, which are required so that ψ(r-vector vertical bar s-vector) can delocalize, in the presence of hard

Interaction effects on dynamic correlations in noncondensed Bose gases

NARCIS (Netherlands)

Bezett, A.; Van Driel, H. J.; Mink, M. P.; Stoof, H. T C; Duine, R. A.

2014-01-01

We consider dynamic, i.e., frequency-dependent, correlations in noncondensed ultracold atomic Bose gases. In particular, we consider the single-particle correlation function and its power spectrum. We compute this power spectrum for a one-component Bose gas, and we show how it depends on the

More accurate theory for Bose-Einstein condensation fraction

International Nuclear Information System (INIS)

Biswas, Shyamal

2008-01-01

Bose-Einstein statistics is derived in the thermodynamic limit when the ratio of system size to thermal de Broglie wavelength goes to infinity. However, according to the experimental setup of Bose-Einstein condensation of harmonically trapped Bose gas of alkali atoms, the ratio near the condensation temperature (T o ) is 30-50. And, at ultralow temperatures well below T o , this ratio becomes comparable to 1. We argue that finite size as well as the ultralow temperature induces corrections to Bose-Einstein statistics. From the corrected statistics we plot condensation fraction versus temperature graph. This theoretical plot satisfies well with the experimental plot [A. Griesmaier et al., Phys. Rev. Lett. 94 (2005) 160401

Light Higgs channel of the resonant decay of magnon condensate in superfluid (3)He-B.

Science.gov (United States)

Zavjalov, V V; Autti, S; Eltsov, V B; Heikkinen, P J; Volovik, G E

2016-01-08

In superfluids the order parameter, which describes spontaneous symmetry breaking, is an analogue of the Higgs field in the Standard Model of particle physics. Oscillations of the field amplitude are massive Higgs bosons, while oscillations of the orientation are massless Nambu-Goldstone bosons. The 125 GeV Higgs boson, discovered at Large Hadron Collider, is light compared with electroweak energy scale. Here, we show that such light Higgs exists in superfluid (3)He-B, where one of three Nambu-Goldstone spin-wave modes acquires small mass due to the spin-orbit interaction. Other modes become optical and acoustic magnons. We observe parametric decay of Bose-Einstein condensate of optical magnons to light Higgs modes and decay of optical to acoustic magnons. Formation of a light Higgs from a Nambu-Goldstone mode observed in (3)He-B opens a possibility that such scenario can be realized in other systems, where violation of some hidden symmetry is possible, including the Standard Model.

Light Higgs channel of the resonant decay of magnon condensate in superfluid 3He-B

Science.gov (United States)

Zavjalov, V. V.; Autti, S.; Eltsov, V. B.; Heikkinen, P. J.; Volovik, G. E.

2016-01-01

In superfluids the order parameter, which describes spontaneous symmetry breaking, is an analogue of the Higgs field in the Standard Model of particle physics. Oscillations of the field amplitude are massive Higgs bosons, while oscillations of the orientation are massless Nambu-Goldstone bosons. The 125 GeV Higgs boson, discovered at Large Hadron Collider, is light compared with electroweak energy scale. Here, we show that such light Higgs exists in superfluid 3He-B, where one of three Nambu-Goldstone spin-wave modes acquires small mass due to the spin–orbit interaction. Other modes become optical and acoustic magnons. We observe parametric decay of Bose-Einstein condensate of optical magnons to light Higgs modes and decay of optical to acoustic magnons. Formation of a light Higgs from a Nambu-Goldstone mode observed in 3He-B opens a possibility that such scenario can be realized in other systems, where violation of some hidden symmetry is possible, including the Standard Model. PMID:26743951

Quantum Impurity in a One-dimensional Trapped Bose Gas

DEFF Research Database (Denmark)

Salami Dehkharghani, Amin; Volosniev, A. G.; Zinner, N. T.

2015-01-01

We present a new theoretical framework for describing an impurity in a trapped Bose system in one spatial dimension. The theory handles any external confinement, arbitrary mass ratios, and a weak interaction may be included between the Bose particles. To demonstrate our technique, we calculate th...... the ground state energy and properties of a sample system with eight bosons and find an excellent agreement with numerically exact results. Our theory can thus provide definite predictions for experiments in cold atomic gases....

Superfluid turbulence

International Nuclear Information System (INIS)

Donnelly, R.J.

1988-01-01

Most flows of fluids, in nature and in technology, are turbulent. Since much of the energy expended by machines and devices that involve fluid flows is spent in overcoming drag caused by turbulence, there is a strong motivation to understand the phenomena. Surprisingly, the peculiar, quantum-mechanical form of turbulence that can form in superfluid helium may turn out to be much simpler to understand that the classical turbulence that forms in normal fluids. It now seems that the study of superfluid turbulence may provide simplified model systems for studying some forms of classical turbulence. There are also practical motivations for studying superfluid turbulence. For example, superfuid helium is often used as a coolant in superconducting machinery. Superfluid turbulence is the primary impediment to the transfer of heat by superfluid helium; an understanding of the phenomena may make it possible to design more efficient methods of refrigeration for superconducting devices. 8 figs

Condensed Fraction of an Atomic Bose Gas Induced by Critical Correlations

International Nuclear Information System (INIS)

Smith, Robert P.; Tammuz, Naaman; Campbell, Robert L. D.; Hadzibabic, Zoran; Holzmann, Markus

2011-01-01

We study the condensed fraction of a harmonically trapped atomic Bose gas at the critical point predicted by mean-field theory. The nonzero condensed fraction f 0 is induced by critical correlations which increase the transition temperature T c above T c MF . Unlike the T c shift in a trapped gas, f 0 is sensitive only to the critical behavior in the quasiuniform part of the cloud near the trap center. To leading order in the interaction parameter a/λ 0 , where a is the s-wave scattering length and λ 0 the thermal wavelength, we expect a universal scaling f 0 ∝(a/λ 0 ) 4 . We experimentally verify this scaling using a Feshbach resonance to tune a/λ 0 . Further, using the local density approximation, we compare our measurements with the universal result obtained from Monte Carlo simulations for a uniform system, and find excellent quantitative agreement.

Influence of quantum degeneracy and regeneration on the performance of Bose-Stirling refrigeration-cycles operated in different temperature regions

International Nuclear Information System (INIS)

Lin Bihong; Zhang Yue; Chen Jincan

2006-01-01

The Stirling refrigeration cycle using an ideal Bose-gas as the working substance is called the Bose-Stirling refrigeration cycle, which is different from other thermodynamic cycles such as the Carnot cycle, Ericsson cycle, Brayton cycle, Otto cycle, Diesel cycle and Atkinson cycle working with an ideal Bose gas and may be operated across the critical temperature of Bose-Einstein condensation of the Bose system. The performance of the cycle is investigated, based on the equation of state of an ideal Bose gas. The inherent regenerative losses of the cycle are considered and the coefficient of performance and the amount of refrigeration of the cycle are calculated. The results obtained here are compared with those derived from the classical Stirling refrigeration cycle, using an ideal gas as the working substance. The influence of quantum degeneracy and inherent regenerative losses on the performance of the Bose Stirling refrigeration cycle operated in different temperature regions is discussed in detail, and consequently, general performance characteristics of the cycle are revealed

Tonks-Girardeau and super-Tonks-Girardeau states of a trapped one-dimensional spinor Bose gas

International Nuclear Information System (INIS)

Girardeau, M. D.

2011-01-01

A harmonically trapped, ultracold, one-dimensional (1D) spin-1 Bose gas with strongly repulsive or attractive 1D even-wave interactions induced by a three-dimensional (3D) Feshbach resonance is studied. The exact ground state, a hybrid of Tonks-Girardeau (TG) and ideal Fermi gases, is constructed in the TG limit of infinite even-wave repulsion by a spinor Fermi-Bose mapping to a spinless ideal Fermi gas. It is then shown that in the limit of infinite even-wave attraction this same state remains an exact many-body eigenstate, now highly excited relative to the collapsed generalized McGuire-cluster ground state, showing that the hybrid TG state is completely stable against collapse to this cluster ground state under a sudden switch from infinite repulsion to infinite attraction. It is shown to be the TG limit of a hybrid super-Tonks-Girardeau (STG) state, which is metastable under a sudden switch from finite but very strong repulsion to finite but very strong attraction. It should be possible to create it experimentally by a sudden switch from strongly repulsive to strongly attractive interaction, as in the recent Innsbruck experiment on a spin-polarized bosonic STG gas. In the case of strong attraction, there should also exist another STG state of much lower energy, consisting of strongly bound dimers, a bosonic analog of a recently predicted STG state which is an ultracold gas of strongly bound bosonic dimers of fermionic atoms, but it is shown that this STG state cannot be created by such a switch from strong repulsion to strong attraction.

Superfluid stirling refrigerator: A new method for cooling below 1 Kelvin

International Nuclear Information System (INIS)

Kotsubo, V.; Swift, G.W.

1990-01-01

We have invented and built a new type of cryocooler, which we call the superfluid Stirling refrigerator (SSR). The first prototype reached 0.6 K from a starting temperature of 1.2 K. The working fluid of the SSR is the 3 He solute in a superfluid 3 He-- 4 He solution. At low temperatures, the superfluid 4 He is in its quantum ground state, and therefore is thermodynamically inert, while the 3 He solute has the thermodynamic properties of a dense ideal gas. Thus, in principle, any refrigeration cycle that can use an ideal gas can also use the 3 He solute as working fluid. In our SSR prototype, bellows-sealed superleak pistons driven by a room-temperature camshaft work on the 3 He solute. Ultimately, we anticipate elimination of moving parts by analogy with pulse-tube refrigeration. 15 refs., 6 figs

Thermodynamic identities and particle number fluctuations in weakly interacting Bose-Einstein condensates

Energy Technology Data Exchange (ETDEWEB)

Illuminati, Fabrizio [Institut fuer Physik, Universitaet Potsdam, Am Neuen Palais 10, D-14415, Potsdam (Germany); Dipartimento di Fisica, Universita di Salerno, and INFM, Unita di Salerno, I-84081 Baronissi SA (Italy); Navez, Patrick [Institut fuer Physik, Universitaet Potsdam, Am Neuen Palais 10, D-14415, Potsdam (Germany); Institute of Materials Science, Demokritos NCSR, POB 60228, 15310 Athens (Greece); Wilkens, Martin [Institut fuer Physik, Universitaet Potsdam, Am Neuen Palais 10, D-14415, Potsdam (Germany)

1999-08-14

We derive exact thermodynamic identities relating the average number of condensed atoms and the root-mean-square fluctuations determined in different statistical ensembles for the weakly interacting Bose gas confined in a box. This is achieved by introducing the concept of auxiliary partition functions for model Hamiltonians that do conserve the total number of particles. Exploiting such thermodynamic identities, we provide the first, completely analytical prediction of the microcanonical particle number fluctuations in the weakly interacting Bose gas. Such fluctuations, as a function of the volume V of the box are found to behave normally, in contrast with the anomalous scaling behaviour V{sup 4/3} of the fluctuations in the ideal Bose gas. (author). Letter-to-the-editor.

Condensate growth in trapped Bose gates

NARCIS (Netherlands)

Bijlsma, M.J.; Zaremba, E.; Stoof, H.T.C.

2000-01-01

We study the dynamics of condensate fromation in an inhomogeneous trapped Bose gas with a positive interatomic scattering length. We take into account both the nonequilibrium kinetics of the thermal cloud and the Hartree-Fock mean-field efects in the condensed and the noncondensed parts of the gas.

Condensate growth in trapped Bose gases

NARCIS (Netherlands)

Bijlsma, M.J.; Zaremba, E.; Stoof, H.T.C.

2000-01-01

We study the dynamics of condensate formation in an inhomogeneous trapped Bose gas with a positive interatomic scattering length. We take into account both the nonequilibrium kinetics of the thermal cloud and the Hartree-Fock mean-field effects in the condensed and the noncondensed parts of the gas.

Coherent tunneling of atoms from Bose-condensed gases at finite temperatures

International Nuclear Information System (INIS)

Luxat, David L.; Griffin, Allan

2002-01-01

Tunneling of atoms between two trapped Bose-condensed gases at finite temperatures is explored using a many-body linear-response tunneling formalism similar to that used in superconductors. To lowest order, the tunneling currents can be expressed quite generally in terms of the single-particle Green's functions of isolated Bose gases. A coherent first-order tunneling Josephson current between two atomic Bose-Einstein condensates is found, in addition to coherent and dissipative contributions from second-order condensate-noncondensate and noncondensate-noncondensate tunneling. Our work is a generalization of Meier and Zwerger, who recently treated tunneling between uniform atomic Bose gases. We apply our formalism to the analysis of an out-coupling experiment induced by light wave fields, using a simple Bogoliubov-Popov quasiparticle approximation for the trapped Bose gas. For tunneling into the vacuum, we recover the results of Japha, Choi, Burnett, and Band, who recently pointed out the usefulness of studying the spectrum of out-coupled atoms. In particular, we show that the small tunneling current of noncondensate atoms from a trapped Bose gas has a broad spectrum of energies, with a characteristic structure associated with the Bogoliubov quasiparticle u 2 and v 2 amplitudes

Coexistence of photonic and atomic Bose-Einstein condensates in ideal atomic gases

Directory of Open Access Journals (Sweden)

N. Boichenko

2015-12-01

Full Text Available We have studied conditions of photon Bose-Einstein condensate formation that is in thermodynamic equilibrium with ideal gas of two-level Bose atoms below the degeneracy temperature. Equations describing thermodynamic equilibrium in the system were formulated; critical temperatures and densities of photonic and atomic gas subsystems were obtained analytically. Coexistence conditions of these photonic and atomic Bose-Einstein condensates were found. There was predicted the possibility of an abrupt type of photon condensation in the presence of Bose condensate of ground-state atoms: it was shown that the slightest decrease of the temperature could cause a significant gathering of photons in the condensate. This case could be treated as a simple model of the situation known as "stopped light" in cold atomic gas. We also showed how population inversion of atomic levels can be created by lowering the temperature. The latter situation looks promising for light accumulation in atomic vapor at very low temperatures.

Violation of self-similarity in the expansion of a one-dimensional Bose gas

International Nuclear Information System (INIS)

Pedri, P.; Santos, L.; Oehberg, P.; Stringari, S.

2003-01-01

The expansion of a one-dimensional Bose gas after releasing its initial harmonic confinement is investigated employing the Lieb-Liniger equation of state within the local-density approximation. We show that during the expansion the density profile of the gas does not follow a self-similar solution, as one would expect from a simple scaling ansatz. We carry out a variational calculation, which recovers the numerical results for the expansion, the equilibrium properties of the density profile, and the frequency of the lowest compressional mode. The variational approach allows for the analysis of the expansion in all interaction regimes between the mean-field and the Tonks-Girardeau limits, and in particular shows the range of parameters for which the expansion violates self-similarity

Superfluid thermodynamic cycle refrigerator

Science.gov (United States)

Swift, Gregory W.; Kotsubo, Vincent Y.

1992-01-01

A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of .sup.3 He in a single phase .sup.3 He-.sup.4 He solution. The .sup.3 He in superfluid .sup.4 He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid .sup.3 He at an initial concentration in superfluid .sup.4 He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of .sup.4 He while restricting passage of .sup.3 He. The .sup.3 He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K.

Noise thermometry with two weakly coupled Bose-Einstein condensates.

Science.gov (United States)

Gati, Rudolf; Hemmerling, Börge; Fölling, Jonas; Albiez, Michael; Oberthaler, Markus K

2006-04-07

Here we report on the experimental investigation of thermally induced fluctuations of the relative phase between two Bose-Einstein condensates which are coupled via tunneling. The experimental control over the coupling strength and the temperature of the thermal background allows for the quantitative analysis of the phase fluctuations. Furthermore, we demonstrate the application of these measurements for thermometry in a regime where standard methods fail. With this we confirm that the heat capacity of an ideal Bose gas deviates from that of a classical gas as predicted by the third law of thermodynamics.

Noise Thermometry with Two Weakly Coupled Bose-Einstein Condensates

International Nuclear Information System (INIS)

Gati, Rudolf; Hemmerling, Boerge; Foelling, Jonas; Albiez, Michael; Oberthaler, Markus K.

2006-01-01

Here we report on the experimental investigation of thermally induced fluctuations of the relative phase between two Bose-Einstein condensates which are coupled via tunneling. The experimental control over the coupling strength and the temperature of the thermal background allows for the quantitative analysis of the phase fluctuations. Furthermore, we demonstrate the application of these measurements for thermometry in a regime where standard methods fail. With this we confirm that the heat capacity of an ideal Bose gas deviates from that of a classical gas as predicted by the third law of thermodynamics

Monopole excitations of a harmonically trapped one-dimensional Bose gas from the ideal gas to the Tonks-Girardeau regime.

Science.gov (United States)

Choi, S; Dunjko, V; Zhang, Z D; Olshanii, M

2015-09-11

Using a time-dependent modified nonlinear Schrödinger equation (MNLSE)-where the conventional chemical potential proportional to the density is replaced by the one inferred from Lieb-Liniger's exact solution-we study frequencies of the collective monopole excitations of a one-dimensional Bose gas. We find that our method accurately reproduces the results of a recent experimental study [E. Haller et al., Science 325, 1224 (2009)] in the full spectrum of interaction regimes from the ideal gas, through the mean-field regime, through the mean-field Thomas-Fermi regime, all the way to the Tonks-Giradeau gas. While the former two are accessible by the standard time-dependent NLSE and inaccessible by the time-dependent local density approximation, the situation reverses in the latter case. However, the MNLSE is shown to treat all these regimes within a single numerical method.

Ground-state properties of a dilute homogeneous Bose gas of hard disks in two dimensions

International Nuclear Information System (INIS)

Mazzanti, F.; Polls, A.; Fabrocini, A.

2005-01-01

The energy and structure of a dilute hard-disks Bose gas are studied in the framework of a variational many-body approach based on a Jastrow correlated ground-state wave function. The asymptotic behaviors of the radial distribution function and the one-body density matrix are analyzed after solving the Euler equation obtained by a free minimization of the hypernetted chain energy functional. Our results show important deviations from those of the available low density expansions, already at gas parameter values x∼0.001. The condensate fraction in 2D is also computed and found generally lower than the 3D one at the same x

Critical behavior of the ideal-gas Bose-Einstein condensation in the Apollonian network.

Science.gov (United States)

de Oliveira, I N; dos Santos, T B; de Moura, F A B F; Lyra, M L; Serva, M

2013-08-01

We show that the ideal Boson gas displays a finite-temperature Bose-Einstein condensation transition in the complex Apollonian network exhibiting scale-free, small-world, and hierarchical properties. The single-particle tight-binding Hamiltonian with properly rescaled hopping amplitudes has a fractal-like energy spectrum. The energy spectrum is analytically demonstrated to be generated by a nonlinear mapping transformation. A finite-size scaling analysis over several orders of magnitudes of network sizes is shown to provide precise estimates for the exponents characterizing the condensed fraction, correlation size, and specific heat. The critical exponents, as well as the power-law behavior of the density of states at the bottom of the band, are similar to those of the ideal Boson gas in lattices with spectral dimension d(s)=2ln(3)/ln(9/5)~/=3.74.

Momentum-Resolved Observation of Thermal and Quantum Depletion in a Bose Gas

Science.gov (United States)

Chang, R.; Bouton, Q.; Cayla, H.; Qu, C.; Aspect, A.; Westbrook, C. I.; Clément, D.

2016-12-01

We report on the single-atom-resolved measurement of the distribution of momenta ℏk in a weakly interacting Bose gas after a 330 ms time of flight. We investigate it for various temperatures and clearly separate two contributions to the depletion of the condensate by their k dependence. The first one is the thermal depletion. The second contribution falls off as k-4, and its magnitude increases with the in-trap condensate density as predicted by the Bogoliubov theory at zero temperature. These observations suggest associating it with the quantum depletion. How this contribution can survive the expansion of the released interacting condensate is an intriguing open question.

On an uncorrelated jet model with Bose-Einstein statistics

International Nuclear Information System (INIS)

Bilic, N.; Dadic, I.; Martinis, M.

1978-01-01

Starting from the density of states of an ideal Bose-Einstein gas, an uncorrelated jet model with Bose-Einstein statistics has been formulated. The transition to continuum is based on the Touschek invariant measure. It has been shown that in this model average multiplicity increases logarithmically with total energy, while the inclusive distribution shows ln s violation of scaling. (author)

Bose-Einstein condensation of excitons in Cu2O

International Nuclear Information System (INIS)

Snoke, D.W.

1990-01-01

Free excitons provide the only experimental system other than helium in which the behavior of particles with mass is known to follow Bose-Einstein statistics. Experimental observations are presented of the kinetic energy distribution of excitons in the direct-gap semiconductor Cu 2 O, both the triplet orthoexciton state and the singlet paraexciton state. The density and temperature of the exciton gas closely follow the phase boundary for Bose-Einstein condensation. At the highest densities, the lower-lying paraexcitons take on an anomalous energy distribution with a sharp, high-energy edge. This odd distribution of particle energies may be associated with Bose-Einstein condensation into a state with nonzero momentum. Indeed, the excitons leave the region of their creation at supersonic velocities. In addition to the experimental observations, theoretical models are presented for several aspects of this nonequilibrium system. The equilibration of a nearly-ideal boson gas is modeled, finding that a significant time is required for the approach to condensation. The temperature and density of the excitons in steady state are modeled based on known classical kinetic effects in semiconductors, and the effects of Bose-Einstein statistics on these processes estimated

Canonical statistics of trapped ideal and interacting Bose gases

International Nuclear Information System (INIS)

Xiong Hongwei; Liu Shujuan; Huang Guoxiang; Xu Zaixin

2002-01-01

The mean ground-state occupation number and condensate fluctuations of interacting and noninteracting Bose gases confined in a harmonic trap are considered by using a canonical ensemble approach. To obtain the mean ground-state occupation number and the condensate fluctuations, an analytical description for the probability distribution function of the condensate is provided directly starting from the analysis of the partition function of the system. For the ideal Bose gas, the probability distribution function is found to be a Gaussian one for the case of the harmonic trap. For the interacting Bose gas, using a unified approach the condensate fluctuations are calculated based on the lowest-order perturbation method and on Bogoliubov theory. It is found that the condensate fluctuations based on the lowest-order perturbation theory follow the law 2 N 0 >∼N, while the fluctuations based on Bogoliubov theory behave as N 4/3

Exact equivalence between one-dimensional Bose gases interacting via hard-sphere and zero-range potentials

DEFF Research Database (Denmark)

Valiente, Manuel

2012-01-01

We prove the equivalence between the hard-sphere Bose gas and a system with momentum-dependent zero-range interactions in one spatial dimension, which we call extended hard-sphere Bose gas. The two-body interaction in the latter model has the advantage of being a regular pseudopotential. The most...

A compact copper nuclear demagnetization cryostat and a search for superfluidity in solid 4He

International Nuclear Information System (INIS)

Haar, P.G. van de.

1991-01-01

The subject of this thesis is the theoretical and experimental study of matter at low temperatures, and the development of techniques to reach and measure these temperatures. A copper nuclear demagnetization cryostat was developed in order to reach low temperatures. This system distinguishes itself from other cryostats by its compact construction. The lowest temperature recorded by a pulsed Pt-NMR thermometer was 115 μK. This system was used to search for superfluidity in solid 4 He. Due to the large zero-point motion of the atoms, 4He remains liquid down to zero temperature; a pressure of 25.3 bar is needed to force the atoms in a lattice. Even in solid state, the 4 He atoms remain very mobile, changing lattice sites at a frequency of approximately 10 7 Hz. It is possible that solid 4 He contains vacancies at zero temperature. These zero point vacancies are expected to behave like a gas of bosons, and should Bose-condense at some temperature. From experiments the upper limit to the vacancy concentration is set of 4·10-5. (author). 217 refs.; 46 figs.; 2 tabs

Observing the drop of resistance in the flow of a superfluid Fermi gas.

Science.gov (United States)

Stadler, David; Krinner, Sebastian; Meineke, Jakob; Brantut, Jean-Philippe; Esslinger, Tilman

2012-11-29

The ability of particles to flow with very low resistance is characteristic of superfluid and superconducting states, leading to their discovery in the past century. Although measuring the particle flow in liquid helium or superconducting materials is essential to identify superfluidity or superconductivity, no analogous measurement has been performed for superfluids based on ultracold Fermi gases. Here we report direct measurements of the conduction properties of strongly interacting fermions, observing the well-known drop in resistance that is associated with the onset of superfluidity. By varying the depth of the trapping potential in a narrow channel connecting two atomic reservoirs, we observed variations of the atomic current over several orders of magnitude. We related the intrinsic conduction properties to the thermodynamic functions in a model-independent way, by making use of high-resolution in situ imaging in combination with current measurements. Our results show that, as in solid-state systems, current and resistance measurements in quantum gases provide a sensitive probe with which to explore many-body physics. Our method is closely analogous to the operation of a solid-state field-effect transistor and could be applied as a probe for optical lattices and disordered systems, paving the way for modelling complex superconducting devices.

Universality and Quantum Criticality of the One-Dimensional Spinor Bose Gas

Science.gov (United States)

PâÅ£u, Ovidiu I.; Klümper, Andreas; Foerster, Angela

2018-06-01

We investigate the universal thermodynamics of the two-component one-dimensional Bose gas with contact interactions in the vicinity of the quantum critical point separating the vacuum and the ferromagnetic liquid regime. We find that the quantum critical region belongs to the universality class of the spin-degenerate impenetrable particle gas which, surprisingly, is very different from the single-component case and identify its boundaries with the peaks of the specific heat. In addition, we show that the compressibility Wilson ratio, which quantifies the relative strength of thermal and quantum fluctuations, serves as a good discriminator of the quantum regimes near the quantum critical point. Remarkably, in the Tonks-Girardeau regime, the universal contact develops a pronounced minimum, reflected in a counterintuitive narrowing of the momentum distribution as we increase the temperature. This momentum reconstruction, also present at low and intermediate momenta, signals the transition from the ferromagnetic to the spin-incoherent Luttinger liquid phase and can be detected in current experiments with ultracold atomic gases in optical lattices.

Stable-unstable transition for a Bose-Hubbard chain coupled to an environment

Science.gov (United States)

Guo, Chu; de Vega, Ines; Schollwöck, Ulrich; Poletti, Dario

2018-05-01

Interactions in quantum systems may induce transitions to exotic correlated phases of matter which can be vulnerable to coupling to an environment. Here, we study the stability of a Bose-Hubbard chain coupled to a bosonic bath at zero and nonzero temperature. We show that only above a critical interaction the chain loses bosons and its properties are significantly affected. The transition is of a different nature than the superfluid-Mott-insulator transition and occurs at a different critical interaction. We explain such a stable-unstable transition by the opening of a global charge gap. The comparison of accurate matrix product state simulations to approximative approaches that miss this transition reveals its many-body origin.

Bose-Einstein condensation of photons in an optical microcavity

OpenAIRE

Klaers, Jan; Schmitt, Julian; Vewinger, Frank; Weitz, Martin

2010-01-01

Bose-Einstein condensation, the macroscopic ground state accumulation of particles with integer spin (bosons) at low temperature and high density, has been observed in several physical systems, including cold atomic gases and solid state physics quasiparticles. However, the most omnipresent Bose gas, blackbody radiation (radiation in thermal equilibrium with the cavity walls) does not show this phase transition, because the chemical potential of photons vanishes and, when the temperature is r...

Bose-Einstein condensation of a charged relativistic ideal gas in a general homogeneous magnetic field

International Nuclear Information System (INIS)

Toms, D.J.

1994-01-01

It is shown how the effective action formalism and ζ-function regularization can be used to study Bose-Einstein condensation for a relativistic charged scalar field in a general homogeneous magnetic field in a spacetime of arbitrary dimension. In the special case where the magnetic field has only one component, Bose-Einstein condensation occurs at high temperature only for D≥5 where D is the spatial dimension. When Bose-Einstein condensation does occur the ground-state expectation value of the scalar field is not constant and we determine its value. If the magnetic field has p independent nonzero components we show that the condition for Bose-Einstein condensation is D≥3+2p. In particular, Bose-Einstein condensation can never occur if the magnetic field has all of its independent components nonzero. The problem of Bose-Einstein condensation in a cylindrical box in D spatial dimensions with a uniform magnetic field directed along the axis of the cylinder is also discussed

Bose gases in one-dimensional harmonic trap

Indian Academy of Sciences (India)

dimensional Bose gas confined by a harmonic potential are studied using different ensemble approaches. Combining number theory methods, a new approach is presented to calculate the occupation numbers of different energy levels in ...

Route to non-Abelian quantum turbulence in spinor Bose-Einstein condensates

Science.gov (United States)

Mawson, Thomas; Ruben, Gary; Simula, Tapio

2015-06-01

We have studied computationally the collision dynamics of spin-2 Bose-Einstein condensates initially confined in a triple-well trap. Depending on the phase structure of the initial-state spinor wave function, the collision of the three condensate fragments produces one of many possible vortex-antivortex lattices, after which the system transitions to quantum turbulence. We find that the emerging vortex lattice structures can be described in terms of multiwave interference. We show that the three-fragment collisions can be used to systematically produce staggered vortex-antivortex honeycomb lattices of fractional-charge vortices, whose collision dynamics are known to be non-Abelian. Such condensate collider experiments could potentially be used as a controllable pathway to generating non-Abelian superfluid turbulence with networks of vortex rungs.

Hypergeometric continuation of divergent perturbation series: I. Critical exponents of the Bose-Hubbard model

Science.gov (United States)

Sanders, Sören; Holthaus, Martin

2017-10-01

We study the connection between the exponent of the order parameter of the Mott insulator-to-superfluid transition occurring in the two-dimensional Bose-Hubbard model, and the divergence exponents of its one- and two-particle correlation functions. We find that at the multicritical points all divergence exponents are related to each other, allowing us to express the critical exponent in terms of one single divergence exponent. This approach correctly reproduces the critical exponent of the three-dimensional XY universality class. Because divergence exponents can be computed in an efficient manner by hypergeometric analytic continuation, our strategy is applicable to a wide class of systems.

Superfluid 3He at very low temperatures: a very unusual excitation gas

International Nuclear Information System (INIS)

Pickett, G.R.; Enrico, M.P.; Fisher, S.N.; Guenault, A.M.; Torizuka, K.

1994-01-01

The excitation gas in superfluid 3 He at low temperatures shows a number of remarkable dynamical properties arising from the unusual dispersion curve. The existence of an energy gap leads to many of the observed properties varying rapidly with temperature, since the excitation density is dominated by the gap Boltzmann factor exp(-Δ/kT). But also, the fact that the minimum energy lies at finite momentum gives rise to Andreev scattering processes, in which the velocity of the excitation is reversed but the momentum left virtually unchanged. Since the dispersion curve looks different to a moving observer, there is the possibility of the free production of quasiparticle-quasihole pairs at a Landau critical velocity. At low temperatures the mean free path becomes much larger than any experimental size. Using vibrating wire resonators as universal probes, we can monitor the temperature, measure the Kapitz resistance, examine the nonlinear regime beyond the two-fluid model, observe the Landau velocity, create and detect thermal beams of excitation with black-body radiators, observe Andreev reflection directly and probe A-phase textures (in which the gas is one-dimensional). Future possibilities are discussed. (orig.)

Slowly rotating general relativistic superfluid neutron stars with relativistic entrainment

International Nuclear Information System (INIS)

Comer, G.L.

2004-01-01

Neutron stars that are cold enough should have two or more superfluids or supercondutors in their inner crusts and cores. The implication of superfluidity or superconductivity for equilibrium and dynamical neutron star states is that each individual particle species that forms a condensate must have its own, independent number density current and equation of motion that determines that current. An important consequence of the quasiparticle nature of each condensate is the so-called entrainment effect; i.e., the momentum of a condensate is a linear combination of its own current and those of the other condensates. We present here the first fully relativistic modeling of slowly rotating superfluid neutron stars with entrainment that is accurate to the second-order in the rotation rates. The stars consist of superfluid neutrons, superconducting protons, and a highly degenerate, relativistic gas of electrons. We use a relativistic σ-ω mean field model for the equation of state of the matter and the entrainment. We determine the effect of a relative rotation between the neutrons and protons on a star's total mass, shape, and Kepler, mass-shedding limit

Critical temperature of Bose-Einstein condensation in trapped atomic Bose-Fermi mixtures

Energy Technology Data Exchange (ETDEWEB)

Albus, A P [Institut fuer Physik, Universitaet Potsdam, D-14469 Potsdam (Germany); Giorgini, S [Dipartimento di Fisica, Universita di Trento, and Istituto Nazionale per la Fisica della Materia, I-38050 Povo (Italy); Illuminati, F [Dipartimento di Fisica, Universita di Salerno, and Istituto Nazionale per la Fisica della Materia, I-84081 Baronissi (Italy); Viverit, L [Dipartimento di Fisica, Universita di Trento, and Istituto Nazionale per la Fisica della Materia, I-38050 Povo (Italy)

2002-12-14

We calculate the shift in the critical temperature of Bose-Einstein condensation for a dilute Bose-Fermi mixture confined by a harmonic potential, to lowest order in both the Bose-Bose and Bose-Fermi coupling constants. The relative importance of the effect on the critical temperature of the boson-boson and boson-fermion interactions is investigated as a function of the parameters of the mixture. The possible relevance of the shift of the transition temperature in current experiments on trapped Bose-Fermi mixtures is discussed. (letter to the editor)

Critical temperature of Bose-Einstein condensation in trapped atomic Bose-Fermi mixtures

International Nuclear Information System (INIS)

Albus, A P; Giorgini, S; Illuminati, F; Viverit, L

2002-01-01

We calculate the shift in the critical temperature of Bose-Einstein condensation for a dilute Bose-Fermi mixture confined by a harmonic potential, to lowest order in both the Bose-Bose and Bose-Fermi coupling constants. The relative importance of the effect on the critical temperature of the boson-boson and boson-fermion interactions is investigated as a function of the parameters of the mixture. The possible relevance of the shift of the transition temperature in current experiments on trapped Bose-Fermi mixtures is discussed. (letter to the editor)

An analytical description of the low temperature behaviour of a weakly interacting Bose gas

International Nuclear Information System (INIS)

Su Guozhen; Chen Lixuan; Chen Jincan

2004-01-01

An analytical description of the low temperature behaviour of a trapped interacting Bose gas is presented by using a simple approach that is based on the principle of the constancy of chemical potentials in equilibrium and the local-density approximation. Several thermodynamic quantities, which include the ground-state fraction, chemical potential, total energy, entropy and heat capacity, are derived analytically. It is shown that the results obtained here are in excellent agreement with the experimental data and the theoretical predictions based on the numerical calculation. Meanwhile, by selecting a suitable variable, the divergent problem existing in some papers is solved

Superfluid plasmas: Multivelocity nonlinear hydrodynamics of superfluid solutions with charged condensates coupled electromagnetically

International Nuclear Information System (INIS)

Holm, D.D.; Kupershmidt, B.A.

1987-01-01

Four levels of nonlinear hydrodynamic description are presented for a nondissipative multicondensate solution of superfluids with vorticity. First, the multivelocity superfluid (MVSF) theory is extended to the case of a multivelocity superfluid plasma (MVSP), in which some of the superfluid condensates (protons, say) are charged and coupled electromagnetically to an additional, normal, charged fluid (electrons). The resulting drag-current density is derived due to the electromagnetic coupling of the condensates with the normal fluids. For the case of one charged condensate, the MVSP equations simplify to what we call superfluid Hall magnetohydrodynamics (SHMHD) in the approximation that displacement current and electron inertia are negligible, and local charge neutrality is imposed. The contribution of the charged condensate to the Hall drift force is determined. In turn, neglecting the Hall effect in SHMHD gives the equations of superfluid magnetohydrodynamics (SMHD). Each set of equations (MVSF, MVSP, SHMHD, and SMHD) is shown to be Hamiltonian and to possess a Poisson bracket associated with the dual space of a corresponding semidirect-product Lie algebra with a generalized two-cocycle defined on it. Topological conservation laws (helicities) associated with the kernels of these Lie algebras are also discussed as well as those associated physically with generalized Kelvin theorems for conservation of superfluid circulation around closed loops moving with the normal fluid

Universality classes far from equilibrium. From heavy-ion collisions to superfluid Bose systems

International Nuclear Information System (INIS)

Boguslavski, Kirill

2016-01-01

Quantum many-body systems far from equilibrium can approach a nonthermal fixed point during their real-time evolution. One example is scalar field theory, which occurs in models of cosmological inflation, and similar examples are found for non-Abelian plasmas relevant for heavy-ion collisions and for ultracold Bose gases. Investigating nonthermal fixed points of different microscopic theories, we present two novel universality classes that provide links between these systems. One of them involves nonrelativistic, N-component relativistic and expanding scalar systems. It occurs in the deep infrared regime of very high occupancies and is governed by a self-similar evolution. Its nonequilibrium dynamics leads to the formation of a Bose-Einstein condensate. The scaling properties of this region can be described by a vertex-resummed kinetic theory that is based on a systematic large-N expansion at next-to-leading order. The other novel universality class encompasses scalar field theories and non-Abelian plasmas in a longitudinally expanding background and corresponds to an early dynamical stage of heavy-ion collisions in the high-energy limit. We show that these systems share the same self-similar scaling properties for a wide range of momenta in a limit where particles are weakly coupled but their occupancy is high. Both universality classes are found in separate momentum regions in a longitudinally expanding N-component scalar field theory. We argue that the important role of the infrared dynamics ensures that key features of our results for scalar and gauge theories cannot be reproduced consistently in conventional kinetic theory frameworks. Moreover, the observed universality connects different physics disciplines from heavy-ion collisions to ultracold atoms, making a remarkable link between the world's hottest and coldest matter.

Universality classes far from equilibrium. From heavy-ion collisions to superfluid Bose systems

Energy Technology Data Exchange (ETDEWEB)

Boguslavski, Kirill

2016-07-27

Quantum many-body systems far from equilibrium can approach a nonthermal fixed point during their real-time evolution. One example is scalar field theory, which occurs in models of cosmological inflation, and similar examples are found for non-Abelian plasmas relevant for heavy-ion collisions and for ultracold Bose gases. Investigating nonthermal fixed points of different microscopic theories, we present two novel universality classes that provide links between these systems. One of them involves nonrelativistic, N-component relativistic and expanding scalar systems. It occurs in the deep infrared regime of very high occupancies and is governed by a self-similar evolution. Its nonequilibrium dynamics leads to the formation of a Bose-Einstein condensate. The scaling properties of this region can be described by a vertex-resummed kinetic theory that is based on a systematic large-N expansion at next-to-leading order. The other novel universality class encompasses scalar field theories and non-Abelian plasmas in a longitudinally expanding background and corresponds to an early dynamical stage of heavy-ion collisions in the high-energy limit. We show that these systems share the same self-similar scaling properties for a wide range of momenta in a limit where particles are weakly coupled but their occupancy is high. Both universality classes are found in separate momentum regions in a longitudinally expanding N-component scalar field theory. We argue that the important role of the infrared dynamics ensures that key features of our results for scalar and gauge theories cannot be reproduced consistently in conventional kinetic theory frameworks. Moreover, the observed universality connects different physics disciplines from heavy-ion collisions to ultracold atoms, making a remarkable link between the world's hottest and coldest matter.

Tunneling dynamics of superfluid Fermi gases in an accelerating optical lattice

International Nuclear Information System (INIS)

Tie Lu; Xue Jukui

2010-01-01

The nonlinear Landau-Zener tunneling and the nonlinear Rabi oscillations of superfluid Fermi gases between Bloch bands in an accelerating optical lattice are discussed. Within the hydrodynamic theory and a two-level model, the tunneling probability of superfluid Fermi gases between Bloch bands is obtained. We find that, as the system crosses from the Bose-Einstein condensation (BEC) side to the BCS side, the tunneling rate is closely related to the particle density: when the density is smaller (larger) than a critical value, the tunneling rate at unitarity is larger (smaller) than that in the BEC limit. This is well explained in terms of an effective interaction and an effective potential. Furthermore, the nonlinear Rabi oscillations of superfluid Fermi gases between the bands are discussed by imposing a periodic modulation on the level bias and the strength of the lattice. Analytical expressions of the critical density for suppressing or enhancing the Rabi oscillations are obtained. It is shown that, as the system crosses from the BEC side to the BCS side, the critical density strongly depends on the modulation parameters (i.e., the modulation amplitude and the modulation frequency). For a fixed density, a high-frequency or low-frequency modulation can suppress or enhance the Rabi oscillations both at unitarity and in the BEC limit. For an intermediate modulation frequency, the Rabi oscillations are chaotic along the entire BEC-BCS crossover, especially, on the BCS side. Interestingly, we find that the modulation of the lattice strength only with an intermediate modulation frequency has significant effect on the Rabi oscillations both in the BEC limit and at unitarity; that is, an intermediate-frequency modulation can enhance the Rabi oscillations, especially on the BCS side.

Vortex lattices in a rotating Fermi superfluid in the BCS–BEC crossover with many Landau levels

International Nuclear Information System (INIS)

Song, Tie-ling; Ma, C.R.; Ma, Yong-li

2012-01-01

We present an explicit analytical analysis of the ground state of vortex lattice structure, based on a minimization of the generalized Gross–Pitaevskii energy functional in a trapped rotating Fermi superfluid gas. By a Bogoliubov-like transformation we find that the coarse-grained average of the atomic density varies as inverted parabola in three dimensional cases; the Fermi superfluid in the BEC regime enters into the lowest Landau level at fast rotation, in which the vortices form an almost regular triangular lattice over a central region and the vortex lattice is expanded along the radial direction in the outer region; the fluid in the unitarity and BCS regimes occupies many low-lying Landau levels, in which a trapped gas with a triangular vortex lattice has a superfluid core surrounded by a normal gas. The calculation is qualitatively consistent with recent numerical and experimental data both in the vortex lattice structure and vortex numbers and in the density profiles versus the stirring frequency in the whole BCS–BEC crossover. - Highlights: ► We present an analysis of vortex lattice in an interacting trapped rotating Fermi superfluid gas. ► Decomposing the vortex from the condensate, we can explain the vortex lattice. ► The calculation is consistent with numerical and experimental data. ► It can characterize experimentally properties in different regimes of the BCS–BEC crossover.

The internal energy and thermodynamic behaviour of a boson gas below the Bose-Einstein temperature

International Nuclear Information System (INIS)

Deeney, F.A.; O'Leary, J.P.

2011-01-01

We have examined the issue of the kinetic energy of particles in the ground state of an ideal boson gas. By assuming that the particles, on dropping into the ground state, retain the kinetic energy they possess at the Bose-Einstein temperature T B , we obtain new expressions for the pressure and internal energy of the gas below T B , that are free of the difficulties associated with the corresponding expressions in current theory. Furthermore, these new equations yield a value for the maximum density temperature in liquid 4 He that is very close to the measured value. - Highlights: → A new equation of state for an ideal boson gas that is anomaly-free. → A prediction of the existence of a density maximum in all ideal boson gases. → Calculation of the temperature at which a density maximum will occur in liquid 4 He.

Relevance of Bose-Einstein condensation to the interference of two independent Bose gases

International Nuclear Information System (INIS)

Iazzi, Mauro; Yuasa, Kazuya

2011-01-01

Interference of two independently prepared ideal Bose gases is discussed, on the basis of the idea of measurement-induced interference. It is known that, even if the number of atoms in each gas is individually fixed finite and the symmetry of the system is not broken, an interference pattern is observed on each single snapshot. The key role is played by the Hanbury Brown and Twiss effect, which leads to an oscillating pattern of the cloud of identical atoms. Then, how essential is the Bose-Einstein condensation to the interference? In this work, we describe two ideal Bose gases trapped in two separate three-dimensional harmonic traps at a finite temperature T, using the canonical ensembles (with fixed numbers of atoms). We compute the full statistics of the snapshot profiles of the expanding and overlapping gases released from the traps. We obtain a simple formula valid for finite T, which shows that the average fringe spectrum (average fringe contrast) is given by the purity of each gas. The purity is known to be a good measure of condensation, and the formula clarifies the relevance of the condensation to the interference. The results for T=0, previously known in the literature, can be recovered from our analysis. The fluctuation of the interference spectrum is also studied, and it is shown that the fluctuation is vanishingly small only below the critical temperature T c , meaning that interference pattern is certainly observed on every snapshot below T c . The fact that the number of atoms is fixed in the canonical ensemble is crucial to this vanishing fluctuation.

Aspects of hyperspherical adiabaticity in an atomic-gas Bose-Einstein condensate

International Nuclear Information System (INIS)

Kushibe, Daisuke; Mutou, Masaki; Morishita, Toru; Watanabe, Shinichi; Matsuzawa, Michio

2004-01-01

Excitation of an atomic-gas Bose-Einstein condensate (BEC) in the zeroth-order ground-state channel is studied with the hyperspherical adiabatic method of Bohn et al. [Bohn et al., Phys. Rev. A 58, 584 (1998)] suitably generalized to accommodate the anisotropic trapping potential. The method exploits the system's size as an adiabatic parameter so that the explicit size dependence is immediately conducive to the virial theorem. The oscillation frequencies associated with the monopole (breathing) and quadrupole modes thus emerge naturally and converge to the well-known Thomas-Fermi limits. Analysis of the single-particle density and the projected excitation wave function shows that the excitation in the single hyperspherical ground-state channel merely represents a progressive increase in occupancy of the first excited single-particle state. The work paves the way for applying the adiabatic picture to other BEC phenomena

Fluctuation-induced forces in confined ideal and imperfect Bose gases.

Science.gov (United States)

Diehl, H W; Rutkevich, Sergei B

2017-06-01

Fluctuation-induced ("Casimir") forces caused by thermal and quantum fluctuations are investigated for ideal and imperfect Bose gases confined to d-dimensional films of size ∞^{d-1}×D under periodic (P), antiperiodic (A), Dirichlet-Dirichlet (DD), Neumann-Neumann (NN), and Robin (R) boundary conditions (BCs). The full scaling functions Υ_{d}^{BC}(x_{λ}=D/λ_{th},x_{ξ}=D/ξ) of the residual reduced grand potential per area φ_{res,d}^{BC}(T,μ,D)=D^{-(d-1)}Υ_{d}^{BC}(x_{λ},x_{ξ}) are determined for the ideal gas case with these BCs, where λ_{th} and ξ are the thermal de Broglie wavelength and the bulk correlation length, respectively. The associated limiting scaling functions Θ_{d}^{BC}(x_{ξ})≡Υ_{d}^{BC}(∞,x_{ξ}) describing the critical behavior at the bulk condensation transition are shown to agree with those previously determined from a massive free O(2) theory for BC=P,A,DD,DN,NN. For d=3, they are expressed in closed analytical form in terms of polylogarithms. The analogous scaling functions Υ_{d}^{BC}(x_{λ},x_{ξ},c_{1}D,c_{2}D) and Θ_{d}^{R}(x_{ξ},c_{1}D,c_{2}D) under the RBCs (∂_{z}-c_{1})ϕ|_{z=0}=(∂_{z}+c_{2})ϕ|_{z=D}=0 with c_{1}≥0 and c_{2}≥0 are also determined. The corresponding scaling functions Υ_{∞,d}^{P}(x_{λ},x_{ξ}) and Θ_{∞,d}^{P}(x_{ξ}) for the imperfect Bose gas are shown to agree with those of the interacting Bose gas with n internal degrees of freedom in the limit n→∞. Hence, for d=3, Θ_{∞,d}^{P}(x_{ξ}) is known exactly in closed analytic form. To account for the breakdown of translation invariance in the direction perpendicular to the boundary planes implied by free BCs such as DDBCs, a modified imperfect Bose gas model is introduced that corresponds to the limit n→∞ of this interacting Bose gas. Numerically and analytically exact results for the scaling function Θ_{∞,3}^{DD}(x_{ξ}) therefore follow from those of the O(2n)ϕ^{4} model for n→∞.

Condensate fluctuations of interacting Bose gases within a microcanonical ensemble.

Science.gov (United States)

Wang, Jianhui; He, Jizhou; Ma, Yongli

2011-05-01

Based on counting statistics and Bogoliubov theory, we present a recurrence relation for the microcanonical partition function for a weakly interacting Bose gas with a finite number of particles in a cubic box. According to this microcanonical partition function, we calculate numerically the distribution function, condensate fraction, and condensate fluctuations for a finite and isolated Bose-Einstein condensate. For ideal and weakly interacting Bose gases, we compare the condensate fluctuations with those in the canonical ensemble. The present approach yields an accurate account of the condensate fluctuations for temperatures close to the critical region. We emphasize that the interactions between excited atoms turn out to be important for moderate temperatures.

Perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases.

Science.gov (United States)

Mohammadzadeh, Hosein; Adli, Fereshteh; Nouri, Sahereh

2016-12-01

We investigate perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases. We show that the intrinsic statistical interaction of nonextensive Bose (Fermi) gas is attractive (repulsive) similar to the extensive case but the value of thermodynamic curvature is changed by a nonextensive parameter. In contrary to the extensive ideal classical gas, the nonextensive one may be divided to two different regimes. According to the deviation parameter of the system to the nonextensive case, one can find a special value of fugacity, z^{*}, where the sign of thermodynamic curvature is changed. Therefore, we argue that the nonextensive parameter induces an attractive (repulsive) statistical interaction for zz^{*}) for an ideal classical gas. Also, according to the singular point of thermodynamic curvature, we consider the condensation of nonextensive Boson gas.

Comparison between microscopic methods for finite-temperature Bose gases

DEFF Research Database (Denmark)

Cockburn, S.P.; Negretti, Antonio; Proukakis, N.P.

2011-01-01

We analyze the equilibrium properties of a weakly interacting, trapped quasi-one-dimensional Bose gas at finite temperatures and compare different theoretical approaches. We focus in particular on two stochastic theories: a number-conserving Bogoliubov (NCB) approach and a stochastic Gross...... on different thermodynamic ensembles (NCB, canonical; SGPE, grand-canonical), they yield the correct condensate statistics in a large Bose-Einstein condensate (BEC) (strong enough particle interactions). For smaller systems, the SGPE results are prone to anomalously large number fluctuations, well known...

New state of matter: Bose-Einstein condensation

International Nuclear Information System (INIS)

Anon.

1995-01-01

70 years after work by the Indian physicist Satyendra Nath Bose led Einstein to predict the existence of a new state of matter, the Bose-Einstein condensate has finally been seen. The discovery was made in July by a team from Colorado, and was followed one month later by a second sighting at Rice University at Houston, Texas. It is Bose's theoretical framework governing the behaviour of the particles we now call bosons which led to Einstein's prediction. Unlike fermions, which obey the Pauli exclusion principle of only one resident particle per allowed quantum state, any number of bosons can pack into an identical quantum state. This led Einstein to suggest that under certain conditions, bosons would lose their individual identities, condensing into a kind of 'superboson'. This condensate forms when the quantum mechanical waves of neighbouring bosons overlap, hiding the identity of the individual particles. Such a condition is difficult to achieve, since most long-lived bosons are composite particles which tend to interact and stick together before a condensate can emerge. Extremely low temperatures and high densities are required to overcome this problem. As bosons lose energy and cool down, their wavelengths become longer, and they can be packed close enough together to merge into a condensate. Up until now, however, the extreme conditions needed have not been attainable. Nevertheless, hints of the Bose- Einstein condensate have been inferred in phenomena such as superconductivity and liquid helium superfluidity. Condensates could also play an important role in particle physics and cosmology, explaining, for example, why the pion as a bound quark-antiquark state is so much lighter than the three-quark proton. A hunt to create a pure Bose- Einstein condensate has been underway for over 15 years, with different groups employing different techniques to cool their bosons. The two recent successes have been achieved by incorporating several

The ideal Bose-Einstein gas, revisited

International Nuclear Information System (INIS)

Ziff, R.M.; Uhlenbeck, G.E.; Kac, M.

1977-01-01

Some questions concerning the ideal Bose-Einstein gas are reviewed and examined further. The bulk behavior including the condensation phenomenon is characterized by the thermodynamical properties, occupations of the states and their fluctuations, and the properties of the density matrices, including the diagonal and off-diagonal long range orders. Particular attention is focused on the difference between the canonical and grand canonical ensembles and a case is made that the latter does not represent any physical system in the condensed region. The properties in a finite region are also examined to study the approach to the bulk limit and secondly to derive the surface properties such as the surface tension (due to the boundary). This is mainly done for the special case of a rectangular parallelopiped (box) for various boundary conditions. The question of the asymptotic behavior of the fluctuations in the occupation of the ground state in the condensed region in the canonical ensemble is examined for these systems. Finally, the local properties near the wall of a half infinite system are calculated and discussed. The surface properties also follow this way and agree with the strictly thermodynamic result. Although it is not intended to be a complete review, it is largely self-contained, with the first section containing the basic formulas and a discussion of some general concepts which will be needed. Especially discussed in detail are the extra considerations that are needed in thermodynamics and statistical mechanics to include the surface properties, and the quantum hierarchy of the density matrices and local conservation laws. In the concluding remarks several problems are mentioned which need further analysis and clarification. (Auth.)

Thermalization of a quenched Bose-Josephson junction

Energy Technology Data Exchange (ETDEWEB)

Posazhennikova, Anna [Royal Holloway, University of London (United Kingdom); Trujillo-Martinez, Mauricio; Kroha, Johann [Universitaet Bonn (Germany)

2015-07-01

The experimental realization and control of quantum systems isolated from the environment, in ultracold atomic gases relaunched the interest in the fundamental non-equilibrium problem of how a finite system approaches thermal equilibrium. Despite intensive research there is still no conclusive answer to this question. We investigate theoretically how a quenched Bose-Josephson junction, where the Josephson coupling is switched on instantaneously, approaches its stationary state. We use the field theoretical approach for bosons out of equilibrium in a trap with discrete levels, developed by us previously. In this approach the operators for Bose-Einstein condensate (BEC) particles are treated on mean-field level, while excitations of the Bose gas in higher trap levels are treated fully quantum-mechanically. This leads to coupled equations of motion for the BEC amplitudes (Gross-Pitaevskii equation) and the quasiparticle propagators. The inelastic quasiparticle collisions responsible for the system relaxation during the time-dependent evolution are described within self-consistent second-order approximation.

Quantum coherence due to Bose-Einstein condensation of parametrically driven magnons

International Nuclear Information System (INIS)

Demokritov, S O; Demidov, V E; Dzyapko, O; Melkov, G A; Slavin, A N

2008-01-01

The room-temperature kinetics and thermodynamics of the magnon gas driven by microwave pumping has been investigated by means of the Brillouin light scattering (BLS) technique. We show that for high enough pumping powers the quantum relaxation of the driven gas results in a quasi-equilibrium state described by the Bose-Einstein statistics with a nonzero chemical potential. Further increase of the pumping power causes a Bose-Einstein condensation in the magnon gas documented by an observation of the magnon accumulation at the lowest energy level. Using the sensitivity of the BLS to the coherence degree of the scattering magnons, we confirm the spontaneous emergence of coherence of the magnons accumulated at the bottom of the spectrum, if their density exceeds a critical value

Mean-field theory of anyons near Bose statistics

International Nuclear Information System (INIS)

McCabe, J.; MacKenzie, R.

1992-01-01

The validity of a mean-field approximation for a boson-based free anyon gas near Bose statistics is shown. The magnetic properties of the system is discussed in the approximation that the statistical magnetic field is uniform. It is proved that the anyon gas does not exhibit a Meissner effect in the domain of validity the approximation. (K.A.) 7 refs

Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus

International Nuclear Information System (INIS)

Teichmann, M.

2007-09-01

We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between 6 Li and 7 Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus; Atomes de lithium-6 ultra froids dans la transition BEC-BCS: experiences et construction d'un montage experimental

Energy Technology Data Exchange (ETDEWEB)

Teichmann, M

2007-09-15

We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between {sup 6}Li and {sup 7}Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus; Atomes de lithium-6 ultra froids dans la transition BEC-BCS: experiences et construction d'un montage experimental

Energy Technology Data Exchange (ETDEWEB)

Teichmann, M

2007-09-15

We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between {sup 6}Li and {sup 7}Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

Coherent decay of positronium bose condensate

International Nuclear Information System (INIS)

Vanyashin, V.S.

1992-07-01

The rate of self-stimulated emission of photon pairs by pseudoscalar particles from Bose condensate is calculated. Growing with density this rate exceeds the density independent rate of spontaneous two photon decay at plausible density values of positronium gas, thus opening in principle, the way to the annihilation gamma ray laser realization. (author). 2 refs

Superfluidity and BCS-BEC crossover of ultracold atomic Fermi gases in mixed dimensions

Science.gov (United States)

Zhang, Leifeng; Chen, Qijin

Atomic Fermi gases have been under active investigation in the past decade. Here we study the superfluid and pairing phenomena of a two-component ultracold atomic Fermi gas in the presence of mixed dimensionality, in which one component is confined on a 1D optical lattice whereas the other is free in the 3D continuum. We assume a short-range pairing interaction and determine the superfluid transition temperature Tc and the phase diagram for the entire BCS-BEC crossover, using a pairing fluctuation theory which includes self-consistently the contributions of finite momentum pairs. We find that, as the lattice depth increases and the lattice spacing decreases, the behavior of Tc becomes very similar to that of a population imbalance Fermi gas in a simple 3D continuum. There is no superfluidity even at T = 0 below certain threshold of pairing strength in the BCS regime. Nonmonotonic Tc behavior and intermediate temperature superfluidity emerge, and for deep enough lattice, the Tc curve will split into two parts. Implications for experiment will be discussed. References: 1. Q.J. Chen, Ioan Kosztin, B. Janko, and K. Levin, Phys. Rev. B 59, 7083 (1999). 2. Chih-Chun Chien, Qijin Chen, Yan He, and K. Levin, Phys. Rev. Lett. 97, 090402(2006). Work supported by NSF of China and the National Basic Research Program of China.

Shrinking of a condensed fermionic cloud in a trap approaching the Bose-Einstein condensation limit

International Nuclear Information System (INIS)

Perali, A.; Pieri, P.; Strinati, G. C.

2003-01-01

We determine the zero-temperature density profile of a cloud of fermionic atoms in a trap subject to a mutual attractive interaction, as the strength of the interaction is progressively increased. We find a significant decrease of the size of the atomic cloud as it evolves from the weak-coupling regime of overlapping Cooper pairs to the strong-coupling (Bose-Einstein) regime of nonoverlapping bound-fermion pairs. Most significantly, we find a pronounced increase of the value of the density at the center of the trap (even by an order of magnitude) when evolving between the two regimes. Our results are based on a generalized Thomas-Fermi approximation for the superfluid state, which covers continuously all coupling regimes

Fluctuation-induced forces in confined ideal and imperfect Bose gases

Science.gov (United States)

Diehl, H. W.; Rutkevich, Sergei B.

2017-06-01

Fluctuation-induced ("Casimir") forces caused by thermal and quantum fluctuations are investigated for ideal and imperfect Bose gases confined to d -dimensional films of size ∞d -1×D under periodic (P), antiperiodic (A), Dirichlet-Dirichlet (DD), Neumann-Neumann (NN), and Robin (R) boundary conditions (BCs). The full scaling functions ΥdBC(xλ=D /λth ,xξ=D /ξ ) of the residual reduced grand potential per area φres,dBC(T ,μ ,D ) =D-(d -1 )ΥdBC(xλ,xξ) are determined for the ideal gas case with these BCs, where λth and ξ are the thermal de Broglie wavelength and the bulk correlation length, respectively. The associated limiting scaling functions ΘdBC(xξ) ≡ΥdBC(∞ ,xξ) describing the critical behavior at the bulk condensation transition are shown to agree with those previously determined from a massive free O (2 ) theory for BC=P,A,DD,DN,NN . For d =3 , they are expressed in closed analytical form in terms of polylogarithms. The analogous scaling functions ΥdBC(xλ,xξ,c1D ,c2D ) and ΘdR(xξ,c1D ,c2D ) under the RBCs (∂z-c1) ϕ |z=0=(∂z+c2) ϕ | z =D=0 with c1≥0 and c2≥0 are also determined. The corresponding scaling functions Υ∞,d P(xλ,xξ) and Θ∞,d P(xξ) for the imperfect Bose gas are shown to agree with those of the interacting Bose gas with n internal degrees of freedom in the limit n →∞ . Hence, for d =3 , Θ∞,d P(xξ) is known exactly in closed analytic form. To account for the breakdown of translation invariance in the direction perpendicular to the boundary planes implied by free BCs such as DDBCs, a modified imperfect Bose gas model is introduced that corresponds to the limit n →∞ of this interacting Bose gas. Numerically and analytically exact results for the scaling function Θ∞,3 DD(xξ) therefore follow from those of the O (2 n ) ϕ4 model for n →∞ .

Multiple condensed phases in attractively interacting Bose systems

Czech Academy of Sciences Publication Activity Database

Männel, M.; Morawetz, K.; Lipavský, Pavel

2010-01-01

Roč. 12, č. 3 (2010), 033013/1-033013/9 ISSN 1367-2630 Institutional research plan: CEZ:AV0Z10100521 Keywords : Bose gas * T-matrix * Evan-Rashid transition Subject RIV: BE - Theoretical Physics Impact factor: 3.849, year: 2010

Bose-Einstein condensation in real space

International Nuclear Information System (INIS)

Valencia, J.J.; Llano, M. de; Solis, M.A.

2004-01-01

We show how Bose-Einstein condensation (BEC) occurs not only in momentum space but also in coordinate (or real) space. Analogies between the isotherms of a van der Waals classical gas of extended (or finite-diameter) identical atoms and the point (or zero-diameter) particles of an ideal BE gas allow concluding that, in contrast with the classical case, the volume per particle vanishes in the pure BE condensate phase precisely because the boson diameters are zero. Thus a BE condensate forms in real space without exhibiting a liquid branch as does the classical gas. (Author)

Effects of impurity and Bose-Fermi interactions on the transition temperature of a dilute dipolar Bose-Einstein condensation in trapped Bose-Fermi mixtures

Science.gov (United States)

Yavari, H.; Mokhtari, M.

2014-03-01

The effects of impurity and Bose-Fermi interactions on the transition temperature of a dipolar Bose-Einstein condensation in trapped Bose-Fermi mixture, by using the two-fluid model, are investigated. The shift of the transition temperature consists of four contributions due to contact, Bose-Fermi, dipole-dipole, and impurity interactions. We will show that in the presence of an anisotropic trap, the Bose-Fermi correction to the shift of transition temperature due to the excitation spectra of the thermal part is independent of anisotropy factor. Applying our results to trapped Bose-Fermi mixtures shows that, by knowing the impurity effect, the shift of the transition temperature due to Bose-Fermi interaction could be measured for isotropic trap (dipole-dipole contributions is zero) and Feshbach resonance technique (contact potential contribution is negligible).

Anomalous Hydrodynamics and Normal Fluids in Rapidly Rotating Bose-Einstein Condensates

International Nuclear Information System (INIS)

Bourne, A.; Wilkin, N.K.; Gunn, J.M.F.

2006-01-01

In rapidly rotating condensed Bose systems we show that there is a regime of anomalous hydrodynamics which coincides with the mean field quantum Hall regime. A consequence is the absence of a normal fluid in any conventional sense. However, even the superfluid hydrodynamics is not described by conventional Bernoulli and continuity equations. We show that there are constraints which connect spatial variations of density and phase and that the vortex positions are not the simplest description of the dynamics. We demonstrate, inter alia, a simple relation between vortices and surface waves. We show that the surface waves can emulate a 'normal fluid', allowing dissipation by energy and angular momentum absorbtion from vortex motion in the trap. The time scale is sensitive to the initial configuration, which can lead to long-lived vortex patches--perhaps related to those observed at JILA

Anomalous Hydrodynamics and Normal Fluids in Rapidly Rotating Bose-Einstein Condensates

Science.gov (United States)

Bourne, A.; Wilkin, N. K.; Gunn, J. M. F.

2006-06-01

In rapidly rotating condensed Bose systems we show that there is a regime of anomalous hydrodynamics which coincides with the mean field quantum Hall regime. A consequence is the absence of a normal fluid in any conventional sense. However, even the superfluid hydrodynamics is not described by conventional Bernoulli and continuity equations. We show that there are constraints which connect spatial variations of density and phase and that the vortex positions are not the simplest description of the dynamics. We demonstrate, inter alia, a simple relation between vortices and surface waves. We show that the surface waves can emulate a “normal fluid,” allowing dissipation by energy and angular momentum absorbtion from vortex motion in the trap. The time scale is sensitive to the initial configuration, which can lead to long-lived vortex patches—perhaps related to those observed at JILA.

Slow quench dynamics of a one-dimensional Bose gas confined to an optical lattice.

Science.gov (United States)

Bernier, Jean-Sébastien; Roux, Guillaume; Kollath, Corinna

2011-05-20

We analyze the effect of a linear time variation of the interaction strength on a trapped one-dimensional Bose gas confined to an optical lattice. The evolution of different observables such as the experimentally accessible on site particle distribution are studied as a function of the ramp time by using time-dependent numerical techniques. We find that the dynamics of a trapped system typically displays two regimes: For long ramp times, the dynamics is governed by density redistribution, while at short ramp times, local dynamics dominates as the evolution is identical to that of an homogeneous system. In the homogeneous limit, we also discuss the nontrivial scaling of the energy absorbed with the ramp time.

Superfluidity of hyperon-mixed neutron stars

International Nuclear Information System (INIS)

Takatsuka, Tatsuyuki; Nishizaki, Shigeru; Yamamoto, Yasuo; Tamagaki, Ryozo

2002-01-01

Superfluidity of hyperons (Y) admixed in neutron star cores is investigated by a realistic approach. It is found that hyperons such as Λ and Σ - are likely to be superfluid due mainly to their large effective masses in the medium, in addition to their 1 S 0 -pairing attraction not so different from that of nucleons. Also the existence of nucleon superfluidity at high-density is investigated under a developed Y-contamination. It is found that the density change of nucleon components due to the Y-mixing does not work for the realization of n-superfluid and makes the existence of p-superfluid more unlikely, as compared to the normal case without the Y-mixing. (author)

Spinning superfluid 4He nanodroplets

Science.gov (United States)

Ancilotto, Francesco; Barranco, Manuel; Pi, Martí

2018-05-01

We have studied spinning superfluid 4He nanodroplets at zero temperature using density functional theory. Due to the irrotational character of the superfluid flow, the shapes of the spinning nanodroplets are very different from those of a viscous normal fluid drop in steady rotation. We show that when vortices are nucleated inside the superfluid droplets, their morphology, which evolves from axisymmetric oblate to triaxial prolate to two-lobed shapes, is in good agreement with experiments. The presence of vortex arrays confers to the superfluid droplets the rigid-body behavior of a normal fluid in steady rotation, and this is the ultimate reason for the surprising good agreement between recent experiments and the classical models used for their description.

Anindita Bose

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education. Anindita Bose. Articles written in Resonance – Journal of Science Education. Volume 6 Issue 11 November 2001 pp 18-26 General Article. Necklaces, Periodic Points and Permutation Representations - Fermat's Little Theorem · Somnath Basu Anindita Bose ...

Dark matter superfluidity and galactic dynamics

Directory of Open Access Journals (Sweden)

Lasha Berezhiani

2016-02-01

Full Text Available We propose a unified framework that reconciles the stunning success of MOND on galactic scales with the triumph of the ΛCDM model on cosmological scales. This is achieved through the physics of superfluidity. Dark matter consists of self-interacting axion-like particles that thermalize and condense to form a superfluid in galaxies, with ∼mK critical temperature. The superfluid phonons mediate a MOND acceleration on baryonic matter. Our framework naturally distinguishes between galaxies (where MOND is successful and galaxy clusters (where MOND is not: dark matter has a higher temperature in clusters, and hence is in a mixture of superfluid and normal phase. The rich and well-studied physics of superfluidity leads to a number of striking observational signatures.

Berezinskii-Kosterlitz-Thouless crossover in a trapped atomic gas.

Science.gov (United States)

Hadzibabic, Zoran; Krüger, Peter; Cheneau, Marc; Battelier, Baptiste; Dalibard, Jean

2006-06-29

Any state of matter is classified according to its order, and the type of order that a physical system can possess is profoundly affected by its dimensionality. Conventional long-range order, as in a ferromagnet or a crystal, is common in three-dimensional systems at low temperature. However, in two-dimensional systems with a continuous symmetry, true long-range order is destroyed by thermal fluctuations at any finite temperature. Consequently, for the case of identical bosons, a uniform two-dimensional fluid cannot undergo Bose-Einstein condensation, in contrast to the three-dimensional case. However, the two-dimensional system can form a 'quasi-condensate' and become superfluid below a finite critical temperature. The Berezinskii-Kosterlitz-Thouless (BKT) theory associates this phase transition with the emergence of a topological order, resulting from the pairing of vortices with opposite circulation. Above the critical temperature, proliferation of unbound vortices is expected. Here we report the observation of a BKT-type crossover in a trapped quantum degenerate gas of rubidium atoms. Using a matter wave heterodyning technique, we observe both the long-wavelength fluctuations of the quasi-condensate phase and the free vortices. At low temperatures, the gas is quasi-coherent on the length scale set by the system size. As the temperature is increased, the loss of long-range coherence coincides with the onset of proliferation of free vortices. Our results provide direct experimental evidence for the microscopic mechanism underlying the BKT theory, and raise new questions regarding coherence and superfluidity in mesoscopic systems.

Shell Models of Superfluid Turbulence

International Nuclear Information System (INIS)

Wacks, Daniel H; Barenghi, Carlo F

2011-01-01

Superfluid helium consists of two inter-penetrating fluids, a viscous normal fluid and an inviscid superfluid, coupled by a mutual friction. We develop a two-fluid shell model to study superfluid turbulence and investigate the energy spectra and the balance of fluxes between the two fluids in a steady state. At sufficiently low temperatures a 'bottle-neck' develops at high wavenumbers suggesting the need for a further dissipative effect, such as the Kelvin wave cascade.

Quantum phase transitions of light in a dissipative Dicke-Bose-Hubbard model

Science.gov (United States)

Wu, Ren-Cun; Tan, Lei; Zhang, Wen-Xuan; Liu, Wu-Ming

2017-09-01

The impact that the environment has on the quantum phase transition of light in the Dicke-Bose-Hubbard model is investigated. Based on the quasibosonic approach, mean-field theory, and perturbation theory, the formulation of the Hamiltonian, the eigenenergies, and the superfluid order parameter are obtained analytically. Compared with the ideal cases, the order parameter of the system evolves with time as the photons naturally decay in their environment. When the system starts with the superfluid state, the dissipation makes the photons more likely to localize, and a greater hopping energy of photons is required to restore the long-range phase coherence of the localized state of the system. Furthermore, the Mott lobes depend crucially on the numbers of atoms and photons (which disappear) of each site, and the system tends to be classical with the number of atoms increasing; however, the atomic number is far lower than that expected under ideal circumstances. As there is an inevitable interaction between the coupled-cavity array and its surrounding environment in the actual experiments, the system is intrinsically dissipative. The results obtained here provide a more realistic image for characterizing the dissipative nature of quantum phase transitions in lossy platforms, which will offer valuable insight into quantum simulation of a dissipative system and which are helpful in guiding experimentalists in open quantum systems.

Non-thermal fixed points and solitons in a one-dimensional Bose gas

International Nuclear Information System (INIS)

Schmidt, Maximilian; Erne, Sebastian; Nowak, Boris; Sexty, Dénes; Gasenzer, Thomas

2012-01-01

Single-particle momentum spectra for a dynamically evolving one-dimensional Bose gas are analysed in the semi-classical wave limit. Representing one of the simplest correlation functions, these provide information on a possible universal scaling behaviour. Motivated by the previously discovered connection between (quasi-) topological field configurations, strong wave turbulence and non-thermal fixed points of quantum field dynamics, soliton formation is studied with respect to the appearance of transient power-law spectra. A random-soliton model is developed for describing the spectra analytically, and the analogies and differences between the emerging power laws and those found in a field theory approach to strong wave turbulence are discussed. The results open a new perspective on solitary wave dynamics from the point of view of critical phenomena far from thermal equilibrium and the possibility of studying this dynamics by experiment without the need for detecting solitons in situ. (paper)

Apparent de-wetting due to superfluid flow

CERN Document Server

Poujade, M; Rolley, E

2002-01-01

We have investigated the wetting behaviour of superfluid helium-4 on silicon. Surprisingly, we observe pseudo-de-wetting: though a thick superfluid film covers the substrate, the meniscus displays a finite contact angle which decreases from about 5 deg C at low temperature down to zero at the superfluid transition. We show that this behaviour can be explained by a pressure decrease due to a superfluid flow, closely related to the Kontorovich effect. (authors)

Dynamics of quantised vortices in superfluids

CERN Document Server

Sonin, Edouard B

2016-01-01

A comprehensive overview of the basic principles of vortex dynamics in superfluids, this book addresses the problems of vortex dynamics in all three superfluids available in laboratories (4He, 3He, and BEC of cold atoms) alongside discussions of the elasticity of vortices, forces on vortices, and vortex mass. Beginning with a summary of classical hydrodynamics, the book guides the reader through examinations of vortex dynamics from large scales to the microscopic scale. Topics such as vortex arrays in rotating superfluids, bound states in vortex cores and interaction of vortices with quasiparticles are discussed. The final chapter of the book considers implications of vortex dynamics to superfluid turbulence using simple scaling and symmetry arguments. Written from a unified point of view that avoids complicated mathematical approaches, this text is ideal for students and researchers working with vortex dynamics in superfluids, superconductors, magnetically ordered materials, neutron stars and cosmological mo...

Bose-Einstein condensation in a general static homogeneous magnetic fieldinebreak and the effective action: The nonrelativistic ideal gas

International Nuclear Information System (INIS)

Toms, D.J.

1995-01-01

We consider the problem of Bose-Einstein condensation for a system of nonrelativistic spin-0 bosons in a space of arbitrary dimension D. A general static homogeneous magnetic field is imposed. The effective action approach and ζ-function regularization are used. If D=2δ or 2δ+1, a constant magnetic field is characterized by δ independent components. If p≤δ of these components are nonzero, the condition for Bose-Einstein condensation to occur is D-2p≥3. This means that if D=2δ, then Bose-Einstein condensation never occurs for p=δ-1 or δ. If D=2δ+1, Bose-Einstein condensation never occurs for p=δ. For D-2p≥3, Bose-Einstein condensation does occur, and we show how it may be interpreted as symmetry breaking to give a ground state which is not constant

Quantized vortices in superfluids and superconductors

International Nuclear Information System (INIS)

Thoulessi, D.J.; Wexler, C.; Ping Ao, Ping; Niu, Qian; Geller, M.R.

1998-01-01

We give a general review of recent developments in the theory of vortices in superfluids and superconductors, discussing why the dynamics of vortices is important, and why some key results are still controversial. We discuss work that we have done on the dynamics of quantized vortices in a superfluid. Despite the fact that this problem has been recognized as important for forty years, there is still a lot of controversy about the forces on and masses of quantized vortices. We think that one can get unambiguous answers by considering a broken symmetry state that consists of one vortex in an infinite ideal system. We argue for a Magnus force that is proportional to the superfluid density, and we find that the effective mass density of a vortex in a neutral superfluid is divergent at low frequencies. We have generalized some of the results for a neutral superfluid to a charged system. (Copyright (1998) World Scientific Publishing Co. Pte. Ltd)

Bose-Einstein condensation of photons in a 'white-wall' photon box

International Nuclear Information System (INIS)

Klaers, Jan; Schmitt, Julian; Vewinger, Frank; Weitz, Martin

2011-01-01

Bose-Einstein condensation, the macroscopic ground state occupation of a system of bosonic particles below a critical temperature, has been observed in cold atomic gases and solid-state physics quasiparticles. In contrast, photons do not show this phase transition usually, because in Planck's blackbody radiation the particle number is not conserved and at low temperature the photons disappear in the walls of the system. Here we report on the realization of a photon Bose-Einstein condensate in a dye-filled optical microcavity, which acts as a 'white-wall' photon box. The cavity mirrors provide a trapping potential and a non-vanishing effective photon mass, making the system formally equivalent to a two-dimensional gas of trapped massive bosons. Thermalization of the photon gas is reached in a number conserving way by multiple scattering off the dye molecules. Signatures for a BEC upon increased photon density are: a spectral distribution that shows Bose-Einstein distributed photon energies with a macroscopically populated peak on top of a broad thermal wing, the observed threshold of the phase transition showing the predicted absolute value and scaling with resonator geometry, and condensation appearing at the trap centre even for a spatially displaced pump spot.

Bose-Einstein condensation of photons in a 'white-wall' photon box

Science.gov (United States)

Klärs, Jan; Schmitt, Julian; Vewinger, Frank; Weitz, Martin

2011-01-01

Bose-Einstein condensation, the macroscopic ground state occupation of a system of bosonic particles below a critical temperature, has been observed in cold atomic gases and solid-state physics quasiparticles. In contrast, photons do not show this phase transition usually, because in Planck's blackbody radiation the particle number is not conserved and at low temperature the photons disappear in the walls of the system. Here we report on the realization of a photon Bose-Einstein condensate in a dye-filled optical microcavity, which acts as a "white-wall" photon box. The cavity mirrors provide a trapping potential and a non-vanishing effective photon mass, making the system formally equivalent to a two-dimensional gas of trapped massive bosons. Thermalization of the photon gas is reached in a number conserving way by multiple scattering off the dye molecules. Signatures for a BEC upon increased photon density are: a spectral distribution that shows Bose-Einstein distributed photon energies with a macroscopically populated peak on top of a broad thermal wing, the observed threshold of the phase transition showing the predicted absolute value and scaling with resonator geometry, and condensation appearing at the trap centre even for a spatially displaced pump spot.

Discrete Bose-Einstein systems in a box with low adiabatic invariant

International Nuclear Information System (INIS)

Vlad, V.I.; Ionescu-Pallas, N.

2002-03-01

The Bose-Einstein energy spectrum of a quantum gas, confined in a (cubic) box, is discrete and strongly dependent on the box geometry and temperature, for low product of the atomic mass number, A at and the adiabatic invariant, TV 2/3 , i.e. on γ=A at TV 2/3 . Even within the approximation of noninteracting particles in the gas, the calculation of the thermodynamic properties of Bose-Einstein systems turns out to be a difficult mathematical problem. It is solved in the textbooks and most papers by approximating the sums by integrals. The present study compares the total number of particles and the total energy obtained by summing up the exact contributions of the eigenvalues and their weights, for defined values of γ, to the results of the approximate integrals. Then, the passage from sums to integrals is done in a more rigorous manner and better analytical approximations are found. The corrected thermodynamic functions depend on γ. The critical temperature is corrected also in order to describe more accurately the discrete Bose-Einstein systems and their onset of the phase transition. (author)

Numerical methods for atomic quantum gases with applications to Bose-Einstein condensates and to ultracold fermions

International Nuclear Information System (INIS)

Minguzzi, A.; Succi, S.; Toschi, F.; Tosi, M.P.; Vignolo, P.

2004-01-01

The achievement of Bose-Einstein condensation in ultra-cold vapours of alkali atoms has given enormous impulse to the study of dilute atomic gases in condensed quantum states inside magnetic traps and optical lattices. High-purity and easy optical access make them ideal candidates to investigate fundamental issues on interacting quantum systems. This review presents some theoretical issues which have been addressed in this area and the numerical techniques which have been developed and used to describe them, from mean-field models to classical and quantum simulations for equilibrium and dynamical properties. After an introductory overview on dilute quantum gases, both in the homogeneus state and under harmonic or periodic confinement, the article is organized in three main sections. The first concerns Bose-condensed gases at zero temperature, with main regard to the properties of the ground state in different confinements and to collective excitations and transport in the condensate. Bose-Einstein-condensed gases at finite temperature are addressed in the next section, the main emphasis being on equilibrium properties and phase transitions and on dynamical and transport properties associated with the presence of the thermal cloud. Finally, the last section is focused on theoretical and computational issues that have emerged from the efforts to drive gases of fermionic atoms and boson-fermion mixtures deep into the quantum degeneracy regime, with the aim of realizing novel superfluids from fermion pairing. The attention given in this article to methods beyond standard mean-field approaches should make it a useful reference point for future advances in these areas

Fourth sound of holographic superfluids

International Nuclear Information System (INIS)

Yarom, Amos

2009-01-01

We compute fourth sound for superfluids dual to a charged scalar and a gauge field in an AdS 4 background. For holographic superfluids with condensates that have a large scaling dimension (greater than approximately two), we find that fourth sound approaches first sound at low temperatures. For condensates that a have a small scaling dimension it exhibits non-conformal behavior at low temperatures which may be tied to the non-conformal behavior of the order parameter of the superfluid. We show that by introducing an appropriate scalar potential, conformal invariance can be enforced at low temperatures.

Relaxation dynamics of a driven two-level system coupled to a Bose-Einstein condensate: application to quantum dot-dipolar exciton gas hybrid systems.

Science.gov (United States)

Kovalev, Vadim M; Tse, Wang-Kong

2017-11-22

We develop a microscopic theory for the relaxation dynamics of an optically pumped two-level system (TLS) coupled to a bath of weakly interacting Bose gas. Using Keldysh formalism and diagrammatic perturbation theory, expressions for the relaxation times of the TLS Rabi oscillations are derived when the boson bath is in the normal state and the Bose-Einstein condensate (BEC) state. We apply our general theory to consider an irradiated quantum dot coupled with a boson bath consisting of a two-dimensional dipolar exciton gas. When the bath is in the BEC regime, relaxation of the Rabi oscillations is due to both condensate and non-condensate fractions of the bath bosons for weak TLS-light coupling and pre dominantly due to the non-condensate fraction for strong TLS-light coupling. Our theory also shows that a phase transition of the bath from the normal to the BEC state strongly influences the relaxation rate of the TLS Rabi oscillations. The TLS relaxation rate is approximately independent of the pump field frequency and monotonically dependent on the field strength when the bath is in the low-temperature regime of the normal phase. Phase transition of the dipolar exciton gas leads to a non-monotonic dependence of the TLS relaxation rate on both the pump field frequency and field strength, providing a characteristic signature for the detection of BEC phase transition of the coupled dipolar exciton gas.

Bose, Prof. Indrani

Indian Academy of Sciences (India)

Home; Fellowship. Fellow Profile. Elected: 2000 Section: Physics. Bose, Prof. Indrani Ph.D. (Calcutta), FNASc. Date of birth: 15 August 1951. Specialization: Theoretical Condensed Matter Physics, Statistical Physics, Biological Physics and Systems Biology Address: Emeritus Scientist, Department of Physics, Bose Institute, ...

Thin accretion disks around cold Bose-Einstein condensate stars

Energy Technology Data Exchange (ETDEWEB)

Danila, Bogdan [Babes-Bolyai University, Department of Physics, Cluj-Napoca (Romania); Harko, Tiberiu [University College London, Department of Mathematics, London (United Kingdom); Kovacs, Zoltan

2015-05-15

Due to their superfluid properties some compact astrophysical objects, like neutron or quark stars, may contain a significant part of their matter in the form of a Bose-Einstein condensate (BEC). Observationally distinguishing between neutron/quark stars and BEC stars is a major challenge for this latter theoretical model. An observational possibility of indirectly distinguishing BEC stars from neutron/quark stars is through the study of the thin accretion disks around compact general relativistic objects. In the present paper, we perform a detailed comparative study of the electromagnetic and thermodynamic properties of the thin accretion disks around rapidly rotating BEC stars, neutron stars and quark stars, respectively. Due to the differences in the exterior geometry, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution, equilibrium radiation spectrum, and efficiency of energy conversion) are different for these classes of compact objects. Hence in this preliminary study we have pointed out some astrophysical signatures that may allow one to observationally discriminate between BEC stars and neutron/quark stars. (orig.)

Dynamic and energetic stabilization of persistent currents in Bose-Einstein condensates

KAUST Repository

Law, Kody; Neely, T. W.; Kevrekidis, P. G.; Anderson, B. P.; Bradley, A. S.; Carretero-Gonzá lez, R.

2014-01-01

We study conditions under which vortices in a highly oblate harmonically trapped Bose-Einstein condensate (BEC) can be stabilized due to pinning by a blue-detuned Gaussian laser beam, with particular emphasis on the potentially destabilizing effects of laser beam positioning within the BEC. Our approach involves theoretical and numerical exploration of dynamically and energetically stable pinning of vortices with winding number up to S=6, in correspondence with experimental observations. Stable pinning is quantified theoretically via Bogoliubov-de Gennes excitation spectrum computations and confirmed via direct numerical simulations for a range of conditions similar to those of experimental observations. The theoretical and numerical results indicate that the pinned winding number, or equivalently the winding number of the superfluid current about the laser beam, decays as a laser beam of fixed intensity moves away from the BEC center. Our theoretical analysis helps explain previous experimental observations and helps define limits of stable vortex pinning for future experiments involving vortex manipulation by laser beams.

Dynamic and energetic stabilization of persistent currents in Bose-Einstein condensates

KAUST Repository

Law, Kody

2014-05-09

We study conditions under which vortices in a highly oblate harmonically trapped Bose-Einstein condensate (BEC) can be stabilized due to pinning by a blue-detuned Gaussian laser beam, with particular emphasis on the potentially destabilizing effects of laser beam positioning within the BEC. Our approach involves theoretical and numerical exploration of dynamically and energetically stable pinning of vortices with winding number up to S=6, in correspondence with experimental observations. Stable pinning is quantified theoretically via Bogoliubov-de Gennes excitation spectrum computations and confirmed via direct numerical simulations for a range of conditions similar to those of experimental observations. The theoretical and numerical results indicate that the pinned winding number, or equivalently the winding number of the superfluid current about the laser beam, decays as a laser beam of fixed intensity moves away from the BEC center. Our theoretical analysis helps explain previous experimental observations and helps define limits of stable vortex pinning for future experiments involving vortex manipulation by laser beams.

Bose-Einstein condensation of light: general theory.

Science.gov (United States)

Sob'yanin, Denis Nikolaevich

2013-08-01

A theory of Bose-Einstein condensation of light in a dye-filled optical microcavity is presented. The theory is based on the hierarchical maximum entropy principle and allows one to investigate the fluctuating behavior of the photon gas in the microcavity for all numbers of photons, dye molecules, and excitations at all temperatures, including the whole critical region. The master equation describing the interaction between photons and dye molecules in the microcavity is derived and the equivalence between the hierarchical maximum entropy principle and the master equation approach is shown. The cases of a fixed mean total photon number and a fixed total excitation number are considered, and a much sharper, nonparabolic onset of a macroscopic Bose-Einstein condensation of light in the latter case is demonstrated. The theory does not use the grand canonical approximation, takes into account the photon polarization degeneracy, and exactly describes the microscopic, mesoscopic, and macroscopic Bose-Einstein condensation of light. Under certain conditions, it predicts sub-Poissonian statistics of the photon condensate and the polarized photon condensate, and a universal relation takes place between the degrees of second-order coherence for these condensates. In the macroscopic case, there appear a sharp jump in the degrees of second-order coherence, a sharp jump and kink in the reduced standard deviations of the fluctuating numbers of photons in the polarized and whole condensates, and a sharp peak, a cusp, of the Mandel parameter for the whole condensate in the critical region. The possibility of nonclassical light generation in the microcavity with the photon Bose-Einstein condensate is predicted.

Quench-Induced Breathing Mode of One-Dimensional Bose Gases

Science.gov (United States)

Fang, Bess; Carleo, Giuseppe; Johnson, Aisling; Bouchoule, Isabelle

2014-07-01

We measure the position- and momentum-space breathing dynamics of trapped one-dimensional Bose gases at finite temperature. The profile in real space reveals sinusoidal width oscillations whose frequency varies continuously through the quasicondensate to ideal Bose gas crossover. A comparison with theoretical models taking temperature into account is provided. In momentum space, we report the first observation of a frequency doubling in the quasicondensate regime, corresponding to a self-reflection mechanism due to the repulsive interactions. Such a mechanism is predicted for a fermionized system, and has not been observed to date. The disappearance of the frequency doubling through the crossover is mapped out experimentally, giving insights into the dynamics of the breathing evolution.

Quench-induced breathing mode of one-dimensional Bose gases.

Science.gov (United States)

Fang, Bess; Carleo, Giuseppe; Johnson, Aisling; Bouchoule, Isabelle

2014-07-18

We measure the position- and momentum-space breathing dynamics of trapped one-dimensional Bose gases at finite temperature. The profile in real space reveals sinusoidal width oscillations whose frequency varies continuously through the quasicondensate to ideal Bose gas crossover. A comparison with theoretical models taking temperature into account is provided. In momentum space, we report the first observation of a frequency doubling in the quasicondensate regime, corresponding to a self-reflection mechanism due to the repulsive interactions. Such a mechanism is predicted for a fermionized system, and has not been observed to date. The disappearance of the frequency doubling through the crossover is mapped out experimentally, giving insights into the dynamics of the breathing evolution.

Coherent magnon optics in a ferromagnetic spinor Bose-Einstein condensate.

Science.gov (United States)

Marti, G Edward; MacRae, Andrew; Olf, Ryan; Lourette, Sean; Fang, Fang; Stamper-Kurn, Dan M

2014-10-10

We measure the dispersion relation, gap, and magnetic moment of a magnon in the ferromagnetic F = 1 spinor Bose-Einstein condensate of (87)Rb. From the dispersion relation we measure an average effective mass 1.033(2)(stat)(10)(sys) times the atomic mass, as determined by interfering standing and running coherent magnon waves within the dense and trapped condensed gas. The measured mass is higher than theoretical predictions of mean-field and beyond-mean-field Beliaev theory for a bulk spinor Bose gas with s-wave contact interactions. We observe a magnon energy gap of h × 2.5(1)(stat)(2)(sys) Hz, which is consistent with the predicted effect of magnetic dipole-dipole interactions. These dipolar interactions may also account for the high magnon mass. The effective magnetic moment of -1.04(2)(stat)(8)(sys) times the atomic magnetic moment is consistent with mean-field theory.

Flowing holographic anyonic superfluid

Science.gov (United States)

Jokela, Niko; Lifschytz, Gilad; Lippert, Matthew

2014-10-01

We investigate the flow of a strongly coupled anyonic superfluid based on the holographic D3-D7' probe brane model. By analyzing the spectrum of fluctuations, we find the critical superfluid velocity, as a function of the temperature, at which the flow stops being dissipationless when flowing past a barrier. We find that at a larger velocity the flow becomes unstable even in the absence of a barrier.

Exact Local Correlations and Full Counting Statistics for Arbitrary States of the One-Dimensional Interacting Bose Gas

Science.gov (United States)

Bastianello, Alvise; Piroli, Lorenzo; Calabrese, Pasquale

2018-05-01

We derive exact analytic expressions for the n -body local correlations in the one-dimensional Bose gas with contact repulsive interactions (Lieb-Liniger model) in the thermodynamic limit. Our results are valid for arbitrary states of the model, including ground and thermal states, stationary states after a quantum quench, and nonequilibrium steady states arising in transport settings. Calculations for these states are explicitly presented and physical consequences are critically discussed. We also show that the n -body local correlations are directly related to the full counting statistics for the particle-number fluctuations in a short interval, for which we provide an explicit analytic result.

Broken superfluid in dense quark matter

Energy Technology Data Exchange (ETDEWEB)

Parganlija, Denis; Schmitt, Andreas [Institut fuer Theoretische Physik, Technische Universitaet Wien, 1040 Vienna (Austria); Alford, Mark [Department of Physics, Washington University St Louis, MO, 63130 (United States)

2014-07-01

Quark matter at high densities is a superfluid. Properties of the superfluid become highly non-trivial if the effects of strange-quark mass and the weak interactions are considered. These properties are relevant for a microscopic description of compact stars. We discuss the effect of a (small) explicitly symmetry-breaking term on the properties of a zero-temperature superfluid in a relativistic φ{sup 4} theory. If the U(1) symmetry is exact, chemical potential and superflow can be equivalently introduced either via (1) a background gauge field or (2) a topologically nontrivial mode. However, in the case of the explicitly broken symmetry, we demonstrate that the scenarios (1) and (2) lead to quantitatively different results for the mass of the pseudo-Goldstone mode and the critical velocity for superfluidity.

Quantum turbulence in superfluids with wall-clamped normal component.

Science.gov (United States)

Eltsov, Vladimir; Hänninen, Risto; Krusius, Matti

2014-03-25

In Fermi superfluids, such as superfluid (3)He, the viscous normal component can be considered to be stationary with respect to the container. The normal component interacts with the superfluid component via mutual friction, which damps the motion of quantized vortex lines and eventually couples the superfluid component to the container. With decreasing temperature and mutual friction, the internal dynamics of the superfluid component becomes more important compared with the damping and coupling effects from the normal component. As a result profound changes in superfluid dynamics are observed: the temperature-dependent transition from laminar to turbulent vortex motion and the decoupling from the reference frame of the container at even lower temperatures.

Relativistic density matrix in the diagonal momentum representation. Bose-gas

International Nuclear Information System (INIS)

Makhlin, A.N.; Sinyukov, Yu.M.

1984-01-01

The relativistic-invariance treatment of the ideal Bose-system arising from the diagonal momentum representation for the density matrix is developed. The average occupation members and their correlators for statistical systems in arbitrary inertial frames are found on the equal-time hypersurfaces. The relativistic partition function method for the calculation of thermodynamic properties of gases moving as a whole is constructed

Phase transitions in ideal and weakly interacting Bose gases with a finite number of particles confined in a box

International Nuclear Information System (INIS)

Wang Jianhui; Ma Yongli

2009-01-01

We generalize the scheme to characterize phase transitions of finite systems in a complex temperature plane and approach the classifications of phase transitions in ideal and weakly interacting Bose gases of a finite number of particles, confined in a cubic box of volume L 3 with different boundary conditions. For this finite ideal Bose system, by extending the classification parameters to all regions, we predict that the phase transition for periodic boundary conditions is of second order, while the transition in Dirichlet boundary conditions is of first order. For a weakly interacting Bose gas with periodic boundary conditions, we discuss the effects of finite particle numbers and inter-particle interactions on the nature of the phase transitions. We show that this homogenous weakly interacting Bose gas undergoes a second-order phase transition, which is in accordance with universality arguments for infinite systems. We also discuss the dependence of transition temperature on interaction strengths and particle numbers.

Equation of state of the one- and three-dimensional Bose-Bose gases

Science.gov (United States)

Chiquillo, Emerson

2018-06-01

We calculate the equation of state of Bose-Bose gases in one and three dimensions in the framework of an effective quantum field theory. The beyond-mean-field approximation at zero temperature and the one-loop finite-temperature results are obtained performing functional integration on a local effective action. The ultraviolet divergent zero-point quantum fluctuations are removed by means of dimensional regularization. We derive the nonlinear Schrödinger equation to describe one- and three-dimensional Bose-Bose mixtures and solve it analytically in the one-dimensional scenario. This equation supports self-trapped brightlike solitonic droplets and self-trapped darklike solitons. At low temperature, we also find that the pressure and the number of particles of symmetric quantum droplets have a nontrivial dependence on the chemical potential and the difference between the intra- and the interspecies coupling constants.

Bloch walls and the non-ideal bose gas spectrum

International Nuclear Information System (INIS)

Vitiello, S.A.S.

1986-05-01

The quasi-particle spectrum of non-ideal Bose gas with domain walls in the condensate is investigated. The existence of such a system is determined from solutions of Gross-Pitaevskii equation which represent many-soliton systems. The walls which make the condensate non-uniform are responsible for density and velocity fields ρ(x) and υ(x) repectively. In the laboratory, the Bogoliubov spectrum, supposed to be true for an uniform condensate at rest, is changed due to the velocity field to which the quasi-particles are submited. The spectrum in the laboratory frame is obtained by considering the Galileu invariance principle and the interaction energy between the quasi-particle and its medium. The importance in considering the last two facts is illustrated by the analyse of a constant density condensate which moves uniformly in the laboratory. The many-soliton spectrum configuration and structure function are studied by the Monte Carlo method. In an approximation that assumes the quasi-particle to be point like, the condensate can be treated as locally uniform. For each event the position x of a quasi-particle and its momentum in a frame with velocity υ(x) are determined. Thus, by a convenient Galileu transformation the energy spectrum in the laboratory an be obtained. The results show a phonon spectrum which splits in two branches in the high momenta region. In this region the lower energy branch exibiths a point of minimum. Analogies with the He II are explored. (author) [pt

Winding Up of the Wave-Function Phase by an Insulator-to-Superfluid Transition in a Ring of Coupled Bose-Einstein Condensates

International Nuclear Information System (INIS)

Dziarmaga, Jacek; Meisner, Jakub; Zurek, Wojciech H.

2008-01-01

We study phase transition from the Mott insulator to superfluid in a periodic optical lattice. Kibble-Zurek mechanism predicts buildup of winding number through random walk of BEC phases, with the step size scaling as a third root of transition rate. We confirm this and demonstrate that this scaling accounts for the net winding number after the transition

Universal fine structure of the specific heat at the critical λ-point for an ideal Bose gas in an arbitrary trap

International Nuclear Information System (INIS)

Tarasov, S V; Kocharovsky, Vl V; Kocharovsky, V V

2014-01-01

We analytically find the universal fine structure of the noted discontinuity in the value and/or derivative of the specific heat of an ideal Bose gas in an arbitrary trap in the whole critical region around the λ-point of the Bose–Einstein condensation. The result reveals a remarkable dependence of the λ-point structure on the trap's form and boundary conditions, even for a macroscopically large system. We suggest measuring this strong effect in the experiments with a controllable trap potential. (paper)

Nonlinear hydrodynamic equations for superfluid helium in aerogel

International Nuclear Information System (INIS)

Brusov, Peter N.; Brusov, Paul P.

2003-01-01

Aerogel in superfluids is studied very intensively during last decade. The importance of these systems is connected to the fact that this allows to investigate the influence of impurities on superfluidity. We have derived for the first time nonlinear hydrodynamic equations for superfluid helium in aerogel. These equations are generalization of McKenna et al. equations for nonlinear hydrodynamics case and could be used to study sound propagation phenomena in aerogel-superfluid system, in particular--to study sound conversion phenomena. We have obtained two alternative sets of equations, one of which is a generalization of a traditional set of nonlinear hydrodynamics equations for the case of an aerogel-superfluid system and, the other one represents a la Putterman equations (equation for v→ s is replaced by equation for A→=((ρ n )/(ρσ))w→, where w→=v→ n -v→ s )

An enlarged superfluid model of atomic nucleus

International Nuclear Information System (INIS)

Dumitrescu, O.; Horoi, M.

1989-01-01

The well known superfluid model (or quasiparticle phonon nuclear model (QPNM)) of atomic nucleus is enlarged by including an adequate four-nucleon effective interaction in addition to the pairing and long-range effective residual interactions. New experimental data can be explained without affecting those observables already described by the QPNM and in addition new features can be enumerated: 1) superfluidities of the neutron and proton systems may be generated by one another; 2) the phase structure is enriched by a new superfluid phase dominated by alpha-type correlations (ATC) and 3) superfluid isomers and their bands of elementary excitations are predicted. Unusual large two-nucleon and alpha transfer reactions cross sections as well as some unusual large alpha decay widths can be explained. (author). 46 refs, 3 figs, 2 tabs

Collective classical and quantum fields in plasmas, superconductors, superfluid $^{3}$He, and liquid crystals

CERN Document Server

Hagen Kleinert

2018-01-01

This is an introductory book dealing with collective phenomena in many-body systems. A gas of bosons or fermions can show oscillations of various types of density. These are described by different combinations of field variables. Especially delicate is the competition of these variables. In superfluid 3He, for example, the atoms can be attracted to each other by molecular forces, whereas they are repelled from each other at short distance due to a hardcore repulsion. The attraction gives rise to Cooper pairs, and the repulsion is overcome by paramagnon oscillations. The combination is what finally led to the discovery of superfluidity in 3He. In general, the competition between various channels can most efficiently be studied by means of a classical version of the Hubbard-Stratonovich transformation. A gas of electrons is controlled by the interplay of plasma oscillations and pair formation. In a system of rod- or disc-like molecules, liquid crystals are observed with directional orientations that behave in ...

The Ground State Energy of a Dilute Bose Gas in Dimension $n\\geq 3$

DEFF Research Database (Denmark)

Aaen, Anders Gottfred

We consider a Bose gas in spatial dimension n≥3 with a repulsive, radially symmetric two-body potential V. In the limit of low density ρ, the ground state energy per particle in the thermodynamic limit is shown to be (n−2)|Sn−1|an−2ρ, where |Sn−1| denotes the surface measure of the unit sphere...... in Rn, and a is the scattering length of V. Furthermore, for smooth and compactly supported two-body potentials, we derive an upper bound to the ground state energy with a correction term (1+γ)8π4a6ρ2|ln(a4ρ)| in 4 dimensions, where 0... dimensions. Finally, we use a grand canonical construction to give a simplified proof of the second order upper bound to the Lee-Huang-Yang formula, a result first obtained by Yau and Yin. We also test this method in 4 dimensions, but with a negative outcome....

Radio-Frequency-Controlled Cold Collisions and Universal Properties of Unitary Bose Gases

Science.gov (United States)

Ding, Yijue

This thesis investigates two topics: ultracold atomic collisions in a radio-frequency field and universal properties of a degenerate unitary Bose gas. One interesting point of the unitary Bose gas is that the system has only one length scale, that is, the average interparticle distance. This single parameter determines all properties of the gas, which is called the universality of the system. We first introduce a renormalized contact interaction to extend the validity of the zero-range interaction to large scattering lengths. Then this renormalized interaction is applied to many-body theories to determined those universal relations of the system. From the few-body perspective, we discuss the scattering between atoms in a single-color radio-frequency field. Our motivation is proposing the radio-frequency field as an effective tool to control interactions between cold atoms. Such a technique may be useful in future experiments such as creating phase transitions in spinor condensates. We also discuss the formation of ultracold molecules using radio-freqency fields from a time-dependent approach.

Dynamics of a quantum phase transition in the Bose-Hubbard model: Kibble-Zurek mechanism and beyond

Science.gov (United States)

Shimizu, Keita; Kuno, Yoshihito; Hirano, Takahiro; Ichinose, Ikuo

2018-03-01

In this paper, we study the dynamics of the Bose-Hubbard model by using time-dependent Gutzwiller methods. In particular, we vary the parameters in the Hamiltonian as a function of time, and investigate the temporal behavior of the system from the Mott insulator to the superfluid (SF) crossing a second-order phase transition. We first solve a time-dependent Schrödinger equation for the experimental setup recently done by Braun et al. [Proc. Natl. Acad. Sci. USA 112, 3641 (2015)] and show that the numerical and experimental results are in fairly good agreement. However, these results disagree with the Kibble-Zurek scaling. From our numerical study, we reveal a possible source of the discrepancy. Next, we calculate the critical exponents of the correlation length and vortex density in addition to the SF order parameter for a Kibble-Zurek protocol. We show that beside the "freeze" time t ̂, there exists another important time, teq, at which an oscillating behavior of the SF amplitude starts. From calculations of the exponents of the correlation length and vortex density with respect to a quench time τQ, we obtain a physical picture of a coarsening process. Finally, we study how the system evolves after the quench. We give a global picture of dynamics of the Bose-Hubbard model.

Disordered spinor Bose-Hubbard model

International Nuclear Information System (INIS)

LaPcki, Mateusz; Paganelli, Simone; Ahufinger, Veronica; Sanpera, Anna; Zakrzewski, Jakub

2011-01-01

We study the zero-temperature phase diagram of the disordered spin-1 Bose-Hubbard model in a two-dimensional square lattice. To this aim, we use a mean-field Gutzwiller ansatz and a probabilistic mean-field perturbation theory. The spin interaction induces two different regimes, corresponding to a ferromagnetic and antiferromagnetic order. In the ferromagnetic case, the introduction of disorder reproduces analogous features of the disordered scalar Bose-Hubbard model, consisting in the formation of a Bose glass phase between Mott insulator lobes. In the antiferromagnetic regime, the phase diagram differs more from the scalar case. Disorder in the chemical potential can lead to the disappearance of Mott insulator lobes with an odd-integer filling factor and, for sufficiently strong spin coupling, to Bose glass of singlets between even-filling Mott insulator lobes. Disorder in the spinor coupling parameter results in the appearance of a Bose glass phase only between the n and the n+1 lobes for n odd. Disorder in the scalar Hubbard interaction inhibits Mott insulator regions for occupation larger than a critical value.

Optomechanics in a Levitated Droplet of Superfluid Helium

Science.gov (United States)

Brown, Charles; Harris, Glen; Harris, Jack

2017-04-01

A critical issue common to all optomechanical systems is dissipative coupling to the environment, which limits the system's quantum coherence. Superfluid helium's extremely low optical and mechanical dissipation, as well as its high thermal conductivity and its ability cool itself via evaporation, makes the mostly uncharted territory of superfluid optomechanics an exciting avenue for exploring quantum effects in macroscopic objects. I will describe ongoing work that aims to exploit the unique properties of superfluid helium by constructing an optomechanical system consisting of a magnetically levitated droplet of superfluid helium., The optical whispering gallery modes (WGMs) of the droplet, as well as the mechanical oscillations of its surface, should offer exceptionally low dissipation, and should couple to each other via the usual optomechanical interactions. I will present recent progress towards this goal, and also discuss the background for this work, which includes prior demonstrations of magnetic levitation of superfluid helium, high finesse WGMs in liquid drops, and the self-cooling of helium drops in vacuum.

Atom-molecule dark states in a Bose-Einstein condensate

International Nuclear Information System (INIS)

Winkler, K.; Thalhammer, G.; Theis, M.; Ritsch, H.; Grimm, R.

2005-01-01

Full text: We have created a dark quantum superposition state of a Rb Bose-Einstein condensate (BEC) and a degenerate gas of Rb 2 ground state molecules in a specific ro-vibrational state using two-color photoassociation. We infer the presence of this coherent atom-molecule gas from a strong resonant suppression of photoassociation loss. In our experiment the maximal molecule population in the dark state is limited to about 100 Rb 2 molecules due to laser induced decay. The experimental findings can be well described by a simple three mode model. (author)

Maria Goeppert Mayer Prize Talk: Superfluid Atom Circuits

Science.gov (United States)

Campbell, Gretchen

2016-05-01

We have performed a series of experiments with ring-shaped Bose-Einstein Condensates, with and without the addition of a ``weak link'' barrier. Weak connections between superconductors or superfluids can differ from classical links due to quantum coherence, which allows for flow without resistance. The properties of a weak link are characterized by a single function, the current-phase relationship. In recent experiments, we have developed a technique to directly measure the current-phase relationship of the weak link. The weak link is created using a laser beam that acts as a barrier across one side of the ring condensate. By rotating the barrier, we can control the current around the ring. When the weak link is rotated at at low rotation rates, we observe phase slips between well-defined, quantized current states, and have demonstrated that the system exhibits hysteresis. At higher rotation rates we have directly measured the onset of resistive flow across the weak link. Such measurements may open new avenues of research in quantum transport. More recently, we have studied the behavior of the ring BEC when the radius is expanded at supersonic rates. Because information can propagate only at the speed of sound, the supersonic expansion creates causally disconnected regions, whose phases evolve at different rates. Such experiments may allow us to study cosmic inflation at laboratory scales.

Biomolecular ions in superfluid helium nanodroplets

Energy Technology Data Exchange (ETDEWEB)

Gonzalez Florez, Ana Isabel

2016-07-01

The function of a biological molecule is closely related to its structure. As a result, understanding and predicting biomolecular structure has become the focus of an extensive field of research. However, the investigation of molecular structure can be hampered by two main difficulties: the inherent complications that may arise from studying biological molecules in their native environment, and the potential congestion of the experimental results as a consequence of the large number of degrees of freedom present in these molecules. In this work, a new experimental setup has been developed and established in order to overcome the afore mentioned limitations combining structure-sensitive gas-phase methods with superfluid helium droplets. First, biological molecules are ionised and brought into the gas phase, often referred to as a clean-room environment, where the species of interest are isolated from their surroundings and, thus, intermolecular interactions are absent. The mass-to-charge selected biomolecules are then embedded inside clusters of superfluid helium with an equilibrium temperature of ∝0.37 K. As a result, the internal energy of the molecules is lowered, thereby reducing the number of populated quantum states. Finally, the local hydrogen bonding patterns of the molecules are investigated by probing specific vibrational modes using the Fritz Haber Institute's free electron laser as a source of infrared radiation. Although the structure of a wide variety of molecules has been studied making use of the sub-Kelvin environment provided by superfluid helium droplets, the suitability of this method for the investigation of biological molecular ions was still unclear. However, the experimental results presented in this thesis demonstrate the applicability of this experimental approach in order to study the structure of intact, large biomolecular ions and the first vibrational spectrum of the protonated pentapeptide leu-enkephalin embedded in helium

Biomolecular ions in superfluid helium nanodroplets

International Nuclear Information System (INIS)

Gonzalez Florez, Ana Isabel

2016-01-01

The function of a biological molecule is closely related to its structure. As a result, understanding and predicting biomolecular structure has become the focus of an extensive field of research. However, the investigation of molecular structure can be hampered by two main difficulties: the inherent complications that may arise from studying biological molecules in their native environment, and the potential congestion of the experimental results as a consequence of the large number of degrees of freedom present in these molecules. In this work, a new experimental setup has been developed and established in order to overcome the afore mentioned limitations combining structure-sensitive gas-phase methods with superfluid helium droplets. First, biological molecules are ionised and brought into the gas phase, often referred to as a clean-room environment, where the species of interest are isolated from their surroundings and, thus, intermolecular interactions are absent. The mass-to-charge selected biomolecules are then embedded inside clusters of superfluid helium with an equilibrium temperature of ∝0.37 K. As a result, the internal energy of the molecules is lowered, thereby reducing the number of populated quantum states. Finally, the local hydrogen bonding patterns of the molecules are investigated by probing specific vibrational modes using the Fritz Haber Institute's free electron laser as a source of infrared radiation. Although the structure of a wide variety of molecules has been studied making use of the sub-Kelvin environment provided by superfluid helium droplets, the suitability of this method for the investigation of biological molecular ions was still unclear. However, the experimental results presented in this thesis demonstrate the applicability of this experimental approach in order to study the structure of intact, large biomolecular ions and the first vibrational spectrum of the protonated pentapeptide leu-enkephalin embedded in helium

Topological superfluids confined in a regular nano-scale slab geometry

Energy Technology Data Exchange (ETDEWEB)

Saunders, John; Bennett, Robert; Levitin, Lev; Casey, Andrew; Cowan, Brian [Department of Physics, Royal Holloway University of London, Egham, Surrey, TW20 0EX (United Kingdom); Parpia, Jeevak [Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Drung, Dietmar; Schurig, Thomas [Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, D-19587, Berlin (Germany)

2012-07-01

Superfluid 3He confined in a regular nano-fabricated slab geometry provides a model system for the investigation of surface and thin film effects in a p-wave superfluid. We have fabricated and cooled such samples to well below 1 mK for the first time, and investigated their NMR response, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We have used NMR on a 650 nm thick superfluid slab to identify the profound effect of confinement on the relative stability of the A and B phases and to make quantitative measurements of the suppression and surface induced distortion of the order parameter. In these systems the effective confinement length scale (slab thickness/superfluid coherence length) is the new tuning parameter. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase or the planar phase. Nanofluidic samples of superfluid 3He promise a route to explore topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions.

Nobel Lecture: Bose-Einstein condensation in a dilute gas, the first 70 years and some recent experiments

International Nuclear Information System (INIS)

Cornell, E.A.; Wieman, C.E.

2002-01-01

Bose-Einstein condensation, or BEC, has a long and rich history dating from the early 1920s. In this article we will trace briefly over this history and some of the developments in physics that made possible our successful pursuit of BEC in a gas. We will then discuss what was involved in this quest. In this discussion we will go beyond the usual technical description to try and address certain questions that we now hear frequently, but are not covered in our past research papers. These are questions along the lines of: How did you get the idea and decide to pursue it? Did you know it was going to work? How long did it take you and why? We will review some our favorites from among the experiments we have carried out with BEC. There will then be a brief encore on why we are optimistic that BEC can be created with nearly any species of magnetically trappable atom. Throughout this article we will try to explain what makes BEC in a dilute gas so interesting, unique, and experimentally challenging

Wave processes in a superfluid liquid

International Nuclear Information System (INIS)

Sanikidze, D.G.

1981-01-01

The monograph is devoted to theory of sound wave propagation in superfluid He 4 and He 3 -He 4 solutions. Hydrodynamic theory of sound oscillation propagation in superfluid liquid under conditions of confined geometry is given. In particular considered are problems of propagation of the first, second and fourth sounds, dispersion, attenuation and absorption, sound propagation in films, channels and waveguides. The monograph summarizes a certain stage of studying different sound oscillations in superfluid liquid and along with original results contains also results obtained by other investigators. The theory and experimental investigations carried on both in the Soviet Union and abroad are compared. The monograph is intended for specialists working in the area of low temperature physics and for students of the given speciality [ru

Vortex structure in superfluid color-flavor locked quark matter

Directory of Open Access Journals (Sweden)

Alford Mark G.

2016-01-01

Full Text Available The core region of a neutron star may feature quark matter in the color-flavor-locked (CFL phase. The CFL condensate breaks the baryon number symmetry, such that the phenomenon of superfluidity arises. If the core of the star is rotating, vortices will form in the superfluid, carrying the quanta of angular momentum. In a previous study we have solved the question of stability of these vortices, where we found numerical proof of a conjectured instability, according to which superfluid vortices will decay into an arrangement of so-called semi-superfluid fluxtubes. Here we report first results of an extension of our framework that allows us to study multi-vortex dynamics. This will in turn enable us to investigate the structure of semi-superfluid string lattices, which could be relevant to study pinning phenomena at the boundary of the core.

Exotic superfluidity and pairing phenomena in atomic Fermi gases in mixed dimensions.

Science.gov (United States)

Zhang, Leifeng; Che, Yanming; Wang, Jibiao; Chen, Qijin

2017-10-11

Atomic Fermi gases have been an ideal platform for simulating conventional and engineering exotic physical systems owing to their multiple tunable control parameters. Here we investigate the effects of mixed dimensionality on the superfluid and pairing phenomena of a two-component ultracold atomic Fermi gas with a short-range pairing interaction, while one component is confined on a one-dimensional (1D) optical lattice whereas the other is in a homogeneous 3D continuum. We study the phase diagram and the pseudogap phenomena throughout the entire BCS-BEC crossover, using a pairing fluctuation theory. We find that the effective dimensionality of the non-interacting lattice component can evolve from quasi-3D to quasi-1D, leading to strong Fermi surface mismatch. Upon pairing, the system becomes effectively quasi-two dimensional in the BEC regime. The behavior of T c bears similarity to that of a regular 3D population imbalanced Fermi gas, but with a more drastic departure from the regular 3D balanced case, featuring both intermediate temperature superfluidity and possible pair density wave ground state. Unlike a simple 1D optical lattice case, T c in the mixed dimensions has a constant BEC asymptote.

Normal-superfluid interface for polarized fermion gases

NARCIS (Netherlands)

Van Schaeybroeck, B.; Lazarides, A.

2009-01-01

Recent experiments on imbalanced fermion gases have proved the existence of a sharp interface between a superfluid and a normal phase. We show that, at the lowest experimental temperatures, a temperature difference between normal N and superfluid SF phases can appear as a consequence of the blocking

Finite-size scaling in two-dimensional superfluids

International Nuclear Information System (INIS)

Schultka, N.; Manousakis, E.

1994-01-01

Using the x-y model and a nonlocal updating scheme called cluster Monte Carlo, we calculate the superfluid density of a two-dimensional superfluid on large-size square lattices LxL up to 400x400. This technique allows us to approach temperatures close to the critical point, and by studying a wide range of L values and applying finite-size scaling theory we are able to extract the critical properties of the system. We calculate the superfluid density and from that we extract the renormalization-group beta function. We derive finite-size scaling expressions using the Kosterlitz-Thouless-Nelson renormalization group equations and show that they are in very good agreement with our numerical results. This allows us to extrapolate our results to the infinite-size limit. We also find that the universal discontinuity of the superfluid density at the critical temperature is in very good agreement with the Kosterlitz-Thouless-Nelson calculation and experiments

Superfluid 3He—the Early Days

Science.gov (United States)

Lee, D. M.; Leggett, A. J.

2011-08-01

A history is given of liquid 3He research from the time when 3He first became available following World War II through 1972 when the discovery of the superfluid phases was made. The Fermi liquid nature was established early on, and the Landau Fermi liquid theory provided a framework for understanding the interactions between the Fermions (quasiparticles). The theory's main triumph was to predict zero sound, which was soon discovered experimentally. Experimental techniques are treated, including adiabatic demagnetization, dilution refrigerator technology, and Pomeranchuk cooling. A description of the superfluid 3He discovery experiments using the latter two of these techniques is given. While existing theories provided a basis for understanding the newly discovered superfluid phases in terms of ℓ>0 Cooper pairs, the unexpected stability of the A phase in the high- P, high- T region of the phase diagram needed for its explanation a creative leap beyond the BCS paradigm. The use of sum rules to interpret some of the unusual magnetic resonance in liquid 3He is discussed. Eventually a complete theory of the spin dynamics of superfluid 3He was developed, which predicted many of the exciting phenomena subsequently discovered.

Magnus force in superfluids and superconductors

International Nuclear Information System (INIS)

Sonin, E.B.

1997-01-01

The forces on the vortex, transverse to its velocity, are considered. In addition to the superfluid Magnus force from the condensate (superfluid component), there are transverse forces from thermal quasiparticles and external fields violating the Galilean invariance. The forces between quasiparticles and the vortex originate from interference of quasiparticles with trajectories on the left and on the right from the vortex like similar forces for electrons interacting with the thin magnetic-flux tube (the Aharonov-Bohm effect). These forces are derived for phonons from the equations of superfluid hydrodynamics, and for BCS quasiparticles from the Bogolyubov endash de Gennes equations. The effect of external fields breaking Galilean invariance is analyzed for vortices in the two-dimensional Josephson junction array. The symmetry analysis of the classical equations for the array shows that the total transverse force on the vortex vanishes. Therefore the Hall effect which is linear in the transverse force is absent also. This means that the Magnus force from the superfluid component exactly cancels with the transverse force from the external fields. The results of other approaches are also brought together for discussion. copyright 1997 The American Physical Society

Static properties and spin dynamics of the ferromagnetic spin-1 Bose gas in a magnetic field

International Nuclear Information System (INIS)

Kis-Szabo, Krisztian; Szepfalusy, Peter; Szirmai, Gergely

2005-01-01

The properties of spin-1 Bose gases with ferromagnetic interactions in the presence of a nonzero magnetic field are studied. The equation of state and thermodynamic quantities are worked out with the help of a mean-field approximation. The phase diagram besides Bose-Einstein condensation contains a first-order transition where two values of the magnetization coexist. The dynamics is investigated with the help of the random phase approximation. The soft mode corresponding to the critical point of the magnetic phase transition is found to behave like in conventional theory

Topological superfluids confined in a nanoscale slab geometry

Science.gov (United States)

Saunders, John

2013-03-01

Nanofluidic samples of superfluid 3He provide a route to explore odd-parity topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions. We have cooled superfluid 3He confined in a precisely defined nano-fabricated cavity to well below 1 mK for the first time. We fingerprint the order parameter by nuclear magnetic resonance, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We demonstrate that dimensional confinement, at length scales comparable to the superfluid Cooper-pair diameter, has a profound influence on the superfluid order of 3He. The chiral A-phase is stabilized at low pressures, in a cavity of height 650 nm. At higher pressures we observe 3He-B with a surface induced planar distortion. 3He-B is a time-reversal invariant topological superfluid, supporting gapless Majorana surface states. In the presence of the small symmetry breaking NMR static magnetic field we observe two possible B-phase states of the order parameter manifold, which can coexist as domains. Non-linear NMR on these states enables a measurement of the surface induced planar distortion, which determines the spectral weight of the surface excitations. The expected structure of the domain walls is such that, at the cavity surface, the line separating the two domains is predicted to host fermion zero modes, protected by symmetry and topology. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase, which breaks time reversal symmetry, has a protected chiral edge mode, and may host half-quantum vortices with a Majorana zero-mode at the core. We discuss experimental progress toward this phase, through measurements on a 100 nm cavity. On the other hand, a cavity height of 1000 nm may stabilize a novel ``striped'' superfluid with spatially modulated order parameter. Supported by EPSRC (UK) GR/J022004/1 and European Microkelvin Consortium, FP7 grant 228464

Identifying a Superfluid Reynolds Number via Dynamical Similarity.

Science.gov (United States)

Reeves, M T; Billam, T P; Anderson, B P; Bradley, A S

2015-04-17

The Reynolds number provides a characterization of the transition to turbulent flow, with wide application in classical fluid dynamics. Identifying such a parameter in superfluid systems is challenging due to their fundamentally inviscid nature. Performing a systematic study of superfluid cylinder wakes in two dimensions, we observe dynamical similarity of the frequency of vortex shedding by a cylindrical obstacle. The universality of the turbulent wake dynamics is revealed by expressing shedding frequencies in terms of an appropriately defined superfluid Reynolds number, Re(s), that accounts for the breakdown of superfluid flow through quantum vortex shedding. For large obstacles, the dimensionless shedding frequency exhibits a universal form that is well-fitted by a classical empirical relation. In this regime the transition to turbulence occurs at Re(s)≈0.7, irrespective of obstacle width.

Vortex sorter for Bose-Einstein condensates

International Nuclear Information System (INIS)

Whyte, Graeme; Veitch, John; Courtial, Johannes; Oehberg, Patrik

2004-01-01

We have designed interferometers that sort Bose-Einstein condensates into their vortex components. The Bose-Einstein condensates in the two arms of the interferometer are rotated with respect to each other through fixed angles; different vortex components then exit the interferometer in different directions. The method we use to rotate the Bose-Einstein condensates involves asymmetric phase imprinting and is itself new. We have modeled rotation through fixed angles and sorting into vortex components with even and odd values of the topological charge of two-dimensional Bose-Einstein condensates in a number of states (pure or superposition vortex states for different values of the scattering length). Our scheme may have applications for quantum information processing

Kinetic theory of collective exitations and damping in Bose-Einstein condensed gases

NARCIS (Netherlands)

Al Khawaja, U.; Stoof, H.T.C.

2000-01-01

We calculate the frequencies and damping rates of the low-lying collective modes of a Bose-Einstein condensed gas at nonzero temperature. We use a complex nonlinear Schrödinger equation to determine the dynamics of the condensate atoms. In this manner we take into account both collisions between

Kinetic theory of collective excitations and damping in Bose-Einstein condensed gases

NARCIS (Netherlands)

Al Khawaja, U.; Stoof, H.T.C.

2000-01-01

We calculate the frequencies and damping rates of the low-lying collective modes of a Bose-Einstein condensed gas at nonzero temperature. We use a complex nonlinear Schrödinger equation to determine the dynamics of the condensate atoms, and couple it to a Boltzmann equation for the noncondensate

Excitations of Bose-Einstein condensates at finite temperatures

International Nuclear Information System (INIS)

Rusch, M.

2000-01-01

Recent experimental observations of collective excitations of Bose condensed atomic vapours have stimulated interest in the microscopic description of the dynamics of a Bose-Einstein condensate confined in an external potential. We present a finite temperature field theory for collective excitations of trapped Bose-Einstein condensates and use a finite-temperature linear response formalism, which goes beyond the simple mean-field approximation of the Gross-Pitaevskii equation. The effect of the non-condensed thermal atoms we include using perturbation theory in a quasiparticle basis. This presents a simple scheme to understand the interaction between condensate and non-condensed atoms and enables us to include the effect the condensate has on collision dynamics. At first we limit our treatment to the case of a spatially homogeneous Bose gas. We include the effect of pair and triplet anomalous averages and thus obtain a gapless theory for the excitations of a weakly interacting system, which we can link to well known results for Landau and Beliaev damping rates. A gapless theory for trapped systems with a static thermal component follows straightforwardly. We then investigate finite temperature excitations of a condensate in a spherically symmetric harmonic trap. We avoid approximations to the density of states and thus emphasise finite size aspects of the problem. We show that excitations couple strongly to a restricted number of modes, giving rise to resonance structure in their frequency spectra. Where possible we derive energy shifts and lifetimes of excitations. For one particular mode, the breathing mode, the effects of the discreteness of the system are sufficiently pronounced that the simple picture of an energy shift and width fails. Experiments in spherical traps have recently become feasible and should be able to test our detailed quantitative predictions. (author)

Transport coefficients in superfluid neutron stars

Energy Technology Data Exchange (ETDEWEB)

Tolos, Laura [Instituto de Ciencias del Espacio (IEEC/CSIC) Campus Universitat Autònoma de Barcelona, Facultat de Ciències, Torre C5, E-08193 Bellaterra (Barcelona) (Spain); Frankfurt Institute for Advances Studies. Johann Wolfgang Goethe University, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main (Germany); Manuel, Cristina [Instituto de Ciencias del Espacio (IEEC/CSIC) Campus Universitat Autònoma de Barcelona, Facultat de Ciències, Torre C5, E-08193 Bellaterra (Barcelona) (Spain); Sarkar, Sreemoyee [Tata Institute of Fundamental Research, Homi Bhaba Road, Mumbai-400005 (India); Tarrus, Jaume [Physik Department, Technische Universität München, D-85748 Garching (Germany)

2016-01-22

We study the shear and bulk viscosity coefficients as well as the thermal conductivity as arising from the collisions among phonons in superfluid neutron stars. We use effective field theory techniques to extract the allowed phonon collisional processes, written as a function of the equation of state and the gap of the system. The shear viscosity due to phonon scattering is compared to calculations of that coming from electron collisions. We also comment on the possible consequences for r-mode damping in superfluid neutron stars. Moreover, we find that phonon collisions give the leading contribution to the bulk viscosities in the core of the neutron stars. We finally obtain a temperature-independent thermal conductivity from phonon collisions and compare it with the electron-muon thermal conductivity in superfluid neutron stars.

Phenomenological theory of superfluidity and superconductivity

International Nuclear Information System (INIS)

Rabinowitz, M.

1994-01-01

Quantum condensation is used here as the basis for a phenomenological theory of superfluidity and superconductivity. It leads to remarkably good calculations of the transition temperatures T c of superfluid 3 He and 4 He, as well as a large number of cuprate, heavy fermion, organic, dichalcogenide, and bismuth oxide superconductors. Although this approach may apply least to the long-coherence-length metallics, reasonably good estimates are made for them and chevral superconductors. T c for atomic H is estimated. T c can be calculated as a function of number density or density of states and effective mass of normal carriers; or alternatively with the Fermi energy as the only input parameter. Predictions are made for a total of 26 superconductors and four superfluids. An estimate is also made for coherence lengths

Accelerated expansion of a universe containing a self-interacting Bose-Einstein gas

Energy Technology Data Exchange (ETDEWEB)

Izquierdo, German; Besprosvany, Jaime, E-mail: german.izquierdo@gmail.co, E-mail: bespro@fisica.unam.m [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion CientIfica S/N, Ciudad Universitaria, CP 04510, Mexico, Distrito Federal (Mexico)

2010-03-21

Acceleration of the universe is obtained from a model of non-relativistic particles with a short-range attractive interaction, at low enough temperature to produce a Bose-Einstein condensate. Conditions are derived for negative-pressure behavior. In particular, we show that a phantom-accelerated regime at the beginning of the universe solves the horizon problem, consistently with nucleosynthesis.

Radioactive ions and atoms in superfluid helium

NARCIS (Netherlands)

Dendooven, P.G.; Purushothaman, S.; Gloos, K.; Aysto, J.; Takahashi, N.; Huang, W.; Harissopulos, S; Demetriou, P; Julin, R

2006-01-01

We are investigating the use of superfluid helium as a medium to handle and manipulate radioactive ions and atoms. Preliminary results on the extraction of positive ions from superfluid helium at temperatures close to 1 K are described. Increasing the electric field up to 1.2 kV/cm did not improve

Helicity conservation and twisted Seifert surfaces for superfluid vortices.

Science.gov (United States)

Salman, Hayder

2017-04-01

Starting from the continuum definition of helicity, we derive from first principles its different contributions for superfluid vortices. Our analysis shows that an internal twist contribution emerges naturally from the mathematical derivation. This reveals that the spanwise vector that is used to characterize the twist contribution must point in the direction of a surface of constant velocity potential. An immediate consequence of the Seifert framing is that the continuum definition of helicity for a superfluid is trivially zero at all times. It follows that the Gauss-linking number is a more appropriate definition of helicity for superfluids. Despite this, we explain how a quasi-classical limit can arise in a superfluid in which the continuum definition for helicity can be used. This provides a clear connection between a microscopic and a macroscopic description of a superfluid as provided by the Hall-Vinen-Bekarevich-Khalatnikov equations. This leads to consistency with the definition of helicity used for classical vortices.

Superfluid response of two-dimensional parahydrogen clusters in confinement

Energy Technology Data Exchange (ETDEWEB)

Idowu, Saheed; Boninsegni, Massimo [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E7 (Canada)

2015-04-07

We study by computer simulations the effect of confinement on the superfluid properties of small two-dimensional (2D) parahydrogen clusters. For clusters of fewer than twenty molecules, the superfluid response in the low temperature limit is found to remain comparable in magnitude to that of free clusters, within a rather wide range of depth and size of the confining well. The resilience of the superfluid response is attributable to the “supersolid” character of these clusters. We investigate the possibility of establishing a bulk 2D superfluid “cluster crystal” phase of p-H{sub 2}, in which a global superfluid response would arise from tunnelling of molecules across adjacent unit cells. The computed energetics suggests that for clusters of about ten molecules, such a phase may be thermodynamically stable against the formation of the equilibrium insulating crystal, for values of the cluster crystal lattice constant possibly allowing tunnelling across adjacent unit cells.

A hydrodynamic model for superfluid helium with vortices

International Nuclear Information System (INIS)

Lhuillier, D.; Francois, M.

1975-01-01

Although their existence is experimentally well verified, the so-called mutual friction force Fsub(sn) and superfluid friction force Fsub(s) cannot emerge from the Landau irrotational model of superfluidity. Up to now these forces have merely been added to the Landau equations but this is untenable since, as a consequence, one destroys the irrotationality condition with which the equations have expressly been built. It is shown that these friction forces appear in a natural way in a model where superfluid helium with vortices is compared to a fluid with a conserved intrinsic momentum. (Auth.)

Towards laboratory detection of topological vortices in superfluid phases of QCD

Science.gov (United States)

Das, Arpan; Dave, Shreyansh S.; de, Somnath; Srivastava, Ajit M.

2017-10-01

Topological defects arise in a variety of systems, e.g. vortices in superfluid helium to cosmic strings in the early universe. There is an indirect evidence of neutron superfluid vortices from the glitches in pulsars. One also expects that the topological defects may arise in various high baryon density phases of quantum chromodynamics (QCD), e.g. superfluid topological vortices in the color flavor locked (CFL) phase. Though vastly different in energy/length scales, there are universal features in the formation of all these defects. Utilizing this universality, we investigate the possibility of detecting these topological superfluid vortices in laboratory experiments, namely heavy-ion collisions (HICs). Using hydrodynamic simulations, we show that vortices can qualitatively affect the power spectrum of flow fluctuations. This can give an unambiguous signal for superfluid transition resulting in vortices, allowing for the check of defect formation theories in a relativistic quantum field theory system, and the detection of superfluid phases of QCD. Detection of nucleonic superfluid vortices in low energy HICs will give opportunity for laboratory controlled study of their properties, providing crucial inputs for the physics of pulsars.

Relativistic mean field model for entrainment in general relativistic superfluid neutron stars

International Nuclear Information System (INIS)

Comer, G.L.; Joynt, R.

2003-01-01

General relativistic superfluid neutron stars have a significantly more intricate dynamics than their ordinary fluid counterparts. Superfluidity allows different superfluid (and superconducting) species of particles to have independent fluid flows, a consequence of which is that the fluid equations of motion contain as many fluid element velocities as superfluid species. Whenever the particles of one superfluid interact with those of another, the momentum of each superfluid will be a linear combination of both superfluid velocities. This leads to the so-called entrainment effect whereby the motion of one superfluid will induce a momentum in the other superfluid. We have constructed a fully relativistic model for entrainment between superfluid neutrons and superconducting protons using a relativistic σ-ω mean field model for the nucleons and their interactions. In this context there are two notions of 'relativistic': relativistic motion of the individual nucleons with respect to a local region of the star (i.e. a fluid element containing, say, an Avogadro's number of particles), and the motion of fluid elements with respect to the rest of the star. While it is the case that the fluid elements will typically maintain average speeds at a fraction of that of light, the supranuclear densities in the core of a neutron star can make the nucleons themselves have quite high average speeds within each fluid element. The formalism is applied to the problem of slowly rotating superfluid neutron star configurations, a distinguishing characteristic being that the neutrons can rotate at a rate different from that of the protons

Dark lump excitations in superfluid Fermi gases

Science.gov (United States)

Xu, Yan-Xia; Duan, Wen-Shan

2012-11-01

We study the linear and nonlinear properties of two-dimensional matter-wave pulses in disk-shaped superfluid Fermi gases. A Kadomtsev—Petviashvili I (KPI) solitary wave has been realized for superfluid Fermi gases in the limited cases of Bardeen—Cooper—Schrieffer (BCS) regime, Bose—Einstein condensate (BEC) regime, and unitarity regime. One-lump solution as well as one-line soliton solutions for the KPI equation are obtained, and two-line soliton solutions with the same amplitude are also studied in the limited cases. The dependence of the lump propagating velocity and the sound speed of two-dimensional superfluid Fermi gases on the interaction parameter are investigated for the limited cases of BEC and unitarity.

Dark lump excitations in superfluid Fermi gases

International Nuclear Information System (INIS)

Xu Yan-Xia; Duan Wen-Shan

2012-01-01

We study the linear and nonlinear properties of two-dimensional matter-wave pulses in disk-shaped superfluid Fermi gases. A Kadomtsev—Petviashvili I (KPI) solitary wave has been realized for superfluid Fermi gases in the limited cases of Bardeen—Cooper—Schrieffer (BCS) regime, Bose—Einstein condensate (BEC) regime, and unitarity regime. One-lump solution as well as one-line soliton solutions for the KPI equation are obtained, and two-line soliton solutions with the same amplitude are also studied in the limited cases. The dependence of the lump propagating velocity and the sound speed of two-dimensional superfluid Fermi gases on the interaction parameter are investigated for the limited cases of BEC and unitarity

Berkeley Experiments on Superfluid Macroscopic Quantum Effects

International Nuclear Information System (INIS)

Packard, Richard

2006-01-01

This paper provides a brief history of the evolution of the Berkeley experiments on macroscopic quantum effects in superfluid helium. The narrative follows the evolution of the experiments proceeding from the detection of single vortex lines to vortex photography to quantized circulation in 3He to Josephson effects and superfluid gyroscopes in both 4He and 3He

Polaron in the dilute critical Bose condensate

Science.gov (United States)

Pastukhov, Volodymyr

2018-05-01

The properties of an impurity immersed in a dilute D-dimensional Bose gas at temperatures close to its second-order phase transition point are considered. Particularly by means of the 1/N-expansion, we calculate the leading-order polaron energy and the damping rate in the limit of vanishing boson–boson interaction. It is shown that the perturbative effective mass and the quasiparticle residue diverge logarithmically in the long-length limit, signalling the non-analytic behavior of the impurity spectrum and pole-free structure of the polaron Green’s function in the infrared region, respectively.

Atomic Evolution and Entanglement of Two Qubits in Photon Superfluid

Science.gov (United States)

Yin, Miao; Zhang, Xiongfeng; Deng, Yunlong; Deng, Huaqiu

2018-03-01

By using reservoir theory, we investigate the evolution of an atom placed in photon superfluid and study the entanglement properties of two qubits interacting with photon superfluid. It is found that the atomic decay rate in photon superfluid changes periodically with position of the atom and the decay rate can be inhibited compared to that in usual electromagnetic environment without photon superfluid. It is also found that when two atoms are separately immersed in their own local photon-superfluid reservoir, the entanglement sudden death or birth occurs or not only depends on the initial state of the qubits. What is more, we find a possible case that the concurrence between two qubits can remain a constant value by choosing proper values of parameters of the system, which may provide a new way to preserve quantum entanglement.

Pinning down the superfluid and measuring masses using pulsar glitches.

Science.gov (United States)

Ho, Wynn C G; Espinoza, Cristóbal M; Antonopoulou, Danai; Andersson, Nils

2015-10-01

Pulsars are known for their superb timing precision, although glitches can interrupt the regular timing behavior when the stars are young. These glitches are thought to be caused by interactions between normal and superfluid matter in the crust of the star. However, glitching pulsars such as Vela have been shown to require a superfluid reservoir that greatly exceeds that available in the crust. We examine a model in which glitches tap the superfluid in the core. We test a variety of theoretical superfluid models against the most recent glitch data and find that only one model can successfully explain up to 45 years of observational data. We develop a new technique for combining radio and x-ray data to measure pulsar masses, thereby demonstrating how current and future telescopes can probe fundamental physics such as superfluidity near nuclear saturation.

What is between Fermi-Dirac and Bose-Einstein Statistics?

OpenAIRE

Byczuk, Krzysztof; Spalek, Jozef; Joyce, Geoffrey; Sarkar, Sarben

2004-01-01

We overwiev the properties of a quantum gas of particles with the intermediate statistics defined by Haldane. Although this statistics has no direct connection to the symmetry of the multiparticle wave function, the statistical distribution function interpolates continuously between the Fermi-Dirac and the Bose-Einstein limits. We present an explicit solution of the transcendental equation for the didtribution function in a general case, as well as determine the thermodynamic properties in bo...

Quasiparticle Properties of a Mobile Impurity in a Bose-Einstein Condensate.

Science.gov (United States)

Christensen, Rasmus Søgaard; Levinsen, Jesper; Bruun, Georg M

2015-10-16

We develop a systematic perturbation theory for the quasiparticle properties of a single impurity immersed in a Bose-Einstein condensate. Analytical results are derived for the impurity energy, effective mass, and residue to third order in the impurity-boson scattering length. The energy is shown to depend logarithmically on the scattering length to third order, whereas the residue and the effective mass are given by analytical power series. When the boson-boson scattering length equals the boson-impurity scattering length, the energy has the same structure as that of a weakly interacting Bose gas, including terms of the Lee-Huang-Yang and fourth order logarithmic form. Our results, which cannot be obtained within the canonical Fröhlich model of an impurity interacting with phonons, provide valuable benchmarks for many-body theories and for experiments.

Occurrence of hyperson superfluidity in neutron star cores

International Nuclear Information System (INIS)

Takatsuka, Tatsuyuki; Nishizaki, Shigeru; Yamamoto, Yasuo; Tamagaki, Ryozo

2006-01-01

Superfluidity of Λ and Σ - admixed in neutron star (NS) cores is investigated realistically for hyperon (Y)-mixed NS models obtained using a G-matrix-based effective interaction approach. Numerical results for the equation of state (EOS) with the mixing ratios of the respective components and the hyperon energy gaps including the temperature dependence are presented. These are meant to serve as physical inputs for Y-cooling calculations of NSs. By paying attention to the uncertainties of the EOS and the YY interactions, it is shown that both Λ and Σ - are superfluid as soon as they appear although the magnitude of the critical temperature and the density region where superfluidity exists depend considerably on the YY pairing potential. Considering momentum triangle condition and the occurrence of superfluidity, it is found that a so-called hyperon cooling'' (neutrino-emission from direct Urca process including Y) combined with Y-superfluidity may be able to account for observations of the colder class of NSs. It is remarked that Λ-hyperons play a decisive role in the hyperon cooling scenario. Some comments are given regarding the consequences of the less attractive ΛΛ interaction recently suggested by the ''NAGARA event'' 6 ΛΛ He. (author)

Hydrodynamics of compressible superfluids in confined geometries

International Nuclear Information System (INIS)

Malmi-Kakkada, Abdul N; Valls, Oriol T; Dasgupta, Chandan

2014-01-01

We present a study of the hydrodynamics of compressible superfluids in confined geometries. We use a perturbative procedure in terms of the dimensionless expansion parameter (v/v s ) 2 where v is the typical speed of the flow and v s is the speed of sound. A zero value of this parameter corresponds to the incompressible limit. We apply the procedure to two specific problems: the case of a trapped superfluid with a Gaussian profile of the local density, and that of a superfluid confined in a rotating obstructed cylinder. We find that the corrections due to finite compressibility which are, as expected, negligible for liquid He, are important but amenable to the perturbative treatment for typical ultracold atomic systems. (paper)

Bose-Einstein Condensation of a Stochastic Liquid

Science.gov (United States)

Maćkowiak, Jan

The Bogoliubov-Lee-Huang theory of superfluid 4He is modified by introducing an effective temperature scale (which accounts for the deep well of the interatomic potential) and by incorporating into the Hamiltonian a stochastic term Vl, which simulates liquidity of HeI and liquidity of the normal and superfluid component of HeII. Vl depends on two independent random angles αn, αs ∈ [0, π], which characterize the locally ordered motion of the two fluids (the normal fluid and superfluid) comprising HeII. The resulting thermodynamics improves the thermodynamic functions and excitation spectrum Ep(αn, αs) of the superfluid phase, obtained previously, leaving the heat capacity CV (T) of the normal phase, with a minimum at Tmin > 2.17K, unchanged. The theoretical velocity of sound in HeII, equal to the initial slope of Ep(π, π), agrees with experiment.

Free energy of superfluid 3He

International Nuclear Information System (INIS)

Rainer, D.; Serene, J.W.

1976-01-01

A systematic scheme is presented for calculating the free energy of superfluid Fermi liquids by an asymptotic expansion in the small parameter T/subc//T/subF/. This scheme is used to evaluate the strong-coupling corrections to the free energy of superfluid 3 He. It is shown that the leading corrections can be expressed in terms of the normal-state quasiparticle scattering amplitude, and the strong-coupling results are discussed using the s-p approximation for the scattering amplitude

Dark matter seen as a Bose-Einstein condensate

International Nuclear Information System (INIS)

Manzoni, Andre; Pires, Marcelo

2011-01-01

Full text: Astronomical observations of the stellar angular velocity in galaxies shows the general relativity theory, which considers that the usual matter changes the space-time, unable to describe the angular velocity to the peripheral stars. There are two possibilities to solve this problem, or the general relativity theory is not adequate to the phenomena or another type of matter must be considered in the composition of the galaxies. Many astrophysicists are in agreement considering another type of matter. This matter, called dark matter (DM), must interact very weakly with the barionic matter and, therefore, is invisible to direct observation. Some of them consider this dark matter made up of weakly interacting massive particles (WIMPs), which were not detected yet due to their very thin cross-section. A cloud of these particles is distributed around the galaxy under a low temperature and density. If we consider the cloud as a quantum gas, with the energies and the densities low enough to have binary interactions between particles, the gas can reach temperature condition to take a phase transition to the Bose-Einstein condensate where there are a constructive interference partner of these WIMPs. We performed an investigation about the dark matter being a Bose-Einstein condensate of WIMPs confined in itself gravitational potential. Taking the Thomas-Fermi approximation where the number of WIMPs is big enough to neglect the kinetic contribution in the total energy, we got the state equation of barotropic gas. Fitting this state equation with the data of rotational curves and density profiles taken from astronomical observations of galaxies, we estimated the mass and the scattering length of these WIMPs. (author)

Population imbalance as a vortex catalyst in Fermi superfluids

International Nuclear Information System (INIS)

Tempere, J.; Devreese, J.T.

2008-01-01

Pairing leads to superfluidity in ultracold atomic gases, but this pairing can be frustrated when a population imbalance is present between the pairing partners. Here we investigate how vortices in the fermionic superfluid are affected by imbalance. We show that the vortex core radius is increased by imbalance, accommodating excess component atoms. This has two intriguing consequences. Firstly, a small imbalance acts as a catalyst for vortex formation, decreasing the critical rotation frequency. Secondly, imbalanced gases near critical imbalance can exhibit rotationally induced superfluidity

The truncated Wigner method for Bose-condensed gases: limits of validity and applications

International Nuclear Information System (INIS)

Sinatra, Alice; Lobo, Carlos; Castin, Yvan

2002-01-01

We study the truncated Wigner method applied to a weakly interacting spinless Bose-condensed gas which is perturbed away from thermal equilibrium by a time-dependent external potential. The principle of the method is to generate an ensemble of classical fields ψ(r) which samples the Wigner quasi-distribution function of the initial thermal equilibrium density operator of the gas, and then to evolve each classical field with the Gross-Pitaevskii equation. In the first part of the paper we improve the sampling technique over our previous work (Sinatra et al 2000 J. Mod. Opt. 47 2629-44) and we test its accuracy against the exactly solvable model of the ideal Bose gas. In the second part of the paper we investigate the conditions of validity of the truncated Wigner method. For short evolution times it is known that the time-dependent Bogoliubov approximation is valid for almost pure condensates. The requirement that the truncated Wigner method reproduces the Bogoliubov prediction leads to the constraint that the number of field modes in the Wigner simulation must be smaller than the number of particles in the gas. For longer evolution times the nonlinear dynamics of the noncondensed modes of the field plays an important role. To demonstrate this we analyse the case of a three-dimensional spatially homogeneous Bose-condensed gas and we test the ability of the truncated Wigner method to correctly reproduce the Beliaev-Landau damping of an excitation of the condensate. We have identified the mechanism which limits the validity of the truncated Wigner method: the initial ensemble of classical fields, driven by the time-dependent Gross-Pitaevskii equation, thermalizes to a classical field distribution at a temperature T class which is larger than the initial temperature T of the quantum gas. When T class significantly exceeds T a spurious damping is observed in the Wigner simulation. This leads to the second validity condition for the truncated Wigner method, T class - T

Simplicity works for superfluid helium

International Nuclear Information System (INIS)

Bowley, Roger

2000-01-01

The famous philosopher Karl Popper once said that ''science is the art of systematic oversimplification''. Indeed, when faced with a new puzzle the trick is to simplify it without losing the essential physics - something that is easier said than done. However, this approach has paid off recently in low-temperature physics. Last year Richard Packard, Seamus Davis and co-workers at the University of California at Berkeley encountered a puzzling new phenomenon in superfluid helium-3, a quantum fluid that remains a liquid close to absolute zero and exhibits unusual properties such as the ability to flow without friction (A Machenkov et al. 1999 Phys. Rev. Lett. 83 3860). Previous experiments had revealed that certain effects in liquid helium are analogous to effects observed in superconductors, materials that lose all resistance to electric current at low temperatures. When the Berkeley researchers connected two reservoirs of superfluid helium-3, the superfluid flowed back and forth through apertures that formed a ''weak link'' between the two containers. This behaviour is similar to the oscillatory current of electrons that can flow across an insulating gap separating two superconductors - a device that is known as a Josephson junction. What was puzzling about the Berkeley results was that the helium-3 had two different stable configurations, both of which behaved in an unconventional way compared with a Josephson junction. This puzzle has now been solved independently by Sidney Yip at the National Center for Theoretical Sciences in Taiwan, and by Janne Viljas and Erkki Thuneberg at the Helsinki University of Technology in Finland (Phys. Rev. Lett. 1999 83 3864 and 3868). In this article the author describes the latest research on superfluid helium. (UK)

Bright solitons in Bose-Fermi mixtures

International Nuclear Information System (INIS)

Karpiuk, Tomasz; Brewczyk, Miroslaw; RzaPewski, Kazimierz

2006-01-01

We consider the formation of bright solitons in a mixture of Bose and Fermi degenerate gases confined in a three-dimensional elongated harmonic trap. The Bose and Fermi atoms are assumed to effectively attract each other whereas bosonic atoms repel each other. Strong enough attraction between bosonic and fermionic components can change the character of the interaction within the bosonic cloud from repulsive to attractive making thus possible the generation of bright solitons in the mixture. On the other hand, such structures might be in danger due to the collapse phenomenon existing in attractive gases. We show, however, that under some conditions (defined by the strength of the Bose-Fermi components attraction) the structures which neither spread nor collapse can be generated. For elongated enough traps the formation of solitons is possible even at the 'natural' value of the mutual Bose-Fermi ( 87 Rb- 40 K in our case) scattering length

Superfluid H3e in globally isotropic random media

Science.gov (United States)

Ikeda, Ryusuke; Aoyama, Kazushi

2009-02-01

Recent theoretical and experimental studies of superfluid H3e in aerogels with a global anisotropy created, e.g., by an external stress have definitely shown that the A -like phase with an equal-spin pairing in such aerogel samples is in the Anderson-Brinkman-Morel (ABM) (or axial) pairing state. In this paper, the A -like phase of superfluid H3e in globally isotropic aerogel is studied in detail by assuming a weakly disordered system in which singular topological defects are absent. Through calculation of the free energy, a disordered ABM state is found to be the best candidate of the pairing state of the globally isotropic A -like phase. Further, it is found through a one-loop renormalization-group calculation that the coreless continuous vortices (or vortex-Skyrmions) are irrelevant to the long-distance behavior of disorder-induced textures, and that the superfluidity is maintained in spite of lack of the conventional superfluid long-range order. Therefore, the globally isotropic A -like phase at weak disorder is, like in the case with a globally stretched anisotropy, a glass phase with the ABM pairing and shows superfluidity.

Superconducting superfluids in neutron stars

International Nuclear Information System (INIS)

Carter, B.

2002-01-01

For treatment of the layers below the crust of a neutron star it is useful to employ a relativistic model involving three independently moving constituents, representing superfluid neutrons, superfluid protons, and degenerate negatively charged leptons. A Kalb-Ramond type formulation is used here to develop such a model for the specific purpose of application at the semi macroscopic level characterised by lengthscales that are long compared with the separation between the highly localised and densely packed proton vortices of the Abrikosov type lattice that carries the main part of the magnetic flux, but that are short compared with the separation between the neutron vortices. (orig.)

Application of exergetic sustainability index to a nano-scale irreversible Brayton cycle operating with ideal Bose and Fermi gasses

Energy Technology Data Exchange (ETDEWEB)

Açıkkalp, Emin, E-mail: eacikkalp@gmail.com [Department of Mechanical and Manufacturing Engineering, Engineering Faculty, Bilecik S.E. University, Bilecik (Turkey); Caner, Necmettin [Department of Chemistry, Faculty of Arts and Sciences, Eskisehir Osmangazi University, Eskisehir (Turkey)

2015-09-25

Highlights: • An irreversible Brayton cycle operating quantum gasses is considered. • Exergetic sustainability index is derived for nano-scale cycles. • Nano-scale effects are considered. • Calculation are conducted for irreversible cycles. • Numerical results are presented and discussed. - Abstract: In this study, a nano-scale irreversible Brayton cycle operating with quantum gasses including Bose and Fermi gasses is researched. Developments in the nano-technology cause searching the nano-scale machines including thermal systems to be unavoidable. Thermodynamic analysis of a nano-scale irreversible Brayton cycle operating with Bose and Fermi gasses was performed (especially using exergetic sustainability index). In addition, thermodynamic analysis involving classical evaluation parameters such as work output, exergy output, entropy generation, energy and exergy efficiencies were conducted. Results are submitted numerically and finally some useful recommendations were conducted. Some important results are: entropy generation and exergetic sustainability index are affected mostly for Bose gas and power output and exergy output are affected mostly for the Fermi gas by x. At the high temperature conditions, work output and entropy generation have high values comparing with other degeneracy conditions.

px+ipy Superfluid from s-Wave Interactions of Fermionic Cold Atoms

International Nuclear Information System (INIS)

Zhang Chuanwei; Tewari, Sumanta; Lutchyn, Roman M.; Das Sarma, S.

2008-01-01

Two-dimensional (p x +ip y ) superfluids or superconductors offer a playground for studying intriguing physics such as quantum teleportation, non-Abelian statistics, and topological quantum computation. Creating such a superfluid in cold fermionic atom optical traps using p-wave Feshbach resonance is turning out to be challenging. Here we propose a method to create a p x +ip y superfluid directly from an s-wave interaction making use of a topological Berry phase, which can be artificially generated. We discuss ways to detect the spontaneous Hall mass current, which acts as a diagnostic for the chiral p-wave superfluid

Bose enhancement and the ridge

Energy Technology Data Exchange (ETDEWEB)

Altinoluk, Tolga [Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Galicia (Spain); Armesto, Néstor, E-mail: nestor.armesto@usc.es [Departamento de Física de Partículas and IGFAE, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Galicia (Spain); Beuf, Guillaume [Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel); Kovner, Alex [Physics Department, University of Connecticut, 2152 Hillside Road, Storrs, CT 06269-3046 (United States); Lublinsky, Michael [Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel)

2015-12-17

We point out that Bose enhancement in a hadronic wave function generically leads to correlations between produced particles. We show explicitly, by calculating the projectile density matrix in the Color Glass Condensate approach to high-energy hadronic collisions, that the Bose enhancement of gluons in the projectile leads to azimuthal collimation of long range rapidity correlations of the produced particles, the so-called ridge correlations.

Holographic p-wave superfluid in Gauss–Bonnet gravity

International Nuclear Information System (INIS)

Liu, Shancheng; Pan, Qiyuan; Jing, Jiliang

2017-01-01

We construct the holographic p-wave superfluid in Gauss–Bonnet gravity via a Maxwell complex vector field model and investigate the effect of the curvature correction on the superfluid phase transition in the probe limit. We obtain the rich phase structure and find that the higher curvature correction hinders the condensate of the vector field but makes it easier for the appearance of translating point from the second-order transition to the first-order one or for the emergence of the Cave of Winds. Moreover, for the supercurrents versus the superfluid velocity, we observe that our results near the critical temperature are independent of the Gauss–Bonnet parameter and agree well with the Ginzburg–Landau prediction.

Holographic p-wave superfluid in Gauss–Bonnet gravity

Energy Technology Data Exchange (ETDEWEB)

Liu, Shancheng [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Pan, Qiyuan, E-mail: panqiyuan@126.com [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Jing, Jiliang, E-mail: jljing@hunnu.edu.cn [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China)

2017-02-10

We construct the holographic p-wave superfluid in Gauss–Bonnet gravity via a Maxwell complex vector field model and investigate the effect of the curvature correction on the superfluid phase transition in the probe limit. We obtain the rich phase structure and find that the higher curvature correction hinders the condensate of the vector field but makes it easier for the appearance of translating point from the second-order transition to the first-order one or for the emergence of the Cave of Winds. Moreover, for the supercurrents versus the superfluid velocity, we observe that our results near the critical temperature are independent of the Gauss–Bonnet parameter and agree well with the Ginzburg–Landau prediction.

Dissipation in the superfluid helium film

International Nuclear Information System (INIS)

Turkington, R.R.; Harris-Lowe, R.F.

1977-01-01

We have measured the rate of energy dissipation in superfluid helium film flow in an attempt to test a recent theory due to Harris-Lowe, which predicts that for superfluid stream velocities v/sub s/ that just exceed the critical velocity v/sub c0/, the rate of dissipation is given by an equation of the form Q=C(v/sub s/-v/sub c0/)/sup 3/2/. Our experiments at 1.33 K show that the exponent, predicted to be 3/2, is 1.491 +- 0.021

Realization of mechanical rotation in superfluid helium

Science.gov (United States)

Gordon, E. B.; Kulish, M. I.; Karabulin, A. V.; Matyushenko, V. I.; Dyatlova, E. V.; Gordienko, A. S.; Stepanov, M. E.

2017-09-01

The possibility of using miniaturized low-power electric motors submerged in superfluid helium for organization of rotation inside a cryostat has been investigated. It has been revealed that many of commercial micromotors can operate in liquid helium consuming low power. Turret with 5 sample holders, assembled on the base of stepper motor, has been successfully tested in experiments on the nanowire production in quantized vortices of superfluid helium. Application of the stepper motor made it possible in a single experiment to study the effect of various experimental parameters on the yield and quality of the nanowires. The promises for continuous fast rotation of the bath filled by superfluid helium by using high-speed brushless micromotor were outlined and tested. Being realized, this approach will open new possibility to study the guest particles interaction with the array of parallel linear vortices in He II.

Pairing and condensation in a resonant Bose-Fermi mixture

International Nuclear Information System (INIS)

Fratini, Elisa; Pieri, Pierbiagio

2010-01-01

We study by diagrammatic means a Bose-Fermi mixture, with boson-fermion coupling tuned by a Fano-Feshbach resonance. For increasing coupling, the growing boson-fermion pairing correlations progressively reduce the boson condensation temperature and make it eventually vanish at a critical coupling. Such quantum critical point depends very weakly on the population imbalance and, for vanishing boson densities, coincides with that found for the polaron-molecule transition in a strongly imbalanced Fermi gas, thus bridging two quite distinct physical systems.

Simplicity works for superfluid helium

Energy Technology Data Exchange (ETDEWEB)

Bowley, Roger [University of Nottingham, Nottingham (United Kingdom)

2000-02-01

The famous philosopher Karl Popper once said that ''science is the art of systematic oversimplification''. Indeed, when faced with a new puzzle the trick is to simplify it without losing the essential physics - something that is easier said than done. However, this approach has paid off recently in low-temperature physics. Last year Richard Packard, Seamus Davis and co-workers at the University of California at Berkeley encountered a puzzling new phenomenon in superfluid helium-3, a quantum fluid that remains a liquid close to absolute zero and exhibits unusual properties such as the ability to flow without friction (A Machenkov et al. 1999 Phys. Rev. Lett. 83 3860). Previous experiments had revealed that certain effects in liquid helium are analogous to effects observed in superconductors, materials that lose all resistance to electric current at low temperatures. When the Berkeley researchers connected two reservoirs of superfluid helium-3, the superfluid flowed back and forth through apertures that formed a ''weak link'' between the two containers. This behaviour is similar to the oscillatory current of electrons that can flow across an insulating gap separating two superconductors - a device that is known as a Josephson junction. What was puzzling about the Berkeley results was that the helium-3 had two different stable configurations, both of which behaved in an unconventional way compared with a Josephson junction. This puzzle has now been solved independently by Sidney Yip at the National Center for Theoretical Sciences in Taiwan, and by Janne Viljas and Erkki Thuneberg at the Helsinki University of Technology in Finland (Phys. Rev. Lett. 1999 83 3864 and 3868). In this article the author describes the latest research on superfluid helium. (UK)

Anomalous tunneling of collective excitations and effects of superflow in the polar phase of a spin-1 spinor Bose-Einstein condensate

International Nuclear Information System (INIS)

Watabe, Shohei; Ohashi, Yoji; Kato, Yusuke

2011-01-01

We investigate tunneling properties of collective modes in the polar phase of a spin-1 spinor Bose-Einstein condensate (BEC). This spinor BEC state has two kinds of gapless modes (i.e., Bogoliubov and spin-wave). Within the framework of mean-field theory at T=0, we show that these Goldstone modes exhibit perfect transmission in the low-energy limit. Their anomalous tunneling behavior still holds in the presence of superflow, except in the critical current state. In the critical current state, while the tunneling of Bogoliubov mode is accompanied by finite reflection, the spin wave still exhibits perfect transmission, unless the strengths of spin-dependent and spin-independent interactions take the same value. We discuss the relation between perfect transmission of a spin wave and underlying superfluidity through a comparison of wave functions of the spin wave and the condensate.

Incompressible flows of superfluid films on multiply-connected surfaces

International Nuclear Information System (INIS)

Corrada-Emmanuel, A.

1989-01-01

The theory of Riemann surfaces is applied to the problem of constructing quantized vortex flows in closed surfaces of arbitrary but finite genus. An in principle procedure for obtaining the lowest energy flow is presented. It is shown that quantized vortices in non-zero genus surfaces are, in general, not isomorphic to a Coulomb gas. This failure has a geometrical origin: the appearance in non-zero genus surfaces of closed curves that are not the boundary of any area. A theorem of Riemann is applied to the genus one surface, the torus, to show quantitatively how to construct the quantized vortices. Because of the breakdown in the isomorphism between quantized vortices and charges, a novel effect is possible: the violation of Earnshaw's theorem. On a torus a single vortex can be placed in local stable equilibrium. The uniform flows around the holes of the torus also lead to a new result: a non-vortex mechanism for the destruction of superfluidity in the film. An explicit formula is derived showing this effect by considering the response of a helium film to a rotation of the torus. The author predicts that torii of dissimilar proportions will exhibit different superfluid densities at the same temperature

Thermo-optically induced interactions in photon Bose-Einstein Condensates

Science.gov (United States)

Alaeian, Hadiseh; Bartels, Clara; Weitz, Martin

Bose-Einstein condensation (BEC), a new state of matter, emerges when the de Broglie wavelength of bosons becomes larger than the particle separation, leading to a macroscopic occupation of the system ground state. Followed by the first experimental demonstrations of BEC in cold atomic gases, this phase transition has been observed in other bosonic gases, as polaritons and phonons. The most recent one, photon BEC, is a promising candidate for a new generation of coherent photon sources. Due to their infancy, however, many of their properties are still unknown or only partly explored. In this talk I will present my latest results on the implications of photon interactions in photon BECs. In particular, I will investigate the effect of a thermo-optic non-linearity, leading to spatially non-local and delayed interactions. Starting from the steady state behavior, I will explore the spectrum of elementary excitations as a small perturbation. Moreover, I will discuss the resulting effective photon dispersion, manifesting various properties including possible superfluidity, as well as roton and maxon modes. The implications of physical parameters as absorption, number of photons in the condensate, and cavity trap on the dispersion will be discussed. The results of this study shed new light on the implication of interactions in photonic many-body systems. Hadiseh Alaeian acknowledges the generous support from Alexander von Humboldt Foundation.

Superfluid phase stiffness in electron doped superconducting Gd-123

Science.gov (United States)

Das, P.; Ghosh, Ajay Kumar

2018-05-01

Current-voltage characteristics of Ce substituted Gd-123 superconductor exhibits nonlinearity below a certain temperature below the critical temperature. An exponent is extracted using the nonlinearity of current-voltage relation. Superfluid phase stiffness has been studied as a function of temperature following the Ambegaokar-Halperin-Nelson-Siggia (AHNS) theory. Phase stiffness of the superfluid below the superconducting transition is found to be sensitive to the change in the carrier concentration in superconducting system. There may be a crucial electron density which affects superfluid stiffness strongly. Electron doping is found to be effective even if the coupling of the superconducting planes is changed.

Observation of spin superfluidity: YIG magnetic films and beyond

Science.gov (United States)

Sonin, Edouard

2018-03-01

From topology of the order parameter of the magnon condensate observed in yttrium-iron-garnet (YIG) magnetic films one must not expect energetic barriers making spin supercurrents metastable. But we show that some barriers of dynamical origin are possible nevertheless until the gradient of the phase (angle of spin precession) does not exceed the critical value (analog of the Landau critical velocity in superfluids). On the other hand, recently published claims of experimental detection of spin superfluidity in YIG films and antiferromagnets are not justified, and spin superfluidity in magnetically ordered solids has not yet been experimentally confirmed.

Bose enhancement and the ridge

Directory of Open Access Journals (Sweden)

Tolga Altinoluk

2015-12-01

Full Text Available We point out that Bose enhancement in a hadronic wave function generically leads to correlations between produced particles. We show explicitly, by calculating the projectile density matrix in the Color Glass Condensate approach to high-energy hadronic collisions, that the Bose enhancement of gluons in the projectile leads to azimuthal collimation of long range rapidity correlations of the produced particles, the so-called ridge correlations.

Electron induced formation and stability of molecular and cluster ions in gas phase and superfluid helium nanodroplets

International Nuclear Information System (INIS)

Aleem, M. A.

2010-01-01

The present PhD thesis represents a broad range study of electron induced formation and stability of positive and negative ions in gas phase and superfluid helium nanodroplets. The molecules studied are of industrial, environmental, plasma and biological relevance. The knowledge obtained from the study provides new insight for the proper understanding and control on energetics and dynamics of the reactions involved in the formation and fragmentation processes of the studied molecules and clusters. The experiments are accomplished and investigated using mass spectrometric techniques for the formation of molecular and cluster ions using different mass spectrometers available in our laboratory. One part of the work is focused on electron-induced reactions of the molecules in gas phase. Especially focus is laid to electron attachment to the isomers of mononitrotolouene used as an additive to explosives. The fragile nature and high internal energy of these molecules has lead to extensive fragmentation following the ionisation process. Dissociative electron attachment to the three different isomers has shown different resonances and therefore this process can be utilized to explicitly distinguish these isomers. Anion efficiency curves of the isomers have been studied using effusive molecular beam source in combination with a hemispherical electron monochromator as well as a Nier-type ion source attached to a sector field mass spectrometer. The outcome of the experiment is a reliable and effective detection method highly desirable for environmental and security reasons. Secondly, dissociative electron ionization of acetylene and propene is studied and their data is directly related to the plasma modelling for plasma fusion and processing reactors. Temperature effects for dissociative electron attachment to halo-hydrocarbons are also measured using a trochoidal electron monochromator. The second part of the work is concerned with the investigation of electron

The mobility of negative ions in superfluid 3He

International Nuclear Information System (INIS)

Solomaa, M.

1982-01-01

This article reviews recent experimental and theoretical work on the mobility of negative ions in the superfluid A and B phases of liquid 3 He. In the normal Fermi liquid at temperatures below approximately 50 mK and also in the superfluid close to the superfluid transition temperature, Tsub(c), the mobility of a negative ion may simply be considered as limited by the elastic scattering of 3 He quasiparticles. This explains the constancy of the ion mobility in the normal phase. However, underlying the rapid increase of the measured mobility in the superfluid phases there is a subtle quantum-mechanical scattering effect. Detailed solutions of the 3 He quasiparticle-negative ion scattering process in the pair-correlated state provide a simple physical picture of an energy-dependent forward-peaking phenomenon. This yields quantitative theoretical results for the ion mobility in the quasi-isotropic B phase and for the ion mobility tensor in the anisotropic A phase which agree with the experimental data. (author)

Second sound velocities in superfluid 3He-4He solutions

International Nuclear Information System (INIS)

Dikina, L.S.; Kotenev, G.Ya.; Rudavskij, Eh.Ya.

1978-01-01

The velocities of the second sound in the superfluid He 3 -He 4 solutions were measured by the pulse method in the range of temperatures from 1.3 K to Tsub(lambda) and for He 3 concentrations up to 13%.The results obtained supplemented by those available before give the complete description of the concentration and temperature dependences of the second sound velocity in superfluid He 3 -He 4 solutions. The comprehensive comparison of the experimental data on the velocity of the second sound with the theoretical calculations for the superfluid solutions with arbitrary content of He 3 is performed. The good agreement is found between experiment and the theory. The experimental data obtained are used for determination of the potential, which determines the properties of the superfluid solutions

Sustained propagation and control of topological excitations in polariton superfluid

Science.gov (United States)

Pigeon, Simon; Bramati, Alberto

2017-09-01

We present a simple method to compensate for losses in a polariton superfluid. Based on a weak support field, it allows for the extended propagation of a resonantly driven polariton superfluid with minimal energetic cost. Moreover, this setup is based on optical bistability and leads to the significant release of the phase constraint imposed by resonant driving. This release, together with macroscopic polariton propagation, offers a unique opportunity to study the hydrodynamics of the topological excitations of polariton superfluids such as quantized vortices and dark solitons. We numerically study how the coherent field supporting the superfluid flow interacts with the vortices and how it can be used to control them. Interestingly, we show that standard hydrodynamics does not apply for this driven-dissipative fluid and new types of behaviour are identified.

Microscopic and hydrodynamic theory of superfluidity in periodic solids

International Nuclear Information System (INIS)

Saslow, W.M.

1977-01-01

The microscopic theory of fourth sound and of the superfluid fraction for perfect one-component periodic solids has been derived. It is applicable to finite temperatures and is restricted to the case of well-defined excitations. One finds that the superfluid fraction is a tensor rho/sub s//sub b//sub β//rho 0 and that the fourth-sound velocity C 4 is a tensor (C 2 4 )/sub b//sub β/ = (partialrho 0 /partialμ 0 ) -1 rho/sub s//sub b//sub β/, where μ 0 and rho 0 are the spatially averaged values of the chemical potential (per unit mass) and of the number density. In addition, the exact nonlinearized hydrodynamics is derived, and for fourth sound is found to give agreement with the microscopic theory. Because the superfluid velocity for a periodic solid cannot be generated by a Galilean transformation, it is found that elastic waves are loaded by the average mass density of the system. This is in contrast to the result of Andreev and Lifshitz, which involves only the superfluid fraction. Therefore one cannot look to (hydrodynamic) elastic waves for an obvious signature of superfluidity. A study of the effect of a transducer indicates that fourth sound will be generated to a non-negligible extent only when the crystal is imperfect (i.e., it has vacancies, interstitials, or impurities). On the other hand, a heater might be an effective generator of fourth sound, provided that the mean free path for umklapp processes is sufficiently small. In the limit of zero crystallinity the theory shows that second sound, rather than fourth sound, occurs. Detection of superflow by rotation experiments is also considered. It is pointed out that, because the superfluid velocity is not Galilean, two-fluid counterflow does not occur. Hence, it appears that rapid angular acceleration or deceleration would be the best technique for bringing the superfluid into rotation

Inflationary Quasiparticle Creation and Thermalization Dynamics in Coupled Bose-Einstein Condensates.

Science.gov (United States)

Posazhennikova, Anna; Trujillo-Martinez, Mauricio; Kroha, Johann

2016-06-03

A Bose gas in a double-well potential, exhibiting a true Bose-Einstein condensate (BEC) amplitude and initially performing Josephson oscillations, is a prototype of an isolated, nonequilibrium many-body system. We investigate the quasiparticle (QP) creation and thermalization dynamics of this system by solving the time-dependent Keldysh-Bogoliubov equations. We find avalanchelike QP creation due to a parametric resonance between BEC and QP oscillations, followed by slow, exponential relaxation to a thermal state at an elevated temperature, controlled by the initial excitation energy of the oscillating BEC above its ground state. The crossover between the two regimes occurs because of an effective decoupling of the QP and BEC oscillations. This dynamics is analogous to elementary particle creation in models of the early universe. The thermalization in our setup occurs because the BEC acts as a grand canonical reservoir for the quasiparticle system.

Inflationary Quasiparticle Creation and Thermalization Dynamics in Coupled Bose-Einstein Condensates

Science.gov (United States)

Posazhennikova, Anna; Trujillo-Martinez, Mauricio; Kroha, Johann

2016-06-01

A Bose gas in a double-well potential, exhibiting a true Bose-Einstein condensate (BEC) amplitude and initially performing Josephson oscillations, is a prototype of an isolated, nonequilibrium many-body system. We investigate the quasiparticle (QP) creation and thermalization dynamics of this system by solving the time-dependent Keldysh-Bogoliubov equations. We find avalanchelike QP creation due to a parametric resonance between BEC and QP oscillations, followed by slow, exponential relaxation to a thermal state at an elevated temperature, controlled by the initial excitation energy of the oscillating BEC above its ground state. The crossover between the two regimes occurs because of an effective decoupling of the QP and BEC oscillations. This dynamics is analogous to elementary particle creation in models of the early universe. The thermalization in our setup occurs because the BEC acts as a grand canonical reservoir for the quasiparticle system.

Role of superconducting energy gap in extended BCS-Bose crossover theory

Science.gov (United States)

Chávez, I.; García, L. A.; de Llano, M.; Grether, M.

2017-10-01

The generalized Bose-Einstein condensation (GBEC) theory of superconductivity (SC) is briefly surveyed. It hinges on three distinct new ingredients: (i) Treatment of Cooper pairs (CPs) as actual bosons since they obey Bose statistics, in contrast to BCS pairs which do not obey Bose commutation relations; (ii) inclusion of two-hole Cooper pairs (2hCPs) on an equal footing with two-electron Cooper pairs (2eCPs), thus making this a complete boson-fermion (BF) model; and (iii) inclusion in the resulting ternary ideal BF gas with particular BF vertex interactions that drive boson formation/disintegration processes. GBEC subsumes as special cases both BCS (having its 50-50 symmetry of both kinds of CPs) and ordinary BEC theories (having no 2hCPs), as well as the now familiar BCS-Bose crossover theory. We extended the crossover theory with the explicit inclusion of 2hCPs and construct a phase diagram of Tc/TF versus n/nf, where Tc and TF are the critical and Fermi temperatures, n is the total number density and nf that of unbound electrons at T = 0. Also, with this extended crossover one can construct the energy gap Δ(T)/Δ(0) versus T/Tc for some elemental SCs by solving at least two equations numerically: a gap-like and a number equation. In 50-50 symmetry, the energy gap curve agrees quite well with experimental data. But ignoring 2hCPs altogether leads to the gap curve falling substantially below that with 50-50 symmetry which already fits the data quite well, showing that 2hCPs are indispensable to describe SCs.

Superfluid helium at subcritical active core

International Nuclear Information System (INIS)

Vasil'ev, V.V.; Lopatkin, A.V.; Muratov, V.G.; Rakhno, I.L.

2002-01-01

Power range and neutron flux wherein super thermal source was realized at high volume of superfluid helium were investigated. MCU, BRAND, MCNP codes were used for the calculation of reactors. It is shown that the availability of full-size diameter for cryogenic source of ultracold neutrons, as the source with superfluid helium is considered, is possible in the reflector of subcritical assembly. Results obtained from the MCNP-4B code application demonstrated that the density of thermal neutron flux in helium must be not higher than 2.3 x 10 11 s -1 cm -2 [ru

Dynamics of superfluid helium-3 in flow channels with restricted geometries

International Nuclear Information System (INIS)

Kopnin, N.B.

1986-01-01

The dynamics of superfluid helium-3 in flow channels with transverse sizes smaller than the mean free path of quasiparticles with respect to collisions with each other is considered, taking into account the diffusive reflection of quasiparticles from the walls. For quasiclassical Green functions the boundary conditions obtained by Ovchinnikov for the similar problem in superconductors have been used. Equations are derived defining the behavior of the difference between chemical potentials of normal and superfluid components of helium-3. These equations describe a phenomenon similar to the branch imbalance (or charge imbalance) in superconductors, and determine the relaxation depth of the pressure gradient in superfluid helium-3. The time-dependent GinzburgLandau equations are also obtained for the order parameter in the case when the transverse size of the channel is close to the critical value when the superfluid transition temperature goes to zero. The approach makes it possible to study theoretically effects related to the overcritical flows of superfluid helium-3 through narrow channels under pressure

Optimized evaporative cooling for sodium Bose-Einstein condensation against three-body loss

International Nuclear Information System (INIS)

Shobu, Takahiko; Yamaoka, Hironobu; Imai, Hiromitsu; Morinaga, Atsuo; Yamashita, Makoto

2011-01-01

We report on a highly efficient evaporative cooling optimized experimentally. We successfully created sodium Bose-Einstein condensates with 6.4x10 7 atoms starting from 6.6x10 9 thermal atoms trapped in a magnetic trap by employing a fast linear sweep of radio frequency at the final stage of evaporative cooling so as to overcome the serious three-body losses. The experimental results such as the cooling trajectory and the condensate growth quantitatively agree with the numerical simulations of evaporative cooling on the basis of the kinetic theory of a Bose gas carefully taking into account our specific experimental conditions. We further discuss theoretically a possibility of producing large condensates, more than 10 8 sodium atoms, by simply increasing the number of initial thermal trapped atoms and the corresponding optimization of evaporative cooling.

Fermi states of Bose systems in three space dimensions

International Nuclear Information System (INIS)

Garbaczewski, P.

1985-01-01

Recently an exact spectral solution was constructed by Sudarshan and Tata for the (NTHETA) Fermi version of the Lee model. We demonstrate that it provides a partial solution for the related pure Bose spectral problems. Moreover, the (NTHETA) Bose (Bolsterli--Nelson) version of the Lee model is shown to possess Fermi partners, both exhibiting the partial solubility interplay: finding solutions in the Fermi case would presumably be easier than in the original Bose model. Fermi states of the underlying Bose systems in three space dimensions are explicitly identified

Soliton resonance in bose-einstein condensate

Science.gov (United States)

Zak, Michail; Kulikov, I.

2002-01-01

A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.

Symmetric structures of coherent states in superfluid helium-4

International Nuclear Information System (INIS)

Ahmad, M.

1981-02-01

Coherent States in superfluid helium-4 are discussed and symmetric structures are assigned to these states. Discrete and continuous series functions are exhibited for such states. Coherent State structure has been assigned to oscillating condensed bosons and their inter-relations and their effects on the superfluid system are analysed. (author)

LAMBDA-hyperon superfluidity in neutron star cores

CERN Document Server

Takatsuka, T

2000-01-01

Superfluidity of LAMBDA hyperons in neutron star cores is investigated by a realistic approach to use reliable LAMBDA LAMBDA interactions and the effective mass of LAMBDA based on the G-matrix calculations. It is found that LAMBDA superfluid can exist at rho approx = (rho sub t approx rho sub d) with rho sub t approx = 2 rho sub 0 (rho sub 0 being the nuclear density) and rho sub d approx = (3 - 4.5)rho sub 0 , depending on hyperon core models.

Shear viscosity and imperfect fluidity in bosonic and fermionic superfluids

Science.gov (United States)

Boyack, Rufus; Guo, Hao; Levin, K.

2014-12-01

In this paper we address the ratio of the shear viscosity to entropy density η /s in bosonic and fermionic superfluids. A small η /s is associated with nearly perfect fluidity, and more general measures of the fluidity perfection/imperfection are of wide interest to a number of communities. We use a Kubo approach to concretely address this ratio via low-temperature transport associated with the quasiparticles. Our analysis for bosonic superfluids utilizes the framework of the one-loop Bogoliubov approximation, whereas for fermionic superfluids we apply BCS theory and its BCS-BEC extension. Interestingly, we find that the transport properties of strict BCS and Bogoliubov superfluids have very similar structures, albeit with different quasiparticle dispersion relations. While there is a dramatic contrast between the power law and exponential temperature dependence for η alone, the ratio η /s for both systems is more similar. Specifically, we find the same linear dependence (on the ratio of temperature T to inverse lifetime γ (T ) ) with η /s ∝T /γ (T ) , corresponding to imperfect fluidity. By contrast, near the unitary limit of BCS-BEC superfluids a very different behavior results, which is more consistent with near-perfect fluidity.

Baryonic 3P2 superfluidity under charged-pion condensation with Δ isobar

International Nuclear Information System (INIS)

Takatsuka, T.; Tamagaki, R.

1999-01-01

We study the baryonic 3 P 2 superfluidity under charged-pion condensation with isobar (Δ) degrees of freedom. After a remark on motivations of the present study, the outline of theoretical framework is briefly described, typical results of the superfluid critical temperature are shown, and the possibility of coexistence of the superfluid with charged-pion condensation is discussed. (author)

Numerical modeling of exciton-polariton Bose-Einstein condensate in a microcavity

Science.gov (United States)

Voronych, Oksana; Buraczewski, Adam; Matuszewski, Michał; Stobińska, Magdalena

2017-06-01

A novel, optimized numerical method of modeling of an exciton-polariton superfluid in a semiconductor microcavity was proposed. Exciton-polaritons are spin-carrying quasiparticles formed from photons strongly coupled to excitons. They possess unique properties, interesting from the point of view of fundamental research as well as numerous potential applications. However, their numerical modeling is challenging due to the structure of nonlinear differential equations describing their evolution. In this paper, we propose to solve the equations with a modified Runge-Kutta method of 4th order, further optimized for efficient computations. The algorithms were implemented in form of C++ programs fitted for parallel environments and utilizing vector instructions. The programs form the EPCGP suite which has been used for theoretical investigation of exciton-polaritons. Catalogue identifier: AFBQ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AFBQ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: BSD-3 No. of lines in distributed program, including test data, etc.: 2157 No. of bytes in distributed program, including test data, etc.: 498994 Distribution format: tar.gz Programming language: C++ with OpenMP extensions (main numerical program), Python (helper scripts). Computer: Modern PC (tested on AMD and Intel processors), HP BL2x220. Operating system: Unix/Linux and Windows. Has the code been vectorized or parallelized?: Yes (OpenMP) RAM: 200 MB for single run Classification: 7, 7.7. Nature of problem: An exciton-polariton superfluid is a novel, interesting physical system allowing investigation of high temperature Bose-Einstein condensation of exciton-polaritons-quasiparticles carrying spin. They have brought a lot of attention due to their unique properties and potential applications in polariton-based optoelectronic integrated circuits. This is an out-of-equilibrium quantum system confined

On the disappearance of superfluidity in helium films

International Nuclear Information System (INIS)

Bannink, G.

1983-01-01

Experiments to investigate the changes in superfluid properties when helium films become thinner are reported. A thin-film oscillator, formed by two large filmreservoirs connected by a long and narrow tube, is used to study both the mass transport properties and the third-sound phenomena. Both sets of data are analysed in the framework of a two-fluid model. Absolute values for the areal superfluid density are deduced from the results, and also the observation of friction in the film itself is briefly discussed. A series of additional measurements of the thermo-mechanical effect in the reservoirs, with the purpose of determing the thickness at which onset of superfluidity occurs, are also reported. Finally the overall picture of the film properties is discussed on the basis of a phase diagram of the observed mobilities. (Auth.)

Symmetry-protected topological superfluids and superconductors. From the basics to 3He

International Nuclear Information System (INIS)

Mizushima, Takeshi; Tsutsumi, Yasumasa; Kawakami, Takuto; Sato, Masatoshi; Ichioka, Masanori; Machida, Kazushige

2016-01-01

In this article, we give a comprehensive review of recent progress in research on symmetry-protected topological superfluids and topological crystalline superconductors, and their physical consequences such as helical and chiral Majorana fermions. We start this review article with the minimal model that captures the essence of such topological materials. The central part of this article is devoted to the superfluid 3 He, which serves as a rich repository of novel topological quantum phenomena originating from the intertwining of symmetries and topologies. In particular, it is emphasized that the quantum fluid confined to nanofabricated geometries possesses multiple superfluid phases composed of the symmetry-protected topological superfluid B-phase, the A-phase as a Weyl superfluid, the nodal planar and polar phases, and the crystalline ordered stripe phase. All these phases generate noteworthy topological phenomena, including topological phase transitions concomitant with spontaneous symmetry breaking, Majorana fermions, Weyl superfluidity, emergent supersymmetry, spontaneous edge mass and spin currents, topological Fermi arcs, and exotic quasiparticles bound to topological defects. In relation to the mass current carried by gapless edge states, we also briefly review a longstanding issue on the intrinsic angular momentum paradox in 3 He-A. Moreover, we share the current status of our knowledge on the topological aspects of unconventional superconductors, such as the heavy-fermion superconductor UPt 3 and superconducting doped topological insulators, in connection with the superfluid 3 He. (author)

Spectroscopy of dark soliton states in Bose-Einstein condensates

International Nuclear Information System (INIS)

Bongs, K; Burger, S; Hellweg, D; Kottke, M; Dettmer, S; Rinkleff, T; Cacciapuoti, L; Arlt, J; Sengstock, K; Ertmer, W

2003-01-01

Experimental and numerical studies of the velocity field of dark solitons in Bose-Einstein condensates are presented. The formation process after phase imprinting as well as the propagation of the emerging soliton are investigated using spatially resolved Bragg spectroscopy of soliton states in Bose-Einstein condensates of 87 Rb. A comparison of experimental data to results from numerical simulations of the Gross-Pitaevskii equation clearly identifies the flux underlying a dark soliton propagating in a Bose-Einstein condensate. The results allow further optimization of the phase imprinting method for creating collective excitations of Bose-Einstein condensates

Adiabatic effective action for vortices in neutral and charged superfluids

International Nuclear Information System (INIS)

Hatsuda, M.; Sato, M.; Yahikozawa, S.; Hatsuda, T.

1996-01-01

Adiabatic effective action for vortices in neutral and charged superfluids at zero temperature are calculated using the topological Landau-Ginzburg theory recently proposed by Hatsuda, Yahikozawa, Ao and Thouless, and vortex dynamics are examined. The Berry phase term arising in the effective action naturally yields the Magnus force in both neutral and charged superfluids. It is shown that in neutral superfluid there is only one degree of freedom, namely the center of vorticities, and the vortex energy is proportional to the sum of all vorticities so that it is finite only for the vanishing total vorticity of the system. On the other hand the effective mass and the vortex energy for a vortex in charged superfluids are defined individually as expected. The effects of the vortex core on these quantities are also estimated. The possible depinning scenario which is governed by the Magnus force and the inertial mass is also discussed

Spin dynamics in a two-dimensional quantum gas

DEFF Research Database (Denmark)

Pedersen, Poul Lindholm; Gajdacz, Miroslav; Deuretzbacher, Frank

2014-01-01

We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimp......We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions...

Superfluidity of nuclei and the nucleon--phonon interaction

International Nuclear Information System (INIS)

Kadmenskii, S.G.; Luk'yanovich, P.A.

1989-01-01

The Lehmann expansion for the exact one-particle Green function in a system with superfluidity is obtained. Expressions for the correlation function and mass operator are derived with allowance for a retarded nucleon--phonon interaction. Within the scope of the formalism developed, equations for the superfluidity of nuclei allowing for quasiparticle fragmentation effects are derived. It is concluded that the retarded nucleon--phonon interaction in the particle--particle channel causes a decrease of the fragmentation of the one-particle force in the vicinity of the Fermi surface. It is shown that inclusion of a nonretarded vacuum interaction of two nucleons and of a retarded interaction due to the exchange between two nucleons of low-lying highly collectivized quadrupole phonons is sufficient to provide the necessary scale of attraction in the description of pair correlations of nucleons in nuclei with developed superfluidity

Self-energy dispersion effects on neutron matter superfluidity

International Nuclear Information System (INIS)

Zuo Wei

2001-01-01

The effects of the dispersion and ground state correlation of the single particle self-energy on neutron matter superfluidity have been investigated in the framework of the Extended Brueckner-Hartree-Fock and the generalized BCS approaches. A sizable reduction of the energy gap is found due to the energy dependence of the self-energy. And the inclusion of the ground state correlations in the self-energy suppresses further the neutron matter superfluidity

Elastic scattering of a Bose-Einstein condensate at a potential landscape

International Nuclear Information System (INIS)

Březinová, Iva; Burgdörfer, Joachim; Lode, Axel U J; Streltsov, Alexej I; Cederbaum, Lorenz S; Alon, Ofir E; Collins, Lee A; Schneider, Barry I

2014-01-01

We investigate the elastic scattering of Bose-Einstein condensates at shallow periodic and disorder potentials. We show that the collective scattering of the macroscopic quantum object couples to internal degrees of freedom of the Bose-Einstein condensate such that the Bose-Einstein condensate gets depleted. As a precursor for the excitation of the Bose-Einstein condensate we observe wave chaos within a mean-field theory

Superfluid response in heavy fermion superconductors

Science.gov (United States)

Zhong, Yin; Zhang, Lan; Shao, Can; Luo, Hong-Gang

2017-10-01

Motivated by a recent London penetration depth measurement [H. Kim, et al., Phys. Rev. Lett. 114, 027003 (2015)] and novel composite pairing scenario [O. Erten, R. Flint, and P. Coleman, Phys. Rev. Lett. 114, 027002 (2015)] of the Yb-doped heavy fermion superconductor CeCoIn5, we revisit the issue of superfluid response in the microscopic heavy fermion lattice model. However, from the literature, an explicit expression for the superfluid response function in heavy fermion superconductors is rare. In this paper, we investigate the superfluid density response function in the celebrated Kondo-Heisenberg model. To be specific, we derive the corresponding formalism from an effective fermionic large- N mean-field pairing Hamiltonian whose pairing interaction is assumed to originate from the effective local antiferromagnetic exchange interaction. Interestingly, we find that the physically correct, temperature-dependent superfluid density formula can only be obtained if the external electromagnetic field is directly coupled to the heavy fermion quasi-particle rather than the bare conduction electron or local moment. Such a unique feature emphasizes the key role of the Kondo-screening-renormalized heavy quasi-particle for low-temperature/energy thermodynamics and transport behaviors. As an important application, the theoretical result is compared to an experimental measurement in heavy fermion superconductors CeCoIn5 and Yb-doped Ce1- x Yb x CoIn5 with fairly good agreement and the transition of the pairing symmetry in the latter material is explained as a simple doping effect. In addition, the requisite formalism for the commonly encountered nonmagnetic impurity and non-local electrodynamic effect are developed. Inspired by the success in explaining classic 115-series heavy fermion superconductors, we expect the present theory will be applied to understand other heavy fermion superconductors such as CeCu2Si2 and more generic multi-band superconductors.

Superconductivity and superfluidity as universal emergent phenomena in diverse physical systems

International Nuclear Information System (INIS)

Guidry, Mike

2014-01-01

Superconductivity and superfluidity are observed across a strikingly broad range of physical systems. This universality seems unlikely to be coincidental but a unified understanding of superconductivity and superfluidity across these highly disparate fields seems impossible in traditional microscopic terms. I give an overview of superconductivity and superfluidity found in various fermionic condensed matter, nuclear physics, and neutron star systems, and propose that all result from generic algebraic structures for the emergent effective Hamiltonian, with the role of underlying microscopic physics largely relegated to influence on parameter values

Chiral superfluidity of the quark-gluon plasma

International Nuclear Information System (INIS)

Kalaydzhyan, Tigran

2012-08-01

In this paper we argue that the strongly coupled quark-gluon plasma can be considered as a chiral superfluid. The ''normal'' component of the fluid is the thermalized matter in common sense, while the ''superfluid'' part consists of long wavelength (chiral) fermionic states moving independently. We use several nonperturbative techniques to demonstrate that. First, we analyze the fermionic spectrum in the deconfinement phase (T c c ) using lattice (overlap) fermions and observe a gap between near-zero modes and the bulk of the spectrum. Second, we use the bosonization procedure with a finite cut-off and obtain a dynamical axion-like field out of the chiral fermionic modes. Third, we use relativistic hydrodynamics for macroscopic description of the effective theory obtained after the bosonization. Finally, solving the hydrodynamic equations in gradient expansion, we find that in the presence of external electromagnetic fields the motion of the ''superfluid'' component gives rise to the chiral magnetic, chiral electric and dipole wave effects. Latter two effects are specific for a two-component fluid, which provides us with crucial experimental tests of the model.

Interactions of Ultracold Impurity Particles with Bose-Einstein Condensates

Science.gov (United States)

2015-06-23

AFRL-OSR-VA-TR-2015-0141 INTERACTIONS OF ULTRACOLD IMPURITY PARTICLES WITH BOSE- EINSTEIN CONDENSATES Georg Raithel UNIVERSITY OF MICHIGAN Final...SUBTITLE Interactions of ultracold impurity particles with Bose- Einstein Condensates 5a. CONTRACT NUMBER FA9550-10-1-0453 5b. GRANT NUMBER 5c...Interactions of ultracold impurity particles with Bose- Einstein Condensates Contract/Grant #: FA9550-10-1-0453 Reporting Period: 8/15/2010 to 2/14

Superfluid helium-4: An introductory review

International Nuclear Information System (INIS)

Vinen, W.F.

1983-01-01

Helium was first liquefied by Kamerlingh Onnes in Leiden in July 1908, an achievement that followed much careful and painstaking work. On the same day Onnes reduced the temperature of his helium to a value approaching lK, and he must therefore have produced and observed the superfluid phase. These experimental discoveries led very quickly to a series of remarkable theoretical contributions that laid the foundations for all subsequent work. The period since the second world war has of course seen an enormous amount of work on superfluid helium-4. In reviewing it the author tries to see it in terms of two threads: one originating from Landau; the other from London

Exciton correlations and input–output relations in non-equilibrium exciton superfluids

International Nuclear Information System (INIS)

Ye, Jinwu; Sun, Fadi; Yu, Yi-Xiang; Liu, Wuming

2013-01-01

The photoluminescence (PL) measurements on photons and the transport measurements on excitons are the two types of independent and complementary detection tools to search for possible exciton superfluids in electron–hole semi-conductor bilayer systems. In fact, it was believed that the transport measurements can provide more direct evidences on superfluids than the spectroscopic measurements. It is important to establish the relations between the two kinds of measurements. In this paper, using quantum Heisenberg–Langevin equations, we establish such a connection by calculating various exciton correlation functions in the putative exciton superfluids. These correlation functions include both normal and anomalous greater, lesser, advanced, retarded, and time-ordered exciton Green functions and also various two exciton correlation functions. We also evaluate the corresponding normal and anomalous spectral weights and the Keldysh distribution functions. We stress the violations of the fluctuation and dissipation theorem among these various exciton correlation functions in the non-equilibrium exciton superfluids. We also explore the input–output relations between various exciton correlation functions and those of emitted photons such as the angle resolved photon power spectrum, phase sensitive two mode squeezing spectrum and two photon correlations. Applications to possible superfluids in the exciton–polariton systems are also mentioned. For a comparison, using conventional imaginary time formalism, we also calculate all the exciton correlation functions in an equilibrium dissipative exciton superfluid in the electron–electron coupled semi-conductor bilayers at the quantum Hall regime at the total filling factor ν T =1. We stress the analogies and also important differences between the correlations functions in the two exciton superfluid systems. - Highlights: ► Establish the relations between photoluminescence and transport measurements. ► Stress the

Mobility of negative ions in superfluid 3He-B

International Nuclear Information System (INIS)

Baym, G.; Pethick, C.J.; Salomaa, M.

1979-01-01

We calculate the mobility of negative ions in superfluid 3 He-B. We first derive the general formula for the mobility, and show that to a good approximation the scattering of quasiparticles from an ion may be treated as elastic, both in the superfluid for temperatures not too far below the transition temperature and also in the normal state. The scattering cross section in the superfluid is then calculated in terms of normal state properties; as we show, it is vital to include the effects of superfluid correlations on intermediate states in the scattering process. We find that for quasiparticles near the gap edge, the quasiparticle: ion scattering amplitude has a resonant behavior, and that as a result of interference among many partial waves, the differential scattering cross section is strongly peaked in the forward direction and reduced at larger angles, in much the same way as in diffraction. The transport cross section for such a quasiparticle is strongly reduced compared to that for a normal state quasiparticle, and the mobility is consequently strongly enhanced. Detailed calculations of the mobility which contain essentially no free parameters, agree well with the experimental data

Bose-Einstein Condensation

Indian Academy of Sciences (India)

absolute zero. These ideas had ... Everybody is talking about Bose-Einstein condensation. This discovery ... needed if we want to find the probability distribution of the x- ... Boltzmann took two approaches to the problem, both of them deep and ...

Bose-Einstein correlations in W-pair decays

CERN Document Server

Barate, R; Ghez, P; Goy, C; Jézéquel, S; Lees, J P; Martin, F; Merle, E; Minard, M N; Pietrzyk, B; Alemany, R; Bravo, S; Casado, M P; Chmeissani, M; Crespo, J M; Fernández, E; Fernández-Bosman, M; Garrido, L; Graugès-Pous, E; Juste, A; Martínez, M; Merino, G; Miquel, R; Mir, L M; Morawitz, P; Pacheco, A; Riu, I; Ruiz, H; Colaleo, A; Creanza, D; De Palma, M; Iaselli, Giuseppe; Maggi, G; Maggi, M; Nuzzo, S; Ranieri, A; Raso, G; Ruggieri, F; Selvaggi, G; Silvestris, L; Tempesta, P; Tricomi, A; Zito, G; Huang, X; Lin, J; Ouyang, Q; Wang, T; Xie, Y; Xu, R; Xue, S; Zhang, J; Zhang, L; Zhao, W; Abbaneo, D; Boix, G; Buchmüller, O L; Cattaneo, M; Cerutti, F; Ciulli, V; Davies, G; Dissertori, G; Drevermann, H; Forty, Roger W; Frank, M; Gianotti, F; Greening, T C; Halley, A W; Hansen, J B; Harvey, J; Janot, P; Jost, B; Kado, M; Leroy, O; Maley, P; Mato, P; Minten, Adolf G; Moutoussi, A; Ranjard, F; Rolandi, Luigi; Schlatter, W D; Schmitt, M; Schneider, O; Spagnolo, P; Tejessy, W; Teubert, F; Tournefier, E; Valassi, Andrea; Wright, A E; Ajaltouni, Ziad J; Badaud, F; Chazelle, G; Deschamps, O; Dessagne, S; Falvard, A; Ferdi, C; Gay, P; Guicheney, C; Henrard, P; Jousset, J; Michel, B; Monteil, S; Montret, J C; Pallin, D; Pascolo, J M; Perret, P; Podlyski, F; Hansen, J D; Hansen, J R; Hansen, P H; Nilsson, B S; Rensch, B; Wäänänen, A; Daskalakis, G; Kyriakis, A; Markou, C; Simopoulou, Errietta; Vayaki, Anna; Blondel, A; Brient, J C; Machefert, F P; Rougé, A; Swynghedauw, M; Tanaka, R; Videau, H L; Focardi, E; Parrini, G; Zachariadou, K; Corden, M; Georgiopoulos, C H; Antonelli, A; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Chiarella, V; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, G P; Passalacqua, L; Pepé-Altarelli, M; Chalmers, M; Kennedy, J; Lynch, J G; Negus, P; O'Shea, V; Räven, B; Smith, D; Teixeira-Dias, P; Thompson, A S; Ward, J J; Cavanaugh, R J; Dhamotharan, S; Geweniger, C; Hanke, P; Hepp, V; Kluge, E E; Leibenguth, G; Putzer, A; Tittel, K; Werner, S; Wunsch, M; Beuselinck, R; Binnie, David M; Cameron, W; Dornan, Peter J; Girone, M; Goodsir, S M; Marinelli, N; Martin, E B; Nash, J; Nowell, J; Przysiezniak, H; Sciabà, A; Sedgbeer, J K; Thompson, J C; Thomson, E; Williams, M D; Ghete, V M; Girtler, P; Kneringer, E; Kuhn, D; Rudolph, G; Bowdery, C K; Buck, P G; Ellis, G; Finch, A J; Foster, F; Hughes, G; Jones, R W L; Robertson, N A; Smizanska, M; Williams, M I; Giehl, I; Hölldorfer, F; Jakobs, K; Kleinknecht, K; Kröcker, M; Müller, A S; Nürnberger, H A; Quast, G; Renk, B; Rohne, E; Sander, H G; Schmeling, S; Wachsmuth, H W; Zeitnitz, C; Ziegler, T; Aubert, Jean-Jacques; Bonissent, A; Carr, J; Coyle, P; Ealet, A; Fouchez, D; Tilquin, A; Aleppo, M; Antonelli, M; Gilardoni, S S; Ragusa, F; Büscher, V; Dietl, H; Ganis, G; Hüttmann, K; Lütjens, G; Mannert, C; Männer, W; Moser, H G; Schael, S; Settles, Ronald; Seywerd, H C J; Stenzel, H; Wiedenmann, W; Wolf, G; Azzurri, P; Boucrot, J; Callot, O; Chen, S; Davier, M; Duflot, L; Grivaz, J F; Heusse, P; Jacholkowska, A; Lefrançois, J; Serin, L; Veillet, J J; Videau, I; De Vivie de Régie, J B; Zerwas, D; Bagliesi, G; Boccali, T; Bozzi, C; Calderini, G; Dell'Orso, R; Ferrante, I; Giassi, A; Gregorio, A; Ligabue, F; Marrocchesi, P S; Messineo, A; Palla, Fabrizio; Rizzo, G; Sanguinetti, G; Sguazzoni, G; Tenchini, Roberto; Venturi, A; Verdini, P G; Blair, G A; Coles, J; Cowan, G D; Green, M G; Hutchcroft, D E; Jones, L T; Medcalf, T; Strong, J A; Botterill, David R; Clifft, R W; Edgecock, T R; Norton, P R; Tomalin, I R; Bloch-Devaux, B; Colas, P; Fabbro, B; Faïf, G; Lançon, E; Lemaire, M C; Locci, E; Pérez, P; Rander, J; Renardy, J F; Rosowsky, A; Seager, P; Trabelsi, A; Tuchming, B; Vallage, B; Black, S N; Dann, J H; Loomis, C; Kim, H Y; Konstantinidis, N P; Litke, A M; McNeil, M A; Taylor, G; Booth, C N; Cartwright, S L; Combley, F; Hodgson, P N; Lehto, M H; Thompson, L F; Affholderbach, K; Böhrer, A; Brandt, S; Grupen, Claus; Hess, J; Misiejuk, A; Prange, G; Sieler, U; Borean, C; Giannini, G; Gobbo, B; Pütz, J; Rothberg, J E; Wasserbaech, S R; Williams, R W; Armstrong, S R; Elmer, P; Ferguson, D P S; Gao, Y; González, S; Hayes, O J; Hu, H; Jin, S; Kile, J; McNamara, P A; Nielsen, J; Orejudos, W; Pan, Y B; Saadi, Y; Scott, I J; Walsh, J; Von Wimmersperg-Töller, J H; Wu Sau Lan; Wu, X; Zobernig, G

2000-01-01

Bose-Einstein correlations are studied in semileptonicWW --> qqbarlnu and fully hadronic WW --> qqbarqqbar W-pair decays with the ALEPH detector at LEP at centre-of-mass energies of 172, 183 and 189GeV. They are compared with those made at the Z peak after correction for the different flavour compositions. A Monte Carlo model of Bose-Einsteincorrelations based on the JETSET hadronization scheme was tuned to the Z data and reproduces the correlations in the WW --> qqbarlnu events. The same Monte Carlo reproduces the correlations in the WW --> qqbarqqbarchannel assuming independent fragmentation of the two W's. A variant thismodel with Bose-Einstein correlations between decay products of different W's is disfavoured.

Gray solitons in a strongly interacting superfluid Fermi gas

International Nuclear Information System (INIS)

Spuntarelli, Andrea; Pieri, Pierbiagio; Strinati, Giancarlo C; Carr, Lincoln D

2011-01-01

The Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) crossover problem is solved for stationary gray solitons via the Boguliubov-de Gennes equations at zero temperature. These crossover solitons exhibit a localized notch in the gap and a characteristic phase difference across the notch for all interaction strengths, from BEC to BCS regimes. However, they do not follow the well-known Josephson-like sinusoidal relationship between velocity and phase difference except in the far BEC limit: at unitarity, the velocity has a nearly linear dependence on phase difference over an extended range. For a fixed phase difference, the soliton is of nearly constant depth from the BEC limit to unitarity and then grows progressively shallower into the BCS limit, and on the BCS side, Friedel oscillations are apparent in both gap amplitude and phase. The crossover soliton appears fundamentally in the gap; we show, however, that the density closely follows the gap, and the soliton is therefore observable. We develop an approximate power-law relationship to express this fact: the density of gray crossover solitons varies as the square of the gap amplitude in the BEC limit and as a power of about 1.5 at unitarity.

Dynamics of Superfluid Helium in Low-Gravity

Science.gov (United States)

Frank, David J.

1997-01-01

This report summarizes the work performed under a contract entitled 'Dynamics of Superfluid Helium in Low Gravity'. This project performed verification tests, over a wide range of accelerations of two Computational Fluid Dynamics (CFD) codes of which one incorporates the two-fluid model of superfluid helium (SFHe). Helium was first liquefied in 1908 and not until the 1930s were the properties of helium below 2.2 K observed sufficiently to realize that it did not obey the ordinary physical laws of physics as applied to ordinary liquids. The term superfluidity became associated with these unique observations. The low temperature of SFHe and it's temperature unifonrmity have made it a significant cryogenic coolant for use in space applications in astronomical observations with infrared sensors and in low temperature physics. Superfluid helium has been used in instruments such as the Shuttle Infrared Astronomy Telescope (IRT), the Infrared Astronomy Satellite (IRAS), the Cosmic Background Observatory (COBE), and the Infrared Satellite Observatory (ISO). It is also used in the Space Infrared Telescope (SIRTF), Relativity Mission Satellite formally called Gravity Probe-B (GP-B), and the Test of the Equivalence Principle (STEP) presently under development. For GP-B and STEP, the use of SFHE is used to cool Superconducting Quantum Interference Detectors (SQUIDS) among other parts of the instruments. The Superfluid Helium On-Orbit Transfer (SHOOT) experiment flown in the Shuttle studied the behavior of SFHE. This experiment attempted to get low-gravity slosh data, however, the main emphasis was to study the low-gravity transfer of SFHE from tank to tank. These instruments carried tanks of SFHE of a few hundred liters to 2500 liters. The capability of modeling the behavior of SFHE is important to spacecraft control engineers who must design systems that can overcome disturbances created by the movement of the fluid. In addition instruments such as GP-B and STEP are very

Collision of Bose Condensate Dark Matter structures

International Nuclear Information System (INIS)

Guzman, F. S.

2008-01-01

The status of the scalar field or Bose condensate dark matter model is presented. Results about the solitonic behavior in collision of structures is presented as a possible explanation to the recent-possibly-solitonic behavior in the bullet cluster merger. Some estimates about the possibility to simulate the bullet cluster under the Bose Condensate dark matter model are indicated.

Thermal and Quantum Mechanical Noise of a Superfluid Gyroscope

Science.gov (United States)

Chui, Talso; Penanen, Konstantin

2004-01-01

A potential application of a superfluid gyroscope is for real-time measurements of the small variations in the rotational speed of the Earth, the Moon, and Mars. Such rotational jitter, if not measured and corrected for, will be a limiting factor on the resolution potential of a GPS system. This limitation will prevent many automation concepts in navigation, construction, and biomedical examination from being realized. We present the calculation of thermal and quantum-mechanical phase noise across the Josephson junction of a superfluid gyroscope. This allows us to derive the fundamental limits on the performance of a superfluid gyroscope. We show that the fundamental limit on real-time GPS due to rotational jitter can be reduced to well below 1 millimeter/day. Other limitations and their potential mitigation will also be discussed.

Laszlo Tisza and the two-fluid model of superfluidity

Science.gov (United States)

Balibar, Sébastien

2017-11-01

The "two-fluid model" of superfluidity was first introduced by Laszlo Tisza in 1938. On that year, Tisza published the principles of his model as a brief note in Nature and two articles in French in the Comptes rendus de l'Académie des sciences, followed in 1940 by two other articles in French in the Journal de physique et le Radium. In 1941, the two-fluid model was reformulated by Lev Landau on a more rigorous basis. Successive experiments confirmed the revolutionary idea introduced by Tisza: superfluid helium is indeed a surprising mixture of two fluids with independent velocity fields. His prediction of the existence of heat waves, a consequence of his model, was also confirmed. Then, it took several decades for the superfluidity of liquid helium to be fully understood.

Superfluidity of a dipolar Fermi gas in 2D optical lattices bilayer

Energy Technology Data Exchange (ETDEWEB)

Camacho-Guardian, A.; Paredes, R. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico (Mexico)

2016-12-15

Ultracold Fermi molecules lying in 2D square optical lattices bilayers with its dipole moment perpendicularly aligned to the layers, having interlayer finite range s-wave interactions, are shown to form superfluid phases, both, in the Bardeen, Cooper and Schrieffer (BCS) regime of Cooper pairs, and in the condensate regime of bound dimeric molecules. We demonstrate this result using a functional integral scheme within the Ginzburg-Landau theory. For the deep Berezinskii-Kosterlitz-Thouless (BKT) phase transition, we predict critical temperatures around 5 nK and 20 nK for {sup 23}Na{sup 40}K and OH molecules, which are within reach of current experiments [J. W. Park, S. Will and M. Zwierlein, Phys. Rev. Lett. 114, 205302 (2015)]. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Observation of Spontaneous Coherence in Bose-Einstein Condensate of Magnons

International Nuclear Information System (INIS)

Demidov, V. E.; Dzyapko, O.; Demokritov, S. O.; Melkov, G. A.; Slavin, A. N.

2008-01-01

The room-temperature dynamics of a magnon gas driven by short microwave pumping pulses is studied. An overpopulation of the lowest energy level of the system following the pumping is observed. Using the sensitivity of the Brillouin light scattering technique to the coherence degree of the scattering magnons we demonstrate the spontaneous emergence of coherence of the magnons at the lowest level, if their density exceeds a critical value. This finding is clear proof of the quantum nature of the observed phenomenon and direct evidence of Bose-Einstein condensation of magnons at room temperature

Scattering resonances in a degenerate Fermi gas

DEFF Research Database (Denmark)

Challis, Katharine; Nygaard, Nicolai; Mølmer, Klaus

2009-01-01

We consider elastic single-particle scattering from a one-dimensional trapped two-component superfluid Fermi gas when the incoming projectile particle is identical to one of the confined species. Our theoretical treatment is based on the Hartree-Fock ground state of the trapped gas...

Unconventional superfluids of fermionic polar molecules in a bilayer system

Energy Technology Data Exchange (ETDEWEB)

Boudjemâa, Abdelâali, E-mail: a.boudjemaa@univhb-chlef.dz

2017-05-25

We study unconventional superfluids of fermionic polar molecules in a two-dimensional bilayer system with dipoles are head-to-tail across the layers. We analyze the critical temperature of several unconventional pairings as a function of different system parameters. The peculiar competition between the d- and the s-wave pairings is discussed. We show that the experimental observation of such unconventional superfluids requires ultralow temperatures, which opens up new possibilities to realize several topological phases. - Highlights: • Investigation of novel superfluids of fermionic polar molecules in a bilayer geometry. • Solving the gap equation and the l-wave interlayer scattering problem. • Calculation of the critical temperature of several competing pairings using the BCS approach.

Analytical study on holographic superfluid in AdS soliton background

International Nuclear Information System (INIS)

Lai, Chuyu; Pan, Qiyuan; Jing, Jiliang; Wang, Yongjiu

2016-01-01

We analytically study the holographic superfluid phase transition in the AdS soliton background by using the variational method for the Sturm–Liouville eigenvalue problem. By investigating the holographic s-wave and p-wave superfluid models in the probe limit, we observe that the spatial component of the gauge field will hinder the phase transition. Moreover, we note that, different from the AdS black hole spacetime, in the AdS soliton background the holographic superfluid phase transition always belongs to the second order and the critical exponent of the system takes the mean-field value in both s-wave and p-wave models. Our analytical results are found to be in good agreement with the numerical findings.

Decoupling of Solid 4He Layers under the Superfluid Overlayer

Science.gov (United States)

Ishibashi, Kenji; Hiraide, Jo; Taniguchi, Junko; Suzuki, Masaru

2018-03-01

It has been reported that in a large oscillation amplitude, the mass decoupling of multilayer 4He films adsorbed on graphite results from the depinning of the second solid atomic layer. This decoupling suddenly vanishes below a certain low temperature TD due to the cancellation of mass decoupling by the superfluid counterflow of the the overylayer. We studied the relaxation of the depinned state at various temperatures, after reduction of oscillation amplitude below TD . It was found that above the superfluid transition temperature the mass decoupling revives with a relaxation time of several 100 s. It strongly supports that the depinned state of the second solid atomic layer remains underneath the superfluid overlayer.

Acquisition system testing with superfluid helium

International Nuclear Information System (INIS)

Anderson, J.E.; Fester, D.A.; DiPirro, M.J.

1988-01-01

NASA is evaluating both a thermomechanical pump and centrifugal pump for the SHOOT experiment using capillary fluid acquisition systems. Tests were conducted for these systems with superfluid helium under adverse operating conditions. Minus one-g outflow tests were run in conjunction with the thermomechanical pump. Both fine mesh screen and porous sponges were tested. A screen acquisition device was also tested with the low-NPSH centrifugal pump. Results to date show that the screen and sponge are capable of supplying superfluid helium to the thermomechanical pump inlet against a one-g head up to four cm. This is more than sufficient for the SHOOT application. Results with the sponge were reproducible while those with the screen could not always be repeated

Mobility of negative ions in superfluid 3He

International Nuclear Information System (INIS)

Ahonen, A.I.; Kokko, J.; Lounasmaa, O.V.; Paalanen, M.A.; Richardson, R.C.; Schoepe, W.; Takano, Y.

1976-01-01

We have found that the mobility of negative ions increases rapidly below T/sub c/ in both superfluid 3 He phases. The ratio μ/μ/sub N/ of superfluid to normal mobility is larger in the B phase than in the A phase. A critical velocity consistent in magnitude with the Landau limit for pair breaking has also been observed. In the normal fluid we find a temperature-independent mobility between 30 mK and T/sub c/ for all pressures between 0 and 28 bars

Hidden vortex lattices in a thermally paired superfluid

International Nuclear Information System (INIS)

Dahl, E. K.; Sudboe, A.; Babaev, E.

2008-01-01

We study the evolution of rotational response of a statistical mechanical model of two-component superfluid with a nondissipative drag interaction as the system undergoes a transition into a paired superfluid phase at finite temperature. The transition manifests itself in a change of (i) vortex-lattice symmetry and (ii) nature of the vortex state. Instead of a vortex lattice, the system forms a highly disordered tangle which constantly undergoes merger and reconnecting processes involving different types of vortices with a 'hidden' breakdown of translation symmetry

Lagrangian of superfluid 3He

International Nuclear Information System (INIS)

Theodorakis, S.

1988-01-01

This paper presents a phenomenological Lagrangian that fully describes the dynamics of any homogeneous phase of superfluid 3 He, unitary or not, omitting relaxation. This Lagrangian is built by using the concept of a local SO(3) x SO(3) x U(1) symmetry. The spin and angular momentum play the role of gauge fields. We derive the Leggett equations for spin and orbital dynamics from the equations of motion, for both the A and the B phase. This Lagrangian not only enables us to describe both the spin and orbital dynamics of superfluid 3 He in a unified fashion, but can also be used for finding the dynamics in any experimental situation. Furthermore, it can describe the dynamics of the magnitude, as well as of the orientation of the order parameter, and thus it can be used to describe the dynamics of the A-B phase transition

Investigation of thermal transfers in super-fluid helium in porous media

International Nuclear Information System (INIS)

Allain, H.

2009-10-01

Particle accelerators are requiring increased magnetic fields for which niobium tin superconducting magnets are considered. This entails electric insulation and cooling problems. Porous ceramic insulations are potential candidates for cable insulation. As they are permeable to helium, they could allow a direct cooling by super-fluid helium. Therefore, this research thesis deals with the investigation of thermal transfers in superfluid helium in porous media. After a description of an accelerator's superconducting magnet, of its thermodynamics and its various cooling modes, the author describes the physical properties of super-fluid helium, its peculiarities with respect to conventional fluids as well as its different phases (fluid and super-fluid), its dynamics under different regimes (the Landau regime which is similar to the laminar regime for a conventional fluid, and the Gorter-Mellink regime which is the super-fluid turbulent regime). He determines the macroscopic equations governing the He II dynamics in porous media by applying the volume averaging method developed by Whitaker. Theoretical results are validated by comparison with a numerical analysis performed with a numerical code. Then, the author presents the various experimental setups which have been developed for the measurement of the intrinsic permeability, one at room temperature and another at high temperature. Experimental results are discussed, notably with respect to pore size and porosity

Chiral superfluidity of the quark-gluon plasma

Energy Technology Data Exchange (ETDEWEB)

Kalaydzhyan, Tigran [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation)

2012-08-15

In this paper we argue that the strongly coupled quark-gluon plasma can be considered as a chiral superfluid. The ''normal'' component of the fluid is the thermalized matter in common sense, while the ''superfluid'' part consists of long wavelength (chiral) fermionic states moving independently. We use several nonperturbative techniques to demonstrate that. First, we analyze the fermionic spectrum in the deconfinement phase (T{sub c}superfluid'' component gives rise to the chiral magnetic, chiral electric and dipole wave effects. Latter two effects are specific for a two-component fluid, which provides us with crucial experimental tests of the model.

Superfluid 3He dynamcs in 3He - 4He solutions

International Nuclear Information System (INIS)

Mejerovich, A.Eh.

1984-01-01

The dynamics of a 3 He- 4 He superfluid solution with two condensates ( 3 He and 4 He) is investigated. Despite the fact that the hydrodynamics of the system is a three-velocity one (two superfluid and one normal velocity), all the thermo- and hydrodynamic functions are determined by the value of only a single linear combination of the velocities. 0n the basis of an analogy between a moving solution and a BCS system with coupling with a non-zero momentum, the dependence of the thermodynamic quantities on the velocities and critical velocities can easily be calculated for both homogeneous and inhomogeneous phases of the solution. In a magnetic field the temperature oscillations (analogue of second sound for a superfluid solution) are accompanied by oscillations of the magnetic moment. The velocity and damping of the spin-temperature waves are determined. The orienting action of a current on the inhomogeneous phases of the solution is discussed. It is shown that the energy and size of the vortexes in a superfluid solution are, due to drag effects, oscillating functions of the effective mass of the 3 He quasirartictes (pressure). At a pressure of the order of 10 atm a first order transition should take place in the vortex line which is accompanied by an abrupt change of the circulations of superfluid velocity of 3 He for a fixed circulation of the 4 He velocity

Bose, Prof. Arup

Indian Academy of Sciences (India)

Home; Fellowship. Fellow Profile. Elected: 2006 Section: Mathematical Sciences. Bose, Prof. Arup Ph.D. (ISI, Calcutta), FNA, FNASc. Date of birth: 1 April 1959. Specialization: Probability and Statistics, Economics Address: Professor, Statistics & Mathematics Unit, Indian Statistical Institute, 203, B.T. Road, Kolkata 700 108, ...

Trapped Bose gas. Mean-field approximation and beyond

International Nuclear Information System (INIS)

Pitaevskii, L.P.

1998-01-01

The recent realization of Bose-Einstein condensation in atomic gases opens new possibilities for observation of macroscopic quantum phenomena. There are two important features of the system - weak interaction and significant spatial inhomogeneity. Because of this inhomogeneity a non-trivial 'zeroth-order' theory exists, compared to the 'first-order' Bogoliubov theory. This theory is based on the mean-field Gross-Pitaevskii equation for the condensate ψ -function. The equation is classical in its essence but contains the ℎ constant explicitly. Phenomena such as collective modes, interference, tunneling, Josephson-like current and quantized vortex lines can be described using this equation. The study of deviations from the zeroth-order theory arising from zero-point and thermal fluctuations is also of great interest. Thermal fluctuations are described by elementary excitations which define the thermodynamic behaviour of the system and result in Landau-type damping of collective modes. Fluctuations of the phase of the condensate wave function restrict the monochromaticity of the Josephson current. Fluctuations of the numbers of quanta result in the quantum collapse-revival of the collective oscillations. This phenomenon is considered in some details. Collapse time for the JILA experimental conditions turns out to be of the order of seconds. (Copyright (1998) World Scientific Publishing Co. Pte. Ltd)

Vortex Dynamics in Two-Dimensional Bose-Einstein Condensates

OpenAIRE

Groszek, Andrew James

2018-01-01

Fluid turbulence remains an open problem in contemporary physics. In gases or liquids encountered in daily life, turbulence is comprised of swirling vortices of varying sizes, shapes and strengths. The impossibility of making detailed predictions of turbulent flows comes, in part, from the complicated nature of these vortices. Turbulence in quantum mechanical superfluids, on the other hand, is comparatively simple. When stirred, a superfluid produces well-defined, discretised vortex lines, an...

Topological charge and chiral anomalies in Fermi superfluids

International Nuclear Information System (INIS)

Stone, M.; Gaitan, F.

1987-01-01

We review some of the topological properties of Fermi superfluids, in particular the persistent currents in superfluid 3 He. We show that the topological charge formalism developed by Garg et al. is related to the chiral anomaly viewpoint of Volovik and co-workers through the Callan--Harvey effect. We stress that the question of the existence of a ''twist'' term in the current induced by a texture is a history-dependent phenomenon which depends on how the textures are envisaged as being created. copyright 1987 Academic Press, Inc

Absorption of electromagnetic field energy by superfluid system of atoms with electric dipole moment

International Nuclear Information System (INIS)

Poluektov, Yu.M.

2014-01-01

The modified Gross-Pitaevskii equation which takes into account relaxation and interaction with alternating electromagnetic field is used to consider the absorption of electromagnetic field energy by a superfluid system on the assumption that the atoms has intrinsic dipole moment. It is shown that the absorption may be of a resonant behavior only if the dispersion curves of the electromagnetic wave and the excitations of the superfluid system intersect. It is remarkable that such a situation is possible if the superfluid system has a branch of excitations with the energy gap at low momenta. The experiments on absorption of microwaves in superfluid helium are interpreted as evidence of existence of such gap excitations. A possible modification of the excitation spectrum of superfluid helium in the presence of excitation branch with energy gap is dis-cussed qualitatively

Angular Momentum of a Bose-Einstein Condensate in a Synthetic Rotational Field

Science.gov (United States)

Qu, Chunlei; Stringari, Sandro

2018-05-01

By applying a position-dependent detuning to a spin-orbit-coupled Hamiltonian with equal Rashba and Dresselhaus coupling, we exploit the behavior of the angular momentum of a harmonically trapped Bose-Einstein condensed atomic gas and discuss the distinctive role of its canonical and spin components. By developing the formalism of spinor hydrodynamics, we predict the precession of the dipole oscillation caused by the synthetic rotational field, in analogy with the precession of the Foucault pendulum, the excitation of the scissors mode, following the sudden switching off of the detuning, and the occurrence of Hall-like effects. When the detuning exceeds a critical value, we observe a transition from a vortex free, rigidly rotating quantum gas to a gas containing vortices with negative circulation which results in a significant reduction of the total angular momentum.

Equilibrium phases of dipolar lattice bosons in the presence of random diagonal disorder

Science.gov (United States)

Zhang, C.; Safavi-Naini, A.; Capogrosso-Sansone, B.

2018-01-01

Ultracold gases offer an unprecedented opportunity to engineer disorder and interactions in a controlled manner. In an effort to understand the interplay between disorder, dipolar interactions, and quantum degeneracy, we study two-dimensional hard-core dipolar lattice bosons in the presence of on-site bound disorder. Our results are based on large-scale path-integral quantum Monte Carlo simulations by the worm algorithm. We study the ground-state phase diagram at a fixed half-integer filling factor for which the clean system is either a superfluid at a lower dipolar interaction strength or a checkerboard solid at a larger dipolar interaction strength. We find that, even for weak dipolar interactions, superfluidity is destroyed in favor of a Bose glass at a relatively low disorder strength. Interestingly, in the presence of disorder, superfluidity persists for values of the dipolar interaction strength for which the clean system is a checkerboard solid. At a fixed disorder strength, as the dipolar interaction is increased, superfluidity is destroyed in favor of a Bose glass. As the interaction is further increased, the system eventually develops extended checkerboard patterns in the density distribution. Due to the presence of disorder, though, grain boundaries and defects, responsible for a finite residual compressibility, are present in the density distribution. Finally, we study the robustness of the superfluid phase against thermal fluctuations.

Quantum Many-Body Dynamics with Driven Bose Condensates: Kibble-Zurek Mechanism and Bose Fireworks

Science.gov (United States)

Clark, Logan William

In recent years there has been an explosion of interest in the field of quantum many-body physics. Understanding the complex and often unintuitive behavior of systems containing interacting quantum constituents is not only fascinating but also crucial for developing the next generation of quantum technology, including better materials, sensors, and computers. Yet understanding such systems remains a challenge, particularly when considering the dynamics which occur when they are excited far from equilibrium. Ultracold atomic gases provide an ideal system with which to study dynamics by enabling clean, well-controlled experiments at length- and time-scales which allow us to observe the dynamics directly. This thesis describes experiments on the many-body dynamics of ultracold, bosonic cesium atoms. Our apparatus epitomizes the versatility of ultracold atoms by providing extensive control over the quantum gas. In particular, we will discuss our use of a digital micromirror device to project arbitrary, dynamic external potentials onto the gas; our development of a powerful new scheme for optically controlling Feshbach resonances to enable spatiotemporal control of the interactions between atoms; and our use of near-resonant shaking lattices to modify the kinetic energy of atoms. Taking advantage of this flexible apparatus, we have been able to test a longstanding conjecture based on the Kibble-Zurek mechanism, which says that the dynamics of a system crossing a quantum phase transition should obey a universal scaling symmetry of space and time. After accounting for this scaling symmetry, critical dynamics would be essentially independent of the rate at which a system crossed a phase transition. We tested the universal scaling of critical dynamics by using near-resonant shaking to drive Bose-Einstein condensates across an effectively ferromagnetic quantum phase transition. After crossing the phase transition, condensates divide themselves spatially into domains with

Holographic anyonic superfluidity

Science.gov (United States)

Jokela, Niko; Lifschytz, Gilad; Lippert, Matthew

2013-10-01

Starting with a holographic construction for a fractional quantum Hall state based on the D3-D7' system, we explore alternative quantization conditions for the bulk gauge fields. This gives a description of a quantum Hall state with various filling fractions. For a particular alternative quantization of the bulk gauge fields, we obtain a holographic anyon fluid in a vanishing background magnetic field. We show that this system is a superfluid, exhibiting the relevant gapless excitation.

Landau superfluids as nonequilibrium stationary states

International Nuclear Information System (INIS)

Wreszinski, Walter F.

2015-01-01

We define a superfluid state to be a nonequilibrium stationary state (NESS), which, at zero temperature, satisfies certain metastability conditions, which physically express that there should be a sufficiently small energy-momentum transfer between the particles of the fluid and the surroundings (e.g., pipe). It is shown that two models, the Girardeau model and the Huang-Yang-Luttinger (HYL) model, describe superfluids in this sense and, moreover, that, in the case of the HYL model, the metastability condition is directly related to Nozières’ conjecture that, due to the repulsive interaction, the condensate does not suffer fragmentation into two (or more) parts, thereby assuring its quantum coherence. The models are rigorous examples of NESS in which the system is not finite, but rather a many-body system

Analog model of a Friedmann-Robertson-Walker universe in Bose-Einstein condensates: Application of the classical field method

International Nuclear Information System (INIS)

Jain, Piyush; Weinfurtner, Silke; Visser, Matt; Gardiner, C. W.

2007-01-01

Analog models of gravity have been motivated by the possibility of investigating phenomena not readily accessible in their cosmological counterparts. In this paper, we investigate the analog of cosmological particle creation in a Friedmann-Robertson-Walker universe by numerically simulating a Bose-Einstein condensate with a time-dependent scattering length. In particular, we focus on a two-dimensional homogeneous condensate using the classical field method via the truncated Wigner approximation. We show that for various forms of the scaling function the particle production is consistent with the underlying theory in the long wavelength limit. In this context, we further discuss the implications of modified dispersion relations that arise from the microscopic theory of a weakly interacting Bose gas

Bose-Einstein Condensation in Complex Networks

International Nuclear Information System (INIS)

Bianconi, Ginestra; Barabasi, Albert-Laszlo

2001-01-01

The evolution of many complex systems, including the World Wide Web, business, and citation networks, is encoded in the dynamic web describing the interactions between the system's constituents. Despite their irreversible and nonequilibrium nature these networks follow Bose statistics and can undergo Bose-Einstein condensation. Addressing the dynamical properties of these nonequilibrium systems within the framework of equilibrium quantum gases predicts that the 'first-mover-advantage,' 'fit-get-rich,' and 'winner-takes-all' phenomena observed in competitive systems are thermodynamically distinct phases of the underlying evolving networks

Transverse effects in nonlinear optics: Toward the photon superfluid

Science.gov (United States)

McCormick, Colin Fraser

Nonlinear optics displays a wealth of transverse effects. These effects are particularly rich in the presence of an optical cavity. Many considerations suggest that in a Kerr nonlinear cavity a new state of light known as a "photon superfluid" can form, with strong analogies to atomic superfluids. The conditions for the formation of the photon superfluid include requirements on the cavity, input light fields and the nonlinear medium as well as various timescales. The most favorable candidate nonlinear medium for observing the photon super-fluid is an atomic vapor. With a strong and fast Kerr effect, atomic vapors also have the advantage of a Kerr coefficient that is tunable in both magnitude and sign. A series of z-scan experiments in far-detuned atomic rubidium vapor is reported, measuring the Kerr coefficient and determining its functional dependence on detuning to be that of a Doppler-broadened two-level model with adiabatic following of the electric field by the atom pseudomoment. Saturation effects are found to be important. Z-scan measurements for detunings within the Doppler profile are shown to agree well with numerical simulations based on the Doppler-broadened model. Agreement between absorptive and refractive non-linear coefficients is evidence of the Kramers-Kronig relations at work, even in this nonlinear system. The formation of the photon superfluid is discussed and the calculation of a new process, nearly collinear four-wave mixing, is presented. This process is essentially an inverse beam filamentation that is likely to be the underlying physical mechanism for transverse cooling and condensation of photons in a nonlinear optical cavity. Nearly collinear four-wave mixing may also be related to phenomena in general nonlinear physics, including modulation instability and Fermi-Pasta-Ulam recurrence.

Thermally activated phase slips of one-dimensional Bose gases in shallow optical lattices

Science.gov (United States)

Kunimi, Masaya; Danshita, Ippei

2017-03-01

We study the decay of superflow via thermally activated phase slips in one-dimensional Bose gases in a shallow optical lattice. By using the Kramers formula, we numerically calculate the nucleation rate of a thermally activated phase slip for various values of the filling factor and flow velocity in the absence of a harmonic trapping potential. Within the local density approximation, we derive a formula connecting the phase-slip nucleation rate with the damping rate of a dipole oscillation of the Bose gas in the presence of a harmonic trap. We use the derived formula to directly compare our theory with the recent experiment done by the LENS group [L. Tanzi et al., Sci. Rep. 6, 25965 (2016), 10.1038/srep25965]. From the comparison, the observed damping of dipole oscillations in a weakly correlated and small velocity regime is attributed dominantly to thermally activated phase slips rather than quantum phase slips.

Effect of Spatial Dimension and External Potential on Joule-Thomson Coefficients of Ideal Bose Gases

International Nuclear Information System (INIS)

Yuan Duqi; Wang Canjun

2010-01-01

Based on the form of the n-dimensional generic power-law potential, the state equation and the heat capacity, the analytical expressions of the Joule-Thomson coefficient (JTC) for an ideal Bose gas are derived in n-dimensional potential. The effect of the spatial dimension and the external potential on the JTC are discussed, respectively. These results show that: (i) For the free ideal Bose gas, when n/s ≤ 2 (n is the spatial dimension, s is the momentum index in the relation between the energy and the momentum), and T → T C (T C is the critical temperature), the JTC can obviously improve by means of changing the throttle valve's shape and decreasing the spatial dimension of gases. (ii) For the inhomogeneous external potential, the discriminant Δ = [1 - Π[ n i=1 (kT/varpi i ) 1/t i Γ(1/t i + 1)] (k is the Boltzmann Constant, T is the thermodynamic temperature, varpi i is the external field's energy), is obtained. The potential makes the JTC increase when Δ > 0, on the contrary, it makes the JTC decrease when Δ i < 1. (general)

Electric response in superfluid helium

Czech Academy of Sciences Publication Activity Database

Chagovets, Tymofiy

2016-01-01

Roč. 488, May (2016), s. 62-66 ISSN 0921-4526 R&D Projects: GA ČR GP13-03806P Institutional support: RVO:68378271 Keywords : superfluid helium * electric response * second sound * ions in He II Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.386, year: 2016

Functional renormalization group study of fluctuation effects in fermionic superfluids

Energy Technology Data Exchange (ETDEWEB)

Eberlein, Andreas

2013-03-22

This thesis is concerned with ground state properties of two-dimensional fermionic superfluids. In such systems, fluctuation effects are particularly strong and lead for example to a renormalization of the order parameter and to infrared singularities. In the first part of this thesis, the fermionic two-particle vertex is analysed and the fermionic renormalization group is used to derive flow equations for a decomposition of the vertex in charge, magnetic and pairing channels. In the second part, the channel-decomposition scheme is applied to various model systems. In the superfluid state, the fermionic two-particle vertex develops rich and singular dependences on momentum and frequency. After simplifying its structure by exploiting symmetries, a parametrization of the vertex in terms of boson-exchange interactions in the particle-hole and particle-particle channels is formulated, which provides an efficient description of the singular momentum and frequency dependences. Based on this decomposition of the vertex, flow equations for the effective interactions are derived on one- and two-loop level, extending existing channel-decomposition schemes to (i) the description of symmetry breaking in the Cooper channel and (ii) the inclusion of those two-loop renormalization contributions to the vertex that are neglected in the Katanin scheme. In the second part, the superfluid ground state of various model systems is studied using the channel-decomposition scheme for the vertex and the flow equations. A reduced model with interactions in the pairing and forward scattering channels is solved exactly, yielding insights into the singularity structure of the vertex. For the attractive Hubbard model at weak coupling, the momentum and frequency dependence of the two-particle vertex and the frequency dependence of the self-energy are determined on one- and two-loop level. Results for the suppression of the superfluid gap by fluctuations are in good agreement with the literature

Fourth sound in relativistic superfluidity theory

International Nuclear Information System (INIS)

Vil'chinskij, S.I.; Fomin, P.I.

1995-01-01

The Lorentz-covariant equations describing propagation of the fourth sound in the relativistic theory of superfluidity are derived. The expressions for the velocity of the fourth sound are obtained. The character of oscillation in sound is determined

Resonances for coupled Bose-Einstein condensates

International Nuclear Information System (INIS)

Haroutyunyan, H.L.; Nienhuis, G.

2004-01-01

The properties of a Bose-Einstein condensate in a two-well potential can be manipulated by periodic modulation of the potential parameters. We study the effects arising from modulating the barrier height and the difference in well depth. At certain modulation frequencies the system exhibits resonances, which may show up in an enhancement of the tunneling rate between the wells. Resonances can be used to control the particle distribution over the wells. Some of the effects occurring in the two-well system also arise for a Bose-Einstein condensate in an optical lattice

Onset of superfluidity in hot asymmetric nuclear matter

International Nuclear Information System (INIS)

Alm, T.; Roepke, G.; Friman, B.L.

1991-05-01

The onset of superfluidity in hot asymmetric nuclear matter is studied within a generalized Beth-Uhlenbeck approach. The finite tempeature t-matrix is of the Bethe-Goldstone type and contains hole-hole propagation not considered in the Brueckner G-matrix approach. It is shown that the phase contour for the onset of superfluidity in this approach is identical to that obtained within Gorkov's approach to BCS theory. Results for the realistic Paris potential imply that the critical temperature in the neutron-proton triplet channel is on the order of 6-8 MeV and thus much larger than that for singlet pairing. (orig.)

Examining empirical evidence of the effect of superfluidity on the fusion barrier

Science.gov (United States)

Scamps, Guillaume

2018-04-01

Background: Recent time-dependent Hartree-Fock-Bogoliubov (TDHFB) calculations predict that superfluidity enhances fluctuations of the fusion barrier. This effect is not fully understood and not yet experimentally revealed. Purpose: The goal of this study is to empirically investigate the effect of superfluidity on the distribution width of the fusion barrier. Method: Two new methods are proposed in the present study. First, the local regression method is introduced and used to determine the barrier distribution. The second method, which requires only the calculation of an integral of the cross section, is developed to determine accurately the fluctuations of the barrier. This integral method, showing the best performance, is systematically applied to 115 fusion reactions. Results: Fluctuations of the barrier for open-shell systems are, on average, larger than those for magic or semimagic nuclei. This is due to the deformation and the superfluidity. To disentangle these two effects, a comparison is made between the experimental width and the width estimated from a model that takes into account the tunneling, the deformation, and the vibration effect. This study reveals that superfluidity enhances the fusion barrier width. Conclusions: This analysis shows that the predicted effect of superfluidity on the width of the barrier is real and is of the order of 1 MeV.

Calculation of thermodynamic properties of finite Bose-Einstein systems

NARCIS (Netherlands)

Borrmann, P.; Harting, J.D.R.; Mülken, O.; Hilf, E.

1999-01-01

We derive an exact recursion formula for the calculation of thermodynamic functions of finite systems obeying Bose-Einstein statistics. The formula is applicable for canonical systems where the particles can be treated as noninteracting in some approximation, e.g., like Bose-Einstein condensates in

Theory for electric dipole superconductivity with an application for bilayer excitons.

Science.gov (United States)

Jiang, Qing-Dong; Bao, Zhi-qiang; Sun, Qing-Feng; Xie, X C

2015-07-08

Exciton superfluid is a macroscopic quantum phenomenon in which large quantities of excitons undergo the Bose-Einstein condensation. Recently, exciton superfluid has been widely studied in various bilayer systems. However, experimental measurements only provide indirect evidence for the existence of exciton superfluid. In this article, by viewing the exciton in a bilayer system as an electric dipole, we derive the London-type and Ginzburg-Landau-type equations for the electric dipole superconductors. By using these equations, we discover the Meissner-type effect and the electric dipole current Josephson effect. These effects can provide direct evidence for the formation of the exciton superfluid state in bilayer systems and pave new ways to drive an electric dipole current.

A Short History of the Theory and Experimental Discovery of Superfluidity in 3He

Science.gov (United States)

Brinkman, W. F.

I discuss the development of the theory and experiments on superfluid 3He. After the discovery of superfluidity in 3He by Osheroff, Richardson and Lee, Phil Anderson quickly recruited Doug Osheroff to come to Bell Labs and set up a dilution fridge to continue his experiments. One of the mysteries at that time was how the high-temperature A-phase, which has a gapless excitation spectrum, could be stabilized relative to the fully gapped, lower temperature B-phase. I explain how Phil Anderson and I developed the spin fluctuation theory of the A-phase of superfluid 3He which accounted for its stability, leading to the Anderson-Brinkman-Morel (ABM) theory of the superfluid A-phase...

Bose-Einstein condensation and chiral phase transition in linear sigma model

International Nuclear Information System (INIS)

Shu Song; Li Jiarong

2005-01-01

With the linear sigma model, we have studied Bose-Einstein condensation and the chiral phase transition in the chiral limit for an interacting pion system. A μ-T phase diagram including these two phenomena is presented. It is found that the phase plane has been divided into three areas: the Bose-Einstein condensation area, the chiral symmetry broken phase area and the chiral symmetry restored phase area. Bose-Einstein condensation can occur either from the chiral symmetry broken phase or from the restored phase. We show that the onset of the chiral phase transition is restricted in the area where there is no Bose-Einstein condensation

Realizing Fulde-Ferrell Superfluids via a Dark-State Control of Feshbach Resonances

Science.gov (United States)

He, Lianyi; Hu, Hui; Liu, Xia-Ji

2018-01-01

We propose that the long-sought Fulde-Ferrell superfluidity with nonzero momentum pairing can be realized in ultracold two-component Fermi gases of K 40 or Li 6 atoms by optically tuning their magnetic Feshbach resonances via the creation of a closed-channel dark state with a Doppler-shifted Stark effect. In this scheme, two counterpropagating optical fields are applied to couple two molecular states in the closed channel to an excited molecular state, leading to a significant violation of Galilean invariance in the dark-state regime and hence to the possibility of Fulde-Ferrell superfluidity. We develop a field theoretical formulation for both two-body and many-body problems and predict that the Fulde-Ferrell state has remarkable properties, such as anisotropic single-particle dispersion relation, suppressed superfluid density at zero temperature, anisotropic sound velocity, and rotonic collective mode. The latter two features can be experimentally probed using Bragg spectroscopy, providing a smoking-gun proof of Fulde-Ferrell superfluidity.

Recent Spin Pump Experiments on Superfluid 3He-A1

Science.gov (United States)

Yamaguchi, A.; Kamada, N.; Motoyama, G.; Sumiyama, A.; Aoki, Y.; Okuda, Y.; Kubota, M.; Kojima, H.

2013-05-01

The superfluid 3He A1 phase, containing a spin-polarized condensate allows us to explore the dynamics of superfluid spin current. In the mechano-spin effect (MSE), a mechanically applied pressure gradient and a superleak-spin filter enable one to directly boost spin polarization of 3He in a small chamber. We are developing new apparatus for achieving greater enhancement of spin density. A development of a new-type 3He-hydraulic actuator has been already reported. We present here the construction of new-type of superleak-spin-filter made of packed powder aluminum oxide (referred as PAP-SL). The PAP-SL is popular in the study of superfluid 4He, but has not been established for that of the superfluid 3He. The attempt to construct the PAP-SL for the spin pump experiment was made by using aluminum oxide powder with nominal 1 μm powder diameter and with packing fraction of 40 %. Before executing the experiment, the nuclear demagnetization cryostat of ISSP, Univ. Tokyo which has been used for this experimental activity, was heavily damaged by the 2011 Great East Japan (Higashi Nihon) Earthquake. The repair work and earthquake damage protection strengthening has just been accomplished.

From ultracold Fermi Gases to Neutron Stars

Science.gov (United States)

Salomon, Christophe

2012-02-01

Ultracold dilute atomic gases can be considered as model systems to address some pending problem in Many-Body physics that occur in condensed matter systems, nuclear physics, and astrophysics. We have developed a general method to probe with high precision the thermodynamics of locally homogeneous ultracold Bose and Fermi gases [1,2,3]. This method allows stringent tests of recent many-body theories. For attractive spin 1/2 fermions with tunable interaction (^6Li), we will show that the gas thermodynamic properties can continuously change from those of weakly interacting Cooper pairs described by Bardeen-Cooper-Schrieffer theory to those of strongly bound molecules undergoing Bose-Einstein condensation. First, we focus on the finite-temperature Equation of State (EoS) of the unpolarized unitary gas. Surprisingly, the low-temperature properties of the strongly interacting normal phase are well described by Fermi liquid theory [3] and we localize the superfluid phase transition. A detailed comparison with theories including recent Monte-Carlo calculations will be presented. Moving away from the unitary gas, the Lee-Huang-Yang and Lee-Yang beyond-mean-field corrections for low density bosonic and fermionic superfluids are quantitatively measured for the first time. Despite orders of magnitude difference in density and temperature, our equation of state can be used to describe low density neutron matter such as the outer shell of neutron stars. [4pt] [1] S. Nascimbène, N. Navon, K. Jiang, F. Chevy, and C. Salomon, Nature 463, 1057 (2010) [0pt] [2] N. Navon, S. Nascimbène, F. Chevy, and C. Salomon, Science 328, 729 (2010) [0pt] [3] S. Nascimbène, N. Navon, S. Pilati, F. Chevy, S. Giorgini, A. Georges, and C. Salomon, Phys. Rev. Lett. 106, 215303 (2011)

A quantitative experiment on the fountain effect in superfluid helium

Science.gov (United States)

Amigó, M. L.; Herrera, T.; Neñer, L.; Peralta Gavensky, L.; Turco, F.; Luzuriaga, J.

2017-09-01

Superfluid helium, a state of matter existing at low temperatures, shows many remarkable properties. One example is the so called fountain effect, where a heater can produce a jet of helium. This converts heat into mechanical motion; a machine with no moving parts, but working only below 2 K. Allen and Jones first demonstrated the effect in 1938, but their work was basically qualitative. We now present data of a quantitative version of the experiment. We have measured the heat supplied, the temperature and the height of the jet produced. We also develop equations, based on the two-fluid model of superfluid helium, that give a satisfactory fit to the data. The experiment has been performed by advanced undergraduate students in our home institution, and illustrates in a vivid way some of the striking properties of the superfluid state.

Superfluid compressibility and the inertial mass of a moving singularity

International Nuclear Information System (INIS)

Duan, J.

1993-01-01

The concept of finite compressibility of a Fermi superfluid is used to reconsider the problem of inertial mass of vortex lines in both neutral and charged superfluids at T=0. For the charged case, in contrast to previous works where perfect screening was assumed, we take proper account of electromagnetic screening and solve the bulk charge distribution caused by a moving vortex line. A similar problem for a superconducting thin film is also considered

Cooling with Superfluid Helium

Energy Technology Data Exchange (ETDEWEB)

Lebrun, P; Tavian, L [European Organization for Nuclear Research, Geneva (Switzerland)

2014-07-01

The technical properties of helium II (‘superfluid’ helium) are presented in view of its applications to the cooling of superconducting devices, particularly in particle accelerators. Cooling schemes are discussed in terms of heat transfer performance and limitations. Large-capacity refrigeration techniques below 2 K are reviewed, with regard to thermodynamic cycles as well as process machinery. Examples drawn from existing or planned projects illustrate the presentation. Keywords: superfluid helium, cryogenics.

There is no explosion risk associated with superfluid Helium in the LHC cooling system

CERN Document Server

Fairbairn, Malcolm

2008-01-01

We evaluate speculation about the possibility of a dangerous release of energy within the liquid Helium of the Large Hadron Collider (LHC) cryogenic system due to the occurrence of a "Bose-Nova". Bose-Novae are radial bursts of rapidly moving atoms which can occur when a Bose-Einstein Condensate (BEC) undergoes a collapse due the interatomic potential being deliberately made attractive using a magnetic field close to the Feshbach resonance. Liquid 4He has a monatomic structure with s-wave electrons, zero nuclear spin, no hyperfine splitting, and as a consequence no Feshbach resonance which would allow one to change its normally repulsive interactions to be attractive. Because of this, a Bose-Nova style collapse of 4He is impossible. Additional speculations concerning cold fusion during these events are easily dismissed using the usual arguments about the Coulomb barrier at low temperatures, and are not needed to explain the Bose-Einstein condensate Bose-Nova phenomenon. We conclude that that there is no physi...

Mutual-friction induced instability of normal-fluid vortex tubes in superfluid helium-4

Science.gov (United States)

Kivotides, Demosthenes

2018-06-01

It is shown that, as a result of its interactions with superfluid vorticity, a normal-fluid vortex tube in helium-4 becomes unstable and disintegrates. The superfluid vorticity acquires only a small (few percents of normal-fluid tube strength) polarization, whilst expanding in a front-like manner in the intervortex space of the normal-fluid, forming a dense, unstructured tangle in the process. The accompanied energy spectra scalings offer a structural explanation of analogous scalings in fully developed finite-temperature superfluid turbulence. A macroscopic mutual-friction model incorporating these findings is proposed.

Mobility of negative ions in superfluid 3He

International Nuclear Information System (INIS)

Ahonen, A.I.; Kokko, J.; Lounasmaa, O.V.; Paalanen, M.A.; Richardson, R.C.; Schoepe, W.; Takano, Y.

1977-01-01

The mobility of negative ions is shown to increase rapidly below T/sub c/ in both superfluid 3 He phases. The ratio μ/μ/sub N/ of superfluid to normal mobility is larger in the B phase than in the A phase. A critical velocity consistent in magnitude with the Landau limit for pair breaking has also been observed. In the normal fluid we find a temperature independent mobility between 40 mK and T/sub c/ for all pressures between 0 and 28 bar. The increase of μ/sub N/ with increasing pressure is in agreement with the bubble model for the negative ion

A charged 3P superfluid in the ABM states

International Nuclear Information System (INIS)

Ohmi, Tetsuo; Nakahara, Mikio; Tsuneto, Toshihiko

1980-01-01

Magnetic properties of a charged 3 P superfluid in the ABM states are studied in the framework of the Ginzburg-Landau theory. A non-singular vortex in a cylindrical sample, similar to the Mermin-Ho structure in the superfluid 3 He-A, is considered. In particular, the analytic solutions for the order parameter and the magnetic field are obtained in the limit lambda sub(L)/R → 0, where lambda sub(L) is the penetration depth and R the radius of the cylinder. The possibility of a non-singular vortex lattice is also discussed. (author)

A Note on the Field-Theoretical Description of Superfluids

CERN Document Server

Andrianopoli, L; Grassi, P A; Trigiante, M

2014-01-01

Recently, a Lagrangian description of superfluids attracted some interest from the fluid/gravity-correspondence viewpoint. In this respect, the work of Dubovksy et al. has proposed a new field theoretical description of fluids, which has several interesting aspects. On another side, we have provided in arXiv:1304.2206 a supersymmetric extension of the original works. In the analysis of the Lagrangian structures a new invariant appeared which, although related to known invariants, provides, in our opinion, a better parametrisation of the fluid dynamics in order to describe the fluid/superfluid phases.

Probing correlated quantum many-body systems at the single-particle level

Energy Technology Data Exchange (ETDEWEB)

Endres, Manuel

2013-02-27

The detection of correlation and response functions plays a crucial role in the experimental characterization of quantum many-body systems. In this thesis, we present novel techniques for the measurement of such functions at the single-particle level. Specifically, we show the single-atom- and single-site-resolved detection of an ultracold quantum gas in an optical lattice. The quantum gas is described by the Bose-Hubbard model, which features a zero temperature phase transition from a superfluid to a Mott-insulating state, a paradigm example of a quantum phase transition. We used the aforementioned detection techniques to study correlation and response properties across the superfluid-Mott-insulator transition. The single-atom sensitivity of our method is achieved by fluorescence detection of individual atoms with a high signal-to-noise ratio. A high-resolution objective collects the fluorescence light and yields in situ 'snapshots' of the quantum gas that allow for a single-site-resolved reconstruction of the atomic distribution. This allowed us to measure two-site and non-local correlation-functions across the superfluid-Mott-insulator transition. Non-local correlation functions are based on the information of an extended region of the system and play an important role for the characterization of low-dimensional quantum phases. While non-local correlation functions were so far only theoretical tools, our results show that they are actually experimentally accessible. Furthermore, we used a new thermometry scheme, based on the counting of individual thermal excitations, to measure the response of the system to lattice modulation. Using this method, we studied the excitation spectrum of the system across the two-dimensional superfluid-Mott-insulator transition. In particular, we detected a 'Higgs' amplitude mode in the strongly-interacting superfluid close to the transition point where the system is described by an effectively Lorentz

Probing correlated quantum many-body systems at the single-particle level

International Nuclear Information System (INIS)

Endres, Manuel

2013-01-01

The detection of correlation and response functions plays a crucial role in the experimental characterization of quantum many-body systems. In this thesis, we present novel techniques for the measurement of such functions at the single-particle level. Specifically, we show the single-atom- and single-site-resolved detection of an ultracold quantum gas in an optical lattice. The quantum gas is described by the Bose-Hubbard model, which features a zero temperature phase transition from a superfluid to a Mott-insulating state, a paradigm example of a quantum phase transition. We used the aforementioned detection techniques to study correlation and response properties across the superfluid-Mott-insulator transition. The single-atom sensitivity of our method is achieved by fluorescence detection of individual atoms with a high signal-to-noise ratio. A high-resolution objective collects the fluorescence light and yields in situ 'snapshots' of the quantum gas that allow for a single-site-resolved reconstruction of the atomic distribution. This allowed us to measure two-site and non-local correlation-functions across the superfluid-Mott-insulator transition. Non-local correlation functions are based on the information of an extended region of the system and play an important role for the characterization of low-dimensional quantum phases. While non-local correlation functions were so far only theoretical tools, our results show that they are actually experimentally accessible. Furthermore, we used a new thermometry scheme, based on the counting of individual thermal excitations, to measure the response of the system to lattice modulation. Using this method, we studied the excitation spectrum of the system across the two-dimensional superfluid-Mott-insulator transition. In particular, we detected a 'Higgs' amplitude mode in the strongly-interacting superfluid close to the transition point where the system is described by an effectively Lorentz-invariant low-energy theory

Non-equilibrium thermodynamics, heat transport and thermal waves in laminar and turbulent superfluid helium

Science.gov (United States)

Mongiovì, Maria Stella; Jou, David; Sciacca, Michele

2018-01-01

This review paper puts together some results concerning non equilibrium thermodynamics and heat transport properties of superfluid He II. A one-fluid extended model of superfluid helium, which considers heat flux as an additional independent variable, is presented, its microscopic bases are analyzed, and compared with the well known two-fluid model. In laminar situations, the fundamental fields are density, velocity, absolute temperature, and heat flux. Such a theory is able to describe the thermomechanical phenomena, the propagation of two sounds in liquid helium, and of fourth sound in superleak. It also leads in a natural way to a two-fluid model on purely macroscopical grounds and allows a small amount of entropy associated with the superfluid component. Other important features of liquid He II arise in rotating situations and in superfluid turbulence, both characterized by the presence of quantized vortices (thin vortex lines whose circulation is restricted by a quantum condition). Such vortices have a deep influence on the transport properties of superfluid helium, as they increase very much its thermal resistance. Thus, heat flux influences the vortices which, in turn, modify the heat flux. The dynamics of vortex lines is the central topic in turbulent superfluid helium. The model is generalized to take into account the vortices in different cases of physical interest: rotating superfluids, counterflow superfluid turbulence, combined counterflow and rotation, and mass flow in addition to heat flow. To do this, the averaged vortex line density per unit volume L, is introduced and its dynamical equations are considered. Linear and non-linear evolution equations for L are written for homogeneous and inhomogeneous, isotropic and anisotropic situations. Several physical experiments are analyzed and the influence of vortices on the effective thermal conductivity of turbulent superfluid helium is found. Transitions from laminar to turbulent flows, from diffusive to

Bose-Einstein correlations

International Nuclear Information System (INIS)

Zalewski, Kacper

2000-01-01

The effect of Bose-Einstein correlations on multiplicity distributions of identical pions is discussed. It is found that these correlations affect significantly the observed multiplicity distributions, but Einstein's condensation is unlikely to be achieved, unless 'cold spots', i.e. regions, where groups of pions with very small relative momenta are produced, occur in high energy heavy-ion collisions

Superfluid Black Holes.

Science.gov (United States)

Hennigar, Robie A; Mann, Robert B; Tjoa, Erickson

2017-01-13

We present what we believe is the first example of a "λ-line" phase transition in black hole thermodynamics. This is a line of (continuous) second order phase transitions which in the case of liquid ^{4}He marks the onset of superfluidity. The phase transition occurs for a class of asymptotically anti-de Sitter hairy black holes in Lovelock gravity where a real scalar field is conformally coupled to gravity. We discuss the origin of this phase transition and outline the circumstances under which it (or generalizations of it) could occur.

Laser assisted tunneling in a Tonks–Girardeau gas

International Nuclear Information System (INIS)

Lelas, Karlo; Drpić, Nikola; Dubček, Tena; Buljan, Hrvoje; Jukić, Dario; Pezer, Robert

2016-01-01

We investigate the applicability of laser assisted tunneling in a strongly interacting one-dimensional (1D) Bose gas (the Tonks–Girardeau gas) in optical lattices. We find that the stroboscopic dynamics of the Tonks–Girardeau gas in a continuous Wannier–Stark-ladder potential, supplemented with laser assisted tunneling, effectively realizes the ground state of 1D hard-core bosons in a discrete lattice with nontrivial hopping phases. We compare observables that are affected by the interactions, such as the momentum distribution, natural orbitals and their occupancies, in the time-dependent continuous system, to those of the ground state of the discrete system. Stroboscopically, we find an excellent agreement, indicating that laser assisted tunneling is a viable technique for realizing novel ground states and phases with hard-core 1D Bose gases. (paper)

Bose-Einstein correlations in W+ W- events at LEP2

CERN Document Server

van Dalen, Jorn A

2000-01-01

Analyses of Bose-Einstein Correlations in w+w- events at LEP2 by the four LEP collaborations are presented. In particular, Bose-Einstein correlations in w+w- overlap are investigated and the possible existence of these correlations between particles coming from different W's, which may influence the W mass measurements in the fully-hadronic channel e+e- --+ w+w- --+ qiihq3ij<. No evidence for such an inter-W Bose-Einstein correlation is found by L3 and ALEPH. Possible indication of these correlations by DELPHI is mentioned.

Didactic demonstrations of superfluidity and superconductivity phenomena

International Nuclear Information System (INIS)

Aniola-Jedrzejak, L.; Lewicki, A.; Pilipowicz, A.; Tarnawski, Z.; Bialek, H.

1980-01-01

In order to demonstrate to students phenomena of superfluidity and superconductivity a special helium cryostat has been constructed. The demonstrated effects, construction of the cryostat and the method of demonstration are described. (author)

Finite temperature effects in Bose-Einstein condensed dark matter halos

International Nuclear Information System (INIS)

Harko, Tiberiu; Madarassy, Enikö J.M.

2012-01-01

Once the critical temperature of a cosmological boson gas is less than the critical temperature, a Bose-Einstein Condensation process can always take place during the cosmic history of the universe. Zero temperature condensed dark matter can be described as a non-relativistic, Newtonian gravitational condensate, whose density and pressure are related by a barotropic equation of state, with barotropic index equal to one. In the present paper we analyze the effects of the finite dark matter temperature on the properties of the dark matter halos. We formulate the basic equations describing the finite temperature condensate, representing a generalized Gross-Pitaevskii equation that takes into account the presence of the thermal cloud. The static condensate and thermal cloud in thermodynamic equilibrium is analyzed in detail, by using the Hartree-Fock-Bogoliubov and Thomas-Fermi approximations. The condensed dark matter and thermal cloud density and mass profiles at finite temperatures are explicitly obtained. Our results show that when the temperature of the condensate and of the thermal cloud are much smaller than the critical Bose-Einstein transition temperature, the zero temperature density and mass profiles give an excellent description of the dark matter halos. However, finite temperature effects may play an important role in the early stages of the cosmological evolution of the dark matter condensates

Small objects in superfluid 3He

International Nuclear Information System (INIS)

Rainer, D.; Vuorio, M.

1977-02-01

Distortions in the superfluid order parameter around a small object in 3 He are calculated together with the supercurrents and the angular momentum induced by it in the liquid. The forces acting on the impurity by the liquid texture structure are also considered. (author)

Grüneisen parameter for gases and superfluid helium

International Nuclear Information System (INIS)

De Souza, Mariano; Menegasso, Paulo; Paupitz, Ricardo; Seridonio, Antonio; Lagos, Roberto E

2016-01-01

The Grüneisen ratio (Γ), i.e. the ratio of the thermal expansivity to the specific heat at constant pressure, quantifies the degree of anharmonicity of the potential governing the physical properties of a system. While Γ has been intensively explored in solid state physics, very little is known about its behavior for gases. This is most likely due to the difficulties posed in carrying out both thermal expansion and specific heat measurements in gases with high accuracy as a function of pressure and temperature. Furthermore, to the best of our knowledge a comprehensive discussion about the peculiarities of the Grüneisen ratio is still lacking in the literature. Here we report on a detailed and comprehensive overview of the Grüneisen ratio. Particular emphasis is placed on the analysis of Γ for gases. The main findings of this work are: (i) for the van der Waals gas Γ depends only on the co-volume b due to interaction effects, it is smaller than that for the ideal gas (Γ = 2/3) and diverges upon approaching the critical volume; (ii) for the Bose–Einstein condensation of an ideal boson gas, assuming the transition as first-order, Γ diverges upon approaching a critical volume, similarly to the van der Waals gas; (iii) for 4 He at the superfluid transition Γ shows a singular behavior. Our results reveal that Γ can be used as an appropriate experimental tool to explore pressure-induced critical points. (paper)

Bose-Einstein condensation and crystallization

International Nuclear Information System (INIS)

Suetoe, A.

2008-01-01

The paper describes history and state of art theory of Bose-Einstein condensation and crystallization as cases of breaking continuous symmetries. Emphasizes that these problems have not been solved exactly. (TRA)

On the possibility of simultaneous spiral and superfluid ordering in a Fermi-liquid

International Nuclear Information System (INIS)

Peletminskij, S.V.; Yatsenko, A.A.; Shulga, S.N.

2004-01-01

The paper concerns a particular possibility of ordering for Fermi systems - a superfluid spiral ordering, at which in addition to the phase invariance breakdown there occurs a violence of the translational and the spin rotation invariance. A general approach of studying of the superfluid spiral ordering is formulated on the basis of the Fermi liquid method. For a monocomponent Fermi system self-consistency equations for four order parameters and the temperature of simultaneous transition to spiral and superfluid states are obtained. The system of equations is studied under the assumption of two order parameters being distinct from zero. The spiral parameter dependences of the transition temperature and the energy gap in the spectrum of elementary fermion excitations are calculated. An interval of the spiral parameter values within which the superfluid spiral ordering can exist is determined. The spin correlation function at the spiral ordering is studied

Damping-free collective oscillations of a driven two-component Bose gas in optical lattices

Science.gov (United States)

Shchedrin, Gavriil; Jaschke, Daniel; Carr, Lincoln D.

2018-04-01

We explore the quantum many-body physics of a driven Bose-Einstein condensate in optical lattices. The laser field induces a gap in the generalized Bogoliubov spectrum proportional to the effective Rabi frequency. The lowest-lying modes in a driven condensate are characterized by zero group velocity and nonzero current. Thus, the laser field induces roton modes, which carry interaction in a driven condensate. We show that collective excitations below the energy of the laser-induced gap remain undamped, while above the gap they are characterized by a significantly suppressed Landau damping rate.

Porous plug phase separator and superfluid film flow suppression system for the soft x-ray spectrometer onboard Hitomi

Science.gov (United States)

Ezoe, Yuichiro; DiPirro, Michael; Fujimoto, Ryuichi; Ishikawa, Kumi; Ishisaki, Yoshitaka; Kanao, Kenichi; Kimball, Mark; Mitsuda, Kazuhisa; Mitsuishi, Ikuyuki; Murakami, Masahide; Noda, Hirofumi; Ohashi, Takaya; Okamoto, Atsushi; Satoh, Yohichi; Sato, Kosuke; Shirron, Peter; Tsunematsu, Shoji; Yamaguchi, Hiroya; Yoshida, Seiji

2018-01-01

When using superfluid helium in low-gravity environments, porous plug phase separators are commonly used to vent boil-off gas while confining the bulk liquid to the tank. Invariably, there is a flow of superfluid film from the perimeter of the porous plug down the vent line. For the soft x-ray spectrometer onboard ASTRO-H (Hitomi), its approximately 30-liter helium supply has a lifetime requirement of more than 3 years. A nominal vent rate is estimated as ˜30 μg/s, equivalent to ˜0.7 mW heat load. It is, therefore, critical to suppress any film flow whose evaporation would not provide direct cooling of the remaining liquid helium. That is, the porous plug vent system must be designed to both minimize film flow and to ensure maximum extraction of latent heat from the film. The design goal for Hitomi is to reduce the film flow losses to knife-edge devices. Design, on-ground testing results, and in-orbit performance are described.

Superfluid and insulating phases in an interacting-boson model: mean-field theory and the RPA

International Nuclear Information System (INIS)

Sheshadri, K.; Pandit, R.; Krishnamurthy, H.R.; Ramakrishnan, T.V.

1993-01-01

The bosonic Hubbard model is studied via a simple mean-field theory. At zero temperature, in addition to yielding a phase diagram that is qualitatively correct, namely a superfluid phase for non-integer fillings and a Mott transition from a superfluid to an insulating phase for integer fillings, this theory gives results that are in good agreement with Monte Carlo simulations. In particular, the superfluid fraction obtained as a function of the interaction strength U for both integer and non-integer fillings is close to the simulation results. In all phases the excitation spectra are obtained by using the random phase approximation (RPA): the spectrum has a gap in the insulating phase and is gapless (and linear at small wave vectors) in the superfluid phase. Analytic results are presented in the limits of large U and small superfluid density. Finite-temperature phase diagrams and the Mott-insulator-normal-phase crossover are also described. (orig.)

Numerical observation of Hawking radiation from acoustic black holes in atomic Bose-Einstein condensates

International Nuclear Information System (INIS)

Carusotto, Iacopo; Recati, Alessio; Fagnocchi, Serena; Balbinot, Roberto; Fabbri, Alessandro

2008-01-01

We report numerical evidence of Hawking emission of Bogoliubov phonons from a sonic horizon in a flowing one-dimensional atomic Bose-Einstein condensate. The presence of Hawking radiation is revealed from peculiar long-range patterns in the density-density correlation function of the gas. Quantitative agreement between our fully microscopic calculations and the prediction of analog models is obtained in the hydrodynamic limit. New features are predicted and the robustness of the Hawking signal against a finite temperature discussed.

Solution of the statistical bootstrap with Bose statistics

International Nuclear Information System (INIS)

Engels, J.; Fabricius, K.; Schilling, K.

1977-01-01

A brief and transparent way to introduce Bose statistics into the statistical bootstrap of Hagedorn and Frautschi is presented. The resulting bootstrap equation is solved by a cluster expansion for the grand canonical partition function. The shift of the ultimate temperature due to Bose statistics is determined through an iteration process. We discuss two-particle spectra of the decaying fireball (with given mass) as obtained from its grand microcanonical level density

Merging and splitting of Bose-Einstein condensates into two translating traps

International Nuclear Information System (INIS)

Sun, B; Pindzola, M S

2009-01-01

We investigate the process of merging and splitting Bose-Einstein condensates into two slowly translating traps, analogous to a dual input atomic beam splitter. With the help of direct three-dimensional numerical simulations, we explore the dependence of population distributions on the initial relative phase and the trap moving speed. For non-interacting Bose-Einstein condensates, we find that our numerical results are in good agreement with a simple theoretical prediction. However, for interacting Bose-Einstein condensates, our results show striking differences with the non-interacting case: the Bose-Einstein condensates are always split towards 50:50 in the slow translation regime. This bosonic anti-bunching effect is interpreted as a consequence of complicated flow patterns due to atomic interactions.

Quantum many-body physics in a nutshell

CERN Document Server

Shuryak, Edward

2018-01-01

This book provides an essential introduction to the physics of quantum many-body systems, which are at the heart of atomic and nuclear physics, condensed matter, and particle physics. Unlike other textbooks on the subject, it covers topics across a broad range of physical fields―phenomena as well as theoretical tools―and does so in a simple and accessible way. Edward Shuryak begins with Feynman diagrams of the quantum and statistical mechanics of a particle―in these applications, the diagrams are easy to calculate and there are no divergencies. He discusses the renormalization group and illustrates its uses and covers systems such as weakly and strongly coupled Bose and Fermi gases, electron gas, nuclear matter, and quark-gluon plasmas. Phenomena include Bose condensation and superfluidity. Shuryak also looks at Cooper pairing and superconductivity for electrons in metals, liquid 3He, nuclear matter, and quark-gluon plasma. A recurring topic throughout is topological matter, ranging from ensembles of q...

A Neutron Scattering Study of Collective Excitations in Superfluid Helium

DEFF Research Database (Denmark)

Graf, E. H.; Minkiewicz, V. J.; Bjerrum Møller, Hans

1974-01-01

Extensive inelastic-neutron-scattering experiments have been performed on superfluid helium over a wide range of energy and momentum transfers. A high-resolution study has been made of the pressure dependence of the single-excitation scattering at the first maximum of the dispersion curve over...... of the multiexcitation scattering was also studied. It is shown that the multiphonon spectrum of a simple Debye solid with the phonon dispersion and single-excitation cross section of superfluid helium qualitatively reproduces these data....

Theory of superfluidity macroscopic quantum waves

International Nuclear Information System (INIS)

Ventura, I.

1978-10-01

A new description of superfluidity is proposed, based upon the fact that Bogoliubov's theory of superfluidity exhibits some so far unsuspected macroscopic quantum waves (MQWs), which have a topological nature and travel within the fluid at subsonic velocities. To quantize the bounded quasi-particles the field theoretic version of the Bohr-Sommerfeld quantization rule, is employed and also resort to a variational computation. In an instantaneous configuration the MQWs cut the condensate into blocks of phase, providing, by analogy with ferromagnetism, a nice explanation of what could be the lambda-transition. A crude estimate of the critical temperature gives T sub(c) approximately equal to 2-4K. An attempt is made to understand Tisza's two-fluid model in terms of the MQWs, and we rise the conjecture that they play an important role in the motion of second. We present also a qualitative prediction concerning to the behavior of the 'phononroton' peak below 1.0K, and propose two experiments to look for MQWs [pt

Modern trends in superconductivity and superfluidity

CERN Document Server

Kagan, M Yu

2013-01-01

This book concisely presents the latest trends in the physics of superconductivity and superfluidity and magnetism in novel systems, as well as the problem of BCS-BEC crossover in ultracold quantum gases and high-Tc superconductors. It further illuminates the intensive exchange of ideas between these closely related fields of condensed matter physics over the last 30 years of their dynamic development. The content is based on the author’s original findings obtained at the Kapitza Institute, as well as advanced lecture courses he held at the Moscow Engineering Physical Institute, Amsterdam University, Loughborough University and LPTMS Orsay between 1994 and 2011. In addition to the findings of his group, the author discusses the most recent concepts in these fields, obtained both in Russia and in the West. The book consists of 16 chapters which are divided into four parts. The first part describes recent developments in superfluid hydrodynamics of quantum fluids and solids, including the fashionable subject...

Disproportionate entrance length in superfluid flows and the puzzle of counterflow instabilities

Science.gov (United States)

Bertolaccini, J.; Lévêque, E.; Roche, P.-E.

2017-12-01

Systematic simulations of the two-fluid model of superfluid helium (He-II) encompassing the Hall-Vinen-Bekharevich-Khalatnikov (HVBK) mutual coupling have been performed in two-dimensional pipe counterflows between 1.3 and 1.96 K. The numerical scheme relies on the lattice Boltzmann method. A Boussinesq-like hypothesis is introduced to omit temperature variations along the pipe. In return, the thermomechanical forcings of the normal and superfuid components are fueled by a pressure term related to their mass-density variations under an approximation of weak compressibility. This modeling framework reproduces the essential features of a thermally driven counterflow. A generalized definition of the entrance length is introduced to suitably compare entry effects (of different nature) at opposite ends of the pipe. This definition is related to the excess of pressure loss with respect to the developed Poiseuille-flow solution. At the heated end of the pipe, it is found that the entrance length for the normal fluid follows a classical law and increases linearly with the Reynolds number. At the cooled end, the entrance length for the superfluid is enhanced as compared to the normal fluid by up to one order of magnitude. At this end, the normal fluid flows into the cooling bath of He-II and produces large-scale superfluid vortical motions in the bath that partly re-enter the pipe along its sidewalls before being damped by mutual friction. In the superfluid entry region, the resulting frictional coupling in the superfluid boundary layer distorts the velocity profiles toward tail flattening for the normal fluid and tail raising for the superfluid. Eventually, a simple analytical model of entry effects allows us to re-examine the long-debated thresholds of T 1 and T 2 instabilities in superfluid counterflows. Inconsistencies in the T 1 thresholds reported since the 1960s disappear if an aspect-ratio criterion based on our modeling is used to discard data sets with the

Critical behavior and dimension crossover of pion superfluidity

Science.gov (United States)

Wang, Ziyue; Zhuang, Pengfei

2016-09-01

We investigate the critical behavior of pion superfluidity in the framework of the functional renormalization group (FRG). By solving the flow equations in the SU(2) linear sigma model at finite temperature and isospin density, and making comparison with the fixed point analysis of a general O (N ) system with continuous dimension, we find that the pion superfluidity is a second order phase transition subject to an O (2 ) universality class with a dimension crossover from dc=4 to dc=3 . This phenomenon provides a concrete example of dimension reduction in thermal field theory. The large-N expansion gives a temperature independent critical exponent β and agrees with the FRG result only at zero temperature.

Renormalization-group study of superfluidity and phase separation of helium mixtures immersed in a disordered porous medium

International Nuclear Information System (INIS)

Lopatnikova, A.; Berker, A.N.

1997-01-01

Superfluidity and phase separation in 3 He- 4 He mixtures immersed in aerogel are studied by renormalization-group theory. The quenched disorder imposed by aerogel, both at the atomic level and at the geometric level, is included. The calculation is conducted via the coupled renormalization-group mappings, near and away from aerogel, of the quenched probability distributions of random interactions. Random-bond effects on the onset of superfluidity and random-field effects on superfluid-superfluid phase separation are seen. The quenched randomness causes the λ line of second-order phase transitions of superfluidity onset to reach zero temperature, in agreement with general predictions and experiments. The effects of the atomic and geometric randomness of aerogel are investigated separately and jointly. copyright 1997 The American Physical Society

Preliminary results of the Spacelab 2 superfluid helium experiment

International Nuclear Information System (INIS)

Mason, P.V.; Collins, D.J.; Elleman, D.D.; Jackson, H.W.; Wang, T.

1986-01-01

An experiment to investigate the properties of superfluid helium in a microgravity environment flew on the Shuttle on the Spacelab 2 mission in July and August of 1985. This paper summarizes the flight experiment and describes some preliminary results. The experiment comprised an investigation of long-wavelength third-sound waves in micron-thick films, a study of the motions of superfluid helium under milli-g and micro-g accelerations, and measurements of the fluctuations in temperature associated with the small motions of the bulk helium. An additional objective was to qualify and characterize a reflyable, space-compatible cryostat

A Study of Schrödinger–Type Equations Appearing in Bohmian Mechanics and in the Theory of Bose–Einstein Condensates

KAUST Repository

Sierra Nunez, Jesus Alfredo

2018-01-01

The Schrödinger equations have had a profound impact on a wide range of fields of modern science, including quantum mechanics, superfluidity, geometrical optics, Bose-Einstein condensates, and the analysis of dispersive phenomena in the theory

Critical velocities in He II for independently varied superfluid and normal fluid velocities

International Nuclear Information System (INIS)

Baehr, M.L.

1984-01-01

Experiments were performed to measure the critical velocity in pure superflow and compare to the theoretical prediction; to measure the first critical velocity for independently varied superfluid and normal fluid velocities; and to investigate the propagation of the second critical velocity from the thermal counterflow line through the V/sub n/,-V/sub s/ quadrant. The experimental apparatus employed a thermal counterflow heater to adjust the normal fluid velocity, a fountain pump to vary the superfluid velocity, and a level sensing capacitor to measure the superfluid velocity. The results of the pure superfluid critical velocity measurements indicate that this velocity is temperature independent contrary to Schwarz's theory. It was found that the first critical velocity for independently varied V/sub n/ and V/sub s/ could be described by a linear function of V/sub n/ and was otherwise temperature independent. It was found that the second critical velocity could only be distinguished near the thermal counterflow line

Bose Condensate in He II

International Nuclear Information System (INIS)

Svensson, E.C.

1984-01-01

The Condensate Saga, now halfway through its fifth decade, is reviewed. The recent neutron-scattering work which has at last convincingly established that there is indeed a Bose Condensate in He II is described

Bose-Einstein condensation in microgravity.

Science.gov (United States)

van Zoest, T; Gaaloul, N; Singh, Y; Ahlers, H; Herr, W; Seidel, S T; Ertmer, W; Rasel, E; Eckart, M; Kajari, E; Arnold, S; Nandi, G; Schleich, W P; Walser, R; Vogel, A; Sengstock, K; Bongs, K; Lewoczko-Adamczyk, W; Schiemangk, M; Schuldt, T; Peters, A; Könemann, T; Müntinga, H; Lämmerzahl, C; Dittus, H; Steinmetz, T; Hänsch, T W; Reichel, J

2010-06-18

Albert Einstein's insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.

Bose-Einstein condensation and applications

International Nuclear Information System (INIS)

Jaksch, D.H.

1999-10-01

After a short introduction on recent developments in the field of Bose-Einstein condensation (BEC) with weakly interacting neutral atoms in the first part of my thesis I investigate the properties of a BEC in its stationary state with the help of quantum kinetic theory in the second part. Especially, I consider the particle number and phase fluctuations of a BEC emerging from the interaction of the condensed particles with the thermal cloud of atoms. In the third part of my thesis I show how one might realize the Bose-Hubbard model in optical lattices by making use of BEC. In the last part of my work I show how one can realize quantum logic with neutral atoms trapped in either optical lattices or in magnetic microtraps. (author)

Superfluid {sup 3}He, a two-fluid system, with the normal-fluid dynamics dominated by Andreev reflection

Energy Technology Data Exchange (ETDEWEB)

Pickett, G. R., E-mail: g.pickett@lancaster.ac.uk [Lancaster University, Department of Physics (United Kingdom)

2014-12-15

As a specific offering towards his festschrift, we present a review the various properties of the excitation gas in superfluid {sup 3}He, which depend on Andreev reflection. This phenomenon dominates many of the properties of the normal fluid, especially at the lowest temperatures. We outline the ideas behind this dominance and describe a sample of the many experiments in this system which the operation of Andreev reflection has made possible, from temperature measurement, particle detection, vortex imaging to cosmological analogues.

Lifshitz effects on holographic p-wave superfluid

Directory of Open Access Journals (Sweden)

Ya-Bo Wu

2015-02-01

Full Text Available In the probe limit, we numerically build a holographic p-wave superfluid model in the four-dimensional Lifshitz black hole coupled to a Maxwell-complex vector field. We observe the rich phase structure and find that the Lifshitz dynamical exponent z contributes evidently to the effective mass of the matter field and dimension of the gravitational background. Concretely, we obtain that the Cave of Winds appeared only in the five-dimensional anti-de Sitter (AdS spacetime, and the increasing z hinders not only the condensate but also the appearance of the first-order phase transition. Furthermore, our results agree with the Ginzburg–Landau results near the critical temperature. In addition, the previous AdS superfluid model is generalized to the Lifshitz spacetime. Keywords: Gauge/gravity duality, Holographic superconductor, Lifshitz black hole, Maxwell-complex vector field

Many-body Anderson localization of strongly interacting bosons in random lattices

International Nuclear Information System (INIS)

Katzer, Roman

2015-05-01

In the present work, we investigate the problem of many-body localization of strongly interacting bosons in random lattices within the disordered Bose-Hubbard model. This involves treating both the local Mott-Hubbard physics as well as the non-local quantum interference processes, which give rise to the phenomenon of Anderson localization, within the same theory. In order to determine the interaction induced transition to the Mott insulator phase, it is necessary to treat the local particle interaction exactly. Therefore, here we use a mean-field approach that approximates only the kinetic term of the Hamiltonian. This way, the full problem of interacting bosons on a random lattice is reduced to a local problem of a single site coupled to a particle bath, which has to be solved self-consistently. In accordance to previous works, we find that a finite disorder width leads to a reduced size of the Mott insulating regions. The transition from the superfluid phase to the Bose glass phase is driven by the non-local effect of Anderson localization. In order to describe this transition, one needs to work within a theory that is non-local as well. Therefore, here we introduce a new approach to the problem. Based on the results for the local excitation spectrum obtained within the mean-field theory, we reduce the full, interacting model to an effective, non-interacting model by applying a truncation scheme to the Hilbert space. Evaluating the long-ranged current density within this approximation, we identify the transition from the Bose glass to the superfluid phase with the Anderson transition of the effective model. Resolving this transition using the self-consistent theory of localization, we obtain the full phase diagram of the disordered Bose-Hubbard model in the regime of strong interaction and larger disorder. In accordance to the theorem of inclusions, we find that the Mott insulator and the superfluid phase are always separated by the compressible, but insulating

Hydrodynamics of rotating superfluids

International Nuclear Information System (INIS)

Chandler, E.A.

1981-01-01

In this thesis, a coarse grained hydrodynamics is developed from the exact description of Tkachenko. To account for the dynamics of the vortex lattice, the macroscopic vortex displacement field is treated as an independent degree of freedom. The conserved energy is written in terms of the coarse-grained normal fluid, superfluid, and vortex velocities and includes an elastic energy associated with deformations of the vortex lattice. Equations of motion consistent with the conservation of energy, entropy and vorticity and containing mutual friction terms arising from microscopic interactions between normal fluid excitations and the vortex lines are derived. When the vortex velocity is eliminated from the damping terms, this system of equations becomes essentially that of BK with added elastic terms in the momentum stress tensor and energy current. The dispersion relation and damping of the first and second sound modes and the two transverse modes sustained by the system are investigated. It is shown that mutual friction mixes the transverse modes of the normal and superfluid components and damps the transverse mode associated with the relative velocity of these components, making this wave evanescent in the plane perpendicular to the rotation axis. The wave associated with transverse motion of the total mass current is a generalized Tkachenko mode, whose dispersion relation reduces to that derived by Tkachenko wave when the wavevector lies in this plane

Sounds in one-dimensional superfluid helium

International Nuclear Information System (INIS)

Um, C.I.; Kahng, W.H.; Whang, E.H.; Hong, S.K.; Oh, H.G.; George, T.F.

1989-01-01

The temperature variations of first-, second-, and third-sound velocity and attenuation coefficients in one-dimensional superfluid helium are evaluated explicitly for very low temperatures and frequencies (ω/sub s/tau 2 , and the ratio of second sound to first sound becomes unity as the temperature decreases to absolute zero

Density-optimized efficiency for magneto-optical production of a stable molecular Bose-Einstein condensate

Energy Technology Data Exchange (ETDEWEB)

Mackie, Matt [Helsinki Institute of Physics, PL 64, FIN-00014 Helsingin yliopisto (Finland); Collin, Anssi [Helsinki Institute of Physics, PL 64, FIN-00014 Helsingin yliopisto (Finland); Suominen, Kalle-Antti [Helsinki Institute of Physics, PL 64, FIN-00014 Helsingin yliopisto (Finland); Javanainen, Juha [Department of Physics, University of Connecticut, Storrs, CT 06269-3046 (United States)

2003-08-01

Although photoassociation and the Feshbach resonance are feasible means in principle for creating a molecular Bose-Einstein condensate (MBEC) from an already quantum-degenerate gas of atoms, collision-induced mean-field shifts and irreversible decay place practical constraints on the efficient Raman delivery of stable molecules. Focusing on stimulated Raman adiabatic passage, we propose that the efficiency of both mechanisms for producing a stable MBEC can be improved by treating the density of the initial atom condensate as an optimization parameter.

Fast and accurate calculation of dilute quantum gas using Uehling–Uhlenbeck model equation

Energy Technology Data Exchange (ETDEWEB)

Yano, Ryosuke, E-mail: ryosuke.yano@tokiorisk.co.jp

2017-02-01

The Uehling–Uhlenbeck (U–U) model equation is studied for the fast and accurate calculation of a dilute quantum gas. In particular, the direct simulation Monte Carlo (DSMC) method is used to solve the U–U model equation. DSMC analysis based on the U–U model equation is expected to enable the thermalization to be accurately obtained using a small number of sample particles and the dilute quantum gas dynamics to be calculated in a practical time. Finally, the applicability of DSMC analysis based on the U–U model equation to the fast and accurate calculation of a dilute quantum gas is confirmed by calculating the viscosity coefficient of a Bose gas on the basis of the Green–Kubo expression and the shock layer of a dilute Bose gas around a cylinder.

Depression of the Superfluid Transition Temperature in 4He by a Heat Flow

International Nuclear Information System (INIS)

Yin Liang; Qi Xin; Lin Peng

2014-01-01

The depression of the superfluid transition temperature T λ in 4 He by a heat flow Q is studied. A small sealed cell with a capillary is introduced and a stable and flat superfluid transition temperature plateau is easily obtained by controlling the temperature of the variable-temperature platform and the bottom chamber of the sealed cell. Owing to the depression effect of the superfluid transition temperature by the heat flow, the heat flow through the capillary is changed by the temperature control to obtain multiple temperature plateaus of different heat flows. The thermometer self-heating effect, the residual heat leak of the 4.2 K environment, the temperature difference on the He II liquid column, the Kapiza thermal resistance between the liquid helium and the copper surface of the sealed cell, the temperature gradient of the sealed cell, the static pressure of the He II liquid column and other factors have influence on the depression effect and the influence is analyzed in detail. Twenty experiments of the depression of the superfluid transition temperature in 4 He by heat flow are made with four sealed cells in one year. The formula of the superfluid transition temperature pressured by the heat flow is T λ (Q) = −0.00000103Q + 2.1769108, and covers the range 229 ≤ Q ≤ 6462 μW/cm 2

Approaching Bose-Einstein Condensation

Science.gov (United States)

Ferrari, Loris

2011-01-01

Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…

Faraday waves in Bose-Einstein condensates

International Nuclear Information System (INIS)

Nicolin, Alexandru I.; Carretero-Gonzalez, R.; Kevrekidis, P. G.

2007-01-01

Motivated by recent experiments on Faraday waves in Bose-Einstein condensates we investigate both analytically and numerically the dynamics of cigar-shaped Bose-condensed gases subject to periodic modulation of the strength of the transverse confinement. We offer a fully analytical explanation of the observed parametric resonance, based on a Mathieu-type analysis of the non-polynomial Schroedinger equation. The theoretical prediction for the pattern periodicity versus the driving frequency is directly compared to the experimental data, yielding good qualitative and quantitative agreement between the two. These results are corroborated by direct numerical simulations of both the one-dimensional non-polynomial Schroedinger equation and of the fully three-dimensional Gross-Pitaevskii equation

Modelling Pulsar Glitches: The Hydrodynamics of Superfluid Vortex Avalanches in Neutron Stars

Science.gov (United States)

Khomenko, V.; Haskell, B.

2018-05-01

The dynamics of quantised vorticity in neutron star interiors is at the heart of most pulsar glitch models. However, the large number of vortices (up to ≈1013) involved in a glitch and the huge disparity in scales between the femtometre scale of vortex cores and the kilometre scale of the star makes quantum dynamical simulations of the problem computationally intractable. In this paper, we take a first step towards developing a mean field prescription to include the dynamics of vortices in large-scale hydrodynamical simulations of superfluid neutron stars. We consider a one-dimensional setup and show that vortex accumulation and differential rotation in the neutron superfluid lead to propagating waves, or `avalanches', as solutions for the equations of motion for the superfluid velocities. We introduce an additional variable, the fraction of free vortices, and test different prescriptions for its advection with the superfluid flow. We find that the new terms lead to solutions with a linear component in the rise of a glitch, and that, in specific setups, they can give rise to glitch precursors and even to decreases in frequency, or `anti-glitches'.

Introduction to superfluidity field-theoretical approach and applications

CERN Document Server

Schmitt, Andreas

2015-01-01

Superfluidity – and closely related to it, superconductivity – are very general phenomena that can occur on vastly different energy scales. Their underlying theoretical mechanism of spontaneous symmetry breaking is even more general and applies to a multitude of physical systems.  In these lecture notes, a pedagogical introduction to the field-theory approach to superfluidity is presented. The connection to more traditional approaches, often formulated in a different language, is carefully explained in order to provide a consistent picture that is useful for students and researchers in all fields of physics. After introducing the basic concepts, such as the two-fluid model and the Goldstone mode, selected topics of current research are addressed, such as the BCS-BEC crossover and Cooper pairing with mismatched Fermi momenta.

Asymmetric Top Rotors in Superfluid Para-Hydrogen Nano-Clusters

Science.gov (United States)

Zeng, Tao; Li, Hui; Roy, Pierre-Nicholas

2012-06-01

We present the first simulation study of bosonic clusters doped with an asymmetric top molecule. A variation of the path-integral Monte Carlo method is developed to study a para-water (pH_2O) impurity in para-hydrogen (pH_2) clusters. The growth pattern of the doped clusters is similar in nature to that of the pure clusters. The pH_2O molecule appears to rotate freely in the cluster due to its large rotational constants and the lack of adiabatic following. The presence of pH_2O substantially quenches the superfluid response of pH_2 with respect to the space fixed frame. We also study the behaviour of a sulphur dioxide (32S16O_2) dopant in the pH_2 clusters. For such a heavy rotor, the adiabatic following of the pH_2 molecules is established and the superfluid renormalization of the rotational constants is observed. The rotational structure of the SO_2-p(H_2)_N clusters' ro-vibrational spectra is predicted. The connection between the superfluid response respect to the external boundary rotation and the dopant rotation is discussed.

Depletion of superfluidity in a disordered non-equilibrium quantum condensate

Energy Technology Data Exchange (ETDEWEB)

Janot, Alexander; Rosenow, Bernd [Institut fuer Theoretische Physik, Universitaet Leipzig, 04009 Leipzig (Germany); Hyart, Timo [Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden (Netherlands); Eastham, Paul [School of Physics, Trinity College, Dublin 2 (Ireland)

2013-07-01

Observations of quantum coherence in driven systems, e.g. polariton condensates, have strongly stimulated experimental as well as theoretical efforts during the last decade. We analyze the superfluid stiffness of a non-equilibrium quantum-condensate in a disordered environment taking gain and loss of particles into account. To this end a modified effective Gross-Pitaevskii equation is employed. We find that the disorder-driven depletion of superfluidity is strongly enhanced due to the gain-loss mechanism. It turns out that the condensate remains stiff at finite length scales only.