Smirnova, N A; Mizusaki, T; Van Isacker, P; Smirnova, Nadya A.; Pietralla, Norbert; Mizusaki, Takahiro; Isacker, Piet Van
2000-01-01
The interrelation between the octupole phonon and the low-lyingproton-neutron mixed-symmetry quadrupole phonon in near-spherical nuclei isinvestigated. The one-phonon states decay by collective E3 and E2 transitionsto the ground state and by relatively strong E1 and M1 transitions to theisoscalar 2^+ state. We apply the proton-neutron version of the InteractingBoson Model including quadrupole and octupole bosons (sdf-IBM-2). Two F-spinsymmetric dynamical symmetry limits of the model, namely the vibrational andthe $\\gamma$-unstable ones, are considered. We derive analytical formulae forexcitation energies as well as B(E1), B(M1), B(E2) and B(E3) values for anumber of transitions between low-lying states. The model well reproduces manyknown transition strengths in the near spherical nuclei ^{142}Ce and ^{94}Mo.
Smirnova, N.A.; Van Isacker, P. [Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (France); Smirnova, N.A [Paris-11 Univ., 91 - Orsay (France). Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse]|[Institute for Nuclear Physics, Moscow State University (Russian Federation); Pietralla, N. [Institut fur Kernphysik, Universitat zu Koln (Germany)]|[Yale Univ., New Haven, CT (United States). Wright Nuclear Structure Lab; Mizusaki, T. [Tokyo Univ. (Japan). Dept. of Physics
2000-07-01
The interrelation between the octupole phonon and the low-lying proton-neutron mixed-symmetry quadrupole in near-spherical nuclei is investigated. The one-phonon states decay by collective E3 and E2 transitions to the ground state and by relatively strong E1 and M1 transitions to the isoscalar 2{sup +}{sub 1} state. We apply the proton-neutron version of the Interacting Boson Model including quadrupole and octupole bosons (sdf-IBM-2). Two F-spin symmetric dynamical symmetry limits of the model, namely the vibrational and the {gamma}-unstable ones, are considered. We derived analytical formulae for excitation energies as well as B(E1), B(M1), B(E2), and B(E3) values for a number of transitions between low-lying states. The model well reproduces many known transition strengths in the near spherical nuclei {sup 142}Ce and {sup 94}Mo. (authors)
Smirnova, N A; Mizusaki, T; Van Isacker, P
2000-01-01
The interrelation between the octupole phonon and the low-lying proton-neutron mixed-symmetry quadrupole phonon in near-spherical nuclei is investigated. The one-phonon states decay by collective E3 and E2 transitions to the ground state and by relatively strong E1 and M1 transitions to the isoscalar 2 sup + sub 1 state. We apply the proton-neutron version of the interacting boson model including quadrupole and octupole bosons ( sdf -IBM-2). Two F -spin symmetric dynamical symmetry limits of the model, namely the vibrational and the gamma -unstable ones, are considered. We derive analytical formulae for excitation energies as well as B(E1) , B(M1) , B(E2) and B(E3) values for a number of transitions between low-lying states.
Mixed-symmetry octupole and hexadecapole excitations in the N=52 isotones
Hennig, A; Werner, V; Ahn, T; Anagnostatou, V; Cooper, N; Derya, V; Elvers, M; Endres, J; Goddard, P; Heinz, A; Huges, R O; Ilie, G; Mineva, M N; Petkov, P; Pickstone, S G; Pietralla, N; Radeck, D; Ross, T J; Savran, D; Zilges, A
2015-01-01
Background: Excitations with mixed proton-neutron symmetry have been previously observed in the $N=52$ isotones. Besides the well established quadrupole mixed-symmetry states (MSS), octupole and hexadecapole MSS have been recently proposed for the nuclei $^{92}$Zr and $^{94}$Mo. Purpose: The heaviest stable $N=52$ isotone $^{96}$Ru was investigated to study the evolution of octupole and hexadecapole MSS with increasing proton number. Methods: Two inelastic proton-scattering experiments on $^{96}$Ru were performed to extract branching ratios, multipole mixing ratios, and level lifetimes. From the combined data, absolute transition strengths were calculated. Results: Strong $M1$ transitions between the lowest-lying $3^-$ and $4^+$ states were observed, providing evidence for a one-phonon mixed-symmetry character of the $3^{(-)}_2$ and $4^+_2$ states. Conclusions: $sdg$-IBM-2 calculations were performed for $^{96}$Ru. The results are in excellent agreement with the experimental data, pointing out a one-phonon he...
Odd-spin yrast states as multiple quadrupole-phonon excitations
Pietralla, N; Otsuka, T; Casten, R F
1995-01-01
The wavefunctions of the lowest odd spin positive parity yrast states in the IBA are shown to be nearly pure multiple quadrupole-phonon excitations even outside the three dynamical symmetries. The empirical data for collective nuclei with 30 < Z < 80 confirm these predictions. The quadrupole-phonon purity of the 2^+_1 state can be measured from E2-branching ratios of the 3^+_1 state. These data show a high correlation to the 2^+_1 Q-phonon purity deduced from the E2-decay of 2^+ states.
Sheikh Obeid, Abdulrahman
2014-11-01
In the framework of this thesis electron scattering experiments on low-energy excitations of {sup 92}Zr and {sup 94}Zr were performed at the S-DALINAC in a momentum transfer range q=0.3-0.6 fm{sup -1}. The nature of one-phonon symmetric and mixed-symmetric 2{sup +} and 3{sup -} states of {sup 92}Zr was investigated by comparison with predictions of the quasi-particle phonon model (QPM). Theoretical (e,e') cross sections have been calculated within the distorted wave Born approximation (DWBA) to account for Coulomb distortion effects. The reduced strengths of the one-quadrupole phonon states and the one-octupole phonon state have been extracted. The similarity of the momentum-transfer dependence of the form factors between the 2{sup +} states supports the one-phonon nature of the 2{sup +}{sub 2} state of {sup 92}Zr. A new method based on the Plane Wave Born Approximation (PWBA) for a model-independent determination of the ratio of the E2 transition strengths of fully symmetric (FSS) and mixed-symmetry (MSS) one-phonon excitations of heavy vibrational nuclei is introduced. Due to the sensitivity of electron scattering to charge distributions, the charge transition-radii difference can be determined. The basic assumptions (independence from the ratio of Coulomb corrections and from absolute values of transition radii) are tested within the Tassie model, which makes no specific assumptions about the structure of the states other than collectivity. It is shown that a PWBA analysis of the form factors, which usually fails for heavy nuclei, can nevertheless be applied in a relative analysis. This is a new promising approach to determine the ground state transition strength of the 2{sup +} MSS of vibrational nuclei with a precision limited only by the experimental information about the B(E2;2{sup +}{sub 1}→0{sup +}{sub 1}) strength. The PWBA approach furthermore provides information about differences of the proton transition radii of the respective states
Saperstein, E E; Krepish, D S; Tolokonnikov, S V; Voitenkov, D
2016-01-01
A model, developed recently within the Theory of Finite Fermi systems to describe phonon coupling (PC) effects in magnetic moments of odd magic and semi-magic nuclei, is applied to quadrupole moments. The model is based on the perturbation theory in $g_L^2$, where $g_L$ is the vertex of creating the $L$-phonon. The phonon tadpole diagrams are taken into account in an approximate way, which turns out to be exact for the spurious $1^-$ phonon. The odd Tl and Sb are considered, which are the proton-odd neighbors of even tin nuclei. The $2^+_1$ phonon is taken into account which is the most collective among the low-laying surface states. Its quadrupole moment is one of ingredients of the calculation scheme, with the corresponding values being found by us previously. The value of total PC correction to quadrupole moments turned out to be moderate due to strong cancelation of two main terms, due to the phonon $Z$-factor and due to the phonon-induced interaction. However, as a rule, the result is, noticeable, thus, ...
Mixed Symmetry Isomeric States in Nuclei
LONG Gui-Lu; RUAN Dong; LI Yan-Song; TU Chang-Cun; TIAN Lin; JI Hua-Ying; ZHU Sheng-Jiang; ZHAO En-Guang; LIU Feng-Ying; ZHANG Jin-Fu
2002-01-01
Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model. It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majorana interaction. Under certain conditions, they become the yrast state or yrare state. These states are difficult to decay and become very stable. This study suggests that a possible new mode of isomers may exist due to the special nature in their proton and neutron degrees of freedom.
Detailed Description of Mixed Symmetry States in 94Mo Using Interacting Boson Model
LONG GuiLu; F.H. Al-Khudair
2002-01-01
We have investigated the low-lying collective states and electromagnetic transitions in 94Mo within the framework of the interacting boson model. The influence of model parameters on the energy levels and electromagnetic properties has been investigated. The analysis of the obtained results and the parameter values predict that the 23+state is the lowest mixed symmetry state with pure F = Fmax - 1 in this nucleus. The calculated results predicate that the 25+ (two-Q-phonon) mixed symmetry state is closed to the J = 2+ at 2.870 MeV in the experimental data, and the 2.965 MeV state is the lowest mixed symmetry with J = 3+.
E Saperstein, E.; Kamerdzhiev, S.; Krepish, D. S.; Tolokonnikov, S. V.; Voitenkov, D.
2017-06-01
The self-consistent model, developed previously to describe phonon coupling (PC) effects in magnetic moments of odd magic and semi-magic nuclei, is extended to quadrupole moments. It is based on the theory of finite Fermi systems with the use of the perturbation theory in g L 2, where g L is the vertex creating the L-phonon. Accounting for the phonon tadpole diagrams is an important ingredient of this model. The calculation scheme is based on the Fayans energy density functional DF3-a and does not contain any adjusted parameters. The odd In and Sb isotopes are considered, which are the proton-odd neighbors of even tin nuclei. The {2}1+ phonon is taken into account in which the quadrupole moment is one ingredient of the calculation scheme. The corresponding values were found by us previously. Two main PC corrections, due to the phonon Z-factor and due to the phonon-induced interaction, have opposite signs and strongly cancel each other, leaving room for other ‘small’ corrections, so that the resulting PC correction is much lower than the absolute values of each of the two main ones. However, it remains noticeable, making the overall agreement with the data significantly better.
Extended M1 sum rule for excited symmetric and mixed-symmetry states in nuclei
Smirnova, N A; Leviatan, A; Ginocchio, J N; Fransen, C
2002-01-01
A generalized M1 sum rule for orbital magnetic dipole strength from excited symmetric states to mixed-symmetry states is considered within the proton-neutron interacting boson model of even-even nuclei. Analytic expressions for the dominant terms in the B(M1) transition rates from the first and second $2^+$ states are derived in the U(5) and SO(6) dynamic symmetry limits of the model, and the applicability of a sum rule approach is examined at and in-between these limits. Lastly, the sum rule is applied to the new data on mixed-symmetry states of 94Mo and a quadrupole d-boson ratio $nd(0^+_1)/nd(2^+_2) \\approx 0.6$ is obtained in a largely parameter-independent way
Non-geometric fluxes and mixed-symmetry potentials
Bergshoeff, E.A.; Penas, V.A.; Riccioni, F.; Risoli, S.
2015-01-01
We discuss the relation between generalised fluxes and mixed-symmetry potentials. We refer to the fluxes that cannot be described even locally in the framework of supergravity as ‘non-geometric’. We first consider the NS fluxes, and point out that the non-geometric R flux is dual to a mixed-symmetry
U-dual branes and mixed symmetry tensor fields
Chatzistavrakidis, A. [Institut fuer Theoretische Physik, Appelstrasse 2, 30167 Hannover (Germany); Gautason, F.F. [Institut fuer Theoretische Physik, Appelstrasse 2, 30167 Hannover (Germany); Center for Quantum Engineering and Spacetime Research, Appelstrasse 2, 30167 Hannover (Germany)
2014-09-11
We review and explain the relation between U-dual branes in string theory and mixed symmetry tensors of various degrees. In certain cases these mixed symmetry tensors can be related to diverse types of fluxes that play an important role in compactifications of string theory. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Non-geometric fluxes and mixed-symmetry potentials
Bergshoeff, E A; Riccioni, F; Risoli, S
2015-01-01
We discuss the relation between generalised fluxes and mixed-symmetry potentials. We first consider the NS fluxes, and point out that the `non-geometric' $R$ flux is dual to a mixed-symmetry potential with a set of nine antisymmetric indices. We then consider the T-duality family of fluxes whose prototype is the Scherk-Schwarz reduction of the S-dual of the RR scalar of IIB supergravity. Using the relation with mixed-symmetry potentials, we are able to give a complete classification of these fluxes, including the ones that are non-geometric. The non-geometric fluxes again turn out to be dual to potentials containing nine antisymmetric indices. Our analysis suggests that all these fluxes can be understood in the context of double field theory, although for the non-geometric ones one expects a violation of the strong constraint.
Unconstrained Higher Spins of Mixed Symmetry. I. Bose Fields
Campoleoni, Andrea; Mourad, Jihad; Sagnotti, Augusto
2008-01-01
This is the first of two papers devoted to the local "metric-like" unconstrained Lagrangians and field equations for higher-spin gauge fields of mixed symmetry in flat space. Here we complete the previous constrained formulation of Labastida for Bose fields. We thus recover his Lagrangians via the Bianchi identities, before extending them to their "minimal" unconstrained form with higher derivatives of the compensator fields and to yet another, non-minimal, form with only two-derivative terms. We also identify classes of these systems that are invariant under Weyl-like symmetries.
Mixed-symmetry multiplets and higher-spin curvatures
Bekaert, Xavier; Francia, Dario
2015-01-01
We study the higher-derivative equations for gauge potentials of arbitrary mixed-symmetry type obtained by setting to zero the divergences of the corresponding curvature tensors. We show that they propagate the same reducible multiplets as the Maxwell-like second-order equations for gauge fields subject to constrained gauge transformations. As an additional output of our analysis, we provide a streamlined presentation of the Ricci-like case, where the traces of the same curvature tensors are set to zero, and we present a simple algebraic evaluation of the particle content associated with the Labastida and with the Maxwell-like second-order equations.
Mixed-Symmetry Shell-Model Calculations in Nuclear Physics
Gueorguiev, V G
2010-01-01
We consider a novel approach to the nuclear shell model. The one-dimensional harmonic oscillator in a box is used to introduce the concept of an oblique-basis shell-model theory. By implementing the Lanczos method for diagonalization of large matrices, and the Cholesky algorithm for solving generalized eigenvalue problems, the method is applied to nuclei. The mixed-symmetry basis combines traditional spherical shell-model states with SU(3) collective configurations. We test the validity of this mixed-symmetry scheme on 24Mg and 44Ti. Results for 24Mg, obtained using the Wilthental USD intersection in a space that spans less than 10% of the full-space, reproduce the binding energy within 2% as well as an accurate reproduction of the low-energy spectrum and the structure of the states - 90% overlap with the exact eigenstates. In contrast, for an m-scheme calculation, one needs about 60% of the full space to obtain compatible results. Calculations for 44Ti support the mixed-mode scheme although the pure SU(3) ca...
Unconstrained Higher Spins of Mixed Symmetry. II. Fermi Fields
Campoleoni, Andrea; Mourad, Jihad; Sagnotti, Augusto
2010-01-01
This paper is a sequel of arXiv:0810.4350 [hep-th], and is also devoted to the local "metric-like" unconstrained Lagrangians and field equations for higher-spin fields of mixed symmetry in flat space. Here we complete the previous constrained on-shell formulation of Labastida for Fermi fields, deriving the corresponding constrained Lagrangians both via the Bianchi identities and via the requirement of self-adjointness. We also describe two types of unconstrained Lagrangian formulations: a "minimal" one, containing higher derivatives of the compensator fields, and another non-minimal one, containing only one-derivative terms. We identify classes of these systems that are invariant under Weyl-like symmetry transformations.
Unconstrained higher spins of mixed symmetry II. Fermi fields
Campoleoni, A., E-mail: a.campoleoni@sns.i [Scuola Normale Superiore and INFN, Piazza dei Cavalieri, 7, I-56126 Pisa (Italy); Francia, D., E-mail: francia@apc.univ-paris7.f [AstroParticule et Cosmologie (APC), Universite Paris VII - Campus Paris Rive Gauche, 10, rue Alice Domon et Leonie Duquet, F-75205 Paris Cedex 13 (France); Mourad, J., E-mail: mourad@apc.univ-paris7.f [AstroParticule et Cosmologie (APC), Universite Paris VII - Campus Paris Rive Gauche, 10, rue Alice Domon et Leonie Duquet, F-75205 Paris Cedex 13 (France); Sagnotti, A., E-mail: sagnotti@sns.i [Scuola Normale Superiore and INFN, Piazza dei Cavalieri, 7, I-56126 Pisa (Italy)
2010-04-01
This paper is a sequel of [A. Campoleoni, D. Francia, J. Mourad, A. Sagnotti, Nucl. Phys. B 815 (2009) 289, (arXiv:0810.4350 [hep-th])], and is also devoted to the local 'metric-like' unconstrained Lagrangians and field equations for higher-spin fields of mixed symmetry in flat space. Here we complete the previous constrained on-shell formulation of Labastida for Fermi fields, deriving the corresponding constrained Lagrangians both via the Bianchi identities and via the requirement of self-adjointness. We also describe two types of unconstrained Lagrangian formulations: a 'minimal' one, containing higher derivatives of the compensator fields, and another non-minimal one, containing only one-derivative terms. We identify classes of these systems that are invariant under Weyl-like symmetry transformations.
Projectors and seed conformal blocks for traceless mixed-symmetry tensors
Costa, Miguel S.; Hansen, Tobias; Penedones, João; Trevisani, Emilio
2016-07-01
In this paper we derive the projectors to all irreducible SO( d) representations (traceless mixed-symmetry tensors) that appear in the partial wave decomposition of a conformal correlator of four stress-tensors in d dimensions. These projectors are given in a closed form for arbitrary length l 1 of the first row of the Young diagram. The appearance of Gegenbauer polynomials leads directly to recursion relations in l 1 for seed conformal blocks. Further results include a differential operator that generates the projectors to traceless mixed-symmetry tensors and the general normalization constant of the shadow operator.
Projectors and seed conformal blocks for traceless mixed-symmetry tensors
Costa, Miguel S. [Centro de Física do Porto, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Theory Division, Department of Physics, CERN, CH-1211 Genève 23 (Switzerland); Hansen, Tobias [Centro de Física do Porto, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); II. Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany); Penedones, João [Centro de Física do Porto, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Theory Division, Department of Physics, CERN, CH-1211 Genève 23 (Switzerland); Fields and Strings Laboratory, Institute of Physics, EPFL, CH-1015 Lausanne (Switzerland); Trevisani, Emilio [Centro de Física do Porto, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal)
2016-07-05
In this paper we derive the projectors to all irreducible SO(d) representations (traceless mixed-symmetry tensors) that appear in the partial wave decomposition of a conformal correlator of four stress-tensors in d dimensions. These projectors are given in a closed form for arbitrary length l{sub 1} of the first row of the Young diagram. The appearance of Gegenbauer polynomials leads directly to recursion relations in l{sub 1} for seed conformal blocks. Further results include a differential operator that generates the projectors to traceless mixed-symmetry tensors and the general normalization constant of the shadow operator.
Projectors and seed conformal blocks for traceless mixed-symmetry tensors
Costa, Miguel S.; Penedones, João; Trevisani, Emilio
2016-01-01
In this paper we derive the projectors to all irreducible SO(d) representations (traceless mixed-symmetry tensors) that appear in the partial wave decomposition of a conformal correlator of four stress-tensors in d dimensions. These projectors are given in a closed form for arbitrary length $l_1$ of the first row of the Young diagram. The appearance of Gegenbauer polynomials leads directly to recursion relations in $l_1$ for seed conformal blocks. Further results include a differential operator that generates the projectors to traceless mixed-symmetry tensors and the general normalization constant of the shadow operator.
Unfolding Mixed-Symmetry Fields in AdS and the BMV Conjecture I. General Formalism
Boulanger, Nicolas; Sundell, Per
2009-01-01
We present some generalities of unfolded on-shell dynamics that are useful in analyzing the BMV conjecture for mixed-symmetry fields in constantly curved backgrounds. In particular we discuss the unfolded notion of local degrees of freedom in theories with and without gravity and with and without massive deformation parameters, using the language of Weyl zero-form modules and their duals.
Mixed symmetry states and isospin excitation in N = Z nucleus 52Fe
2008-01-01
The interacting boson model with isospin (IBM-3) was applied to study the band structure and electromagnetic transition properties of the low-lying states in the even-even N = Z nucleus 52Fe. The isospin excitation states with T = 0, 1 and 2 were identified, and compared with the available data. The study shows that the 2+3 state is the lowest mixed symmetry state in 52Fe. The excitation energy of the second 0+2 state with T = 0 in nucleus 52Fe was identified. The model calculations with the data show a reasonably good agreement.
Frame-like off-shell dualization for mixed-symmetry gauge fields
Boulanger, Nicolas; Ponomarev, Dmitry
2013-05-01
We construct a purely frame-like parent action that allows us to dualize, at the off-shell level, an arbitrary mixed-symmetry bosonic massless field in Minkowski background of dimensions d. Starting from any massless mixed-symmetry gauge field in the standard Skvortsov frame-like formulation and following an off-shell dualization procedure, we obtain dual theories which are on-shell related by so(d - 2) Hodge duality. The Hodge dualization can be done on any column of the Young diagram characterizing the generalized spin of the original frame-like field. Dualization with respect to the first column of the Young diagram leads to a standard frame-like action for the dual field. Any other dualization results in an action which cannot be described by the standard frame-like formalism, as the on-shell field is not so(d - 2) traceless. Instead, the latter field is given by the product of an irreducible traceless tensor and a certain number of so(d - 2)-invariant metrics, and the corresponding dual frame-like action is new. Such actions require supplementary fields, which naturally arise along the lines of the approach that we propose. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Higher spin theories and holography’.
Symmetries of Quadrupole-Collective Vibrational Motion in Transitional Even-Even 124−134Xenon Nuclei
Pietralla, N; Rainovski, G; Ahn, T; Bauer, C; Leske, J; Möller, O; Möller, T
2010-01-01
Projectile-Coulomb excitation of Xe isotopes has been performed at ANL using the Gammasphere array for the detection of γ-rays. The one-quadrupole phonon 2+ 1,ms mixed-symmetry state (MSS) has been traced in the stable N=80 isotones down to 134Xe. First, the data on absolute E2 andM1 transition rates quantify the amount of F-spin symmetry in these nuclei and provide a new local measure for the pn-QQ interaction. Second, the evolution of the 2+ 1,ms state has been studied along the sequence of stable even-even 124−134Xe isotopes that are considered to form a shape transition path from vibrational nuclei with vibrational U(5) symmetry near N=82 to γ-softly deformed shapes with almost O(6) symmetry. Third, our data on more than 50 absolute E2 transition rates between off-yrast low-spin states of 124,126Xe enable us to quantitatively test O(6) symmetry in these nuclei. As a result we find that O(6) symmetry is more strongly broken in the A=130 mass region than previously thought. The data will be discussed.
Description of mixed symmetry states in 96Ru using IBM-2
Zhang, DaLi; Mu, ChengFu
2017-04-01
We have investigated the properties of low-lying states in 96Ru within the framework of the neutron-proton interacting boson model (IBM-2), with special attention paid to the characteristics of the mixed symmetry states. By considering the relative energy of d proton boson to be different from that of neutron boson, the level energies and M1, E2 transition strengths have been calculated. The IBM-2 calculation is consistent with the experimental data of 96Ru both quantitatively and qualitatively. Particularly, the strong M1 transition between the 42 + and 41 + states has been reproduced nicely. The calculated results show that the M1 transition strength of B( M1; 42 + → 41 +) in 96Ru can be described successfully by the IBM-2.
Description of mixed symmetry states in 96Ru using IBM-2
Zhang, DaLi; Mu, ChengFu
2017-04-01
We have investigated the properties of low-lying states in 96Ru within the framework of the neutron-proton interacting boson model (IBM-2), with special attention paid to the characteristics of the mixed symmetry states. By considering the relative energy of d proton boson to be different from that of neutron boson, the level energies and M1, E2 transition strengths have been calculated. The IBM-2 calculation is consistent with the experimental data of 96Ru both quantitatively and qualitatively. Particularly, the strong M1 transition between the 42 + and 41 + states has been reproduced nicely. The calculated results show that the M1 transition strength of B( M1; 42 + → 41 +) in 96Ru can be described successfully by the IBM-2.
1990-01-01
The gap between the nonlocalized lattice-phonon description and the localized Einstein oscillator treatment is filled by transforming the phonon Hamiltonian back to the particle variables. The particle-coordinate, normalized, wave function for the phonon vacuum state is exhibited.
Power spectrum of nuclear spectra with missing levels and mixed symmetries
Molina, R.A. [Max-Planck-Institut fuer Physik Komplexer Systeme, Noethnitzer Str. 38, D-01187 Dresden (Germany) and Instituto de Estructura de la Materia, CSIC, Serrano 123, E-28006 Madrid (Spain)]. E-mail: molina@iem.cfmac.csic.es; Retamosa, J. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Munoz, L. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Relano, A. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Instituto de Estructura de la Materia, CSIC, Serrano 123, E-28006 Madrid (Spain); Faleiro, E. [Departamento de Fisica Aplicada, Universidad Politecnica de Madrid, E-28012 (Spain)
2007-01-04
Sequences of energy levels in nuclei are often plagued with missing levels whose number and position are unknown. It is also quite usual that all the quantum numbers of certain levels cannot be experimentally determined, and thus levels of different symmetries are mixed in the same sequence. The analysis of these imperfect spectra (from the point of view of spectral statistics) is unavoidable if one wants to extract some statistical information. The power spectrum of the {delta}{sub q} statistic has emerged in recent years as an important tool for the study of quantum chaos and spectral statistics. We derive analytical expressions for the observed power spectrum in terms of the fraction of observed levels and the number of mixed sequences. These expressions are tested with large shell model spectra simulating realistic experimental situations. A good estimation of the number of mixed symmetries and the fraction of missing levels is obtained by means of a least-squares fit in a wide set of different situations.
Coulomb Excitation of a Neutron-Rich $^{88}$Kr Beam Search for Mixed Symmetry States
Andreoiu, C; Napiorkowski, P J; Iwanicki, J S
2002-01-01
We propose to use the ISOLDE/REX/MINIBALL/CD set-up to perform a Coulomb Excitation experiment with a $^{88}$Kr radioactive beam. The motivation includes a search for $Mixed$ $Symmetry$ states predicted by the IBM-2 model, gathering more spectroscopy data about the $^{88}$Kr nucleus and extending shape coexistence studies (performed previously by the proposers for neutron-deficient Kr isotopes) to the neutron-rich side. The proposed experiment will provide data complementary to the Coulomb Excitation of a relativistic $^{88}$Kr beam proposed by D. Tonev et al. for a RISING experiment. A total of 12 days of beam time is necessary for the experiment, equally divided into two runs. One run with a 2.2 MeV/A beam energy on a $^{48}$Ti target and a second run with the maximum available REX energy of 3.1 MeV/A on a $^{208}$Pb target are requested. Using either a UC$_{x}$ or ThC$_{x}$ fissioning primary target coupled with a plasma source by a cooled transfer line seems to be the best choice for the proposed experime...
Description of the evolution of mixed-symmetry states in the N = 78 isotonic chain with IBM2
Zhang, Da-Li; Yuan, Shu-Qing; Ding, Bin-Gang
2015-07-01
The characteristics of the lowest mixed-symmetry states 2+ms and 1+ms for 132Xe, 134Ba and 136Ce in the even-even N = 78 isotones are investigated within the framework of the IBM2 model. The lowest mixed-symmetry state 2+ms levels for both a single isolated state in 132Xe and 136Ce and a fragmented state in 134Ba are reproduced by the predictions. The agreement between the IBM2 calculation and the experimental values is good for the B(E2) and B(M1) transition probabilities both quantitatively and qualitatively. The predicted summed B(M1) strength follows the experimental data, remaining nearly constant as a function of proton number along the chain of the N = 78 isotones. Supported by National Natural Science Foundation of China (11475062) and Natural Science Foundation of Zhejiang Province, China (KY6100135)
Wette, Frederik
1991-01-01
In recent years substantial progress has been made in the detection of surface phonons owing to considerable improvements in inelastic rare gas scattering tech niques and electron energy loss spectroscopy. With these methods it has become possible to measure surface vibrations in a wide energy range for all wave vectors in the two-dimensional Brillouin zone and thus to deduce the complete surface phonon dispersion curves. Inelastic atomic beam scattering and electron energy loss spectroscopy have started to play a role in the study of surface phonons similar to the one played by inelastic neutron scattering in the investigation of bulk phonons in the last thirty years. Detailed comparison between experimen tal results and theoretical studies of inelastic surface scattering and of surface phonons has now become feasible. It is therefore possible to test and to improve the details of interaction models which have been worked out theoretically in the last few decades. At this point we felt that a concise, co...
Mannarelli, Massimo
2013-01-01
We analyze the effect of restricted geometries on the contribution of Nambu-Goldstone bosons (phonons) to the shear viscosity, $\\eta$, of a superfluid. For illustrative purpose we examine a simplified system consisting of a circular boundary of radius $R$, confining a two-dimensional rarefied gas of phonons. Considering the Maxwell-type conditions, we show that phonons that are not in equilibrium with the boundary and that are not specularly reflected exert a shear stress on the boundary. In this case it is possible to define an effective (ballistic) shear viscosity coefficient $\\eta \\propto \\rho_{\\rm ph} \\chi R$, where $\\rho_{\\rm ph}$ is the density of phonons and $\\chi$ is a parameter which characterizes the type of scattering at the boundary. For an optically trapped superfluid our results corroborate the findings of Refs. \\cite{Mannarelli:2012su, Mannarelli:2012eg}, which imply that at very low temperature the shear viscosity correlates with the size of the optical trap and decreases with decreasing tempe...
1990-01-01
An atomic lattice in its ground state is excited by the rapid displacement and release of an atomic constituent. The time dependence of the energy transfer to other constituents is studied by using a phonon dispersion relation that is linear in frequency and propagation vector components.
Gravitational cubic interactions for a simple mixed-symmetry gauge field in AdS and flat backgrounds
Boulanger, Nicolas [Service de Mecanique et Gravitation, Universite de Mons-UMONS, 20 Place du Parc, 7000 Mons (Belgium); Skvortsov, E D [P. N. Lebedev Physical Institute, Leninsky Prospect 53, 119991 Moscow (Russian Federation); Zinoviev, Yu M, E-mail: nicolas.boulanger@umons.ac.be, E-mail: skvortsov@lpi.ru, E-mail: Yurii.Zinoviev@ihep.ru [Institute for High Energy Physics Protvino, Moscow Region 142280 (Russian Federation)
2011-10-14
Cubic interactions between the simplest mixed-symmetry gauge field and gravity are constructed in anti-de Sitter (AdS) and flat backgrounds. Non-Abelian cubic interactions are obtained in AdS following various perturbative methods including the Fradkin-Vasiliev construction, with and without Stueckelberg fields. The action that features the maximal number of Stueckelberg fields can be considered in the flat limit without loss of physical degrees of freedom. The resulting interactions in flat space are compared with a classification of vertices obtained via the antifield cohomological perturbative method. It is shown that the gauge algebra becomes Abelian in the flat limit, in contrast to what happens for totally symmetric gauge fields in AdS. (paper)
Microscopic Description of Low-Lying Isovector Quadrupole States in /sup 56/Fe
Nikolaeva, R.; Stoyanov, C.; Vdovin, A.I.
1989-01-01
Microscopic calculations of energies, structure and transition probabilities of low-lying 2/sup +/ states in /sup 56/Fe have been performed in the framework of the quasi-particle phonon nuclear model. The interaction of the phonons appears to play an important role in determination of the isotopic character of low-lying quadrupole states.
Cooper, W.E.; Fisk, H.E.; Gross, D.A.; Lundy, R.A.; Schmidt, E.E.; Turkot, F.
1983-03-01
Details on the design, construction, and performance tests of Energy Saver/Doubler quadrupoles are presented along with recent data from the test of a special high gradient low beta prototype quadrupole.
Phonon manipulation with phononic crystals.
Kim Bongsang; Hopkins, Patrick Edward; Leseman, Zayd C.; Goettler, Drew F.; Su, Mehmet F. (University of New Mexico, Albuquerque, NM); El-Kady, Ihab Fathy; Reinke, Charles M.; Olsson, Roy H., III
2012-01-01
In this work, we demonstrated engineered modification of propagation of thermal phonons, i.e. at THz frequencies, using phononic crystals. This work combined theoretical work at Sandia National Laboratories, the University of New Mexico, the University of Colorado Boulder, and Carnegie Mellon University; the MESA fabrication facilities at Sandia; and the microfabrication facilities at UNM to produce world-leading control of phonon propagation in silicon at frequencies up to 3 THz. These efforts culminated in a dramatic reduction in the thermal conductivity of silicon using phononic crystals by a factor of almost 30 as compared with the bulk value, and about 6 as compared with an unpatterned slab of the same thickness. This work represents a revolutionary advance in the engineering of thermoelectric materials for optimal, high-ZT performance. We have demonstrated the significant reduction of the thermal conductivity of silicon using phononic crystal structuring using MEMS-compatible fabrication techniques and in a planar platform that is amenable to integration with typical microelectronic systems. The measured reduction in thermal conductivity as compared to bulk silicon was about a factor of 20 in the cross-plane direction [26], and a factor of 6 in the in-plane direction. Since the electrical conductivity was only reduced by a corresponding factor of about 3 due to the removal of conductive material (i.e., porosity), and the Seebeck coefficient should remain constant as an intrinsic material property, this corresponds to an effective enhancement in ZT by a factor of 2. Given the number of papers in literature devoted to only a small, incremental change in ZT, the ability to boost the ZT of a material by a factor of 2 simply by reducing thermal conductivity is groundbreaking. The results in this work were obtained using silicon, a material that has benefitted from enormous interest in the microelectronics industry and that has a fairly large thermoelectric power
Meyer, R. A.; Scholten, O.; Brant, S.; Paar, V.
1990-01-01
We have investigated the structure of 144Nd84 within the framework of the cluster vibration model. Further, we have mapped, approximately, the cluster vibration model states into the proton-neutron interacting-boson model, with particular emphasis on the mixed-symmetry states, hindered transitions,
El-Kady, Ihab F.; Olsson, Roy H.
2012-01-10
Phononic crystals that have the ability to modify and control the thermal black body phonon distribution and the phonon component of heat transport in a solid. In particular, the thermal conductivity and heat capacity can be modified by altering the phonon density of states in a phononic crystal. The present invention is directed to phononic crystal devices and materials such as radio frequency (RF) tags powered from ambient heat, dielectrics with extremely low thermal conductivity, thermoelectric materials with a higher ratio of electrical-to-thermal conductivity, materials with phononically engineered heat capacity, phononic crystal waveguides that enable accelerated cooling, and a variety of low temperature application devices.
Model for topological phononics and phonon diode
Liu, Yizhou; Xu, Yong; Zhang, Shou-Cheng; Duan, Wenhui
2017-08-01
The quantum anomalous Hall effect, an exotic topological state first theoretically predicted by Haldane and recently experimentally observed, has attracted enormous interest for low-power-consumption electronics. In this work, we derived a Schrödinger-like equation of phonons, where topology-related quantities, time-reversal symmetry, and its breaking can be naturally introduced similar to the process for electrons. Furthermore, we proposed a phononic analog of the Haldane model, which makes the novel quantum (anomalous) Hall-like phonon states characterized by one-way gapless edge modes immune to scattering. The topologically nontrivial phonon states are useful not only for conducting phonons without dissipation but also for designing highly efficient phononic devices, like an ideal phonon diode, which could find important applications in future phononics.
Phononic High Harmonic Generation
Ganesan, Adarsh; Seshia, Ashwin A
2016-01-01
This paper reports the first experimental evidence for phononic low-order to high-order harmonic conversion leading to high harmonic generation. Similar to parametric resonance, phononic high harmonic generation is also mediated by a threshold dependent instability of a driven phonon mode. Once the threshold for instability is met, a cascade of harmonic generation processes is triggered. Firstly, the up-conversion of first harmonic phonons into second harmonic phonons is established. Subsequently, the down-conversion of second harmonic phonons into first harmonic phonons and conversion of first and second harmonic phonons into third harmonic phonons occur. On the similar lines, an eventual conversion of third harmonic phonons to high orders is also observed to commence. This surprising physical pathway for phononic low-order to high-order harmonic conversion may find general relevance to other physical systems.
Manipulation of Phonons with Phononic Crystals
Leseman, Zayd Chad [Univ. of New Mexico, Albuquerque, NM (United States)
2015-07-09
There were three research goals associated with this project. First, was to experimentally demonstrate phonon spectrum control at THz frequencies using Phononic Crystals (PnCs), i.e. demonstrate coherent phonon scattering with PnCs. Second, was to experimentally demonstrate analog PnC circuitry components at GHz frequencies. The final research goal was to gain a fundamental understanding of phonon interaction using computational methods. As a result of this work, 7 journal papers have been published, 1 patent awarded, 14 conference presentations given, 4 conference publications, and 2 poster presentations given.
Petzenhauser, I.; Spiller, P.; Tenholt, C.
2016-01-01
In order to raise the focusing gradient in case of bunched beam lines, a pulsed quadrupole was designed. The transfer channels between synchrotrons as well as the final focusing for the target line are possible applications. The quadrupole is running in a pulsed mode, which means an immense saving of energy by avoiding standby operation. Still the high gradients demand high currents. Hence a circuit had to be developed which is able to recover a significant amount of the pulsing energy for following shots. The basic design of the electrical circuit of the quadrupole is introduced. Furthermore more energy efficient circuits are presented and the limits of adaptability are considered.
Superconducting magnetic quadrupole
Kim, J.W.; Shepard, K.W.; Nolen, J.A.
1995-08-01
A design was developed for a 350 T/m, 2.6-cm clear aperture superconducting quadrupole focussing element for use in a very low q/m superconducting linac as discussed below. The quadrupole incorporates holmium pole tips, and a rectangular-section winding using standard commercially-available Nb-Ti wire. The magnet was modeled numerically using both 2D and 3D codes, as a basis for numerical ray tracing using the quadrupole as a linac element. Components for a prototype singlet are being procured during FY 1995.
1991-01-01
The concepts of source and quantum action principle are used to produce the phonon Green's function appropriate for an initial phonon vacuum state. An application to the Mossbauer effect is presented.
1974-01-01
A stack of SPS Quadrupole Magnets ready for installation in the tunnel. The SPS uses a total of 216 laminated normal conducting lattice quadrupoles with a length of 3.13 m for the core, 3.3 m overall. The F and D quads. have identical characteristics: inscribed circle radius 44 mm, core height and width 800 mm, maximum gradient 20 Tesla/m.
Burda, Oleksiy
2007-07-15
The present work contains two parts. The first one is devoted to the investigation of mixed-symmetry structure in {sup 94}Mo and the second one to the astrophysical relevant line shape of the first excited 1/2{sup +} state in {sup 9}Be. In the first part of the thesis the nature of one- and two-phonon symmetric and mixed-symmetric 2{sup +} states in {sup 94}Mo is investigated with high-resolution inelastic electron and proton scattering experiments in a combined analysis. The (e,e') experiments were carried out at the 169 magnetic spectrometer at the S-DALINAC. Data were taken at a beam energy E e=70 MeV and scattering angles {theta}{sub e}=93 -165 . In dispersion-matching mode an energy resolution {delta}{sub E}=30-45 keV (full width at half maximum) was achieved. The (p,p') measurements were performed at iThemba LABS, South Africa, using a K600 magnetic spectrometer at a proton energy E p=200 MeV and scattering angles {theta}{sub p}=4.5 -26 . Typical energy resolutions were {delta}{sub E}{approx_equal}35 keV. The combined analysis reveals a dominant one-phonon structure of the transitions to the first and third 2{sup +} states, as well as an isovector character of the transition to the one-phonon mixed-symmetric state within the valence shell. Quantitatively consistent estimates of the one-phonon admixtures are obtained from both experimental probes when two-step contributions to the proton scattering cross sections are taken into account. In the second part of the thesis the line shape of the first excited 1/2{sup +} state in {sup 9}Be is studied. Spectra of the {sup 9}Be(e,e') reaction were measured at the S-DALINAC at an electron energy E e=73 MeV and scattering angles of 93 and 141 with high energy resolution up to excitation energies E{sub x}=8 MeV. The form factor of the first excited state has been extracted from the data. The astrophysical relevant {sup 9}Be({gamma},n) cross sections have been extracted from the (e,e') data. The
Puzzle of B(E2) strengths of the symmetric and mixed-symmetry 2{sup +} states in {sup 94}Zr
Scheikh Obeid, Abdulrahman; Krugmann, Andreas; Neumann-Cosel, Peter von; Pietralla, Norbert; Poltoratska, Iryna; Ponomarev, Vladimir [Technische Univ. Darmstadt (Germany). Inst. fuer Kernphysik
2013-07-01
Recently, E. Elhami et al. (2008) reported on a study of the low-spin structure of {sup 94}Zr with the (n,n',γ) reaction. The author claimed observation of an anomalous situation where the E2 excitation strength of the mixed-symmetry 2{sup +}{sub 2} exceeds the strength of the symmetric 2{sup +}{sub 1} state. Those excitations of {sup 94}Zr have been investigated with electron scattering at the S-DALINAC and a model-independent analysis of our (e,e') data has been performed. The extracted ratio of the E2 strengths, B(E2,0{sup +}{sub 1} → 2{sup +}{sub ms})/B(E2,0{sup +}{sub 1} → 2{sup +}{sub 1}) is less than the unity, which contradicts the (n,n',γ) results. The data analysis and the results are presented. The same analysis has been applied to a set of electron scattering data on {sup 94}Mo. The ratio of the of B(E2) strengths of the symmetric and mixed-symmetry 2{sup +} states in {sup 94}Mo and their transition radius difference have been extracted for the first time.
1983-01-01
There were 48 of these Quadrupoles in the ISR. They were distributed around the rings according to the so-called Terwilliger scheme. Their aperture was 184 mm, their core length 300 mm, their gradient 5 T/m. Due to their small length as compared to the aperture, the end fringe field errors had to be compensated by suitably shaping the poles.
ISR Superconducting Quadrupoles
1977-01-01
Michel Bouvier is preparing for curing the 6-pole superconducting windings inbedded in the cylindrical wall separating liquid helium from vacuum in the quadrupole aperture. The heat for curing the epoxy glue was provided by a ramp of infrared lamps which can be seen above the slowly rotating cylinder. See also 7703512X, 7702690X.
Gorishnyy, T; Ullal, C K; Maldovan, M; Fytas, G; Thomas, E L
2005-03-25
In this Letter we propose the use of hypersonic phononic crystals to control the emission and propagation of high frequency phonons. We report the fabrication of high quality, single crystalline hypersonic crystals using interference lithography and show that direct measurement of their phononic band structure is possible with Brillouin light scattering. Numerical calculations are employed to explain the nature of the observed propagation modes. This work lays the foundation for experimental studies of hypersonic crystals and, more generally, phonon-dependent processes in nanostructures.
Consistent quadrupole-octupole collective model
Dobrowolski, A.; Mazurek, K.; Góźdź, A.
2016-11-01
Within this work we present a consistent approach to quadrupole-octupole collective vibrations coupled with the rotational motion. A realistic collective Hamiltonian with variable mass-parameter tensor and potential obtained through the macroscopic-microscopic Strutinsky-like method with particle-number-projected BCS (Bardeen-Cooper-Schrieffer) approach in full vibrational and rotational, nine-dimensional collective space is diagonalized in the basis of projected harmonic oscillator eigensolutions. This orthogonal basis of zero-, one-, two-, and three-phonon oscillator-like functions in vibrational part, coupled with the corresponding Wigner function is, in addition, symmetrized with respect to the so-called symmetrization group, appropriate to the collective space of the model. In the present model it is D4 group acting in the body-fixed frame. This symmetrization procedure is applied in order to provide the uniqueness of the Hamiltonian eigensolutions with respect to the laboratory coordinate system. The symmetrization is obtained using the projection onto the irreducible representation technique. The model generates the quadrupole ground-state spectrum as well as the lowest negative-parity spectrum in 156Gd nucleus. The interband and intraband B (E 1 ) and B (E 2 ) reduced transition probabilities are also calculated within those bands and compared with the recent experimental results for this nucleus. Such a collective approach is helpful in searching for the fingerprints of the possible high-rank symmetries (e.g., octahedral and tetrahedral) in nuclear collective bands.
Phonon engineering for nanostructures.
Aubry, Sylvie (Stanford University); Friedmann, Thomas Aquinas; Sullivan, John Patrick; Peebles, Diane Elaine; Hurley, David H. (Idaho National Laboratory); Shinde, Subhash L.; Piekos, Edward Stanley; Emerson, John Allen
2010-01-01
Understanding the physics of phonon transport at small length scales is increasingly important for basic research in nanoelectronics, optoelectronics, nanomechanics, and thermoelectrics. We conducted several studies to develop an understanding of phonon behavior in very small structures. This report describes the modeling, experimental, and fabrication activities used to explore phonon transport across and along material interfaces and through nanopatterned structures. Toward the understanding of phonon transport across interfaces, we computed the Kapitza conductance for {Sigma}29(001) and {Sigma}3(111) interfaces in silicon, fabricated the interfaces in single-crystal silicon substrates, and used picosecond laser pulses to image the thermal waves crossing the interfaces. Toward the understanding of phonon transport along interfaces, we designed and fabricated a unique differential test structure that can measure the proportion of specular to diffuse thermal phonon scattering from silicon surfaces. Phonon-scale simulation of the test ligaments, as well as continuum scale modeling of the complete experiment, confirmed its sensitivity to surface scattering. To further our understanding of phonon transport through nanostructures, we fabricated microscale-patterned structures in diamond thin films.
Hyperfine phononic frequency comb
Ganesan, Adarsh; Seshia, Ashwin A
2016-01-01
Optical frequency combs [1-8] have resulted in significant advances in optical frequency metrology and found wide application to precise physical measurements [1-4, 9] and molecular fingerprinting [8]. A direct analogue of frequency combs in the phononic or acoustic domain has not been reported to date. In this letter, we report the first clear experimental evidence for a phononic frequency comb. In contrast to the Kerr nonlinearity [10] in optical frequency comb formation, the phononic frequency comb is generated through the intrinsic coupling of a driven phonon mode with an auto-parametrically excited sub-harmonic mode [16]. Through systematic experiments at different drive frequencies and amplitudes, we portray the well-connected process of phononic frequency comb formation and define attributes to control the features [17-18] associated with comb formation in such a system. Further, the interplay between these nonlinear resonances and the well-known Duffing phenomenon [12-14] is also observed. The present...
Quadrupole collectivity with isospin
Ginocchio, J.N.; Leviatan, A. (Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States) Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel))
1994-10-03
We study intrinsic aspects of quadrupole collectivity with conserved isospin in the framework of the interacting boson model (IBM-3) of nuclei. A geometric visualization is achieved by means of a novel type of intrinsic states which are deformed in angular momentum yet have well defined isospin. The energy surface of the general IBM-3 Hamiltonian is derived and normal modes are identified for prolate deformations.
1980-01-01
Focusing magnet used for the AA (antiproton accumulator).Making an antiproton beam took a lot of time and effort. Firstly, protons were accelerated to an energy of 26 GeV in the PS and ejected onto a metal target. From the spray of emerging particles, a magnetic horn picked out 3.6 GeV antiprotons for injection into the AA through a wide-aperture focusing quadrupole magnet. For a million protons hitting the target, just one antiproton was captured, 'cooled' and accumulated. It took 3 days to make a beam of 3 x 10^11 - three hundred thousand million - antiprotons. About focusing magnets (quadrupoles): Quadrupole magnets are needed to focus the particle beams and squeeze them so that more particles collide when the beams cross. Particle beams are stored for about 10 hours in the LHC. During this time, the particles make four hundred million revolutions around the machine, travelling a distance equivalent to the diameter of the solar system.
Phonon-induced polariton superlattices
de Lima, Jr., M. M.; Poel, Mike van der; Santos, P. V.;
2006-01-01
We show that the coherent interaction between microcavity polaritons and externally stimulated acoustic phonons forms a tunable polariton superlattice with a folded energy dispersion determined by the phonon population and wavelength. Under high phonon concentration, the strong confinement of the...... of the optical and excitonic polariton components in the phonon potential creates weakly coupled polariton wires with a virtually flat energy dispersion....
Pseudogap and anharmonic phonon behavior in Ba8Ga16Ge30: An NMR study
Sirusi, Ali A.; Ross, Joseph H.
2016-08-01
We have performed 69Ga, 71Ga, and 137Ba NMR on Ba8Ga16Ge30, a clathrate semiconductor which has been of considerable interest due to its large figure of merit for thermoelectric applications. In measurements from 4 K to 450 K, we used measurements on the two Ga nuclei to separate the magnetic and electric quadrupole hyperfine contributions and thereby gain information about the metallic and phonon behavior. The results show the presence of a pseudogap in the Ga electronic states within the conduction band, superposed upon a large Ba contribution to the conduction band. Meanwhile the phonon contributions to the Ga relaxation rates are large and increase more rapidly with temperature than typical semiconductors. These results provide evidence for enhanced anharmonicity of the propagative phonon modes over a wide range, providing experimental evidence for enhanced phonon-phonon scattering as a mechanism for the reduced thermal conductivity.
The first LHC insertion quadrupole
2004-01-01
An important milestone was reached in December 2003 at the CERN Magnet Assembly Facility. The team from the Accelerator Technology - Magnet and Electrical Systems group, AT-MEL, completed the first special superconducting quadrupole for the LHC insertions which house the experiments and major collider systems. The magnet is 8 metres long and contains two matching quadrupole magnets and an orbit corrector, a dipole magnet, used to correct errors in quadrupole alignment. All were tested in liquid helium and reached the ultimate performance criteria required for the LHC. After insertion in the cryostat, the superconducting magnet will be installed as the Q9 quadrupole in sector 7-8, the first sector of the LHC to be put in place in 2004. Members of the quadrupole team, from the AT-MEL group, gathered around the Q9 quadrupole at its inauguration on 12 December 2003 in building 181.
MQXFS1 Quadrupole Design Report
Ambrosio, Giorgio [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); et al.
2016-04-14
This report presents the reference design of MQXFS1, the first 1.5 m prototype of the low-beta quadrupoles (MQXF) for the LHC High Luminosity Upgrade. The MQXF quadrupoles have 150 mm aperture, coil peak field of about 12 T, and use $Nb_{3}Sn$ conductor. The design is based on the LARP HQ quadrupoles, which had 120 mm aperture. MQXFS1 has 1st generation cable cross-section and magnetic design.
O. Rafil; M. Tamine; B. Bourahla; R. Tigrine; S. Amoudache; A. Khater
2006-01-01
We have theoretically resolved phonon excitations in quasi-two-dimensional organic crystals of polyacenic semiconductor material which may be obtained by the pyrolytic treatment of phenol-formaldehyde resin. A model for studying the dynamical properties using three polyacene chains is proposed with the aim to present the vibrational properties of this structure. It employs the formalism of solid states in two dimensions which admit phonons. A simulation process of the two-dimensional lattice structure shows that elastic waves may explain the existence of vibrational modes in the frequency range 100-400 cm-1. The presence of acoustic and optical like phonons is discussed in terms of the elastic force constants. A hyperfine resonance structure is obtained. It allows the analysis of the dynamical evolution in thin films of polyacene. It is found that the behavior of the phonon density of states exhibits resonance between modes in the structure.
Birefringent phononic structures
I. E. Psarobas
2014-12-01
Full Text Available Within the framework of elastic anisotropy, caused in a phononic crystal due to low crystallographic symmetry, we adopt a model structure, already introduced in the case of photonic metamaterials, and by analogy, we study the effect of birefringence and acoustical activity in a phononic crystal. In particular, we investigate its low-frequency behavior and comment on the factors which determine chirality by reference to this model.
Quadrupole splitting and Eu partial lattice dynamics in europium orthophosphate EuPO 4
Klobes, B.; Arinicheva, Y.; Neumeier, S.; Simon, R. E.; Jafari, A.; Bosbach, D.; Hermann, R. P.
2016-12-01
Hyperfine interactions in europium orthophosphate EuPO4 were investigated using 151Eu Mössbauer spectroscopy from 6 to 300 K. The value of the quadrupole splitting and the asymmetry parameter were refined and further substantiated by nuclear forward scattering data obtained at room temperature. The temperature dependence of the relative absorption was modeled with an Eu specific Debye temperature of 221(1) K. Eu partial lattice dynamics were probed by means of nuclear inelastic scattering and the mean force constant, the Lamb-Mössbauer factor, the internal energy, the vibrational entropy, the average phonon group velocity were calculated using the extracted density of phonon states. In general, Eu specific vibrations are characterized by rather small phonon energies and contribute strongly to the total entropy of the system. Although there is no classical Debye like behavior at low vibrational energies, the average phonon group velocity can be reasonably approximated using a linear fit.
CLIC Quadrupole Module final report
Artoos, K; Mainaud-Durand, H
2013-01-01
Future Linear colliders will need particle beam sizes in the nanometre range. The beam also needs to be stable all along the beam line. The CLIC Main Beam Quadrupole (MBQ) module has been defined and studied. It is meant as a test stand for stabilisation and pre-alignment with a MB Quadrupole. The main topic that has been tackled concerns the Quadrupole magnet stabilisation to 1nm at 1Hz. This is needed to obtain the desired CLIC luminosity of 2.1034 cm-2m-1. The deliverable was demonstrated by procuring a MBQ and by stabilising a powered and cooled CLIC MBQ quadrupole. In addition, the stabilisation system has to be compatible with the pre-alignment procedures. Pre-alignment movement resolution has been demonstrated to 1m. The last step is the combined test of stability with a quadrupole on a CLIC Module with the pre-alignment.
Phonon waveguides for electromechanical circuits
Hatanaka, D.; Mahboob, I.; Onomitsu, K.; Yamaguchi, H.
2014-07-01
Nanoelectromechanical systems (NEMS), utilizing localized mechanical vibrations, have found application in sensors, signal processors and in the study of macroscopic quantum mechanics. The integration of multiple mechanical elements via electrical or optical means remains a challenge in the realization of NEMS circuits. Here, we develop a phonon waveguide using a one-dimensional array of suspended membranes that offers purely mechanical means to integrate isolated NEMS resonators. We demonstrate that the phonon waveguide can support and guide mechanical vibrations and that the periodic membrane arrangement also creates a phonon bandgap that enables control of the phonon propagation velocity. Furthermore, embedding a phonon cavity into the phonon waveguide allows mobile mechanical vibrations to be dynamically switched or transferred from the waveguide to the cavity, thereby illustrating the viability of waveguide-resonator coupling. These highly functional traits of the phonon waveguide architecture exhibit all the components necessary to permit the realization of all-phononic NEMS circuits.
Perrin, Bernard
2007-06-01
The conference PHONONS 2007 was held 15-20 July 2007 in the Conservatoire National des Arts et Métiers (CNAM) Paris, France. CNAM is a college of higher technology for training students in the application of science to industry, founded by Henri Grégoire in 1794. This was the 12th International Conference on Phonon Scattering in Condensed Matter. This international conference series, held every 3 years, started in France at Sainte-Maxime in 1972. It was then followed by meetings at Nottingham (1975), Providence (1979), Stuttgart (1983), Urbana-Champaign (1986), Heidelberg (1989), Ithaca (1992), Sapporo (1995), Lancaster (1998), Dartmouth (2001) and St Petersburg (2004). PHONONS 2007 was attended by 346 delegates from 37 different countries as follows: France 120, Japan 45, Germany 25, USA 25, Russia 21, Italy 13, Poland 9, UK 9, Canada 7, The Netherlands 7, Finland 6, Spain 6, Taiwan 6, Greece 4, India 4, Israel 4, Ukraine 4, Serbia 3, South Africa 3, Argentina 2, Belgium 2, China 2, Iran 2, Korea 2, Romania 2, Switzerland 2, and one each from Belarus, Bosnia-Herzegovina, Brazil, Bulgaria, Egypt, Estonia, Mexico, Moldova, Morocco, Saudi Arabia, Turkey. There were 5 plenary lectures, 14 invited talks and 84 oral contributions; 225 posters were presented during three poster sessions. The first plenary lecture was given by H J Maris who presented fascinating movies featuring the motion of a single electron in liquid helium. Robert Blick gave us a review on the new possibilities afforded by nanotechnology to design nano-electomechanical systems (NEMS) and the way to use them to study elementary and fundamental processes. The growing interest for phonon transport studies in nanostructured materials was demonstrated by Arun Majumdar. Andrey Akimov described how ultrafast acoustic solitons can monitor the optical properties of quantum wells. Finally, Maurice Chapellier told us how phonons can help tracking dark matter. These 328 presentations gave rise to 185 articles
PHONONS IN INTRINSIC JOSEPHSON SYSTEMS
C. PREIS; K. SCHMALZL; ET AL
2000-10-01
Subgap structures in the I-V curves of layered superconductors are explained by the excitation of phonons by Josephson oscillations. In the presence of a magnetic field applied parallel to the layers additional structures due to fluxon motion appear. Their coupling with phonons is investigated theoretically and a shift of the phonon resonances in strong magnetic fields is predicted.
Phononic crystals fundamentals and applications
Adibi, Ali
2016-01-01
This book provides an in-depth analysis as well as an overview of phononic crystals. This book discusses numerous techniques for the analysis of phononic crystals and covers, among other material, sonic and ultrasonic structures, hypersonic planar structures and their characterization, and novel applications of phononic crystals. This is an ideal book for those working with micro and nanotechnology, MEMS (microelectromechanical systems), and acoustic devices. This book also: Presents an introduction to the fundamentals and properties of phononic crystals Covers simulation techniques for the analysis of phononic crystals Discusses sonic and ultrasonic, hypersonic and planar, and three-dimensional phononic crystal structures Illustrates how phononic crystal structures are being deployed in communication systems and sensing systems.
Quadrupole Induced Resonant Particle Transport
Gilson, Erik; Fajans, Joel
1999-11-01
We have performed experiments that explore the effects of a magnetic quadrupole field on a pure electron plasma confined in a Malmberg-Penning trap. A model that we have developed describes the shape of the plasma and shows that a certain class of resonant particles follows trajectories that take them out of the plasma. Even though the quadrupole field destroys the cylindrical symmetry of the system, our theory predicts that if the electrons are off resonance, then the lifetime of the plasma will not be greatly affected by the quadrupole field. Our preliminary experimental results show that the shape of the plasma and the plasma lifetime agree with our model. We are investigating the scaling of this behavior with various experimental parameters such as the plasma length, density, and strength of the quadrupole field. In addition to being an example of resonant particle transport, this effect may find practical applications in experiments that plan to use magnetic quadrupole neutral atom traps to confine anti-hydrogen created in double-well positron/anti-proton Malmberg-Penning traps. (ATHENA Collaboration.)
Yu, Si-Yuan; Sun, Xiao-Chen; Ni, Xu; Wang, Qing; Yan, Xue-Jun; He, Cheng; Liu, Xiao-Ping; Feng, Liang; Lu, Ming-Hui; Chen, Yan-Feng
2016-12-01
Strategic manipulation of wave and particle transport in various media is the key driving force for modern information processing and communication. In a strongly scattering medium, waves and particles exhibit versatile transport characteristics such as localization, tunnelling with exponential decay, ballistic, and diffusion behaviours due to dynamical multiple scattering from strong scatters or impurities. Recent investigations of graphene have offered a unique approach, from a quantum point of view, to design the dispersion of electrons on demand, enabling relativistic massless Dirac quasiparticles, and thus inducing low-loss transport either ballistically or diffusively. Here, we report an experimental demonstration of an artificial phononic graphene tailored for surface phonons on a LiNbO3 integrated platform. The system exhibits Dirac quasiparticle-like transport, that is, pseudo-diffusion at the Dirac point, which gives rise to a thickness-independent temporal beating for transmitted pulses, an analogue of Zitterbewegung effects. The demonstrated fully integrated artificial phononic graphene platform here constitutes a step towards on-chip quantum simulators of graphene and unique monolithic electro-acoustic integrated circuits.
Nuclear Quadrupole Moments and Nuclear Shell Structure
Townes, C. H.; Foley, H. M.; Low, W.
1950-06-23
Describes a simple model, based on nuclear shell considerations, which leads to the proper behavior of known nuclear quadrupole moments, although predictions of the magnitudes of some quadrupole moments are seriously in error.
Accretion disks around a mass with quadrupole
Abishev, Medeu; Quevedo, Hernando; Toktarbay, Saken
2015-01-01
We consider the stability properties of test particles moving along circular orbits around a mass with quadrupole. We show that the quadrupole modifies drastically the properties of an accretion disk made of such test particles.
Accretion disks around a mass with quadrupole
Abishev, M.; Boshkayev, K.; Quevedo, H.; Toktarbay, S.
We consider the stability properties of circular orbits of test particles moving around a mass with quadrupole. We show that the quadrupole modifies drastically the properties of an accretion disk made of such test particles.
LCLS Undulator Quadrupole Fiducialization Plan
Wolf, Zachary; Levashov, Michael; Lundahl, Eric; Reese, Ed; LeCocq, Catherine; Ruland, Robert; /SLAC
2010-11-24
This note presents the fiducialization plan for the LCLS undulator quadrupoles. The note begins by summarizing the requirements for the fiducialization. A discussion of the measurement equipment is presented, followed by the methods used to perform the fiducialization and check the results. This is followed by the detailed fiducialization plan in which each step is enumerated. Finally, the measurement results and data storage formats are presented. The LCLS is made up of 33 assemblies consisting of an undulator, quadrupole, beam finder wire, and other components mounted on a girder. The components must be mounted in such a way that the beam passes down the axis of each component. In this note, we describe how the ideal beam axis is related to tooling balls on the quadrupole. This step, called fiducialization, is necessary because the ideal beam axis is determined magnetically, whereas tangible objects must be used to locate the quadrupole. The note begins with the list of fiducialization requirements. The laboratory in which the work will be performed and the relevant equipment is then briefly described. This is followed by a discussion of the methods used to perform the fiducialization and the methods used to check the results. A detailed fiducialization plan is presented in which all the steps of fiducialization are enumerated. A discussion of the resulting data files and directory structure concludes the note.
Tunable Topological Phononic Crystals
Chen, Ze-Guo
2016-05-27
Topological insulators first observed in electronic systems have inspired many analogues in photonic and phononic crystals in which remarkable one-way propagation edge states are supported by topologically nontrivial band gaps. Such band gaps can be achieved by breaking the time-reversal symmetry to lift the degeneracy associated with Dirac cones at the corners of the Brillouin zone. Here, we report on our construction of a phononic crystal exhibiting a Dirac-like cone in the Brillouin zone center. We demonstrate that simultaneously breaking the time-reversal symmetry and altering the geometric size of the unit cell result in a topological transition that we verify by the Chern number calculation and edge-mode analysis. We develop a complete model based on the tight binding to uncover the physical mechanisms of the topological transition. Both the model and numerical simulations show that the topology of the band gap is tunable by varying both the velocity field and the geometric size; such tunability may dramatically enrich the design and use of acoustic topological insulators.
The interacting quasiparticle-phonon picture and odd-even nuclei. Overview and perspectives
Mishev, S.; Voronov, V. V.
2016-11-01
The role of the nucleon correlations in the ground states of even-even nuclei on the properties of low-lying states in odd-even spherical and transitional nuclei is studied. We reason about this subject using the language of the quasiparticle-phonon model which we extend to take account of the existence of quasiparticle⊗phonon configurations in the wave functions of the ground states of the even-even cores. Of paramount importance to the structure of the low-lying states happens to be the quasiparticle-phonon interaction in the ground states which we evaluated using both the standard and the extended random phase approximations. Numerical calculations for nuclei in the barium and cadmium regions are performed using pairing and quadrupole-quadrupole interaction modes which have the dominant impact on the lowest-lying states' structure. It is found that states with same angular momentum and parity become closer in energy as compared to the predictions of models disregarding the backward amplitudes, which turns out to be in accord with the experimental data. In addition we found that the interaction between the last quasiparticle and the ground-state phonon admixtures produces configurations which contribute significantly to the magnetic dipolemoment of odd- A nuclei. It also reveals a potential for reproducing their experimental values which proves impossible if this interaction is neglected.
Wong, Joe
2004-03-01
The phonon spectra of plutonium and its alloys have been sought after in the past few decades following the discovery of this actinide element in 1941, but with no success. This was due to a combination of the high neutron absorption cross section of 239Pu, the common isotope, and non-availability of large single crystals of any Pu-bearing materials. We have recent designed a high resolution inelastic x-ray scattering experiment using a bright synchrotron x-ray beam at the European Sychrotron Radiation Facility (ESRF), Grenoble and mapped the full phonon dispersion curves of an fcc delta-phase polycrystalline Pu-Ga alloy (1). Several unusual features including, a large elastic anisotropy, a small shear elastic modulus C', a Kohn-like anomaly in the T1[011] branch, and a pronounced softening of the [111] transverse modes are found. These features can be related to the phase transitions of plutonium and to strong coupling between the lattice structure and the 5f valence instabilities. Our results also provide a critical test for theoretical treatments of highly correlated 5f electron systems as exemplified by recent dynamical mean field theory (DMFT) calculations for d-plutonium.(2) This work was performed in collaboration with Dr. M. Krisch (ESRF)) and Prof. T.-C. Chiang (UIU), and under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. 1. Joe Wong et al. Science, vol.301, 1078 (2003) 2. X. Dai et al. Science, vol.300, 953 (2003)
Gravitational Perturbation in Topological Phonon Space
李芳昱; 罗俊; 唐孟希
1994-01-01
The effect of gravitational wave (GW) on phonon in crystal lattice space with spiral dislocation is expressed as a gravitational perturbation in topological phonon space with background of the spiral dislocation.This is a new-type effect form of the GW field to the phonon.The corresponding phonon solutions are given.
Phonon-drag effects on thermoelectric power
Wu, M. W.; Horing, N. J. M.; Cui, H. L.
1995-01-01
We carry out a calculation of the phonon-drag contribution $S_g$ to the thermoelectric power of bulk semiconductors and quantum well structures for the first time using the balance equation transport theory extended to the weakly nonuniform systems. Introducing wavevector and phonon-mode dependent relaxation times due to phonon-phonon interactions, the formula obtained can be used not only at low temperatures where the phonon mean free path is determined by boundary scattering, but also at hi...
Phonons with orbital angular momentum
Ayub, M. K. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Ali, S. [National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2011-10-15
Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.
Search for the 3-phonon state of {sup 40}Ca; Recherche de l'etat a trois phonons dans le {sup 40}Ca
Fallot, M
2002-09-01
We study collective vibrational states of the nucleus: giant resonances and multiphonon states. It has been shown that multiphonon states, which are built with several superimposed giant resonances, can be excited in inelastic heavy ion scattering near the grazing angle. No three photon states have been observed until now. An experiment has been performed at GANIL, aiming at the observation of the 3-phonon state built with the giant quadrupole resonance (GQR) in {sup 40}Ca, with the reaction {sup 40}Ca + {sup 40}Ca at 50 A.Me.V. The ejectile was identified in the SPEG spectrometer. Light charged particles were detected in 240 CsI scintillators of the INDRA 4{pi} array. The analysis confirms the previous results about the GQR and the 2-phonon state in {sup 40}Ca. For the first time, we have measured an important direct decay branch of the GQR by alpha particles. Applying the so-called 'missing energy method' to events containing three protons measured in coincidence with the ejectile, we observe a direct decay branch revealing the presence of a 3-phonon state in the excitation energy region expected for the triple GQR. Dynamical processes are also studied in the inelastic channel, emphasizing a recently discovered mechanism named towing-mode. We observe for the first time the towing-mode of alpha particles. The energies of multiphonon states in {sup 40}Ca and {sup 208}Pb have been computed microscopically including some anharmonicities via boson mapping methods. The basis of the calculation has been extended to the 3-phonon states. Our results show large anharmonicities (several MeV), due to the coupling of 3-phonon states to 2-phonon states. The extension of the basis to 4-phonon states has been performed for the first time. The inclusion of the 4 phonon states in the calculation did not affect the previous observations concerning the 2-phonon states. Preliminary results on the anharmonicities of the 3-phonon states are presented. (author)
Spectroscopy of quadrupole and octupole states in rare-earth nuclei from a Gogny force
Nomura, K; Robledo, L M
2015-01-01
Collective quadrupole and octupole states are described in a series of Sm and Gd isotopes within the framework of the interacting boson model (IBM), whose Hamiltonian parameters are deduced from mean field calculations with the Gogny energy density functional. The link between both frameworks is the ($\\beta_2\\beta_3$) potential energy surface computed within the Hartree-Fock-Bogoliubov framework in the case of the Gogny force. The diagonalization of the IBM Hamiltonian provides excitation energies and transition strengths of an assorted set of states including both positive and negative parity states. The resultant spectroscopic properties are compared with the available experimental data and also with the results of the configuration mixing calculations with the Gogny force within the generator coordinate method (GCM). The structure of excited $0^{+}$ states and its connection with double octupole phonons is also addressed. The model is shown to describe the empirical trend of the low-energy quadrupole and o...
Photonic and phononic quasicrystals
Steurer, Walter; Sutter-Widmer, Daniel [Laboratory of Crystallography, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich (Switzerland)
2007-07-07
This review focuses on the peculiarities of quasiperiodic order for the properties of photonic and phononic (sonic) heterostructures. The most beneficial feature of quasiperiodicity is that it can combine perfectly ordered structures with purely point-diffractive spectra of arbitrarily high rotational symmetry. Both are prerequisites for the construction of isotropic band gap composites, in particular from materials with low index contrast, which are required for numerous applications. Another interesting property of quasiperiodic structures is their scaling symmetry, which may be exploited to create spectral gaps in the sub-wavelength regime. This review covers structure/property relationships of heterostructures based on one-dimensional (1D) substitutional sequences such as the Fibonacci, Thue-Morse, period-doubling, Rudin-Shapiro and Cantor sequence as well as on 1D modulated structures, further on 2D tilings with 8-, 10-, 12- and 14-fold symmetry as well as on the pinwheel tiling, the Sierpinski gasket and on curvilinear tilings and, finally, on the 3D icosahedral Penrose tiling. (topical review)
MQXFS1 Quadrupole Fabrication Report
Ambrosio, G.; et al.
2017-07-16
This report presents the fabrication and QC data of MQXFS1, the first short model of the low-beta quadrupoles (MQXF) for the LHC High Luminosity Upgrade. It describes the conductor, the coils, and the structure that make the MQXFS1 magnet. Qualification tests and non-conformities are also presented and discussed. The fabrication of MQXFS1 was started before the finalization of conductor and coil design for MQXF magnets. Two strand design were used (RRP 108/127 and RRP 132/169). Cable and coil cross-sections were “first generation”.
Localized surface phonon polariton resonances in polar gallium nitride
Feng, Kaijun, E-mail: kfeng@nd.edu; Islam, S. M.; Verma, Jai; Hoffman, Anthony J. [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Streyer, William; Wasserman, Daniel [Department of Electrical and Computer Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801 (United States); Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14850 (United States)
2015-08-24
We demonstrate the excitation of localized surface phonon polaritons in an array of sub-diffraction pucks fabricated in an epitaxial layer of gallium nitride (GaN) on a silicon carbide (SiC) substrate. The array is characterized via polarization- and angle-dependent reflection spectroscopy in the mid-infrared, and coupling to several localized modes is observed in the GaN Reststrahlen band (13.4–18.0 μm). The same structure is simulated using finite element methods and the charge density of the modes are studied; transverse dipole modes are identified for the transverse electric and magnetic polarizations and a quadrupole mode is identified for the transverse magnetic polarization. The measured mid-infrared spectrum agrees well with numerically simulated spectra. This work could enable optoelectronic structures and devices that support surface modes at mid- and far-infrared wavelengths.
Phononics in low-dimensional materials
Alexander A. Balandin
2012-06-01
Full Text Available Phonons – quanta of crystal lattice vibrations – reveal themselves in all electrical, thermal, and optical phenomena in materials. Nanostructures open exciting opportunities for tuning the phonon energy spectrum and related material properties for specific applications. The possibilities for controlled modification of the phonon interactions and transport – referred to as phonon engineering or phononics – increased even further with the advent of graphene and two-dimensional van der Waals materials. We describe methods for tuning the phonon spectrum and engineering the thermal properties of the low-dimensional materials via ribbon edges, grain boundaries, isotope composition, defect concentration, and atomic-plane orientation.
Scattering of phonons by dislocations
Anderson, A. C.
1979-01-01
By 1950, an explicit effort had been launched to use lattice thermal conductivity measurements in the investigation of defect structures in solids. This technique has been highly successful, especially when combined with the measurements of other properties such as optical absorption. One exception has been the study of dislocations. Although dislocations have a profound effect on the phonon thermal conductivity, the mechanisms of the phonon-dislocation interaction are poorly understood. The most basic questions are still debated in the literature. It therefore is pointless to attempt a quantitative comparison between an extensive accumulation of experimental data on the one hand, and the numerous theoretical models on the other. Instead, this chapter will attempt to glean a few qualitative conclusions from the existing experimental data. These results will then be compared with two general models which incorporate, in a qualitative manner, most of the proposed theories of the phonon-dislocation interaction. Until very recently, measurement of thermal conductivity was the only means available to probe the interaction between phonons and defects at phonon frequencies above the standard ultrasonic range of approx. = 10/sup 9/ Hz. The introductory paragraphs provide a brief review of the thermal-conductivity technique and the problems which are encountered in practice. There is also a brief presentation of the theoretical models and the complications that may occur in more realistic situations.
Phonon spectra in quantum wires
Ilić Dušan
2007-01-01
Full Text Available Green's function method, adjusted to bound crystalline structures, was applied to obtain the phonon dispersion law in quantum wires. The condition of the existence of small mechanical atom movements defining phonon spectra can be found by solving the secular equation. This problem was presented graphically for different boundary parameters. The presence of boundaries, as well as the change of boundary parameters, leads to the appearance of new properties of the layered structure. The most important feature is that, beside the allowed energy zones (which are continuous as in the bulk structure, zones of forbidden states appear. Different values of the boundary parameters lead to the appearance of lower and upper energy gaps, or dispersion branches spreading out of the bulk energy zone. The spectra of phonons in corresponding unbound structures were correlated to those in bound structures.
A quantum cascade phonon-polariton laser
Ohtani, Keita; Bosco, Lorenzo; Beck, Mattias; Faist, Jérôme
2016-01-01
We report a laser that coherently emits phonon-polaritons, quasi-particles arising from the coupling between photons and transverse optical phonons. The gain is provided by an intersubband transition in a quantum cascade structure. The polaritons at h$\
Phonon creation by gravitational waves
Sabín, Carlos; Ahmadi, Mehdi; Fuentes, Ivette
2014-01-01
We show that gravitational waves create phonons in a Bose-Einstein condensate (BEC). A traveling spacetime distortion produces particle creation resonances that correspond to the dynamical Casimir effect in a BEC phononic field contained in a cavity-type trap. We propose to use this effect to detect gravitational waves. The amplitude of the wave can be estimated applying recently developed relativistic quantum metrology techniques. We provide the optimal precision bound on the estimation of the wave's amplitude. Finally, we show that the parameter regime required to detect gravitational waves with this technique is within experimental reach.
The radio-frequency quadrupole
Vretenar, Maurizio
2013-01-01
Radio-frequency quadrupole (RFQ) linear accelerators appeared on the accelerator scene in the late 1970s and have since revolutionized the domain of low-energy proton and ion acceleration. The RFQ makes the reliable production of unprecedented ion beam intensities possible within a compact radio-frequency (RF) resonator which concentrates the three main functions of the low-energy linac section: focusing, bunching and accelerating. Its sophisticated electrode structure and strict beam dynamics and RF requirements, however, impose severe constraints on the mechanical and RF layout, making the construction of RFQs particularly challenging. This lecture will introduce the main beam optics, RF and mechanical features of a RFQ emphasizing how these three aspects are interrelated and how they contribute to the final performance of the RFQ.
U(6)-Phonon model of nuclear collective motion
Ganev, H. G.
2015-05-01
The U(6)-phonon model of nuclear collective motion with the semi-direct product structure [HW(21)]U(6) is obtained as a hydrodynamic (macroscopic) limit of the fully microscopic proton-neutron symplectic model (PNSM) with Sp(12, R) dynamical group. The phonon structure of the [HW(21)]U(6) model enables it to simultaneously include the giant monopole and quadrupole, as well as dipole resonances and their coupling to the low-lying collective states. The U(6) intrinsic structure of the [HW(21)]U(6) model, from the other side, gives a framework for the simultaneous shell-model interpretation of the ground state band and the other excited low-lying collective bands. It follows then that the states of the whole nuclear Hilbert space which can be put into one-to-one correspondence with those of a 21-dimensional oscillator with an intrinsic (base) U(6) structure. The latter can be determined in such a way that it is compatible with the proton-neutron structure of the nucleus. The macroscopic limit of the Sp(12, R) algebra, therefore, provides a rigorous mechanism for implementing the unified model ideas of coupling the valence particles to the core collective degrees of freedom within a fully microscopic framework without introducing redundant variables or violating the Pauli principle.
Otelaja, O. O. [School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853 (United States); Robinson, R. D., E-mail: rdr82@cornell.edu [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853 (United States)
2015-10-26
In this work, the mechanism for enhanced phonon backscattering in silicon is investigated. An understanding of phonon propagation through substrates has implications for engineering heat flow at the nanoscale, for understanding sources of decoherence in quantum systems, and for realizing efficient phonon-mediated particle detectors. In these systems, phonons that backscatter from the bottom of substrates, within the crystal or from interfaces, often contribute to the overall detector signal. We utilize a microscale phonon spectrometer, comprising superconducting tunnel junction emitters and detectors, to specifically probe phonon backscattering in silicon substrates (∼500 μm thick). By etching phonon “enhancers” or deep trenches (∼90 μm) around the detectors, we show that the backscattered signal level increases by a factor of ∼2 for two enhancers versus one enhancer. Using a geometric analysis of the phonon pathways, we show that the mechanism of the backscattered phonon enhancement is due to confinement of the ballistic phonon pathways and increased scattering off the enhancer walls. Our result is applicable to the geometric design and patterning of substrates that are employed in phonon-mediated detection devices.
Nonlinear phononics using atomically thin membranes
Midtvedt, Daniel; Isacsson, Andreas; Croy, Alexander
2014-09-01
Phononic crystals and acoustic metamaterials are used to tailor phonon and sound propagation properties by utilizing artificial, periodic structures. Analogous to photonic crystals, phononic band gaps can be created, which influence wave propagation and, more generally, allow engineering of the acoustic properties of a system. Beyond that, nonlinear phenomena in periodic structures have been extensively studied in photonic crystals and atomic Bose-Einstein condensates in optical lattices. However, creating nonlinear phononic crystals or nonlinear acoustic metamaterials remains challenging and only few examples have been demonstrated. Here, we show that atomically thin and periodically pinned membranes support coupled localized modes with nonlinear dynamics. The proposed system provides a platform for investigating nonlinear phononics.
Theory of coherent phonons in graphene
Sanders, G. D.; Stanton, C. J.; Kim, J.-H.; Yee, K.-J.; Jung, M. H.; Hong, B. H.; Haroz, E. H.; Kono, J.
2011-03-01
We develop a theory for the generation and detection of coherent phonons in graphene. Coherent phonons are generated via the deformation potential electron-phonon interaction with photogenerated carriers. In our theory the electronic states are treated in a third nearest neighbor extended tight binding formalism which gives a good description of the states over the entire graphene Brillouin zone while the phonon states are treated in a valence force field model. The equations of motion for the coherent phonon amplitudes are obtained in a density matrix formalism and we find that the coherent phonon amplitudes satisfy driven oscillator equations for each value of the phonon wavevector. Comparison is made with recent experimental measurements. Supported by NSF through grants OISE-0530220 and DMR-0706313 and the ONR through grant ONR-00075094, and the Robert A. Welch Foundation through grant No. C-1509.
AA, shims and washers on quadrupole ends
CERN PhotoLab
1981-01-01
Due to the fact that much of the field of the quadrupoles was outside the iron (in particular with the wide quadrupoles) and that thus the fields of quadrupoles and bending magnets interacted, the lattice properties of the AA could not be predicted with the required accuracy. After a first running period in 1980, during which detailed measurements were made with proton test beams, corrections to the quadrupoles were made in 1981, in the form of laminated shims at the ends of the poles, and with steel washers. With the latter ones, further refinements were made in an iterative procedure with measurements on the circulating beam. This eventually resulted, amongst other things, in a very low chromaticity, with the Q-values being constant to within +- 0.001 over the total momentum range of 6 %. Here we see the shims and washers on a narrow qudrupole (QFN, QDN). See also 8103203, 8103204, 8103205, 8103206.
ISR Superconducting Quadrupole in its cryostat
1978-01-01
The picture shows a superconducting quadrupole for the ISR high luminosity (low beta) insertion in its cryostat during final tests before installation in the ISR.The person is W.Burgess. See also photo 7702690X.
Sandor, R.K.J.; Blok, H.P.; Harakeh, M.N. (Vrije Univ., Amsterdam (Netherlands). Natuurkundig Lab.); Garg, U. (Vrije Univ., Amsterdam (Netherlands). Natuurkundig Lab. Notre Dame Univ., IN (USA). Dept. of Physics); Jager, C.W. de; Vries, H. de (Nationaal Inst. voor Kernfysica en Hoge-Energiefysica (NIKHEF), Amsterdam (Netherlands). Sectie K); Ponomarev, V.Yu.; Vdovin, A.I. (Joint Inst. for Nuclear Research, Dubna (USSR). Lab. of Theoretical Physics)
1989-12-21
The low-lying quadrupole states in {sup 142}Nd were investigated by inelastic electron scattering. The momentum transfer range covered was 0.5-2.8 fm{sup -1}. The extracted transition charge densities indicate quite different characters for these states. On the basis of a quasiparticle-phonon nuclear model calculation this difference can be understood as arising from an interplay between collective and single-particle aspects. (orig.).
A holographic perspective on phonons and pseudo-phonons
Amoretti, Andrea; Argurio, Riccardo; Musso, Daniele; Zayas, Leopoldo A Pando
2016-01-01
We analyze the concomitant spontaneous breaking of translation and conformal symmetries by introducing in a CFT a complex scalar operator that acquires a spatially dependent expectation value. The model, inspired by the holographic Q-lattice, provides a privileged setup to study the emergence of phonons from a spontaneous translational symmetry breaking in a conformal field theory and offers valuable hints for the treatment of phonons in QFT at large. We first analyze the Ward identity structure by means of standard QFT techniques, considering both spontaneous and explicit symmetry breaking. Next, by implementing holographic renormalization, we show that the same set of Ward identities holds in the holographic Q-lattice. Eventually, relying on the holographic and QFT results, we study the correlators realizing the symmetry breaking pattern and how they encode information about the low-energy spectrum.
AA, wide quadrupole on measurement stand
CERN PhotoLab
1981-01-01
Please look up 8101024 first. Shims and washers on the wide quadrupoles (QFW, QDW; located in the lattice where dispersion was large) served mostly for corrections of those lattice parameters which were a function of momentum. After mounting shims and washers, the quadrupoles were measured to determine their magnetic centre and to catalogue the effect of washer constellations. Raymond Brown is busy measuring a wide quad.
The decay of quadrupole-octupole $1^-$ states in $^{40}$Ca and $^{140}$Ce
Derya, V; Aumann, T; Bhike, M; Endres, J; Gooden, M; Hennig, A; Isaak, J; Lenske, H; Löher, B; Pietralla, N; Savran, D; Tornow, W; Werner, V; Zilges, A
2016-01-01
Background: Two-phonon excitations originating from the coupling of two collective one-phonon states are of great interest in nuclear structure physics. One possibility to generate low-lying $E1$ excitations is the coupling of quadrupole and octupole phonons. Purpose: In this work, the $\\gamma$-decay behavior of candidates for the $(2_1^+\\otimes 3_1^-)_{1^-}$ state in the doubly-magic nucleus $^{40}$Ca and in the heavier and semi-magic nucleus $^{140}$Ce is investigated. Methods: $(\\vec{\\gamma},\\gamma')$ experiments have been carried out at the High Intensity $\\gamma$-ray Source (HI${\\gamma}$S) facility in combination with the high-efficiency $\\gamma$-ray spectroscopy setup $\\gamma^3$ consisting of HPGe and LaBr$_3$ detectors. The setup enables the acquisition of $\\gamma$-$\\gamma$ coincidence data and, hence, the detection of direct decay paths. Results: In addition to the known ground-state decays, for $^{40}$Ca the decay into the $3^-_1$ state was observed, while for $^{140}$Ce the direct decays into the $2...
Engineering dissipation with phononic spectral hole burning
Behunin, R. O.; Kharel, P.; Renninger, W. H.; Rakich, P. T.
2017-03-01
Optomechanics, nano-electromechanics, and integrated photonics have brought about a renaissance in phononic device physics and technology. Central to this advance are devices and materials supporting ultra-long-lived photonic and phononic excitations that enable novel regimes of classical and quantum dynamics based on tailorable photon-phonon coupling. Silica-based devices have been at the forefront of such innovations for their ability to support optical excitations persisting for nearly 1 billion cycles, and for their low optical nonlinearity. While acoustic phonon modes can persist for a similar number of cycles in crystalline solids at cryogenic temperatures, it has not been possible to achieve such performance in silica, as silica becomes acoustically opaque at low temperatures. We demonstrate that these intrinsic forms of phonon dissipation are greatly reduced (by >90%) by nonlinear saturation using continuous drive fields of disparate frequencies. The result is a form of steady-state phononic spectral hole burning that produces a wideband transparency window with optically generated phonon fields of modest (nW) powers. We developed a simple model that explains both dissipative and dispersive changes produced by phononic saturation. Our studies, conducted in a microscale device, represent an important step towards engineerable phonon dynamics on demand and the use of glasses as low-loss phononic media.
Edge phonons in black phosphorus
Ribeiro, H. B.; Villegas, C. E. P.; Bahamon, D. A.; Muraca, D.; Castro Neto, A. H.; de Souza, E. A. T.; Rocha, A. R.; Pimenta, M. A.; de Matos, C. J. S.
2016-07-01
Black phosphorus has recently emerged as a new layered crystal that, due to its peculiar and anisotropic crystalline and electronic band structures, may have important applications in electronics, optoelectronics and photonics. Despite the fact that the edges of layered crystals host a range of singular properties whose characterization and exploitation are of utmost importance for device development, the edges of black phosphorus remain poorly characterized. In this work, the atomic structure and behaviour of phonons near different black phosphorus edges are experimentally and theoretically studied using Raman spectroscopy and density functional theory calculations. Polarized Raman results show the appearance of new modes at the edges of the sample, and their spectra depend on the atomic structure of the edges (zigzag or armchair). Theoretical simulations confirm that the new modes are due to edge phonon states that are forbidden in the bulk, and originated from the lattice termination rearrangements.
Phononic crystals of poroelastic spheres
Alevizaki, A.; Sainidou, R.; Rembert, P.; Morvan, B.; Stefanou, N.
2016-11-01
An extension of the layer-multiple-scattering method to phononic crystals of poroelastic spheres immersed in a fluid medium is developed. The applicability of the method is demonstrated on specific examples of close-packed fcc crystals of submerged water-saturated meso- and macroporous silica microspheres. It is shown that, by varying the pore size and/or the porosity, the transmission, reflection, and absorption spectra of finite slabs of these crystals are significantly altered. Strong absorption, driven by the slow waves in the poroelastic material and enhanced by multiple scattering, leads to negligible transmittance over an extended frequency range, which might be useful for practical applications in broadband acoustic shielding. The results are analyzed by reference to relevant phononic dispersion diagrams in the viscous and inertial coupling limits, and a consistent interpretation of the underlying physics is provided.
Measuring phonons in protein crystals
Niessen, Katherine A.; Snell, Edward; Markelz, A. G.
2013-03-01
Using Terahertz near field microscopy we find orientation dependent narrow band absorption features for lysozyme crystals. Here we discuss identification of protein collective modes associated with the observed features. Using normal mode calculations we find good agreement with several of the measured features, suggesting that the modes arise from internal molecular motions and not crystal phonons. Such internal modes have been associated with protein function.
Circular Phonon Dichroism in Weyl Semimetals
Liu, Donghao; Shi, Junren
2017-08-01
We derive the phonon dynamics of magnetic metals in the presence of strong spin-orbit coupling. We show that both a dissipationless viscosity and a dissipative viscosity arise in the dynamics. While the dissipationless viscosity splits the dispersion of left-handed and right-handed circularly polarized phonons, the dissipative viscosity damps them differently, inducing circular phonon dichroism. The effect offers a new degree of manipulation of phonons, i.e., the control of the phonon polarization. We investigate the effect in Weyl semimetals. We find that there exists strong circular phonon dichroism in Weyl semimetals breaking both the time-reversal and the inversion symmetry, making them potential materials for realizing the acoustic circular polarizer.
Phonon-Assisted Resonant Tunnelling through a Triple-Quantum-Dot: a Phonon-Signal Detector
SHEN Xiao-Yun; DONG Bing; LEI Xiao-lin
2008-01-01
We study the effect of electron-phonon interaction on current and zero-frequency shot noise in resonant tunnelling through a series triple-quantum-dot coupling to a local phonon mode by means of a nonperturbative mapping technique along with the Green function formulation.By fixing the energy difference between the first two quantum dots to be equal to phonon frequency and sweeping the level of the third quantum dot,we find a largely enhanced current spectrum due to phonon effect,and in particular we predict current peaks corresponding to phonon-absorption and phonon-emission assisted resonant tunnelling processes,which show that this system can be acted as a sensitive phonon-signal detector or as a cascade phonon generator.
2005-05-09
Carbon Nanotubes with Enhanced K(T) CNT in CNT Yarns and Oriented CNT bucky- aerogels 4Anvar A. Zakhidov, University of Texas at Dallas Our Main...CNT Fibers and Yarns and - Oriented CNT-ribbon aerogels 50Anvar A. Zakhidov, University of Texas at Dallas PHONON TRANSISTOR in NANOTUBE FIBERS with...100µm) of copper and gold are much lower: Dcopper = 117 mm2/s, Dgold = 130 mm2/s. 60Anvar A. Zakhidov, University of Texas at Dallas Multifunctional
SUPERCONDUCTING QUADRUPOLE ARRAYS FOR MULTIPLE BEAM TRANSPORT
Rainer Meinke
2003-10-01
The goal of this research was to develop concepts for affordable, fully functional arrays of superconducting quadrupoles for multi-beam transport and focusing in heavy ion fusion (HIF)accelerators. Previous studies by the Virtual National Laboratory (VNL) collaboration have shown that the multi-beam transport system (consisting of alternating gradient quadrupole magnets, a beam vacuum system, and the beam monitor and control system) will likely be one of the most expensive and critical parts of such an accelerator. This statement is true for near-term fusion research accelerators as well as accelerators for the ultimate goal of power production via inertial fusion. For this reason, research on superconducting quadrupole arrays is both timely and important for the inertial fusion energy (IFE) research program. This research will also benefit near-term heavy ion fusion facilities such as the Integrated Research Experiment (IRE)and/or the Integrated Beam Experiment (IBX). We considered a 2-prong approach that addresses the needs of both the nearer and longer term requirements of the inertial fusion program. First, we studied the flat coil quadrupole design that was developed by LLNL; this magnet is 150 mm long with a 50 mm aperture and thus is suitable for near term experiments that require magnets of a small length to aperture ratio. Secondly, we studied the novel double-helix quadrupole (DHQ) design in a small (3 x 3) array configuration; this design can provide an important step to the longer term solution of low-cost, easy to manufacture array constructions. Our Phase I studies were performed using the AMPERES magnetostatic analysis software. Consideration of these results led to plans for future magnet R&D construction projects. The first objective of Phase I was to develop the concept of a superconducting focusing array that meets the specific requirements of a heavy ion fusion accelerator. Detailed parameter studies for such quadrupole arrays were performed
CLIC Main Beam Quadrupole Eigen Mode computation
Deleglise, Guillaume
2010-01-01
In this report, we summarise the work done on the CLIC Main Beam Quadrupole. There are about 4000 MB quadrupoles of 4 types with lengths ranging from 420mm to 1900mm. In order to obtain the desired CLIC luminosity, the MB quadrupoles have to be stable to 1nm above 1Hz. The region of interest for the study is between 0.5Hz and about 100Hz. In order to achieve the specifications, the magnet should not have any resonance peaks in this region of Interest. In addition, the magnet on its support shouldn’t have any resonance peak in the same frequency range. The first step is to determine if the designed magnet has its first resonance peak above 100Hz. We are studying the longest quadrupole more susceptible to internal resonances. In a second step, the magnet on ideal supporting points has been evaluated. The current magnet design can be seen on following figure. One can see that it is composed of 4 quadrants assembled so as to have a quadrupole magnetic field. As a last step, the mechanical model has been used to...
Focusing properties of discrete RF quadrupoles
Li, Zhi-Hui; Wang, Zhi-Jun
2017-08-01
The particle motion equation for a Radio Frequency (RF) quadrupole is derived. The motion equation shows that the general transform matrix of a RF quadrupole with length less than or equal to 0.5βλ (β is the relativistic velocity of particles and λ is wavelength of radio frequency electromagnetic field) can describe the particle motion in an arbitrarily long RF quadrupole. By iterative integration, the general transform matrix of a discrete RF quadrupole is derived from the motion equation. The transform matrix is in form of a power series of focusing parameter B. It shows that for length less than βλ, the series up to the 2nd order of B agrees well with the direct integration results for B up to 30, while for length less than 0.5βλ, the series up to 1st order is already a good approximation of the real solution for B less than 30. The formula of the transform matrix can be integrated into linac or beam line design code to deal with the focusing of discrete RF quadrupoles. Supported by National Natural Science Foundation of China (11375122, 11511140277) and Strategic Priority Research Program of the Chinese Academy of Sciences (XDA03020705)
Electron-phonon interactions from first principles
Giustino, Feliciano
2017-01-01
This article reviews the theory of electron-phonon interactions in solids from the point of view of ab initio calculations. While the electron-phonon interaction has been studied for almost a century, predictive nonempirical calculations have become feasible only during the past two decades. Today it is possible to calculate from first principles many materials properties related to the electron-phonon interaction, including the critical temperature of conventional superconductors, the carrier mobility in semiconductors, the temperature dependence of optical spectra in direct and indirect-gap semiconductors, the relaxation rates of photoexcited carriers, the electron mass renormalization in angle-resolved photoelectron spectra, and the nonadiabatic corrections to phonon dispersion relations. In this article a review of the theoretical and computational framework underlying modern electron-phonon calculations from first principles as well as landmark investigations of the electron-phonon interaction in real materials is given. The first part of the article summarizes the elementary theory of electron-phonon interactions and their calculations based on density-functional theory. The second part discusses a general field-theoretic formulation of the electron-phonon problem and establishes the connection with practical first-principles calculations. The third part reviews a number of recent investigations of electron-phonon interactions in the areas of vibrational spectroscopy, photoelectron spectroscopy, optical spectroscopy, transport, and superconductivity.
Yao, J M
2016-01-01
We discuss anharmonicity of the multi-octupole-phonon states in $^{208}$Pb based on a covariant density functional theory, by fully taking into account the interplay between the quadrupole and the octupole degrees of freedom. Our results indicate the existence of a large anharmonicity in the transition strengths, even though the excitation energies are similar to those in the harmonic limit. We also show that the quadrupole-shape fluctuation significantly enhances the fragmentation of the two-octupole-phonon states in $^{208}$Pb. Using those transition strengths as inputs to coupled channels calculations, we then discuss the fusion reaction of $^{16}$O+$^{208}$Pb at energies around the Coulomb barrier. We show that the anharmonicity of the octupole vibrational excitation considerably improves previous coupled-channels calculations in the harmonic oscillator limit, significantly reducing the height of the main peak in the fusion barrier distribution.
Influence of the electron-phonon iinteraction on phonon heat conduction in a molecular nanowire
Galović Slobodanka P.
2006-01-01
Full Text Available A model for phonon heat conduction in a molecular nanowire is developed. The calculation takes into account modification of the acoustic phonon dispersion relation due to the electron-phonon interaction. The results obtained are compared with models based upon a simpler, Callaway formula.
Resonance methods in quadrupole ion traps
Snyder, Dalton T.; Peng, Wen-Ping; Cooks, R. Graham
2017-01-01
The quadrupole ion trap is widely used in the chemical physics community for making measurements on dynamical systems, both intramolecular (e.g. ion fragmentation reactions) and intermolecular (e.g. ion/molecule reactions). In this review, we discuss linear and nonlinear resonances in quadrupole ion traps, an understanding of which is critical for operation of these devices and interpretation of the data which they provide. The effect of quadrupole field nonlinearity is addressed, with important implications for promoting fragmentation and achieving unique methods of mass scanning. Methods that depend on ion resonances (i.e. matching an external perturbation with an ion's induced frequency of motion) are discussed, including ion isolation, ion activation, and ion ejection.
Mixed symmetry tensors in the worldline formalism
Corradini, Olindo; Edwards, James P.
2016-05-01
We consider the first quantised approach to quantum field theory coupled to a non-Abelian gauge field. Representing the colour degrees of freedom with a single family of auxiliary variables the matter field transforms in a reducible representation of the gauge group which — by adding a suitable Chern-Simons term to the particle action — can be projected onto a chosen fully (anti-)symmetric representation. By considering F families of auxiliary variables, we describe how to extend the model to arbitrary tensor products of F reducible representations, which realises a U( F ) "flavour" symmetry on the world-line particle model. Gauging this symmetry allows the introduction of constraints on the Hilbert space of the colour fields which can be used to project onto an arbitrary irreducible representation, specified by a certain Young tableau. In particular the occupation numbers of the wavefunction — i.e. the lengths of the columns (rows) of the Young tableau — are fixed through the introduction of Chern-Simons terms. We verify this projection by calculating the number of colour degrees of freedom associated to the matter field. We suggest that, using the worldline approach to quantum field theory, this mechanism will allow the calculation of one-loop scattering amplitudes with the virtual particle in an arbitrary representation of the gauge group.
Mixed symmetry tensors in the worldline formalism
Corradini, Olindo
2016-01-01
We consider the first quantised approach to quantum field theory coupled to a non-Abelian gauge field. Representing the colour degrees of freedom with a single family of auxiliary variables the matter field transforms in a reducible representation of the gauge group which - by adding a suitable Chern-Simons term to the particle action - can be projected onto a chosen fully (anti-)symmetric representation. By considering F families of auxiliary variables, we describe how to extend the model to arbitrary tensor products of F reducible representations, which realises a U(F) "flavour" symmetry on the worldline particle model. Gauging this symmetry allows the introduction of constraints on the Hilbert space of the colour fields which can be used to project onto an arbitrary irreducible representation, specified by a certain Young Tableau. In particular the occupation numbers of the wavefunction - i.e. the lengths of the columns (rows) of the Young Tableau - are fixed through the introduction of Chern-Simons terms....
Analytical transfer matrix of a quadrupole fringe
PENG Yue-Mei; XU Gang
2011-01-01
The analytical linear transfer matrices for different quadrupole fringes including quadratic,high order power and exponential models are deduced in this paper.As an example,the transfer matrices of the quadrupole BEPC Ⅱ 105Q are computed for the above three models and compared with hard edge and sliceby-slice models in cases of near 60° and 90° FODO cells.These models' results are much better than the hard edge model's,and can meet the requirement of accurate calculation.
Tunable high-gradient permanent magnet quadrupoles
Shepherd, B J A; Marks, N; Collomb, N A; Stokes, D G; Modena, M; Struik, M; Bartalesi, A
2014-01-01
A novel type of highly tunable permanent magnet (PM) based quadrupole has been designed by the ZEPTO collaboration. A prototype of the design (ZEPTO-Q1), intended to match the specification for the CLIC Drive Beam Decelerator, was built and magnetically measured at Daresbury Laboratory and CERN. The prototype utilises two pairs of PMs which move in opposite directions along a single vertical axis to produce a quadrupole gradient variable between 15 and 60 T/m. The prototype meets CLIC's challenging specification in terms of the strength and tunability of the magnet.
Dynamical stabilization by phonon-phonon interaction exemplified in cubic zirconia
Souvatsos, [etrps G [Los Alamos National Laboratory; Rudin, Sven P [Los Alamos National Laboratory
2008-01-01
Cubic zirconia exhibits a soft phonon mode (X{sup -}{sub 2}), which becomes dynamically unstable at low temperatures. Previous ab initio invest.igations into the temperature-induced stabilization of the soft mode treated it as an independent anharmonic oscillator. Calculations presented here, using the self consistent ab initio lattice dynamical (SCAILD) method to evaluate the phonons at 2570 K, show that the soft mode should not be treated independently of other phonon modes. Phonon-phonon interactions stabilize the X{sup -}{sub 2} mode. Furthermore, the effective potential experienced by the mode takes on a quadratic form.
Splash, pop, sizzle: Information processing with phononic computing
Sophia R. Sklan
2015-05-01
Full Text Available Phonons, the quanta of mechanical vibration, are important to the transport of heat and sound in solid materials. Recent advances in the fundamental control of phonons (phononics have brought into prominence the potential role of phonons in information processing. In this review, the many directions of realizing phononic computing and information processing are examined. Given the relative similarity of vibrational transport at different length scales, the related fields of acoustic, phononic, and thermal information processing are all included, as are quantum and classical computer implementations. Connections are made between the fundamental questions in phonon transport and phononic control and the device level approach to diodes, transistors, memory, and logic.
Interaction of coherent phonons with defects and elementary excitations
Hase, Muneaki [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573 (Japan); Kitajima, Masahiro, E-mail: mhase@bk.tsukuba.ac.j, E-mail: kitaji@nda.ac.j [Department of Applied Physics, School of Applied Science, National Defense Academy of Japan, Hashirimizu 1-10-20, Yokosuka, Kanagawa 239-8686 (Japan)
2010-02-24
We present an overview of the feasibility of using coherent phonon spectroscopy to study interaction dynamics of excited lattice vibrations with their environments. By exploiting the features of coherent phonons with a pump-probe technique, one can study lattice motions in a sub-picosecond time range. The dephasing properties tell us not only about interaction dynamics with carriers (electrons and holes) or thermal phonons but also about point defects in crystals. Modulations of the coherent phonon amplitude by more than two modes are closely related to phonon-carrier or phonon-phonon interferences. Related to this phenomenon, formation of coherent phonons at higher harmonics gives direct evidence for phonon-phonon couplings. A combined study of coherent phonons and ultrafast carrier response can be useful for understanding phonon-carrier interaction dynamics. For metals like zinc, nonequilibrium electrons may dominate the dynamics of both relaxation and generation of coherent phonons. The frequency chirp of coherent phonons can be a direct measure of how and when phonon-phonon and phonon-carrier couplings occur. Carbon nanotubes show some complicated behavior due to the existence of many modes with different symmetries, resulting in superposition or interference. To illustrate one of the most interesting applications, the selective excitation of specific phonon modes through the use of a pulse train technique is shown. (topical review)
Phonon dispersion relation of liquid metals
P B Thakor; P N Gajjar; A R Jani
2009-06-01
The phonon dispersion curves of some liquid metals, viz. Na ( = 1), Mg ( = 2), Al ( = 3) and Pb ( = 4), have been computed using our model potential. The charged hard sphere (CHS) reference system is applied to describe the structural information. Our model potential along with CHS reference system is capable of explaining the phonon dispersion relation for monovalent, divalent, trivalent and tetravalent liquid metals.
Anharmonic phonons and high-temperature superconductivity
Crespi, V.H.; Cohen, M.L. (Department of Physics, University of California at Berkeley, and Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States))
1993-07-01
We examine a simple model of anharmonic phonons with application to the superconducting isotope effect. Linear and quadratic electron-phonon coupling are considered for various model potentials. The results of the model calculations are compared with the high-temperature superconductors La[sub 2[minus][ital x
Resonant tunneling in a pulsed phonon field
Kral, P.; Jauho, Antti-Pekka
1999-01-01
, The nonequilibrium spectral function for the resonance displays the formation and decay of the phonon sidebands on ultrashort time scales. The time-dependent tunneling current through the individual phonon satellites reflects this quasiparticle formation by oscillations, whose time scale is set by the frequency...
The phonon Hall effect: theory and application
Zhang Lifa; Wang Jiansheng; Li Baowen [Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, Singapore 117542 (Singapore); Ren Jie [NUS Graduate School for Integrative Sciences and Engineering, Singapore 117456 (Singapore)
2011-08-03
We present a systematic theory of the phonon Hall effect in a ballistic crystal lattice system, and apply it on the kagome lattice which is ubiquitous in various real materials. By proposing a proper second quantization for the non-Hermitian in the polarization-vector space, we obtain a new heat current density operator with two separate contributions: the normal velocity responsible for the longitudinal phonon transport, and the anomalous velocity manifesting itself as the Hall effect of transverse phonon transport. As exemplified in kagome lattices, our theory predicts that the direction of Hall conductivity at low magnetic field can be reversed by tuning the temperatures, which we hope can be verified by experiments in the future. Three phonon-Hall-conductivity singularities induced by phonon-band-topology change are discovered as well, which correspond to the degeneracies at three different symmetric center points, {Gamma}, K, X, in the wavevector space of the kagome lattice.
Phononic crystals and elastodynamics: Some relevant points
N. Aravantinos-Zafiris
2014-12-01
Full Text Available In the present paper we review briefly some of the first works on wave propagation in phononic crystals emphasizing the conditions for the creation of acoustic band-gaps and the role of resonances to the band-gap creation. We show that useful conclusions in the analysis of phononic band gap structures can be drawn by considering the mathematical similarities of the basic classical wave equation (Helmholtz equation with Schrödinger equation and by employing basic solid state physics concepts and conclusions regarding electronic waves. In the second part of the paper we demonstrate the potential of phononic systems to be used as elastic metamaterials. This is done by demonstrating negative refraction in phononic crystals and subwavelength waveguiding in a linear chain of elastic inclusions, and by proposing a novel structure with close to pentamode behavior. Finally the potential of phononic structures to be used in liquid sensor applications is discussed and demonstrated.
Phononic crystals and elastodynamics: Some relevant points
Aravantinos-Zafiris, N. [Dept. of Materials Science, University of Patras, Patras 26504 (Greece); Department of Sound and Musical Instruments Technology, Ionian Islands Technological Educational Institute, Lixouri, 28200 (Greece); Sigalas, M. M. [Dept. of Materials Science, University of Patras, Patras 26504 (Greece); Kafesaki, M. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology, Hellas (FORTH), P.O. Box 1387, 70013 Heraklion, Crete (Greece); Dept. of Materials Science and Technology, Univ. of Crete (Greece); Economou, E. N. [Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology, Hellas (FORTH), P.O. Box 1387, 70013 Heraklion, Crete (Greece); Dept. of Physics, Univ. of Crete (Greece)
2014-12-15
In the present paper we review briefly some of the first works on wave propagation in phononic crystals emphasizing the conditions for the creation of acoustic band-gaps and the role of resonances to the band-gap creation. We show that useful conclusions in the analysis of phononic band gap structures can be drawn by considering the mathematical similarities of the basic classical wave equation (Helmholtz equation) with Schrödinger equation and by employing basic solid state physics concepts and conclusions regarding electronic waves. In the second part of the paper we demonstrate the potential of phononic systems to be used as elastic metamaterials. This is done by demonstrating negative refraction in phononic crystals and subwavelength waveguiding in a linear chain of elastic inclusions, and by proposing a novel structure with close to pentamode behavior. Finally the potential of phononic structures to be used in liquid sensor applications is discussed and demonstrated.
Ultrafast Structure Switching through Nonlinear Phononics
Juraschek, D. M.; Fechner, M.; Spaldin, N. A.
2017-02-01
We describe a mechanism by which nonlinear phononics allows ultrafast coherent and directional control of transient structural distortions. With ErFeO3 as a model system, we use density functional theory to calculate the structural properties as input into an anharmonic phonon model that describes the response of the system to a pulsed optical excitation. We find that the trilinear coupling of two orthogonal infrared-active phonons to a Raman-active phonon causes a transient distortion of the lattice. In contrast to the quadratic-linear coupling that has been previously explored, the direction of the distortion is determined by the polarization of the exciting light, introducing a novel mechanism for nonlinear phononic switching. Since the occurrence of the coupling is determined by the symmetry of the system we propose that it is a universal feature of orthorhombic and tetragonal perovskites.
AA, wide quadrupole on measurement stand
CERN PhotoLab
1981-01-01
Please look up 8101024 and 8103203 first. Wide quadrupole (QFW, QDW) with end-shims and shimming washers on the measurement stand. With the measurement coil one measured the harmonics of the magnetic field, determined the magnetic centre, and catalogued the effect of washer constellations.
General quadrupole nuclear shapes. An algebraic perspective
Leviatan, A. (Los Alamos National Lab. (LANL), NM (USA). Theoretical Div.); Shao Bin (Yale Univ., New Haven, CT (USA). Sloane Physics Lab.)
1990-07-05
Spherical, axial and non-axial quadrupole shapes are investigated within the algebraic interacting boson model. For each shape the hamiltonian is resolved into intrinsic and collective parts, normal modes are identified and intrinsic states are constructed. Special emphasis is paid to new features (e.g. rigid triaxiality and coexisting deformed shapes) that emerge in the presence of three-body interactions. (orig.).
All systems go for LHC quadrupoles
2003-01-01
The series fabrication of the Main Quadrupole cold masses for the LHC has begun with the delivery of the first unit on February 12th. The superconducting dipole magnets required to bend the proton beams around the LHC are often in the news. Less famous, perhaps, but equally important are the 360 main quadrupole (MQ) magnets, which will perform the principal focusing around the 27 km ring. CERN and CEA-Saclay began collaborating on the development and prototyping of these magnets in 1989. This resulted in five highly successful quadrupole units - also known as short straight sections - one of which was integrated for testing in String 1, and two others of the final design in String 2. Once the tests had confirmed the validity of the design and realization, the fabrication of the 360 cold masses had to be transferred to industry. After highly competitive tendering, the German firm ACCEL Instruments was entrusted both with the construction of the quadrupole magnets themselves, and with their assembly into the co...
Closed orbit response to quadrupole strength variation
Wolski, Andrzej; Zimmermann, Frank
2004-01-20
We derive two formulae relating the variation in closed orbit in a storage ring to variations in quadrupole strength, neglecting nonlinear and dispersive effects. These formulae correct results previously reported [1,2,3]. We compare the results of the formulae applied to the ATF with simulations using MAD, and consider their application to beam-based alignment.
Model of an LHC superconducting quadrupole magnet
Laurent Guiraud
2000-01-01
Model of a superconducting quadrupole magnet for the LHC project. These magnets are used to focus the beam by squeezing it into a smaller cross-section, a similar effect to a lens focusing light. However, each magnet only focuses the beam in one direction so alternating magnet arrangements are required to produce a fully focused beam.
Laser-induced quadrupole-quadrupole collisional energy transfer in Xe-Kr
Lu Zhen-Zhong; Chen De-Ying; Fan Rong-Wei; Xia Yuan-Qin
2011-01-01
By considering the relative velocity distribution function and multipole expansion interaction Hamiltonian, a three-state model for calculating the cross section of laser-induced quadrupole-quadrupole collisional energy transfer is presented. Calculated results in Xe-Kr system show that in the present system, the laser-induced collision process occurs for ～4 ps, which is much shorter than the dipole-dipole laser-induced collisional energy transfer (LICET) process.The spectrum of laser-induced quadrupole-quadrupole collisional energy transfer in Xe-Kr system has wider tunable range in an order of magnitude than the dipole-dipole LICET spectra. The peak cross section decreases and moves to the quasi-static wing with increasing temperature and the full width at half peak of the profile becomes larger as the system temperature increases.
Light-enhanced electron-phonon coupling from nonlinear electron-phonon coupling
Sentef, M. A.
2017-05-01
We investigate an exact nonequilibrium solution of a two-site electron-phonon model, where an infrared-active phonon that is nonlinearly coupled to the electrons is driven by a laser field. The time-resolved electronic spectrum shows coherence-incoherence spectral weight transfer, a clear signature of light-enhanced electron-phonon coupling. The present study is motivated by recent evidence for enhanced electron-phonon coupling in pump-probe terahertz and angle-resolved photoemission spectroscopy in bilayer graphene when driven near resonance with an infrared-active phonon mode [E. Pomarico et al., Phys. Rev. B 95, 024304 (2017), 10.1103/PhysRevB.95.024304], and by a theoretical study suggesting that transient electronic attraction arises from nonlinear electron-phonon coupling [D. M. Kennes et al., Nat. Phys. 13, 479 (2017), 10.1038/nphys4024]. We show that a linear scaling of light-enhanced electron-phonon coupling with the pump field intensity emerges, in accordance with a time-nonlocal self-energy based on a mean-field decoupling using quasiclassical phonon coherent states. Finally, we demonstrate that this leads to enhanced double occupancies in accordance with an effective electron-electron attraction. Our results suggest that materials with strong phonon nonlinearities provide an ideal playground to achieve light-enhanced electron-phonon coupling and possibly light-induced superconductivity.
Two-Dimensional Phononic Crystals: Disorder Matters.
Wagner, Markus R; Graczykowski, Bartlomiej; Reparaz, Juan Sebastian; El Sachat, Alexandros; Sledzinska, Marianna; Alzina, Francesc; Sotomayor Torres, Clivia M
2016-09-14
The design and fabrication of phononic crystals (PnCs) hold the key to control the propagation of heat and sound at the nanoscale. However, there is a lack of experimental studies addressing the impact of order/disorder on the phononic properties of PnCs. Here, we present a comparative investigation of the influence of disorder on the hypersonic and thermal properties of two-dimensional PnCs. PnCs of ordered and disordered lattices are fabricated of circular holes with equal filling fractions in free-standing Si membranes. Ultrafast pump and probe spectroscopy (asynchronous optical sampling) and Raman thermometry based on a novel two-laser approach are used to study the phononic properties in the gigahertz (GHz) and terahertz (THz) regime, respectively. Finite element method simulations of the phonon dispersion relation and three-dimensional displacement fields furthermore enable the unique identification of the different hypersonic vibrations. The increase of surface roughness and the introduction of short-range disorder are shown to modify the phonon dispersion and phonon coherence in the hypersonic (GHz) range without affecting the room-temperature thermal conductivity. On the basis of these findings, we suggest a criteria for predicting phonon coherence as a function of roughness and disorder.
Tsoneva, N., E-mail: Nadia.Tsoneva@theo.physik.uni-giessen.de [Frankfurt Institute for Advanced Studies (FIAS) (Germany); Lenske, H. [Universität Gießen, Institut für Theoretische Physik (Germany)
2016-11-15
During the last decade, a theoretical method based on the energy–density functional theory and quasiparticle–phonon model, including up to three-phonon configurations was developed. The main advantages of themethod are that it incorporates a self-consistentmean-field and multi-configuration mixing which are found of crucial importance for systematic investigations of nuclear low-energy excitations, pygmy and giant resonances in an unified way. In particular, the theoretical approach has been proven to be very successful in predictions of new modes of excitations, namely pygmy quadrupole resonance which is also lately experimentally observed. Recently, our microscopically obtained dipole strength functions are implemented in predictions of nucleon-capture reaction rates of astrophysical importance. A comparison to available experimental data is discussed.
The pygmy quadrupole resonance and neutron-skin modes in 124Sn
Spieker, M.; Tsoneva, N.; Derya, V.; Endres, J.; Savran, D.; Harakeh, M. N.; Harissopulos, S.; Herzberg, R.-D.; Lagoyannis, A.; Lenske, H.; Pietralla, N.; Popescu, L.; Scheck, M.; Schlüter, F.; Sonnabend, K.; Stoica, V. I.; Wörtche, H. J.; Zilges, A.
2016-01-01
We present an extensive experimental study of the recently predicted pygmy quadrupole resonance (PQR) in Sn isotopes, where complementary probes were used. In this study, (α ,α‧ γ) and (γ ,γ‧) experiments were performed on 124Sn. In both reactions, Jπ =2+ states below an excitation energy of 5 MeV were populated. The E2 strength integrated over the full transition densities could be extracted from the (γ ,γ‧) experiment, while the (α ,α‧ γ) experiment at the chosen kinematics strongly favors the excitation of surface modes because of the strong α-particle absorption in the nuclear interior. The excitation of such modes is in accordance with the quadrupole-type oscillation of the neutron skin predicted by a microscopic approach based on self-consistent density functional theory and the quasiparticle-phonon model (QPM). The newly determined γ-decay branching ratios hint at a non-statistical character of the E2 strength, as it has also been recently pointed out for the case of the pygmy dipole resonance (PDR). This allows us to distinguish between PQR-type and multiphonon excitations and, consequently, supports the recent first experimental indications of a PQR in 124Sn.
Acoustic superfocusing by solid phononic crystals
Zhou, Xiaoming; Assouar, M. Badreddine; Oudich, Mourad
2014-12-01
We propose a solid phononic crystal lens capable of acoustic superfocusing beyond the diffraction limit. The unit cell of the crystal is formed by four rigid cylinders in a hosting material with a cavity arranged in the center. Theoretical studies reveal that the solid lens produces both negative refraction to focus propagating waves and surface states to amplify evanescent waves. Numerical analyses of the superfocusing effect of the considered solid phononic lens are presented with a separated source excitation to the lens. In this case, acoustic superfocusing beyond the diffraction limit is evidenced. Compared to the fluid phononic lenses, the solid lens is more suitable for ultrasonic imaging applications.
One-dimensional hypersonic phononic crystals.
Gomopoulos, N; Maschke, D; Koh, C Y; Thomas, E L; Tremel, W; Butt, H-J; Fytas, G
2010-03-10
We report experimental observation of a normal incidence phononic band gap in one-dimensional periodic (SiO(2)/poly(methyl methacrylate)) multilayer film at gigahertz frequencies using Brillouin spectroscopy. The band gap to midgap ratio of 0.30 occurs for elastic wave propagation along the periodicity direction, whereas for inplane propagation the system displays an effective medium behavior. The phononic properties are well captured by numerical simulations. The porosity in the silica layers presents a structural scaffold for the introduction of secondary active media for potential coupling between phonons and other excitations, such as photons and electrons.
Kuleev, I G
2001-01-01
The effect of normal processes of the phonon-phonon scattering on the thermal conductivity of the germanium crystals with various isotopic disorder degrees is considered. The phonon pulse redistribution in the normal scattering processes both inside each oscillatory branch (the Simons mechanism) and between various phonon oscillatory branches (the Herring mechanism) is accounted for. The contributions of the longitudinal and cross-sectional phonons drift motion into the thermal conductivity are analyzed. It is shown that the pulse redistribution in the Herring relaxation mechanism leads to essential suppression of the longitudinal phonons drift motion in the isotopically pure germanium crystals. The calculations results of thermal conductivity for the Herring relaxation mechanism agree well with experimental data on the germanium crystals with various isotopic disorder degrees
Effects of phonon-phonon coupling on properties of pygmy resonance in 124-132Sn
Voronov V. V.
2012-12-01
Full Text Available Starting from an effective Skyrme interaction we study effects of phonon-phonon coupling on the low-energy electric dipole response in 124-132Sn. The QRPA calculations are performed within a finite rank separable approximation. The inclusion of two-phonon configurations gives a considerable contribution to low-lying strength. Comparison with available experimental data shows a reasonable agreement for the low-energy E1 strength distribution.
LARP Long Nb3Sn Quadrupole Design.
Ambrosio,G.; Andreev, N.; Anerella, M.; Barzi, E.; Bossert, R.; Caspi, S.; Chlachidize, G.; Dietderich, D.; Feher, S.; Felice, H.; Ferracin, P.; Ghosh, A.; Hafalia, A.R.; Hannaford, C.R.; Kashikhin, V.V.; Kerby, J.; Lamm, M.; Lietzke, A.; McInturff, A.; Muratore, J.; Nobrega, F.; Novitsky, I.; Sabbi, G.L.; Schmalzle, J.; Tartaglia, M.; Turrioni, D.; Wanderer, P.; Whitson, G.; Zlobin, A.V.
2007-08-27
A major milestone for the LHC Accelerator Research Program (LARP) is the test, by the end of 2009, of two 4m-long quadrupole magnets (LQ) wound with Nb{sub 3}Sn conductor. The goal of these magnets is to be a proof of principle that Nb{sub 3}Sn is a viable technology for a possible LHC luminosity upgrade. The design of the LQ is based on the design of the LARP Technological Quadrupoles, presently under development at FNAL and LBNL, with 90-mm aperture and gradient higher than 200 T/m. The design of the first LQ model will be completed by the end of 2007 with the selection of a mechanical design. In this paper we present the coil design addressing some fabrication technology issues, the quench protection study, and three designs of the support structure.
Exterior and interior metrics with quadrupole moment
Quevedo, Hernando
2010-01-01
We present the Ernst potential and the line element of an exact solution of Einstein's vacuum field equations that contains as arbitrary parameters the total mass, the angular momentum, and the quadrupole moment of a rotating mass distribution. We show that in the limiting case of slowly rotating and slightly deformed configuration, there exists a coordinate transformation that relates the exact solution with the approximate Hartle solution. It is shown that this approximate solution can be smoothly matched with an interior perfect fluid solution with physically reasonable properties. This opens the possibility of considering the quadrupole moment as an additional physical degree of freedom that could be used to search for a realistic exact solution, representing both the interior and exterior gravitational field generated by a self-gravitating axisymmetric distribution of mass of perfect fluid in stationary rotation.
Yudistira, D; Boes, A; Djafari-Rouhani, B; Pennec, Y; Yeo, L Y; Mitchell, A; Friend, J R
2014-11-21
We theoretically and experimentally demonstrate the existence of complete surface acoustic wave band gaps in surface phonon-polariton phononic crystals, in a completely monolithic structure formed from a two-dimensional honeycomb array of hexagonal shape domain-inverted inclusions in single crystal piezoelectric Z-cut lithium niobate. The band gaps appear at a frequency of about twice the Bragg band gap at the center of the Brillouin zone, formed through phonon-polariton coupling. The structure is mechanically, electromagnetically, and topographically homogeneous, without any physical alteration of the surface, offering an ideal platform for many acoustic wave applications for photonics, phononics, and microfluidics.
Theory of temperature dependent phonon-renormalized properties
Monserrat, Bartomeu; Conduit, G. J.; Needs, R. J.
2013-01-01
We present a general harmonic theory for the temperature dependence of phonon-renormalized properties of solids. Firstly, we formulate a perturbation theory in phonon-phonon interactions to calculate the phonon renormalization of physical quantities. Secondly, we propose two new schemes for extrapolating phonon zero-point corrections from temperature dependent data that improve the accuracy by an order of magnitude compared to previous approaches. Finally, we consider the low-temperature limi...
Splice testing for LHC quadrupole magnets
Barzi, E; Fehér, S; Kashikhin, V V; Kerby, J S; Lamm, M J; Orris, D; Ray, G; Tartaglia, M; Zlobin, A V
2003-01-01
Electrical splices between NbTi Rutherford type cables need to be made for the LHC IR inner triplet quadrupoles. Splices between magnets as well as internal to the magnets are necessary. Various splice configurations, solders, and fluxes have been considered. Testing of these splices at cryogenic temperatures and at various currents has been completed. The results were satisfactory; Fermilab is capable of making excellent low resistance (<1n Omega ) solder joints for the LHC project. (4 refs).
Electrostatic quadrupole DC accelerators for BNCT applications
Kwan, J.W.; Anderson, O.A.; Reginato, L.L.; Vella, M.C.; Yu, S.S.
1994-04-01
A dc electrostatic quadrupole (ESQ) accelerator is capable of producing a 2.5 MeV, 100 mA proton beam for the purpose of generating neutrons for Boron Neutron Capture Therapy. The ESQ accelerator is better than the conventional aperture column in high beam current application due to the presence of stronger transverse field for beam focusing and for suppressing secondary electrons. The major challenge in this type of accelerator is in developing the proper power supply system.
Quadrupole transitions revealed by Borrmann spectroscopy.
Pettifer, Robert F; Collins, Stephen P; Laundy, David
2008-07-10
The Borrmann effect-a dramatic increase in transparency to X-ray beams-is observed when X-rays satisfying Bragg's law diffract through a perfect crystal. The minimization of absorption seen in the Borrmann effect has been explained by noting that the electric field of the X-ray beam approaches zero amplitude at the crystal planes, thus avoiding the atoms. Here we show experimentally that under conditions of absorption suppression, the weaker electric quadrupole absorption transitions are effectively enhanced to such a degree that they can dominate the absorption spectrum. This effect can be exploited as an atomic spectroscopy technique; we show that quadrupole transitions give rise to additional structure at the L(1), L(2) and L(3) absorption edges of gadolinium in gadolinium gallium garnet, which mark the onset of excitations from 2s, 2p(1/2) and 2p(3/2) atomic core levels, respectively. Although the Borrmann effect served to underpin the development of the theory of X-ray diffraction, this is potentially the most important experimental application of the phenomenon since its first observation seven decades ago. Identifying quadrupole features in X-ray absorption spectroscopy is central to the interpretation of 'pre-edge' spectra, which are often taken to be indicators of local symmetry, valence and atomic environment. Quadrupolar absorption isolates states of different symmetries to that of the dominant dipole spectrum, and typically reveals orbitals that dominate the electronic ground-state properties of lanthanides and 3d transition metals, including magnetism. Results from our Borrmann spectroscopy technique feed into contemporary discussions regarding resonant X-ray diffraction and the nature of pre-edge lines identified by inelastic X-ray scattering. Furthermore, because the Borrmann effect has been observed in photonic materials, it seems likely that the quadrupole enhancement reported here will play an important role in modern optics.
TOUTATIS: A radio frequency quadrupole code
Romuald Duperrier
2000-01-01
A cw high power linear accelerator can only work with very low particle losses and structure activation. At low energy, the radio frequency quadrupole (RFQ) is an accelerator element that is very sensitive to losses. To design this structure, a good understanding of the beam dynamics is required. Generally, the reference code PARMTEQM is enough to design the accelerator. TOUTATIS has been written with the goals of cross-checking results and obtaining more reliable dynamics. This paper relates...
Influence of phonons on semiconductor quantum emission
Feldtmann, Thomas
2009-07-06
A microscopic theory of interacting charge carriers, lattice vibrations, and light modes in semiconductor systems is presented. The theory is applied to study quantum dots and phonon-assisted luminescence in bulk semiconductors and heterostructures. (orig.)
Length-scale dependent phonon interactions
Srivastava, Gyaneshwar
2014-01-01
This book presents a comprehensive description of phonons and their interactions in systems with different dimensions and length scales. Internationally-recognized leaders describe theories and measurements of phonon interactions in relation to the design of materials with exotic properties such as metamaterials, nano-mechanical systems, next-generation electronic, photonic, and acoustic devices, energy harvesting, optical information storage, and applications of phonon lasers in a variety of fields. The emergence of techniques for control of semiconductor properties and geometry has enabled engineers to design structures in which functionality is derived from controlling electron behavior. As manufacturing techniques have greatly expanded the list of available materials and the range of attainable length scales, similar opportunities now exist for designing devices whose functionality is derived from controlling phonon behavior. However, progress in this area is hampered by gaps in our knowledge of phono...
Watching surface waves in phononic crystals.
Wright, Oliver B; Matsuda, Osamu
2015-08-28
In this paper, we review results obtained by ultrafast imaging of gigahertz surface acoustic waves in surface phononic crystals with one- and two-dimensional periodicities. By use of quasi-point-source optical excitation, we show how, from a series of images that form a movie of the travelling waves, the dispersion relation of the acoustic modes, their corresponding mode patterns and the position and widths of phonon stop bands can be obtained by temporal and spatio-temporal Fourier analysis. We further demonstrate how one can follow the temporal evolution of phononic eigenstates in k-space using data from phononic-crystal waveguides as an example. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
Nanoscale pillar hypersonic surface phononic crystals
Yudistira, D.; Boes, A.; Graczykowski, B.; Alzina, F.; Yeo, L. Y.; Sotomayor Torres, C. M.; Mitchell, A.
2016-09-01
We report on nanoscale pillar-based hypersonic phononic crystals in single crystal Z-cut lithium niobate. The phononic crystal is formed by a two-dimensional periodic array of nearly cylindrical nanopillars 240 nm in diameter and 225 nm in height, arranged in a triangular lattice with a 300-nm lattice constant. The nanopillars are fabricated by the recently introduced nanodomain engineering via laser irradiation of patterned chrome followed by wet etching. Numerical simulations and direct measurements using Brillouin light scattering confirm the simultaneous existence of nonradiative complete surface phononic band gaps. The band gaps are found below the sound line at hypersonic frequencies in the range 2-7 GHz, formed from local resonances and Bragg scattering. These hypersonic structures are realized directly in the piezoelectric material lithium niobate enabling phonon manipulation at significantly higher frequencies than previously possible with this platform, opening new opportunities for many applications in plasmonic, optomechanic, microfluidic, and thermal engineering.
Acoustic and optical phonons in metallic diamond
M. Hoesch, T. Fukuda, T. Takenouchi, J.P. Sutter, S. Tsutsui, A.Q.R. Baron, M. Nagao, Y. Takano, H. Kawarada and J. Mizuki
2006-01-01
Full Text Available The dispersion of acoustic and optical phonons in highly boron-doped diamond has been measured by inelastic X-ray scattering at an energy resolution of 6.4 meV. The sample is doped in the metallic regime and shows superconductivity below 4.2 K (midpoint. The data are compared to pure and nitrogen-doped diamond that represent the non-metallic state. No difference is found for the acoustic phonons in the three samples, while the optical phonons show a shift of the dispersion (softening in qualitative agreement with earlier results from Raman spectroscopy. The presence of boron and nitrogen incorporated into the diamond lattice leads to structural disorder. Evidence for this is found both in the observation of otherwise symmetry-forbidded Bragg intensity at (0 0 2 and intensity from acoustic phonon modes in the vicinity of (0 0 2.
Acoustic Phonon Thermal Transport through a Nanostructure
LI Wen-Xia; LIU Tian-Yu; LIU Chang-Long
2006-01-01
@@ Using the scattering matrix method, we investigate the thermal transport in a nanostructure at low temperatures.It is found that phonon transport exhibits some novel and interesting features: resonant transmission, resonant reflection, and small thermal conductance.
Single-photon indistinguishability: influence of phonons
Nielsen, Per Kær; Lodahl, Peter; Jauho, Antti-Pekka
2012-01-01
effects is important in linear optical quantum computing [1], where a device emitting fully coherent indistinguishable single photons on demand, is the essential ingredient. In this contribution we present a numerically exact simulation of the effect of phonons on the degree of indistinguishability......Recent years have demonstrated that the interaction with phonons plays an important role in semiconductor based cavity QED systems [2], consisting of a quantum dot (QD) coupled to a single cavity mode [Fig. 1(a)], where the phonon interaction is the main decoherence mechanism. Avoiding decoherence...... of photons emitted from a solid-state cavity QED system. Our model rigorously describes non-Markovian effects to all orders in the phonon coupling constant, being based on an exact diagonalization procedure accounting for the time evoluiton of one-time and two-time photon correlation funcitons. We compare...
Seweryniak D.
2012-12-01
Full Text Available The chain of Barium isotopes enables us to study experimentally the evolution of nuclear quadrupole collectivity from the shell closure at N = 82 towards neutron-deficient or neutron-rich deformed nuclei. The TU Darmstadt group has investigated several nuclei from stable 130,132Ba up to radioactive 140,142Ba with the projectile-Coulomb excitation technique including the use of the Doppler-shift attenuation method (DSAM. Lifetimes of quadrupole-collective states of 132Ba and 140Ba were obtained for the first time as well as the static electric quadrupole moments Q(21+ for 130,132Ba and 140,142Ba. The results are compared to Monte Carlo shell model and Beyond-Mean-Field calculations. The phenomenon of shell stabilization in the N = 80 isotones is further investigated by measurements of the B(E2;21+ → 01+ values of 140Nd and 142Sm and comparison to the quasi-particle phonon model and shell-model calculations.
CLIC quadrupole stabilization and nano-positioning
Collette, C; Artoos, K; Fernandez Carmona, P; Guinchard, M; Hauviller, C
2010-01-01
In the Compact LInear Collider (CLIC) currently under study, electrons and positrons will be accelerated in two linear accelerators to collide at the interaction point with an energy of 0.5- 3 TeV. This machine is constituted of a succession of accelerating structures, used to accelerate the beams of particles, and electromagnets (quadrupoles) used to focus the beams. In order to ensure good performances, the quadrupoles have to be extremely stable. Additionally, they should also have the capability to move by steps of some tens of nanometers every 20 ms with a precision of +/- 1nm. This paper proposes a holistic approach to fulfill alternatively both requirements using the same device. The concept is based on piezoelectric hard mounts to isolate the quadrupoles from the ground vibrations in the sensitive range between 1 and 20 Hz, and to provide nano-positioning capabilities. It is also shown that this strategy ensures robustness to external forces (acoustic noise, water flow for the cooling, air flow for th...
Table of nuclear electric quadrupole moments
Stone, N. J.
2016-09-01
This Table is a compilation of experimental measurements of static electric quadrupole moments of ground states and excited states of atomic nuclei throughout the periodic table. To aid identification of the states, their excitation energy, half-life, spin and parity are given, along with a brief indication of the method and any reference standard used in the particular measurement. Experimental data from all quadrupole moment measurements actually provide a value of the product of the moment and the electric field gradient [EFG] acting at the nucleus. Knowledge of the EFG is thus necessary to extract the quadrupole moment. A single recommended moment value is given for each state, based, for each element, wherever possible, upon a standard reference moment for a nuclear state of that element studied in a situation in which the electric field gradient has been well calculated. For several elements one or more subsidiary EFG/moment reference is required and their use is specified. The literature search covers the period to mid-2015.
Strongly Nonlinear Transverse Perturbations in Phononic Crystals
S. Nikitenkova
2014-01-01
Full Text Available The dynamics of the surface heterogeneities formation in low-dimensional phononic crystals is studied. It is shown that phononic transverse perturbations in this medium are highly nonlinear. They can be described with the help of the Riemann wave and may form stable wave structures of the finite amplitude. The Riemann wave deformation is described analytically. The Riemann wave time existence up to the beginning of the gradient catastrophe is calculated.
Phonon broadening in high entropy alloys
Körmann, Fritz; Ikeda, Yuji; Grabowski, Blazej; Sluiter, Marcel H. F.
2017-09-01
Refractory high entropy alloys feature outstanding properties making them a promising materials class for next-generation high-temperature applications. At high temperatures, materials properties are strongly affected by lattice vibrations (phonons). Phonons critically influence thermal stability, thermodynamic and elastic properties, as well as thermal conductivity. In contrast to perfect crystals and ordered alloys, the inherently present mass and force constant fluctuations in multi-component random alloys (high entropy alloys) can induce significant phonon scattering and broadening. Despite their importance, phonon scattering and broadening have so far only scarcely been investigated for high entropy alloys. We tackle this challenge from a theoretical perspective and employ ab initio calculations to systematically study the impact of force constant and mass fluctuations on the phonon spectral functions of 12 body-centered cubic random alloys, from binaries up to 5-component high entropy alloys, addressing the key question of how chemical complexity impacts phonons. We find that it is crucial to include both mass and force constant fluctuations. If one or the other is neglected, qualitatively wrong results can be obtained such as artificial phonon band gaps. We analyze how the results obtained for the phonons translate into thermodynamically integrated quantities, specifically the vibrational entropy. Changes in the vibrational entropy with increasing the number of elements can be as large as changes in the configurational entropy and are thus important for phase stability considerations. The set of studied alloys includes MoTa, MoTaNb, MoTaNbW, MoTaNbWV, VW, VWNb, VWTa, VWNbTa, VTaNbTi, VWNbTaTi, HfZrNb, HfMoTaTiZr.
Phonon Cooling by an Optomechanical Heat Pump.
Dong, Ying; Bariani, F; Meystre, P
2015-11-27
We propose and analyze theoretically a cavity optomechanical analog of a heat pump that uses a polariton fluid to cool mechanical modes coupled to a single precooled phonon mode via external modulation of the substrate of the mechanical resonator. This approach permits us to cool phonon modes of arbitrary frequencies not limited by the cavity-optical field detuning deep into the quantum regime from room temperature.
Singh, P.; Kharb, S.; Singh, M.
2014-02-01
The effects of electric quadrupole ( E2) and dipole-quadrupole interference ( E1- E2) terms in the Coulomb breakup of 15C have been investigated within the framework of eikonal approximation. The sensitivity of Coulomb breakup cross section, differential in relative energy and Longitudinal Momentum Distribution (LMD) of core fragments, towards these terms have been examined. A very small (1% of E1) contribution of E2 transition has been predicted in integrated Coulomb breakup cross section. Further it is also found that the inclusion of E2 and E1- E2 terms introduces a small asymmetry in the peak of relative energy spectrum and also increases the peak height of the spectrum. The contribution of dipole-quadrupole interference terms is clearly shown in LMD, as it introduces an asymmetry in the shape of LMD and enhances the matching between the data and predictions.
Squeezed Phonons: Modulating Quantum Fluctuations of Atomic Displacements.
Hu, Xuedong; Nori, Franco
1997-03-01
We have studied phonon squeezed states and also put forward several proposals for their generation(On phonon parametric process, X. Hu and F. Nori, Phys. Rev. Lett. 76), 2294 (1996); on polariton mechanism, X. Hu and F. Nori, Phys. Rev. B 53, 2419 (1996); on second-order Raman scattering, X. Hu and F. Nori, preprint.. Here, we compare the relative merits and limitations of these approaches, including several factors that will limit the amount of phonon squeezing. In particular, we investigate the effect of the initial thermal states on the phonon modes. Using a model for the phonon density matrix, we also study the mixing of the phonon squeezed states with thermal states, which describes the decay of the phonon coherence. Finally, we calculate the maximum possible squeezing from a phonon parametric process limited by phonon decay.
Lüer, Larry; Gadermaier, Christoph; Crochet, Jared; Hertel, Tobias; Brida, Daniele; Lanzani, Guglielmo
2009-03-27
We excite and detect coherent phonons in semiconducting (6,5) carbon nanotubes via a sub-10-fs pump-probe technique. Simulation of the amplitude and phase profile via time-dependent wave packet theory yields excellent agreement with experimental results under the assumption of molecular excitonic states and allows determining the electron-phonon coupling strength for the two dominant vibrational modes.
Rury, Aaron S.
2016-06-01
This study reports experimental, computational, and theoretical evidence for a previously unobserved coherent phonon-phonon interaction in an organic solid that can be described by the application of Fano's analysis to a case without the presence of a continuum. Using Raman spectroscopy of the hydrogen-bonded charge-transfer material quinhydrone, two peaks appear near 700 cm-1 we assign as phonons whose position and line-shape asymmetry depend on the sample temperature and light scattering excitation energy. Density functional theory calculations find two nearly degenerate phonons possessing frequencies near the values found in experiment that share similar atomic motion out of the aromatic plane of electron donor and acceptor molecules of quinhydrone. Further analytical modeling of the steady-state light scattering process using the Peierls-Hubbard Hamiltonian and time-dependent perturbation theory motivates assignment of the physical origin of the asymmetric features of each peak's line shape to an interaction between two discrete phonons via nonlinear electron-phonon coupling. In the context of analytical model results, characteristics of the experimental spectra upon 2.33 eV excitation of the Raman scattering process are used to qualify the temperature dependence of the magnitude of this coupling in the valence band of quinhydrone. These results broaden the range of phonon-phonon interactions in materials in general while also highlighting the rich physics and fundamental attributes specific to organic solids that may determine their applicability in next generation electronics and photonics technologies.
Nuclear electric quadrupole interactions in liquids entrapped in cavities
Furman, Gregory B., E-mail: gregoryf@bgu.ac.il; Meerovich, Victor M.; Sokolovsky, Vladimir L. [Ben Gurion University of the Negev, Physics Department (Israel)
2016-12-15
Liquids entrapped in cavities and containing quadrupole nuclei are considered. The interaction of the quadrupole moment of a nucleus with the electric field gradient is studied. In such a system, molecules are in both rotational and translational Brownian motions which are described by the diffusion equation. Solving this equation, we show that the intra- and intermolecular nuclear quadrupole interactions are averaged to zero in cavities with the size larger than several angstroms.
Phonon surface mapping of graphite: Disentangling quasi-degenerate phonon dispersions
Grüneis, A.; Serrano, J.; Bosak, A.; Lazzeri, M.; Molodtsov, S. L.; Wirtz, L.; Attaccalite, C.; Krisch, M.; Rubio, A.; Mauri, F.; Pichler, T.
2009-08-01
The two-dimensional mapping of the phonon dispersions around the K point of graphite by inelastic x-ray scattering is provided. The present work resolves the longstanding issue related to the correct assignment of transverse and longitudinal phonon branches at K . We observe an almost degeneracy of the three TO-, LA-, and LO-derived phonon branches and a strong phonon trigonal warping. Correlation effects renormalize the Kohn anomaly of the TO mode, which exhibits a trigonal warping effect opposite to that of the electronic band structure. We determined the electron-phonon coupling constant to be 166(eV/Å)2 in excellent agreement to GW calculations. These results are fundamental for understanding angle-resolved photoemission, double-resonance Raman and transport measurements of graphene-based systems.
Magnetic mirror structure for testing shell-type quadrupole coils
Andreev, N.; Barzi, E.; Bossert, R.; Chlachidze, G.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; Nobrega, F.; Novitski, I.; Tartaglia, N.; Turrioni, D.; /Fermilab
2009-10-01
This paper presents magnetic and mechanical designs and analyses of the quadrupole mirror structure to test single shell-type quadrupole coils. Several quadrupole coils made of different Nb{sub 3}Sn strands, cable insulation and pole materials were tested using this structure at 4.5 and 1.9 K. The coils were instrumented with voltage taps, spot heaters, temperature sensors and strain gauges to study their mechanical and thermal properties and quench performance. The results of the quadrupole mirror model assembly and test are reported and discussed.
Magnetic mirror structure for testing shell-type quadrupole coils
Andreev, N.; Barzi, E.; Bossert, R.; Chlachidze, G.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; Nobrega, F.; Novitski, I.; Tartaglia, N.; Turrioni, D.; /Fermilab
2009-10-01
This paper presents magnetic and mechanical designs and analyses of the quadrupole mirror structure to test single shell-type quadrupole coils. Several quadrupole coils made of different Nb{sub 3}Sn strands, cable insulation and pole materials were tested using this structure at 4.5 and 1.9 K. The coils were instrumented with voltage taps, spot heaters, temperature sensors and strain gauges to study their mechanical and thermal properties and quench performance. The results of the quadrupole mirror model assembly and test are reported and discussed.
Trainor, Thomas A
2016-01-01
According to the flow narrative commonly applied to high-energy nuclear collisions a 1D cylindrical-quadrupole component of 2D angular correlations conventionally denoted by quantity $v_2$ is interpreted to represent elliptic flow: azimuth modulation of transverse or radial flow in noncentral nucleus-nucleus (A-A) collisions. The nonjet (NJ) quadrupole component exhibits various properties inconsistent with a flow or hydro interpretation, including the observation that NJ-quadrupole centrality variation in $A$-$A$ collisions has no relation to strongly-varying jet modification ("jet quenching") in those collisions commonly attributed to jet interaction with a dense flowing medium. In the present study I report isolation of quadrupole spectra from $p_t$-differential $v_2(p_t)$ data obtained at the relativistic heavy ion collider (RHIC) and large hadron collider (LHCr). I demonstrate that NJ quadrupole spectra have characteristics very different from the single-particle spectra for most hadrons, that quadrupole...
Quadrupole Transfer Function for Emittance Measurement
Cameron, Peter; Jansson, Andreas; Tan, Cheng-Yang
2008-01-01
Historically the use of the quadrupole moment measurement has been impeded by the requirement for large dynamic range, as well as measurement sensitivity to beam position. We investigate the use of the transfer function technique [1-3] in combination with the sensitivity and 160dB revolution line rejection of the direct diode detection analog front end [4] to open the possibility of an emittance diagnostic that may be implemented without operational complication, quasi- parasitic to the operation of existing tune measurement systems. Such a diagnostic would be particularly useful as an emittance monitor during acceleration ramp development in machines like RHIC and the LHC.
A Compact High Gradient Pulsed Magnetic Quadrupole
Shuman, Derek; Kireeff Covo, Michel; Ritchie, Gary; Seidl, Peter
2005-01-01
A design for a high gradient, low inductance pulsed quadrupole magnet is presented. The magnet is a circular current dominated design with a circular iron return yoke. Features include a five turn eddy current compensated solid conductor coil design which theoretically eliminates the first four higher order multipole field components, a single layer "non-spiral bedstead" coil design which both minimizes utilization of radial space and maximizes utilization of axial space, and allows incorporation of steering and correction coils within existing radial space. The coils are wound and stretched straight in a special winder, then bent in simple fixtures to form the upturned ends, simplifying fabrication and assembly.
Multi-Pass Quadrupole Mass Analyzer
Prestage, John D.
2013-01-01
Analysis of the composition of planetary atmospheres is one of the most important and fundamental measurements in planetary robotic exploration. Quadrupole mass analyzers (QMAs) are the primary tool used to execute these investigations, but reductions in size of these instruments has sacrificed mass resolving power so that the best present-day QMA devices are still large, expensive, and do not deliver performance of laboratory instruments. An ultra-high-resolution QMA was developed to resolve N2 +/CO+ by trapping ions in a linear trap quadrupole filter. Because N2 and CO are resolved, gas chromatography columns used to separate species before analysis are eliminated, greatly simplifying gas analysis instrumentation. For highest performance, the ion trap mode is used. High-resolution (or narrow-band) mass selection is carried out in the central region, but near the DC electrodes at each end, RF/DC field settings are adjusted to allow broadband ion passage. This is to prevent ion loss during ion reflection at each end. Ions are created inside the trap so that low-energy particles are selected by low-voltage settings on the end electrodes. This is beneficial to good mass resolution since low-energy particles traverse many cycles of the RF filtering fields. Through Monte Carlo simulations, it is shown that ions are reflected at each end many tens of times, each time being sent back through the central section of the quadrupole where ultrahigh mass filtering is carried out. An analyzer was produced with electrical length orders of magnitude longer than its physical length. Since the selector fields are sized as in conventional devices, the loss of sensitivity inherent in miniaturizing quadrupole instruments is avoided. The no-loss, multi-pass QMA architecture will improve mass resolution of planetary QMA instruments while reducing demands on the RF electronics for high-voltage/high-frequency production since ion transit time is no longer limited to a single pass. The
Nuclear quadrupole resonance echoes from hexamethylenetetramine.
Ota, Go; Itozaki, Hideo
2006-10-01
We investigated the echo phenomenon of nuclear quadrupole resonance (NQR) from hexamethylenetetramine (HMT). We detected the pure NQR echo signal of HMT with a short pulse interval. The intensity of the echo signal increased as the pulse interval time was decreased. We observed that a clean echo signal was generated even when the pulse interval was shorter than the decay time constant T(2)(*). Since the short interval time gives a strong echo, our result insists that shorter interval time is preferred for the NQR detection.
Precise calculations of the deuteron quadrupole moment
Gross, Franz L. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-06-01
Recently, two calculations of the deuteron quadrupole moment have have given predictions that agree with the measured value to within 1%, resolving a long-standing discrepancy. One of these uses the covariant spectator theory (CST) and the other chiral effective field theory (cEFT). In this talk I will first briefly review the foundations and history of the CST, and then compare these two calculations with emphasis on how the same physical processes are being described using very different language. The comparison of the two methods gives new insights into the dynamics of the low energy NN interaction.
Phonon Recycling for Ultrasensitive Kinetic Inductance Detectors
Zmuidzinas, Jonas
Initially proposed (Day et al. 2003; Zmuidzinas 2012) in 1999 by our Caltech/JPL group, and thanks to strong support from NASA, the superconducting (microwave) kinetic inductance detector (MKID or KID) technology continues to develop rapidly as it transitions into applications. The development effort worldwide is intensifying and NASA's continued support of KID development is essential in order to keep pace. Here we propose to investigate and demonstrate a new, low-TRL concept, which we call phonon recycling, that promises to open broad new avenues in KID design and performance. Briefly, phonon recycling allows the detector designer to tailor the responsivity and sensitivity of a KID to match the needs of the application by using geometry to restrict the rate at which recombination phonons are allowed to escape from the detector. In particular, phonon recycling should allow very low noise-equivalent power (NEP) to be achieved without requiring very low operating tem- peratures. Phonon recycling is analogous to the use of micromachined suspension legs to control the flow of heat in a bolometer, as measured by the thermal conductivity G. However, phonon recycling exploits the non-thermal distribution of recombination phonons as well as their very slow decay in crystals at low temperatures. These properties translate to geometrical and mechanical requirements for a phonon-recycled KID that are considerably more relaxed than for a bolometer operating at the same temperature and NEP. Our ultimate goal is to develop detector arrays suitable for a far-infrared (FIR) space mission, which will impose strict requirements on the array sensitivity, yield, uniformity, multiplexing density, etc. Through previous NASA support under the Strategic Astrophysics Technology (SAT) program, we have successfully demonstrated the MAKO submillimeter camera at the Caltech Submillimeter Observatory and have become familiar with these practical issues. If our demonstration of phonon recycling
Coherent phonons in carbon based nanostructures
Sanders, G. D.; Nugraha, A. R. T.; Sato, K.; Kim, J.-H.; Lim, Y.-S.; Kono, J.; Saito, R.; Stanton, C. J.
2014-06-01
We have developed a theory for the generation and detection of coherent phonons in carbon based nanotstructures such as single walled nanotubes (SWNTs), graphene, and graphene nanoribbons. Coherent phonons are generated via the deformation potential electron/hole-phonon interaction with ultrafast photo-excited carriers. They modulate the reflectance or absorption of an optical probe pules on a THz time scale and might be useful for optical modulators. In our theory the electronic states are treated in a third nearest neighbor extended tight binding formalism which gives a good description of the states over the entire Brillouin zone while the phonon states are treated using valence force field models which include bond stretching, in-plane and out-of-plane bond bending, and bond twisting interactions up to fourth neighbor distances. We compare our theory to experiments for the low frequency radial breathing mode (RBM) in micelle suspended single-walled nanotubes (SWNTs). The analysis of such data provides a wealth of information on the dynamics and interplay of photons, phonons and electrons in these carbon based nanostructures.
Ionizing particle detection based on phononic crystals
Aly, Arafa H.; Mehaney, Ahmed; Eissa, Mostafa F.
2015-08-01
Most conventional radiation detectors are based on electronic or photon collections. In this work, we introduce a new and novel type of ionizing particle detector based on phonon collection. Helium ion radiation treats tumors with better precision. There are nine known isotopes of helium, but only helium-3 and helium-4 are stable. Helium-4 is formed in fusion reactor technology and in enormous quantities during Big Bang nucleo-synthesis. In this study, we introduce a technique for helium-4 ion detection (sensing) based on the innovative properties of the new composite materials known as phononic crystals (PnCs). PnCs can provide an easy and cheap technique for ion detection compared with conventional methods. PnC structures commonly consist of a periodic array of two or more materials with different elastic properties. The two materials are polymethyl-methacrylate and polyethylene polymers. The calculations showed that the energies lost to target phonons are maximized at 1 keV helium-4 ion energy. There is a correlation between the total phonon energies and the transmittance of PnC structures. The maximum transmission for phonons due to the passage of helium-4 ions was found in the case of making polyethylene as a first layer in the PnC structure. Therefore, the concept of ion detection based on PnC structure is achievable.
Ionizing particle detection based on phononic crystals
Aly, Arafa H., E-mail: arafa16@yahoo.com, E-mail: arafa.hussien@science.bsu.edu.eg; Mehaney, Ahmed; Eissa, Mostafa F. [Physics Department, Faculty of Science, Beni-Suef University, Beni-Suef (Egypt)
2015-08-14
Most conventional radiation detectors are based on electronic or photon collections. In this work, we introduce a new and novel type of ionizing particle detector based on phonon collection. Helium ion radiation treats tumors with better precision. There are nine known isotopes of helium, but only helium-3 and helium-4 are stable. Helium-4 is formed in fusion reactor technology and in enormous quantities during Big Bang nucleo-synthesis. In this study, we introduce a technique for helium-4 ion detection (sensing) based on the innovative properties of the new composite materials known as phononic crystals (PnCs). PnCs can provide an easy and cheap technique for ion detection compared with conventional methods. PnC structures commonly consist of a periodic array of two or more materials with different elastic properties. The two materials are polymethyl-methacrylate and polyethylene polymers. The calculations showed that the energies lost to target phonons are maximized at 1 keV helium-4 ion energy. There is a correlation between the total phonon energies and the transmittance of PnC structures. The maximum transmission for phonons due to the passage of helium-4 ions was found in the case of making polyethylene as a first layer in the PnC structure. Therefore, the concept of ion detection based on PnC structure is achievable.
Kuleyev, I. G., E-mail: kuleev@imp.uran.ru; Kuleyev, I. I.; Bakharev, S. M.; Ustinov, V. V. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)
2016-09-15
We study the effect of anisotropy in elastic properties on the electron–phonon drag and thermoelectric phenomena in gapless semiconductors with degenerate charge-carrier statistics. It is shown that phonon focusing leads to a number of new effects in the drag thermopower at low temperatures, when diffusive phonon scattering from the boundaries is the predominant relaxation mechanism. We analyze the effect of phonon focusing on the dependences of the thermoelectromotive force (thermopower) in HgSe:Fe crystals on geometric parameters and the heat-flow directions relative to the crystal axes in the Knudsen regime of the phonon gas flow. The crystallographic directions that ensure the maximum and minimum values of the thermopower are determined and the role of quasi-longitudinal and quasi-transverse phonons in the drag thermopower in HgSe:Fe crystals at low temperatures is analyzed. It is shown that the main contribution to the drag thermopower comes from slow quasi-transverse phonons in the directions of focusing in long samples.
Phonon tunneling through a double barrier system
Villegas, Diosdado [Departamento de Física, Universidad Central “Marta Abreu” de Las Villas, CP 54830, Santa Clara, Villa Clara (Cuba); Instituto de Física, Universidad Autónoma de Puebla, 18 Sur y San Claudio, Edif. 110A, Ciudad Universitaria, 72570 Puebla (Mexico); León-Pérez, Fernando de [Centro Universitario de la Defensa de Zaragoza, Ctra. de Huesca s/n, E-50090 Zaragoza (Spain); Pérez-Álvarez, R. [Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca (Mexico); Arriaga, J., E-mail: arriaga@ifuap.buap.mx [Instituto de Física, Universidad Autónoma de Puebla, 18 Sur y San Claudio, Edif. 110A, Ciudad Universitaria, 72570 Puebla (Mexico)
2015-04-15
The tunneling of optical and acoustic phonons at normal incidence on a double-barrier is studied in this paper. Transmission coefficients and resonance conditions are derived theoretically under the assumption that the long-wavelength approximation is valid. It is shown that the behavior of the transmission coefficients for the symmetric double barrier has a Lorentzian form close to resonant frequencies and that Breit–Wigner's formula have a general validity in one-dimensional phonon tunneling. Authors also study the so-called generalized Hartman effect in the tunneling of long-wavelength phonons and show that this effect is a numerical artifact resulting from taking the opaque limit before exploring the variation with a finite barrier width. This study could be useful for the design of acoustic devices.
Phonon heat transport in gallium arsenide
Richa Saini; Vinod Ashokan; B D Indu; R Kumar
2012-03-01
The lifetimes of quantum excitations are directly related to the electron and phonon energy linewidths of a particular scattering event. Using the versatile double time thermodynamic Green’s function approach based on many-body theory, an ab-initio formulation of relaxation times of various contributing processes has been investigated with newer understanding in terms of the linewidths of electrons and phonons. The energy linewidth is found to be an extremely sensitive quantity in the transport phenomena of crystalline solids as a collection of large number of scattering processes, namely, boundary scattering, impurity scattering, multiphonon scattering, interference scattering, electron–phonon processes and resonance scattering. The lattice thermal conductivities of three samples of GaAs have been analysed on the basis of modiﬁed Callaway model and a fairly good agreement between theory and experimental observations has been reported.
Toward quantitative modeling of silicon phononic thermocrystals
Lacatena, V. [STMicroelectronics, 850, rue Jean Monnet, F-38926 Crolles (France); IEMN UMR CNRS 8520, Institut d' Electronique, de Microélectronique et de Nanotechnologie, Avenue Poincaré, F-59652 Villeneuve d' Ascq (France); Haras, M.; Robillard, J.-F., E-mail: jean-francois.robillard@isen.iemn.univ-lille1.fr; Dubois, E. [IEMN UMR CNRS 8520, Institut d' Electronique, de Microélectronique et de Nanotechnologie, Avenue Poincaré, F-59652 Villeneuve d' Ascq (France); Monfray, S.; Skotnicki, T. [STMicroelectronics, 850, rue Jean Monnet, F-38926 Crolles (France)
2015-03-16
The wealth of technological patterning technologies of deca-nanometer resolution brings opportunities to artificially modulate thermal transport properties. A promising example is given by the recent concepts of 'thermocrystals' or 'nanophononic crystals' that introduce regular nano-scale inclusions using a pitch scale in between the thermal phonons mean free path and the electron mean free path. In such structures, the lattice thermal conductivity is reduced down to two orders of magnitude with respect to its bulk value. Beyond the promise held by these materials to overcome the well-known “electron crystal-phonon glass” dilemma faced in thermoelectrics, the quantitative prediction of their thermal conductivity poses a challenge. This work paves the way toward understanding and designing silicon nanophononic membranes by means of molecular dynamics simulation. Several systems are studied in order to distinguish the shape contribution from bulk, ultra-thin membranes (8 to 15 nm), 2D phononic crystals, and finally 2D phononic membranes. After having discussed the equilibrium properties of these structures from 300 K to 400 K, the Green-Kubo methodology is used to quantify the thermal conductivity. The results account for several experimental trends and models. It is confirmed that the thin-film geometry as well as the phononic structure act towards a reduction of the thermal conductivity. The further decrease in the phononic engineered membrane clearly demonstrates that both phenomena are cumulative. Finally, limitations of the model and further perspectives are discussed.
A chip-integrated coherent photonic-phononic memory
Merklein, Moritz; Vu, Khu; Madden, Stephen J; Eggleton, Benjamin J
2016-01-01
Controlling and manipulating quanta of coherent acoustic vibrations - phonons - in integrated circuits has recently drawn a lot of attention, as phonons can function as unique links between radiofrequency and optical signals and access quantum regimes. It has been shown that radiofrequency signals can be controlled and stored via piezo-electrically actuated coherent phonons. Coherent phonons, however, can also be directly excited by optical photons through strong acousto-optic coupling in integrated circuits that guide photons as well as phonons. These hypersound phonons have similar wavelength as the exciting optical field but travel at a 5-orders of magnitude lower velocity. This allows the realization of a coherent optical buffer, a long time desired yet elusive device for on-chip optical signal processing. In this letter we demonstrate a coherent on-chip memory storing the entire coherent information carried by light, phase and amplitude, as acoustic phonons. The photonic-phononic memory provides GHz-band...
Theory of coherent phonons in carbon nanotubes and graphene nanoribbons
Sanders, G. D.; Stanton, C. J.; Nugraha, A. R. T.; Saito, R.
2013-03-01
We have performed theoretical studies on generating and detecting coherent radial breathing mode (RBM) phonons in single-walled carbon nanotubes and coherent radial breathing like mode (RBLM) phonons in graphene nanoribbons. A microscopic theory incorporating electronic states, phonon modes, optical matrix elements, and electron-phonon interaction matrix elements allows us to calculate the coherent phonon spectrum. The coherent phonon amplitudes satisfy a driven oscillator equation with a driving term that depends on photoexcited carrier density. We study the coherent phonon spectrum for nanotubes of different chirality and for armchair and zigzag graphene nanoribbons. We compare our results with a simpler, effective mass theory where we find reasonable agreement with the main features of our computed coherent phonon spectrum. Supported by NSF through grants OISE-0968405 and DMR-1105437 and MEXT through grant No. 20241023
Phonon dispersion curves of CsCN
N K Gaur; Preeti Singh; E G Rini; Jyotsna Galgale; R K Singh
2004-08-01
The motivation for the present work was gained from the recent publication on phonon dispersion curves (PDCs) of CsCN from the neutron scattering technique. We have applied the extended three-body force shell model (ETSM) by incorporating the effect of coupling between the translation modes and the orientation of cyanide molecules for the description of phonon dispersion curves of CsCN between the temperatures 195 and 295 K. Our results on PDCs in symmetric direction are in good agreement with the experimental data measured with inelastic neutron scattering technique.
Phonon-Josephson resonances in atomtronic circuits
Bidasyuk, Y. M.; Prikhodko, O. O.; Weyrauch, M.
2016-09-01
We study the resonant excitation of sound modes from Josephson oscillations in Bose-Einstein condensates. From the simulations for various setups using the Gross-Pitaevskii mean-field equations and Josephson equations we observe additional tunneling currents induced by resonant phonons. The proposed experiment may be used for spectroscopy of phonons as well as other low-energy collective excitations in Bose-Einstein condensates. We also argue that the observed effect may mask the observation of Shapiro resonances if not carefully controlled.
Differentially pumped dual linear quadrupole ion trap mass spectrometer
Owen, Benjamin C.; Kenttamaa, Hilkka I.
2015-10-20
The present disclosure provides a new tandem mass spectrometer and methods of using the same for analyzing charged particles. The differentially pumped dual linear quadrupole ion trap mass spectrometer of the present disclose includes a combination of two linear quadrupole (LQIT) mass spectrometers with differentially pumped vacuum chambers.
Differentially pumped dual linear quadrupole ion trap mass spectrometer
Owen, Benjamin C.; Kenttamaa, Hilkka I.
2016-11-15
The present disclosure provides a new tandem mass spectrometer and methods of using the same for analyzing charged particles. The differentially pumped dual linear quadrupole ion trap mass spectrometer of the present disclose includes a combination of two linear quadrupole (LQIT) mass spectrometers with differentially pumped vacuum chambers.
Optical phonons in Ge quantum dots obtained on Si(111)
Talochkin, A B
2002-01-01
The light combination scattering on the optical phonons in the Ge quantum dots, obtained on the Si surface of the (111) orientation through the molecular-beam epitaxy, is studied. The series of lines, connected with the phonon spectrum quantization, was observed. It is shown, that the phonon modes frequencies are well described by the elastic properties and dispersion of the voluminous Ge optical phonons. The value of the Ge quantum dots deformation is determined
Band structure characteristics of T-square fractal phononic crystals
Liu Xiao-Jian; Fan You-Hua
2013-01-01
The T-square fractal two-dimensional phononic crystal model is presented in this article.A comprehensive study is performed for the Bragg scattering and locally resonant fractal phononic crystal.We find that the band structures of the fractal and non-fractal phononic crystals at the same filling ratio are quite different through using the finite element method.The fractal design has an important impact on the band structures of the two-dimensional phononic crystals.
Intrinsic Third Order Aberrations in Electrostatic and Magnetic Quadrupoles
Baartman, R
2015-01-01
Intrinsic aberrations are those which occur due to the finite length of the desired field configuration. They are often loosely ascribed to the fringing field. This is misleading as it implies that the effects can be minimized by shaping the fields. In fact, there is an irreducible component related to the broken symmetry. It is present even in the hard-edge limit, and moreover, the other (soft-edge) effects can be simply ascribed to the intrinsic aberration spread over a finite length. We rederive the aberration formulas for quadrupoles using a Hamiltonian formalism. This allows for an easy comparison of electrostatic and magnetic quadrupoles. For different combinations of large and small emittances in the two transverse planes, it is found that in some situations electrostatic quadrupoles have lower aberrations, while in others, magnetic quadrupoles are better. As well, we discuss the ways in which existing transport codes handle quadrupole fringe fields. Pitfalls are pointed out and improvements proposed.
Rescuing the nonjet (NJ) azimuth quadrupole from the flow narrative
Trainor, Thomas A
2016-01-01
According to the flow narrative commonly applied to high-energy nuclear collisions a cylindrical-quadrupole component of 1D azimuth angular correlations is conventionally denoted by quantity $v_2$ and interpreted to represent elliptic flow. Jet angular correlations may also contribute to $v_2$ data as "nonflow" depending on the method used to calculate $v_2$, but 2D graphical methods are available to insure accurate separation. The nonjet (NJ) quadrupole has various properties inconsistent with a flow interpretation, including the observation that NJ quadrupole centrality variation in A-A collisions has no relation to strongly-varying jet modification ("jet quenching") in those collisions commonly attributed to jet interaction with a flowing dense medium. In this presentation I describe isolation of quadrupole spectra from pt-differential $v_2(p_t)$ data from the RHIC and LHC. I demonstrate that quadrupole spectra have characteristics very different from the single-particle spectra for most hadrons, that quad...
Yi, Kyung-Soo; Kim, Hye-Jung
2017-02-01
We investigate spectral behavior of phonon spectral functions in an interacting multi-component hot carrier plasma. Spectral analysis of various phonon spectral functions is performed considering carrier-phonon channels of polar and nonpolar optical phonons, acoustic deformation-potential, and piezoelectric Coulomb couplings. Effects of phonon self-energy corrections are examined at finite temperature within a random phase approximation extended to include the effects of dynamic screening, plasmon-phonon coupling, and local-field corrections of the plasma species. We provide numerical data for the case of a photo-generated electron-hole plasma formed in a wurtzite GaN. Our result shows the clear significance of the multiplicity of the plasma species in the phonon spectral functions of a multi-component plasma giving rise to a variety of spectral behaviors of carrier-phonon coupled collective modes. A useful sum rule on the plasma-species-resolved dielectric functions is also found.
Manipulating Heat Flow through 3 Dimensional Nanoscale Phononic Crystal Structure
2014-06-02
SUBJECT TERMS phonon transport , Thermoelectric, nano structures, nano photonics 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as...conductivity is also studied. 15. SUBJECT TERMS phonon transport , Thermoelectric, nano structures, nano photonics 16. SECURITY CLASSIFICATION OF: 17...but not yet published L-N Yang, J Chen, N Yang, and B Li, Manipulating Graphene Thermal Conductivity by Phononic
Wang, Yan; Lu, Zexi; Ruan, Xiulin
2016-06-01
The effect of phonon-electron (p-e) scattering on lattice thermal conductivity is investigated for Cu, Ag, Au, Al, Pt, and Ni. We evaluate both phonon-phonon (p-p) and p-e scattering rates from first principles and calculate the lattice thermal conductivity (κL). It is found that p-e scattering plays an important role in determining the κL of Pt and Ni at room temperature, while it has negligible effect on the κL of Cu, Ag, Au, and Al. Specifically, the room temperature κLs of Cu, Ag, Au, and Al predicted from density-functional theory calculations with the local density approximation are 16.9, 5.2, 2.6, and 5.8 W/m K, respectively, when only p-p scattering is considered, while it is almost unchanged when p-e scattering is also taken into account. However, the κL of Pt and Ni is reduced from 7.1 and 33.2 W/m K to 5.8 and 23.2 W/m K by p-e scattering. Even though Al has quite high electron-phonon coupling constant, a quantity that characterizes the rate of heat transfer from hot electrons to cold phonons in the two-temperature model, p-e scattering is not effective in reducing κL owing to the relatively low p-e scattering rates in Al. The difference in the strength of p-e scattering in different metals can be qualitatively understood by checking the amount of electron density of states that is overlapped with the Fermi window. Moreover, κL is found to be comparable to the electronic thermal conductivity in Ni.
Parity-Time Synthetic Phononic Media
Christensen, Johan; Willatzen, Morten; Velasco, V. R.
2016-01-01
, are achieved through electrically biased piezoelectric semiconductors. We study first how wave attenuation and amplification can be tuned, and when combined, can give rise to a phononic PT synthetic media with unidirectional suppressed reflectance, a feature directly applicable to evading sonar detection....
Phonon scattering in graphene over substrate steps
Sevincli, Haldun; Brandbyge, Mads
2014-01-01
We calculate the effect on phonon transport of substrate-induced bends in graphene. We consider bending induced by an abrupt kink in the substrate, and provide results for different step-heights and substrate interaction strengths. We find that individual substrate steps reduce thermal conductance...
``Forbidden'' phonon in the iron chalcogenide series
Fobes, David M.; Zaliznyak, Igor A.; Xu, Zhijun; Gu, Genda; Tranquada, John M.
2015-03-01
Recently, we uncovered evidence for the formation of a bond-order wave (BOW) leading to ferro-orbital order at low temperature, acting to stabilize the bicollinear AFM order, in the iron-rich parent compound, Fe1+yTe. Investigating the inelastic spectra centered near (100) in Fe1+yTe, a signature peak for the BOW formation in the monoclinic phase, we observed an acoustic phonon dispersion in both tetragonal and monoclinic phases. While a structural Bragg peak accompanies the mode in the monoclinic phase, in the tetragonal phase Bragg scattering at this Q is forbidden by symmetry, and we observed no elastic peak. This phonon mode was also observed in superconducting FeTe0.6Se0.4, where structural and magnetic transitions are suppressed. LDA frozen phonon calculations suggested that this mode could result from a spin imbalance between neighboring Fe atoms, but polarized neutron measurements revealed no additional magnetic scattering. We propose that this ``forbidden'' phonon mode may originate from dynamically broken symmetry, perhaps related to the strong dynamic spin correlations in these materials. Work at BNL was supported by BES, US DOE, under Contract No. DE-AC02-98CH10886. Research at ORNL's HFIR and SNS sponsored by Scientific User Facilities Division, BES, US DOE. We acknowledge the support of NIST, in providing neutron research facilities.
Hyperbolic phonon polaritons in hexagonal boron nitride
Dai, Siyuan
2015-03-01
Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. While hyperbolic responses are normally achieved with metamaterials, hexagonal boron nitride (hBN) naturally possesses this property due to the anisotropic phonons in the mid-infrared. Using scattering-type scanning near-field optical microscopy, we studied polaritonic phenomena in hBN. We performed infrared nano-imaging of highly confined and low-loss hyperbolic phonon polaritons in hBN. The polariton wavelength was shown to be governed by the hBN thickness according to a linear law persisting down to few atomic layers [Science, 343, 1125-1129 (2014)]. Additionally, we carried out the modification of hyperbolic response in heterostructures comprised of a mononlayer graphene deposited on hBN. Electrostatic gating of the top graphene layer allows for the modification of wavelength and intensity of hyperbolic phonon polaritons in bulk hBN. The physics of the modification originates from the plasmon-phonon coupling in the hyperbolic medium. Furthermore, we demonstrated the ``hyperlens'' for subdiffractional imaging and focusing using a slab of hBN.
Synthetic thermoelectric materials comprising phononic crystals
El-Kady, Ihab F; Olsson, Roy H; Hopkins, Patrick; Reinke, Charles; Kim, Bongsang
2013-08-13
Synthetic thermoelectric materials comprising phononic crystals can simultaneously have a large Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Such synthetic thermoelectric materials can enable improved thermoelectric devices, such as thermoelectric generators and coolers, with improved performance. Such synthetic thermoelectric materials and devices can be fabricated using techniques that are compatible with standard microelectronics.
Hybrid high gradient permanent magnet quadrupole
N'gotta, P.; Le Bec, G.; Chavanne, J.
2016-12-01
This paper presents an innovative compact permanent magnet quadrupole with a strong gradient for potential use in future light source lattices. Its magnetic structure includes simple mechanical parts, rectangular permanent magnet blocks and soft iron poles. It has a wide aperture in the horizontal plane to accommodate an x-ray beam port, a common constraint in storage ring-based light sources. This specificity introduces field quality deterioration because of the resulting truncation of the poles; a suitable field quality can be restored with an optimized pole shape. A 82 T /m prototype with a bore radius of 12 mm and a 10 mm vertical gap between poles has been constructed and magnetically characterized. Gradient inhomogeneities better than 10-3 in the good field region were obtained after the installation of special shims.
Quadrupole magnet for a rapid cycling synchrotron
Witte, H. [Brookhaven National Lab. (BNL), Upton, NY (United States); Berg, J. S. [Brookhaven National Lab. (BNL), Upton, NY (United States)
2015-05-03
Rapid Cycling Synchrotrons (RCS) feature interleaved warm and cold dipole magnets; the field of the warm magnets is used to modulate the average bending field depending on the particle energy. It has been shown that RCS can be an attractive option for fast acceleration of particles, for example, muons, which decay quickly. In previous studies it was demonstrated that in principle warm dipole magnets can be designed which can provide the required ramp rates, which are equivalent to frequencies of about 1 kHz. To reduce the losses it is beneficial to employ two separate materials for the yoke; it was also shown that by employing an optimized excitation coil geometry the eddy current losses are acceptable. In this paper we show that the same principles can be applied to quadrupole magnets targeting 30 T/m with a repetition rate of 1kHz and good field quality.
Quench Protection of the LHC Quadrupole Magnets
Kurfuerst, Christoph; Dehning, Bernd; Sapoinski, Mariusz
2010-01-01
CERNs Large Hadron Collider (LHC) is a new high energy proton accelerator and storage ring. Its design allows to reach unprecedented beam energies and beam intensities, resulting in a largely increased particle physics discovery potential. The combination of its high beam energy and intensity may lead to beam losses which can have a severe impact on the LHC equipment and damage sensitive elements. To protect those and to measure operational losses, a Beam Loss Monitoring system has been installed all along the ring. The protection is achieved by extracting the beam from the ring in case thresholds imposed on measured radiation levels are exceeded. The thresholds are estimated through particle shower simulations. The simulated geometry and physic processes need to be precise in order to determine an optimum value, which therefore assures a high availability of the LHC for operation. This study is focused on the interconnection region between the main dipole and the main quadrupole magnet of the LHC. Six monito...
Atomic Quadrupole Moment Measurement Using Dynamic Decoupling.
Shaniv, R; Akerman, N; Ozeri, R
2016-04-01
We present a method that uses dynamic decoupling of a multilevel quantum probe to distinguish small frequency shifts that depend on m_{j}^{2}, where m_{j}^{2} is the angular momentum of level |j⟩ along the quantization axis, from large noisy shifts that are linear in m_{j}, such as those due to magnetic field noise. Using this method we measured the electric-quadrupole moment of the 4D_{5/2} level in ^{88}Sr^{+} to be 2.973_{-0.033}^{+0.026}ea_{0}^{2}. Our measurement improves the uncertainty of this value by an order of magnitude and thus helps mitigate an important systematic uncertainty in ^{88}Sr^{+} based optical atomic clocks and verifies complicated many-body quantum calculations.
TOUTATIS: A radio frequency quadrupole code
Romuald Duperrier
2000-12-01
Full Text Available A cw high power linear accelerator can only work with very low particle losses and structure activation. At low energy, the radio frequency quadrupole (RFQ is an accelerator element that is very sensitive to losses. To design this structure, a good understanding of the beam dynamics is required. Generally, the reference code PARMTEQM is enough to design the accelerator. TOUTATIS has been written with the goals of cross-checking results and obtaining more reliable dynamics. This paper relates the different numerical methods used in the code. It is time based, using multigrids methods and adaptive mesh for a fine description of the forces without being time consuming. The field is calculated through a Poisson solver and the vanes are fully described, allowing it to properly simulate the coupling gaps and the RFQs extremities. Theoretical and experimental tests are also described and show a good agreement between simulations and reference cases.
Unified theory of electron-phonon renormalization and phonon-assisted optical absorption.
Patrick, Christopher E; Giustino, Feliciano
2014-09-10
We present a theory of electronic excitation energies and optical absorption spectra which incorporates energy-level renormalization and phonon-assisted optical absorption within a unified framework. Using time-independent perturbation theory we show how the standard approaches for studying vibronic effects in molecules and those for addressing electron-phonon interactions in solids correspond to slightly different choices for the non-interacting Hamiltonian. Our present approach naturally leads to the Allen-Heine theory of temperature-dependent energy levels, the Franck-Condon principle, the Herzberg-Teller effect and to phonon-assisted optical absorption in indirect band gap materials. In addition, our theory predicts sub-gap phonon-assisted optical absorption in direct gap materials, as well as an exponential edge which we tentatively assign to the Urbach tail. We also consider a semiclassical approach to the calculation of optical absorption spectra which simultaneously captures energy-level renormalization and phonon-assisted transitions and is especially suited to first-principles electronic structure calculations. We demonstrate this approach by calculating the phonon-assisted optical absorption spectrum of bulk silicon.
Molding Phonon Flow with Symmetry: Rational Design of Hypersonic Phononic Crystals
Koh, Cheong Yang; Thomas, Edwin L.
2009-03-01
Phononic crystals structured at appropriate length scales allow control over the flow of phonons, leading to new possibilities in applications such as heat-management, sound isolation and even energy transfer and conversion. Symmetry provides a unified framework for the interpretation 1D to 3D phononic band structures, allowing utilization of a common set of principles for designing band structures of phononic crystals as well as actual purposeful defects such as waveguide location and boundary termination in finite devices. In this work, we explore the band structure properties of phononic crystals with non-symmorphic space groups, as well as those having quasi-crystalline approximants. We demonstrate gap opening abilities from both anti-crossing and Bragg scattering, as well as unique features like ``sticking'' bands. Symmetry concepts are also powerful means to tune the density of states of the structures. Importantly, we fabricate various theoretical designs and measure their experimental dispersion diagrams for comparison with theoretical calculation. This affords an elegant approach toward a design blueprint for fabricating phononic structures for applications such as opto-acoustic coupling.
The phonon and thermal properties of a ladder nanostructure
M Mardaani
2011-12-01
Full Text Available In this paper, we study the phonon thermal properties of a ladder nanostructure in harmonic approximation. We present a model consisting of two infinite chains with different masses. Then, we investigate the effect of different masses on the phonon spectrum. Moreover, as a specific case, in the absence of the second neighbor interaction, we calculate the phonon density of states/modes. Finally, we consider the thermal conductivity of the system. The results show that the phonon spectrum shifts down to the lower frequencies by increasing the masses. Furthermore, a frequency gap appears in the phonon spectrum. By increasing the springs constants, the thermal conductance decreases.
Molecular dynamics study of phonon screening in graphene
Javvaji, Brahmanandam; Roy Mahapatra, D.; Raha, S.
2014-04-01
Phonon interaction with electrons or phonons or with structural defects result in a phonon mode conversion. The mode conversion is governed by the frequency wave-vector dispersion relation. The control over phonon mode or the screening of phonon in graphene is studied using the propagation of amplitude modulated phonon wave-packet. Control over phonon properties like frequency and velocity opens up several wave guiding, energy transport and thermo-electric applications of graphene. One way to achieve this control is with the introduction of nano-structured scattering in the phonon path. Atomistic model of thermal energy transport is developed which is applicable to devices consisting of source, channel and drain parts. Longitudinal acoustic phononmode is excited fromone end of the device. Molecular dynamics based time integration is adopted for the propagation of excited phonon to the other end of the device. The amount of energy transfer is estimated from the relative change of kinetic energy. Increase in the phonon frequency decreases the kinetic energy transmission linearly in the frequency band of interest. Further reduction in transmission is observed with the tuning of channel height of the device by increasing the boundary scattering. Phonon mode selective transmission control have potential application in thermal insulation or thermo-electric application or photo-thermal amplification.
Phonon density of states in nanocrystalline 57Fe
Ranber Singh; S Prakash; R Meyer; P Entel
2003-03-01
The Born–von Karman model is used to calculate phonon density of states (DOS) of nanocrystalline bcc Fe. It is found that there is an anisotropic stiffening in the interatomic force constants and hence there is shrinking in the nearest-neighbour distances in the nanophase. This leads to additional vibrational modes above the bulk phonons near the bottom of the phonon band. It is found that the high energy phonon modes of nanophase Fe are the surface modes. The calculated phonon DOS closely agree with the experimental data except a peak at 37 meV. The calculated phonon dispersion relations are also compared with those of the bulk phonons and anomalous behaviour is discussed in detail. The speciﬁc heat in nanophase enhances as compared to bulk phase at low temperatures and the calculated Debye temperature agrees with the experimental results. It is predicted that the nanocrystalline Fe may consist of about 14 GPa pressure.
Development of Superconducting Focusing Quadrupoles for Heavy Ion Drivers
Martovetsky, N; Manahan, R; Lietzke, A F
2001-09-10
Heavy Ion Fusion (HIF) is exploring a promising path to a practical inertial-confinement fusion reactor. The associated heavy ion driver will require a large number of focusing quadrupole magnets. A concept for a superconducting quadrupole array, using many simple racetrack coils, was developed at LLNL. Two, single-bore quadrupole prototypes of the same design, with distinctly different conductor, were designed, built, and tested. Both prototypes reached their short sample currents with little or no training. Magnet design, and test results, are presented and discussed.
Emission of nuclear quadrupole resonance from polycrystalline hexamethylenetetramine.
Ota, G; Itozaki, H
2008-03-01
The angular dependence of the nuclear quadrupole resonance (NQR) signal intensity emitted from polycrystalline hexamethylenetetramine has been analytically investigated for all directions for non-contact detection of chemicals by nuclear quadrupole resonance. The field pattern of the NQR signal from a column sample was measured. The emitted patterns were the same as that from a united single magnetic dipole, which fitted well to the estimation based on quadrupole principle axis system. This result is helpful to design an antenna for NQR remote detection.
Yu, Jen-Kan; Mitrovic, Slobodan; Heath, James R.
2016-08-16
A nanomesh phononic structure includes: a sheet including a first material, the sheet having a plurality of phononic-sized features spaced apart at a phononic pitch, the phononic pitch being smaller than or equal to twice a maximum phonon mean free path of the first material and the phononic size being smaller than or equal to the maximum phonon mean free path of the first material.
Kyrchev, G.; Paar, V.
1983-03-01
It is shown that TQM is capable of treating two-nucleon transfer (TNT) reactions in an analogous manner to IBM. A proof that the IBM two-nucleon transfer amplitudes can be identically converted into standard matrix elements for TQM, is presented, using the relation between the Schwinger and Holstein-Primakoff representations of the SU(6) generators.
Spin and quadrupole contributions to the motion of astrophysical binaries
Steinhoff, Jan
2014-01-01
Compact objects in general relativity approximately move along geodesics of spacetime. It is shown that the corrections to geodesic motion due to spin (dipole), quadrupole, and higher multipoles can be modeled by an extension of the point mass action. The quadrupole contributions are discussed in detail for astrophysical objects like neutron stars or black holes. Implications for binaries are analyzed for a small mass ratio situation. There quadrupole effects can encode information about the internal structure of the compact object, e.g., in principle they allow a distinction between black holes and neutron stars, and also different equations of state for the latter. Furthermore, a connection between the relativistic oscillation modes of the object and a dynamical quadrupole evolution is established.
ISR Superconducting Quadrupole under test in its cryostat
1979-01-01
One of the Superconducting Quadrupoles for the ISR high luminosity (low-beta) insertion is seen here during final test in building 230 before installation in the ISR. See also photos 7812609X and 7702690X.
End view of ISR Superconducting Quadrupole in its cryostat
1977-01-01
This view shows the cold mass of the prototype ISR Superconducting Quadrupole suspended to the outer vacuum tank by means of titanium alloy rods.The heat shield wrapped with superinsulation can also be seen. See also photo 7702690X.
Electro-Magnetic Quadrupole Magnets in the LCLS FEL Undulator
Emma, P.
2005-01-31
We discuss various aspects of electro-magnetic quadrupole (EMQ) magnets for the LCLS FEL undulator, including their utility in beam-based alignment (BBA), magnet design issues, and impact on tunnel environment, reliability, and cost.
PRINCIPLE OF SKEW QUADRUPOLE MODULATION TO MEASURE BETATRON COUPLING.
LUO.Y.PILAT,F.ROSER,T.ET AL.
2004-07-05
The measurement of the residual betatron coupling via skew quadrupole modulation is a new diagnostics technique that has been developed and tested at the Relativistic Heavy Ion Collider (RHIC) as a very promising method for the linear decoupling on the ramp. By modulating the strengths of different skew quadrupole families the two eigentunes are precisely measured with the phase lock loop system. The projections of the residual coupling coefficient onto the skew quadrupole coupling modulation directions are determined. The residual linear coupling could be corrected according to the measurement. An analytical solution for skew quadrupole modulation based on Hamiltonian perturbation approximation is given, and simulation code using smooth accelerator model is also developed. Some issues concerning the practical applications of this technique are discussed.
L Pintschovius; F Weber; W Reichardt; A Kreyssig; R Heid; D Reznik; O Stockert; K Hradil
2008-10-01
Phonons in a metal interact with conduction electrons which give rise to a finite linewidth. In the normal state, this leads to a Lorentzian shape of the phonon line. Density functional theory is able to predict the phonon linewidths as a function of wave vector for each branch of the phonon dispersion. An experimental verification of such predictions is feasible only for compounds with very strong electron–phonon coupling. YN2B2C was chosen as a test example because it is a conventional superconductor with a fairly high c (15.2 K). Inelastic neutron scattering experiments did largely confirm the theoretical predictions. Moreover, they revealed a strong temperature dependence of the linewidths of some phonons with particularly strong electron–phonon coupling which can as yet only qualitatively be accounted for by theory. For such phonons, marked changes of the phonon frequencies and linewidths were observed from room temperature down to 15 K. Further changes were observed on entering into the superconducting state. These changes can, however, not be described simply by a change of the phonon linewidth.
Scattering of thermal phonons by extended defects in dielectric crystals
Roth, E. P.
1975-01-01
The scattering of thermal phonons by extended defects in dielectric crystals has been observed through measurements of thermal conductivity and ballistic heat pulse propagation. The thermal conductivities of LiF and NaCl conatining 500 low-angle grain boundaries per cm were measured in the range 0.08-5 K. The measurements gave little or no evidence for phonon scattering from the grain boundaries. Measurements of phonon scattering at a 10 deg. grain boundary in silicon using direct generation and detection of ballistically propagating heat pulses were made over an effective phonon temperature range of 2 to 20 K. The grain boundary reflection coefficient was determined to be < 2%. The thermal conductivities of LiF crystals containing 5 x 10/sup 6/ - 3 x 10/sup 7/ dislocations per square cm were measured over the temperature range 0.1 to 10 K. The measurements of the sheared crystal indicated that the slow transverse phonon mode was strongly scattered by a dynamic phonon-dislocation interaction at T approximately < 2 K, while the remaining modes were scattered primarily by the boundaries. The measurements of the bent crystals indicated that, for T approximately < 2 K, the slow transverse and possibly the longitudinal phonons were strongly scattered by a dynamic phonon-dislocation interaction. For T approximately > 2 k, some fraction of the phonons (at least the slow transverse mode) were still strongly scattered, even after long exposure to ..gamma.. irradiation, while the remaining phonons were scattered primarily by the boundaries.
Structural Properties and Phonon dispertion of NACl
R. Khoda-Bakhsh
2001-06-01
Full Text Available Although many phenomena in condensed matter Physics can be understood on the basis of a model, there are also considerable number of physical properties of solid which can not be explained except in the framework of lattice dynamics. We have calculated the phonon frequencies of Na Cl, using an approach which is a combination of frozen phonon and force constants methods in the framework of density functional pseudopotential theory. The dispersion relation curves, were calculated along symmetry direction Δ, Σ and Ù. We also calculated Grunesein parameters for all modes at X and L points in Brillion zone. The calcutions are made in the framework of density functional and pseudopotential theory, using super cell method, with the valence orbitals expanded in plane waves.
Theory of coherent phonons in carbon nanotubes and graphene nanoribbons
Sanders, G. D.; Nugraha, A. R. T.; Sato, K.; Kim, J.-H.; Kono, J.; Saito, R.; Stanton, C. J.
2013-04-01
We survey our recent theoretical studies on the generation and detection of coherent radial breathing mode (RBM) phonons in single-walled carbon nanotubes and coherent radial breathing like mode (RBLM) phonons in graphene nanoribbons. We present a microscopic theory for the electronic states, phonon modes, optical matrix elements and electron-phonon interaction matrix elements that allows us to calculate the coherent phonon spectrum. An extended tight-binding (ETB) model has been used for the electronic structure and a valence force field (VFF) model has been used for the phonon modes. The coherent phonon amplitudes satisfy a driven oscillator equation with the driving term depending on the photoexcited carrier density. We discuss the dependence of the coherent phonon spectrum on the nanotube chirality and type, and also on the graphene nanoribbon mod number and class (armchair versus zigzag). We compare these results with a simpler effective mass theory where reasonable agreement with the main features of the coherent phonon spectrum is found. In particular, the effective mass theory helps us to understand the initial phase of the coherent phonon oscillations for a given nanotube chirality and type. We compare these results to two different experiments for nanotubes: (i) micelle suspended tubes and (ii) aligned nanotube films. In the case of graphene nanoribbons, there are no experimental observations to date. We also discuss, based on the evaluation of the electron-phonon interaction matrix elements, the initial phase of the coherent phonon amplitude and its dependence on the chirality and type. Finally, we discuss previously unpublished results for coherent phonon amplitudes in zigzag nanoribbons obtained using an effective mass theory.
Electron-phonon coupling and the soft phonon mode in TiSe{<_2}.
Weber, F.; Rosenkranz, S.; Castellan, J.-P.; Osborn, R.; Karapetrov, G.; Hott, R.; Heid, R.; Bohnen, K.-P.; Alatas, A. (Materials Science Division); ( XSD); (Institut fur Festkorperphysik)
2011-01-01
We report high-resolution inelastic x-ray measurements of the soft phonon mode in the charge-density-wave compound TiSe{sub 2}. We observe a complete softening of a transverse optic phonon at the L point, i.e., q = (0.5,0,0.5), at T {approx} T{sub CDW}. Detailed ab initio calculations for the electronic and lattice dynamical properties of TiSe{sub 2} are in quantitative agreement with experimental frequencies for the soft phonon mode. The observed broad range of renormalized phonon frequencies, (0.3,0,0.5) {<=} q {<=} (0.5,0,0.5), is directly related to a broad peak in the electronic susceptibility stabilizing the charge-density-wave ordered state. Our analysis demonstrates that a conventional electron-phonon coupling mechanism can explain a structural instability and the charge-density-wave order in TiSe{sub 2} although other mechanisms might further boost the transition temperature.
Zhang, Zhan; Wei, Shaoqing; Lee, Sang Jin [Uiduk University, Gyeongju (Korea, Republic of); Jo, Hyun Chul; Kim, Do Gyun; Kim, Jong Won [Rare Isotope Science Project, Institute for Basic Science, Daejeon (Korea, Republic of)
2016-06-15
In recent years, the iron-dominated high-temperature superconductor (HTS) quadrupole magnets are being developed for heavy ion accelerators. Field analyses for iron-dominated quadrupole magnets were based on the normal-conducting (NC) quadrupole magnet early in the development for accelerators. Some conclusions are still in use today. However, the magnetic field of iron-dominated HTS quadrupole magnets cannot fully follow these conclusions. This study established an HTS quadrupole magnet model and an NC quadrupole magnet model, respectively. The harmonic characteristics of two magnets were analyzed and compared. According to the comparison, the conventional iron-dominated quadrupole magnets can be designed for maximum field gradient; the HTS quadrupole magnet, however, should be considered with varying field gradient. Finally, the HTS quadrupole magnet was designed for the changing field gradient. The field quality of the design was improved comparing with the result of the previous study. The new design for the HTS quadrupole magnet has been suggested.
Quantum mode phonon forces between chainmolecules
Bohr, Jakob
2001-01-01
A phenomenological description of the contributions of phonons to molecular force is developed. It uses an approximation to consider macromolecules as solid continua. The molecular modes of a molecule can then be characterized by a Debye-like description of the partition function. The resulting b....... For the later case, a significant change in zero-point energy is found. This may be the underlying cause for cold denaturation of proteins. (C) 2001 John Wiley & Sons, Inc....
Quantum Coherent Electron-Phonon Nanolaboratories
2006-05-31
published as “Single-crystal aluminum nitride nanomechanical resonators”, A.N. Cleland, M. Pophristic and I. Ferguson , Appl. Phys. Lett. 79, 2070 (2001...nanostructured phononic crystals”, Phys. Rev. B 64, 172301 (2001) A.N. Cleland, M. Pophristic and I. Ferguson , “Single-crystal aluminum nitride...Phys. Lett. 79, 1202 ~2001!. 6 M. J. Kelly, R. J. Brown, C. G. Smith, D. A. Wharam, M. Pepper , H. Ahmed, D. G. Hasko, D. C. Peacock, J. E. F. Frost, and
Quantum mode phonon forces between chainmolecules
Bohr, Jakob
2001-01-01
bimolecular interaction is a truly many-body force that is temperature dependent and can be of the order of 1 eV. These phonon forces depend on molecular shape, composition, and density. They may therefore also be important for large molecular conformational changes, including the unfolding of chain molecules....... For the later case, a significant change in zero-point energy is found. This may be the underlying cause for cold denaturation of proteins. (C) 2001 John Wiley & Sons, Inc....
Relaxation of quadrupole orientation in an optically pumped alkali vapour
Bernabeu, E.; Tornos, J.
1985-04-01
The relaxation of quadrupole orientation (alignment) in an optically pumped alkali vapour is theoretically studied by taking into account the relaxation processes by alkali-buffer gas, alkali-alkali with spin exchange and alkali-cell wall (diffusion process) collisions. The relaxation transients of the quadrupole orientation are obtained by introducing a first-order weak-pumping approximation (intermediate pumping) less restrictive than the usually considered (zeroth order) one.
Quadrupole collectivity in {sup 128}Cd
Boenig, Esther Sabine
2014-07-07
The regions around shell closures, especially around doubly magic nuclei, are of major interest in nuclear structure physics, as they provide a perfect test for nuclear structure theory. The neutron-rich Cd isotopes in the region of {sup 132}Sn are only two protons away from the shell closure at Z=50 and in close proximity to the N=82 magic number. Nevertheless they show an irregular behaviour regarding the excitation energy of the first excited 2{sup +} state. This is not reproduced by shell model calculations, which is astonishing due to the proximity of the shell closures. In order to shed light on the much discussed region around doubly magic {sup 132}Sn, a Coulomb excitation experiment of {sup 128}Cd has been performed at REX-ISOLDE, CERN. The reduced transition strength B(E2;0{sup +}{sub gs} → 2{sup +}{sub 1}), which is a measure of collectivity, and the spectroscopic quadrupole moment Q{sub s}(2{sup +}{sub 1}) as a measure of deformation could be determined for the first time. The results are shown as the continuation of already measured neutron-rich Cd isotopes and are compared to both beyond mean field and shell model calculations, which give different predictions for these observables.
Nuclear spin squeezing via electric quadrupole interaction
Aksu Korkmaz, Yaǧmur; Bulutay, Ceyhun
2016-01-01
Control over nuclear-spin fluctuations is essential for processes that rely on preserving the quantum state of an embedded system. For this purpose, squeezing is a viable alternative, so far that has not been properly exploited for the nuclear spins. Of particular relevance in solids is the electric quadrupole interaction (QI), which operates on nuclei having spin higher than 1/2. In its general form, QI involves an electric-field gradient (EFG) biaxiality term. Here, we show that as this EFG biaxiality increases, it enables continuous tuning of single-particle squeezing from the one-axis twisting to the two-axis countertwisting limits. A detailed analysis of QI squeezing is provided, exhibiting the intricate consequences of EFG biaxiality. The initial states over the Bloch sphere are mapped out to identify those favorable for fast initial squeezing, or for prolonged squeezings. Furthermore, the evolution of squeezing in the presence of a phase-damping channel and an external magnetic field are investigated. We observe that dephasing drives toward an antisqueezed terminal state, the degree of which increases with the spin angular momentum. Finally, QI squeezing in the limiting case of a two-dimensional EFG with a perpendicular magnetic field is discussed, which is of importance for two-dimensional materials, and the associated beat patterns in squeezing are revealed.
Quadrupole Focusing Lenses for Charged Particles
Cork, Bruce; Zajec, Emery
1953-04-15
A set of four strong focusing magnetic quadrupole lenses has been constructed and operated. Each lens consists of four air cooled electromagnets with pole tips having a hyperbolic cross section. Each lens is 4 in. long and has an aperture 2 in. in diameter. Measurements of the magnetic field demonstrate that the hyperbolic cross section satisfies the requirements of a constant magnetic field gradient very well. The technique of deflecting a current carrying flexible wire has been used to measure the trajectory of charged particles through the system of lenses. It has been observed that the strong focusing requirements are satisfied. The system of lenses was then used to focus 0.5 Mev protons, 20 Mev deuterons, and 40 Mev alpha particles. The parallel beam of 0.5 Mev protons was detected by observing the incandescence of a quartz plate while the protons were bombarding it. The focused beam was less than 1 mm in diameter. The astigmatic 20 Mev deuteron beam from the 60 in. cyclotron was increased in current density by a factor greater than 30.
Nonlocal dynamics of dissipative phononic fluids
Nemati, Navid; Lee, Yoonkyung E.; Lafarge, Denis; Duclos, Aroune; Fang, Nicholas
2017-06-01
We describe the nonlocal effective properties of a two-dimensional dissipative phononic crystal made by periodic arrays of rigid and motionless cylinders embedded in a viscothermal fluid such as air. The description is based on a nonlocal theory of sound propagation in stationary random fluid/rigid media that was proposed by Lafarge and Nemati [Wave Motion 50, 1016 (2013), 10.1016/j.wavemoti.2013.04.007]. This scheme arises from a deep analogy with electromagnetism and a set of physics-based postulates including, particularly, the action-response procedures, whereby the effective density and bulk modulus are determined. Here, we revisit this approach, and clarify further its founding physical principles through presenting it in a unified formulation together with the two-scale asymptotic homogenization theory that is interpreted as the local limit. Strong evidence is provided to show that the validity of the principles and postulates within the nonlocal theory extends to high-frequency bands, well beyond the long-wavelength regime. In particular, we demonstrate that up to the third Brillouin zone including the Bragg scattering, the complex and dispersive phase velocity of the least-attenuated wave in the phononic crystal which is generated by our nonlocal scheme agrees exactly with that reproduced by a direct approach based on the Bloch theorem and multiple scattering method. In high frequencies, the effective wave and its associated parameters are analyzed by treating the phononic crystal as a random medium.
Novel information theory techniques for phonon spectroscopy
Hague, J P [Department of Physics, Loughborough University, Loughborough, LE11 3TU (United Kingdom)
2007-12-15
The maximum entropy method (MEM) and spectral reverse Monte Carlo (SRMC) techniques are applied to the determination of the phonon density of states (PDOS) from heat-capacity data. The approach presented here takes advantage of the standard integral transform relating the PDOS with the specific heat at constant volume. MEM and SRMC are highly successful numerical approaches for inverting integral transforms. The formalism and algorithms necessary to carry out the inversion of specific heat curves are introduced, and where possible, I have concentrated on algorithms and experimental details for practical usage. Simulated data are used to demonstrate the accuracy of the approach. The main strength of the techniques presented here is that the resulting spectra are always physical: Computed PDOS is always positive and properly applied information theory techniques only show statistically significant detail. The treatment set out here provides a simple, cost-effective and reliable method to determine phonon properties of new materials. In particular, the new technique is expected to be very useful for establishing where interesting phonon modes and properties can be found, before spending time at large scale facilities.
Swinteck, Nichlas Z.
This dissertation contains research directed at investigating the behavior and properties of a class of composite materials known as phononic crystals. Two categories of phononic crystals are explicitly investigated: (I) elastic phononic crystals and (II) nano-scale phononic crystals. For elastic phononic crystals, attention is directed at two-dimensional structures. Two specific structures are evaluated (1) a two-dimensional configuration consisting of a square array of cylindrical Polyvinylchloride inclusions in air and (2) a two-dimensional configuration consisting of a square array of steel cylindrical inclusions in epoxy. For the first configuration, a theoretical model is developed to ascertain the necessary band structure and equi-frequency contour features for the realization of phase control between propagating acoustic waves. In contrasting this phononic crystal with a reference system, it is shown that phononic crystals with equifrequency contours showing non-collinear wave and group velocity vectors are ideal systems for controlling the phase between propagating acoustic waves. For the second configuration, it is demonstrated that multiple functions can be realized of a solid/solid phononic crystal. The epoxy/steel phononic crystal is shown to behave as (1) an acoustic wave collimator, (2) a defect-less wave guide, (3) a directional source for elastic waves, (4) an acoustic beam splitter, (5) a phase-control device and (6) a k-space multiplexer. To transition between macro-scale systems (elastic phononic crystals) and nano-scale systems (nano-phononic crystals), a toy model of a one-dimensional chain of masses connected with non-linear, anharmonic springs is utilized. The implementation of this model introduces critical ideas unique to nano-scale systems, particularly the concept of phonon mode lifetime. The nano-scale phononic crystal of interest is a graphene sheet with periodically spaced holes in a triangular array. It is found through equilibrium
X. Ding
2015-05-01
Full Text Available Thermal conductivity of ferroelastic device materials can be reversibly controlled by strain. The nucleation and growth of twin boundaries reduces thermal conductivity if the heat flow is perpendicular to the twin wall. The twin walls act as phonon barriers whereby the thermal conductivity decreases linearly with the number of such phonon barriers. Ferroelastic materials also show elasto-caloric properties with a high frequency dynamics. The upper frequency limit is determined by heat generation on a time scale, which is some 5 orders of magnitude below the typical bulk phonon times. Some of these nano-structural processes are irreversible under stress release (but remain reversible under temperature cycling, in particular the annihilation of needle domains that are a key indicator for ferroelastic behaviour in multiferroic materials.
Raman spectra of semiconductor nanoparticles: Disorder-activated phonons
Ingale, Alka; Rustagi, K. C.
1998-09-01
We present Raman spectra of four semiconductor doped glasses and a single crystal of CdS0.55Se0.45 in the range 30-800 cm-1 in the backscattering geometry. This includes the first-order Raman scattering from the disorder-activated zone-edge phonons and the LO phonons. TO phonon modes are not observed, as in bulk CdS, for the excitation well above the lowest gap. We show that the asymmetric line profile of the LO phonon structure can be understood as a composite of two phonon modes: the zone center and the zone edge phonons. Disorder-activated modes in the (30-130)-cm-1 range and the higher-order Raman spectra are also observed and found to be consistent with this assignment.
Coherent radial-breathing-like phonons in graphene nanoribbons
Sanders, G. D.; Nugraha, A. R. T.; Saito, R.; Stanton, C. J.
2012-05-01
We have developed a microscopic theory for the generation and detection of coherent phonons in armchair and zigzag graphene nanoribbons using an extended tight-binding model for the electronic states and a valence force field model for the phonons. The coherent phonon amplitudes satisfy a driven oscillator equation with the driving term depending on photoexcited carrier density. We examine the coherent phonon radial-breathing-like mode amplitudes as a function of excitation energies and nanoribbon types. For photoexcitation near the optical absorption edge the coherent phonon driving term for the radial-breathing-like mode is much larger for zigzag nanoribbons where transitions between localized edge states provide the dominant contribution to the coherent phonon driving term. Using an effective mass theory, we explain how the armchair nanoribbon width changes in response to laser excitation.
NATO Advanced Study Institute on Nonequilibrium Phonon Dynamics
1985-01-01
Phonons are always present in the solid state even at an absolute temperature of 0 K where zero point vibrations still abound. Moreover, phonons interact with all other excitations of the solid state and, thereby, influence most of its properties. Historically experimental information on phonon transport came from measurements of thermal conductivity. Over the past two decades much more, and much more detailed, information on phonon transport and on many of the inherent phonon interaction processes have come to light from experiments which use nonequilibrium phonons to study their dynamics. The resultant research field has most recently blossomed with the development of ever more sophisticated experimental and theoretical methods which can be applied to it. In fact, the field is moving so rapidly that new members of the research community have difficulties in keeping up to date. This NATO Advanced Study Institute (ASI) was organized with the objective of overcoming the information barrier between those expert...
Phonon Scattering Dynamics of Thermophoretic Motion in Carbon Nanotube Oscillators.
Prasad, Matukumilli V D; Bhattacharya, Baidurya
2016-04-13
Using phonon wave packet molecular dynamics simulations, we find that anomalous longitudinal acoustic (LA) mode phonon scattering in low to moderate energy ranges is responsible for initiating thermophoretic motion in carbon nanotube oscillators. The repeated scattering of a single mode LA phonon wave packet near the ends of the inner nanotube provides a net unbalanced force that, if large enough, initiates thermophoresis. By applying a coherent phonon pulse on the outer tube, which generalizes the single mode phonon wave packet, we are able to achieve thermophoresis in a carbon nanotube oscillator. We also find the nature of the unbalanced force on end-atoms to be qualitatively similar to that under an imposed thermal gradient. The thermodiffusion coefficient obtained for a range of thermal gradients and core lengths suggest that LA phonon scattering is the dominant mechanism for thermophoresis in longer cores, whereas for shorter cores, it is the highly diffusive mechanism that provides the effective force.
Electron-phonon coupling in anthracene-pyromellitic dianhydride
Vermeulen, Derek; Corbin, Nathan; Goetz, Katelyn P.; Jurchescu, Oana D.; Coropceanu, Veaceslav; McNeil, L. E.
2017-06-01
In this study, the electron-phonon coupling constants of the mixed-stack organic semiconductor anthracene-pyromellitic dianhydride (A-PMDA) are determined from experimental resonant Raman and absorption spectra of the charge transfer (CT) exciton using a time-dependent resonant Raman model. The reorganization energies of both intermolecular and intramolecular phonons are determined and compared with theoretical estimates derived from density functional theory calculations; they are found to agree well. We found that the dominant contribution to the total reorganization energy is due to intramolecular phonons, with intermolecular phonons only contributing a small percentage. This work goes beyond prior studies of the electron-phonon coupling in A-PMDA by including the coupling of all Raman-active phonons to the charge transfer exciton. The possibility of orientational disorder in A-PMDA at 80 K is inferred from the inhomogeneous broadening of the absorption line shape.
Coupled bloch-phonon oscillations in semiconductor superlattices
Dekorsy; Bartels; Kurz; Kohler; Hey; Ploog
2000-07-31
We investigate coherent Bloch oscillations in GaAs/AlxGa1-xAs superlattices with electronic miniband widths larger than the optical phonon energy. In these superlattices the Bloch frequency can be tuned into resonance with the optical phonon. Close to resonance a direct coupling of Bloch oscillations to LO phonons is observed which gives rise to the coherent excitation of LO phonons. The density necessary for driving coherent LO phonons via Bloch oscillations is about 2 orders of magnitude smaller than the density necessary to drive coherent LO phonons in bulk GaAs. The experimental observations are confirmed by the theoretical description of this phenomenon [A.W. Ghosh et al., Phys. Rev. Lett. 85, 1084 (2000)].
Reduction of thermal conductivity by nanoscale 3D phononic crystal.
Yang, Lina; Yang, Nuo; Li, Baowen
2013-01-01
We studied how the period length and the mass ratio affect the thermal conductivity of isotopic nanoscale three-dimensional (3D) phononic crystal of Si. Simulation results by equilibrium molecular dynamics show isotopic nanoscale 3D phononic crystals can significantly reduce the thermal conductivity of bulk Si at high temperature (1000 K), which leads to a larger ZT than unity. The thermal conductivity decreases as the period length and mass ratio increases. The phonon dispersion curves show an obvious decrease of group velocities in 3D phononic crystals. The phonon's localization and band gap is also clearly observed in spectra of normalized inverse participation ratio in nanoscale 3D phononic crystal.
Interaction of excitons with optical phonons in layer crystals
Nitsovich, Bohdan M.; Zenkova, C. Y.; Kramar, N. K.
2002-02-01
The investigation is concerned with layer crystals of the GaSe, InSe, GaTe, MoS2-type and other inorganic semiconductors, whose phonon spectrum has a great number of peculiarities, among them the availability of low-energy optical phonons. In this case the dispersion of these phonons can be essential and vary in character. The mass operator of the exciton-phonon system and the light absorption coefficient for different dispersion laws of optical phonons have been calculated. The influence of the sign of the phonon 'effective mass' on the exciton absorption band of layer crystals, which causes the opposite in sign dynamics of the absorption maximum shift, and the change of the absorption curve asymmetry have been determined.
Phonons and electron-phonon coupling in graphene-h-BN heterostructures
Slotman, Guus J.; Wijs, Gilles A. de; Fasolino, Annalisa; Katsnelson, Mikhail I. [Institute for Molecules and Materials, Radboud University Nijmegen (Netherlands)
2014-10-15
First principle calculations of the phonons of graphene-h-BN heterostructures are presented and compared to those of the constituents. It is shown that AA and AB' stacking are not only energetically less favoured than AB but also dynamically unstable. Low energy flat phonon branches of h-BN character with out of plane displacement have been identified and their coupling to electrons in graphene has been evaluated. (copyright 2014 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Observation of anomalous phonons in orthorhombic rare-earth manganites
Gao, P.; Chen, H. Y.; Tyson, T. A.; Liu, Z. X.; Bai, J. M.; Wang, L. P.; Choi, Y. J.; Cheong, S.-W.
2010-12-01
We observe the appearance of a phonon near the lock-in temperature in orthorhombic REMnO3 (RE denotes rare earth) (RE: Lu and Ho) and anomalous phonon hardening in orthorhombic LuMnO3. The anomalous phonon occurs at the onset of spontaneous polarization. No such changes were found in incommensurate orthorhombic DyMnO3. These observations directly reveal different electric polarization mechanisms in the E-type and incommensurate-type orthorhombic REMnO3.
Weak phonon scattering effect of twin boundaries on thermal transmission.
Dong, Huicong; Xiao, Jianwei; Melnik, Roderick; Wen, Bin
2016-01-29
To study the effect of twin boundaries on thermal transmission, thermal conductivities of twinned diamond with different twin thicknesses have been studied by NEMD simulation. Results indicate that twin boundaries show a weak phonon scattering effect on thermal transmission, which is only caused by the additional twin boundaries' thermal resistance. Moreover, according to phonon kinetic theory, this weak phonon scattering effect of twin boundaries is mainly caused by a slightly reduced average group velocity.
Weak phonon scattering effect of twin boundaries on thermal transmission
Huicong Dong; Jianwei Xiao; Roderick Melnik; Bin Wen
2016-01-01
To study the effect of twin boundaries on thermal transmission, thermal conductivities of twinned diamond with different twin thicknesses have been studied by NEMD simulation. Results indicate that twin boundaries show a weak phonon scattering effect on thermal transmission, which is only caused by the additional twin boundaries’ thermal resistance. Moreover, according to phonon kinetic theory, this weak phonon scattering effect of twin boundaries is mainly caused by a slightly reduced averag...
Isotopic effects on the phonon modes in boron carbide.
Werheit, H; Kuhlmann, U; Rotter, H W; Shalamberidze, S O
2010-10-01
The effect of isotopes ((10)B-(11)B; (12)C-(13)C) on the infrared- and Raman-active phonons of boron carbide has been investigated. For B isotopes, the contributions of the virtual crystal approximation, polarization vector and isotopical disorder are separated. Boron and carbon isotope effects are largely opposite to one another and indicate the share of the particular atoms in the atomic assemblies vibrating in specific phonon modes. Some infrared-active phonons behave as expected for monatomic boron crystals.
Interface phonon effect on optical spectra of quantum nanostructures
Maslov, Alexander Yu., E-mail: maslov.ton@mail.ioffe.r [Ioffe Physical Technical Institute, Polytechnicheskaya st., 26, 194021 Saint Petersburg (Russian Federation); Proshina, Olga V.; Rusina, Anastasia N. [Ioffe Physical Technical Institute, Polytechnicheskaya st., 26, 194021 Saint Petersburg (Russian Federation)
2009-12-15
This paper deals with theory of large radius polaron effect in quantum wells, wires and dots. The interaction of charge particles and excitons with both bulk and interface optical phonons is taken into consideration. The analytical expression for polaron binding energy is obtained for different types of nanostructures. It is shown that the contribution of interface phonons to the polaron binding energy may exceed the bulk phonon part. The manifestation of polaron effects in optical spectra of quantum nanostructures is discussed.
Phonon dispersion and lifetimes in MgB2.
Shukla, Abhay; Calandra, Matteo; D'Astuto, Matteo; Lazzeri, Michele; Mauri, Francesco; Bellin, Christophe; Krisch, Michael; Karpinski, J; Kazakov, S M; Jun, J; Daghero, D; Parlinski, K
2003-03-01
We measure phonon dispersion and linewidth in a single crystal of MgB2 along the Gamma-A, Gamma-M, and A-L directions using inelastic x-ray scattering. We use density functional theory to compute the effect of both electron-phonon coupling and anharmonicity on the linewidth, obtaining excellent agreement with experiment. Anomalous broadening of the E(2g) phonon mode is found all along Gamma-A. The dominant contribution to the linewidth is always the electron-phonon coupling.
Engineering interactions between superconducting qubits and phononic nanostructures
Arrangoiz-Arriola, Patricio; Safavi-Naeini, Amir H.
2016-12-01
Nanomechanical systems can support highly coherent microwave-frequency excitations at cryogenic temperatures. However, generating sufficient coupling between these devices and superconducting quantum circuits is challenging due to the vastly different length scales of acoustic and electromagnetic excitations. Here we demonstrate a general method for calculating piezoelectric interactions between quantum circuits and arbitrary phononic nanostructures. We illustrate our technique by studying the coupling between a transmon qubit and bulk acoustic-wave, Lamb-wave, and phononic crystal resonators, and show that very large coupling rates are possible in all three cases. Our results suggest a route to phononic circuits and systems that are nonlinear at the single-phonon level.
Bloch oscillations in the presence of plasmons and phonons
Ghosh; Jonsson; Wilkins
2000-07-31
The coupling between Bloch oscillating electrons and longitudinal optical phonons in a superlattice leads to resonant phonon excitation but no gap in the Bloch-phonon spectrum. In addition, we predict a sharp transition from plasma to Bloch oscillations at nu(B) = 2nu(P). From a microscopic description with phenomenological dampings, we numerically map out the behavior of coupled Bloch-plasmon-phonon modes for a wide range of parameters, and mimic experimental conditions. Our results are in good agreement with recent experiments by Dekorsy et al. [Phys. Rev. Lett. 85, 1080 (2000)].
Phononic glass: a robust acoustic-absorption material.
Jiang, Heng; Wang, Yuren
2012-08-01
In order to achieve strong wide band acoustic absorption under high hydrostatic pressure, an interpenetrating network structure is introduced into the locally resonant phononic crystal to fabricate a type of phononic composite material called "phononic glass." Underwater acoustic absorption coefficient measurements show that the material owns high underwater sound absorption coefficients over 0.9 in 12-30 kHz. Moreover, the quasi-static compressive behavior shows that the phononic glass has a compressive strength over 5 MPa which is crucial for underwater applications.
Phonon counting and intensity interferometry of a nanomechanical resonator
Cohen, Justin D; MacCabe, Gregory S; Groblacher, Simon; Safavi-Naeini, Amir H; Marsili, Francesco; Shaw, Matthew D; Painter, Oskar
2014-01-01
Using an optical probe along with single photon detection we have performed effective phonon counting measurements of the acoustic emission and absorption processes in a nanomechanical resonator. Applying these measurements in a Hanbury Brown and Twiss set-up, phonon correlations of the nanomechanical resonator are explored from below to above threshold of a parametric instability leading to self-oscillation of the resonator. Discussion of the results in terms of a "phonon laser", and analysis of the sensitivity of the phonon counting technique are presented.
Nonperturbative theory of exciton-phonon resonances in semiconductor absorption
Hannewald, K.; Bobbert, P. A.
2005-09-01
We develop a theory of exciton-phonon sidebands in the absorption spectra of semiconductors. The theory does not rely on an ad hoc exciton-phonon picture, but is based on a more fundamental electron-phonon Hamiltonian, thus avoiding a priori assumptions about excited-state properties. We derive a nonperturbative compact solution that can be looked upon as the semiconductor version of the textbook absorption formula for a two-level system coupled to phonons. Accompanied by an illustrative numerical example, the importance and usefulness of our approach with respect to practical applications for semiconductors is demonstrated.
Souvatzis, P; Rudin, S P [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Bjoerkman, T; Eriksson, O [Department of Physics, Uppsala University, Box 530, SE-75121, Uppsala (Sweden); Andersson, P [FOI, Swedish Defence Research Agency, SE-164 90 Stockholm (Sweden); Katsnelson, M I [Institute for Molecules and Materials, Radboud University Nijmegen, NL-6525 ED, Nijmegen (Netherlands)], E-mail: petros.souvatzis@gmail.com
2009-04-29
A recently developed self-consistent ab initio lattice dynamical method has been applied to the high temperature body centered cubic (bcc) phase of La and Th, which are dynamically unstable at low temperatures. The bcc phase of these metals is found to be stabilized by phonon-phonon interactions. The calculated high temperature phonon frequencies for La are found to be in good agreement with the corresponding experimental data.
Phonon excitations and magnetoelectric coupling in multiferroic RMn2O5
Golrokh Bahoosh, Safa; Wesselinowa, Julia M.; Trimper, Steffen
2013-05-01
Multiferroic rare-earth manganites are theoretically studied by focusing on the coupling to the lattice degrees of freedom. We demonstrate analytically that the phonon excitations in the multiferroic phase are strongly affected by the magnetoelectric coupling, the spin-phonon interaction and the anharmonic phonon-phonon interaction. Based on a microscopic model, the temperature dependence of the phonon dispersion relation is analyzed. It offers an anomaly at both the ferroelectric and the magnetic transition indicating the mutual coupling between multiferroic orders and lattice distortions. Depending on the sign of the spin-phonon coupling the phonon modes become softer or harder in accordance with experimental observations. We show that the phonon spectrum can be also controlled by an external magnetic field. The phonon energy is enhanced by increasing that field. The applied Green's function technique allows the calculation of the macroscopic magnetization depending on both the phonon-phonon and the spin-phonon couplings.
Coherent phonon optics in a chip with an electrically controlled active device.
Poyser, Caroline L; Akimov, Andrey V; Campion, Richard P; Kent, Anthony J
2015-02-05
Phonon optics concerns operations with high-frequency acoustic waves in solid media in a similar way to how traditional optics operates with the light beams (i.e. photons). Phonon optics experiments with coherent terahertz and sub-terahertz phonons promise a revolution in various technical applications related to high-frequency acoustics, imaging, and heat transport. Previously, phonon optics used passive methods for manipulations with propagating phonon beams that did not enable their external control. Here we fabricate a phononic chip, which includes a generator of coherent monochromatic phonons with frequency 378 GHz, a sensitive coherent phonon detector, and an active layer: a doped semiconductor superlattice, with electrical contacts, inserted into the phonon propagation path. In the experiments, we demonstrate the modulation of the coherent phonon flux by an external electrical bias applied to the active layer. Phonon optics using external control broadens the spectrum of prospective applications of phononics on the nanometer scale.
Phonons in Quantum-Dot Quantum Well
QINGuo-Yi
2004-01-01
Phonon modes of A1As/GaAs/A1As and GaAs/A1As/metal Pb quantum-dot quantum wells (QDQW's) with the whole scale up to 90 AО are calculated by using valence force field model (VFFM) based on group theory.Their optical frequency spectra are divided into two nonoverlapping bands, the AlAs-like band and the GaAs-like band,originated from and having frequency interval inside the bulk AlAs optical band and bulk GaAs optical band, respectively.The GaAs-LO (Г)-like modes of QDQW's that have maximum bulk GaAs-LO (Г) parentages in all modes covering thewhole frequency region and all symmetries have always A1 symmetry. Its frequency is controllable by adjusting thestructure parameters. In A1As/GaAs/A1As, it may be controlled to meet any designed frequency in GaAs-like band.The results on GaAs/A1As/metal Pb QDQW's show the same effect of reducing in interface optical phonons by using the metal/semiconductor interface revealed ever by macroscopic model The frequency spectra in both GaAs-like andAlAs-like optical phonon bands are independent of the thickness of Pb shell as long as the thickness of Pb shell is no less than 5 AО Defects at metal/A1As interface have significant influence to AlAs-like optical modes but have only minor influence to GaAs-like optical modes. All these results are important for the studying of the e-ph interaction in QD structures.
Phonons in Quantum-Dot Quantum Well
QIN Guo-Yi
2004-01-01
Phonon modes of AlAs/GaAs/AlAs and GaAs/AlAs/metal Pb quantum-dot quantum wells (QDQW's)with the whole scale up to 90 A are calculated by using valence force field model (VFFM) based on group theory.Their optical frequency spectra are divided into two nonoverlapping bands, the AMs-like band and the GaAs-like band,originated from and having frequency interval inside the bulk AlAs optical band and bulk GaAs optical band, respectively.The GaAs-LO (F)-like modes of QDQW's that have maximum bulk GaAs-LO (F) parentages in all modes covering the whole frequency region and all symmetries have always A1 symmetry. Its frequency is controllable by adjusting the structure parameters. In AlAs/GaAs/AlAs, it may be controlled to meet any designed frequency in GaAs-like band.The results on GaAs/AMs/metal Pb QDQW's show the same effect of reducing in interface optical phonons by using the metal/semiconductor interface revealed ever by macroscopic model. The frequency spectra in both GaAs-like and AlAs-like optical phonon bands are independent of the thickness of Pb shell as long as the thickness of Pb shell is no less than 5 A. Defects at metal/AlAs interface have significant influence to AMs-like optical modes but have only minor influence to GaAs-like optical modes. All these results are important for the studying of the e-ph interaction in QD structures.
Spectroscopy of nonequilibrium electrons and phonons
Shank, CV
1992-01-01
The physics of nonequilibrium electrons and phonons in semiconductors is an important branch of fundamental physics that has many practical applications, especially in the development of ultrafast and ultrasmall semiconductor devices. This volume is devoted to different trends in the field which are presently at the forefront of research. Special attention is paid to the ultrafast relaxation processes in bulk semiconductors and two-dimensional semiconductor structures, and to their study by different spectroscopic methods, both pulsed and steady-state. The evolution of energy and space distrib
Semi-Dirac points in phononic crystals
Zhang, Xiujuan
2014-01-01
A semi-Dirac cone refers to a peculiar type of dispersion relation that is linear along the symmetry line but quadratic in the perpendicular direction. It was originally discovered in electron systems, in which the associated quasi-particles are massless along one direction, like those in graphene, but effective-mass-like along the other. It was reported that a semi-Dirac point is associated with the topological phase transition between a semi-metallic phase and a band insulator. Very recently, the classical analogy of a semi-Dirac cone has been reported in an electromagnetic system. Here, we demonstrate that, by accidental degeneracy, two-dimensional phononic crystals consisting of square arrays of elliptical cylinders embedded in water are also able to produce the particular dispersion relation of a semi-Dirac cone in the center of the Brillouin zone. A perturbation method is used to evaluate the linear slope and to affirm that the dispersion relation is a semi-Dirac type. If the scatterers are made of rubber, in which the acoustic wave velocity is lower than that in water, the semi-Dirac dispersion can be characterized by an effective medium theory. The effective medium parameters link the semi-Dirac point to a topological transition in the iso-frequency surface of the phononic crystal, in which an open hyperbola is changed into a closed ellipse. This topological transition results in drastic change in wave manipulation. On the other hand, the theory also reveals that the phononic crystal is a double-zero-index material along the x-direction and photonic-band-edge material along the perpendicular direction (y-direction). If the scatterers are made of steel, in which the acoustic wave velocity is higher than that in water, the effective medium description fails, even though the semi-Dirac dispersion relation looks similar to that in the previous case. Therefore different wave transport behavior is expected. The semi-Dirac points in phononic crystals described in
Phonon scattering in graphene over substrate steps
Sevinçli, H., E-mail: haldunsevincli@iyte.edu.tr [Department of Materials Science and Engineering, Izmir Institute of Technology, Gülbahçe Kampüsü, 35430 Urla, Izmir (Turkey); Department of Micro- and Nano-technology (DTU Nanotech), Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Brandbyge, M., E-mail: mads.brandbyge@nanotech.dtu.dk [Department of Micro- and Nano-technology (DTU Nanotech), Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Center for Nanostructured Graphene(CNG), Department of Micro- and Nano-technology, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark)
2014-10-13
We calculate the effect on phonon transport of substrate-induced bends in graphene. We consider bending induced by an abrupt kink in the substrate, and provide results for different step-heights and substrate interaction strengths. We find that individual substrate steps reduce thermal conductance in the range between 5% and 47%. We also consider the transmission across linear kinks formed by adsorption of atomic hydrogen at the bends and find that individual kinks suppress thermal conduction substantially, especially at high temperatures. Our analysis show that substrate irregularities can be detrimental for thermal conduction even for small step heights.
Band gaps in bubble phononic crystals
V. Leroy
2016-12-01
Full Text Available We investigate the interaction between Bragg and hybridization effects on the band gap properties of bubble phononic crystals. These latter consist of air cavities periodically arranged in an elastomer matrix and are fabricated using soft-lithography techniques. Their transmission properties are affected by Bragg effects due to the periodicity of the structure as well as hybridization between the propagating mode of the embedding medium and bubble resonance. The hybridization gap survives disorder while the Bragg gap requires a periodic distribution of bubbles. The distance between two bubble layers can be tuned to make the two gaps overlap or to create a transmission peak in the hybridization gap.
Large scale phononic metamaterials for seismic isolation
Aravantinos-Zafiris, N. [Department of Sound and Musical Instruments Technology, Ionian Islands Technological Educational Institute, Stylianou Typaldou ave., Lixouri 28200 (Greece); Sigalas, M. M. [Department of Materials Science, University of Patras, Patras 26504 (Greece)
2015-08-14
In this work, we numerically examine structures that could be characterized as large scale phononic metamaterials. These novel structures could have band gaps in the frequency spectrum of seismic waves when their dimensions are chosen appropriately, thus raising the belief that they could be serious candidates for seismic isolation structures. Different and easy to fabricate structures were examined made from construction materials such as concrete and steel. The well-known finite difference time domain method is used in our calculations in order to calculate the band structures of the proposed metamaterials.
Nuclear Quadrupole Resonance Study of Potassium - - Chloride.
Ramia, Maximo Elias
Fast Fourier transform nuclear quadrupole resonance (NQR) was used to study the cubic antifluorite crystal potassium hexacloro-osmate, K(,2)OsCl(,6). The study of the ('35)Cl and ('37)Cl resonances were performed on three samples of K(,2)OsCl(,6), a powder sample, a powder sample recrystallized from D(,2)O and a single crystal sample. The studies were carried out in the temperature range 300 to 6K. A detailed study of the ('35)Cl and ('37)Cl NQR lineshapes, in the temperature range 70 to 300K, showed that the lineshapes reflect the strain fields produced by lattice dislocations and point defects. The temperature evolution of these strain fields give rise to a satellite line which previously was attributed to H('+) ion impurities present in the samples. A comprehensive study of the temperature evolution of the NQR spectrum in the vicinity of the phase transition revealed a drop of line intensity and the progressive appearance of an extra broad resonance component. Both effects are associated with the existence of precursor dynamic clusters at temperatures higher than T(,C). Qualitatively similar but quantitatively different behaviour was observed in the powder and single crystal samples. Although the precursor clusters are an intrinsic property of the phrase transition, their detailed dynamics is sample independent. A NQR study of the tetragonal phase showed that at the lowest temperature the ratio of line intensities is 2:1. The phase shift effect previously observed in the tetragonal phase of K(,2)ReCl(,6) was also observed in K(,2)OsCl(,6). The effect has been explained as an experimental artifact introduced by the truncation of the FID due to the spectrometer dead time. Spin-lattice relaxation measurements in the cubic phase show two component relaxation in the vicinity of T(,C). The behaviour is quantitatively different in the powder and single crystal samples. The short relaxation time is associated with dynamic clusters. Spin-lattice relaxation time
TOPICAL REVIEW: Interaction of coherent phonons with defects and elementary excitations
Hase, Muneaki; Kitajima, Masahiro
2010-02-01
We present an overview of the feasibility of using coherent phonon spectroscopy to study interaction dynamics of excited lattice vibrations with their environments. By exploiting the features of coherent phonons with a pump-probe technique, one can study lattice motions in a sub-picosecond time range. The dephasing properties tell us not only about interaction dynamics with carriers (electrons and holes) or thermal phonons but also about point defects in crystals. Modulations of the coherent phonon amplitude by more than two modes are closely related to phonon-carrier or phonon-phonon interferences. Related to this phenomenon, formation of coherent phonons at higher harmonics gives direct evidence for phonon-phonon couplings. A combined study of coherent phonons and ultrafast carrier response can be useful for understanding phonon-carrier interaction dynamics. For metals like zinc, nonequilibrium electrons may dominate the dynamics of both relaxation and generation of coherent phonons. The frequency chirp of coherent phonons can be a direct measure of how and when phonon-phonon and phonon-carrier couplings occur. Carbon nanotubes show some complicated behavior due to the existence of many modes with different symmetries, resulting in superposition or interference. To illustrate one of the most interesting applications, the selective excitation of specific phonon modes through the use of a pulse train technique is shown.
Phonon excitation and instabilities in biased graphene nanoconstrictions
Gunst, Tue; Lu, Jing Tao; Hedegård, Per;
2013-01-01
We investigate how a high current density perturbs the phonons in a biased graphene nanoconstriction coupled to semi-infinite electrodes. The coupling to electrode phonons, electrode electrons under bias, Joule heating, and current-induced forces is evaluated using first principles density...
First-principles dynamics of electrons and phonons
Bernardi, Marco
2016-01-01
First-principles calculations combining density functional theory and many-body perturbation theory can provide microscopic insight into the dynamics of electrons and phonons in materials. We review this theoretical and computational framework, focusing on perturbative treatments of scattering, dynamics and transport of coupled electrons and phonons. We discuss application of these first-principles calculations to electronics, lighting, spectroscopy and renewable energy.
Low Temperature Phonon Properties of Orthorhombic REMnO3
Liu, Zhenxian; Gao, Peng; Chen, Haiyan; Tyson, Trevor A.
2010-03-01
We present the temperature dependent phonon spectra of orthorhombic-LuMnO3 and DyMnO3. The temperature dependent phonon spectra results are compared with the XAFS measurement results to probe for structural changes in the low temperature region which may coincide with ferroelectric behavior.
Remarkable reduction of thermal conductivity in phosphorene phononic crystal.
Xu, Wen; Zhang, Gang
2016-05-05
Phosphorene has received much attention due to its interesting physical and chemical properties, and its potential applications such as thermoelectricity. In thermoelectric applications, low thermal conductivity is essential for achieving a high figure of merit. In this work, we propose to reduce the thermal conductivity of phosphorene by adopting the phononic crystal structure, phosphorene nanomesh. With equilibrium molecular dynamics simulations, we find that the thermal conductivity is remarkably reduced in the phononic crystal. Our analysis shows that the reduction is due to the depressed phonon group velocities induced by Brillouin zone folding, and the reduced phonon lifetimes in the phononic crystal. Interestingly, it is found that the anisotropy ratio of thermal conductivity could be tuned by the 'non-square' pores in the phononic crystal, as the phonon group velocities in the direction with larger projection of pores is more severely suppressed, leading to greater reduction of thermal conductivity in this direction. Our work provides deep insight into thermal transport in phononic crystals and proposes a new strategy to reduce the thermal conductivity of monolayer phosphorene.
Modelling exciton–phonon interactions in optically driven quantum dots
Nazir, Ahsan; McCutcheon, Dara
2016-01-01
We provide a self-contained review of master equation approaches to modelling phonon effects in optically driven self-assembled quantum dots. Coupling of the (quasi) two-level excitonic system to phonons leads to dissipation and dephasing, the rates of which depend on the excitation conditions...
Multiple Quantum Wells for P T -Symmetric Phononic Crystals
Poshakinskiy, A. V.; Poddubny, A. N.; Fainstein, A.
2016-11-01
We demonstrate that the parity-time symmetry for sound is realized in laser-pumped multiple-quantum-well structures. Breaking of the parity-time symmetry for the phonons with wave vectors corresponding to the Bragg condition makes the structure a highly selective acoustic wave amplifier. Single-mode distributed feedback phonon lasing is predicted for structures with realistic parameters.
Linear Quadrupole Cooling Channel for a Neutrino Factory
Johnstone, Carol; Makino, Kyoko
2005-01-01
The staging and optimization in the design of a Neutrino Factory are critically dependent on the choice and format of accelerator. Possibly the simplest, lowest-cost scenario is a nonscaling FFAG machine coupled to a linear (no bending) transverse cooling channel constructed from the simplest quadrupole lens system, a FODO cell. In such a scenario, transverse cooling demands are reduced by a factor of 4 and no longitudinal cooling is required relative to acceleration using a Recirculating Linac (RLA). Detailed simulations further show that a quadrupole-based channel cools efficiently and over a momentum range which is well-matched to FFAG acceleration. Details and cooling performance for a quadrupole channel are summarized in this work.
One-phonon excitations in hot nuclei
Vdovin, A.I.; Kosov, D.S. [Joint Institute for Nuclear Research, Moscow (Russian Federation)
1995-05-01
Equations of the random-phase approximation for hot nuclei are derived in the formalism of thermo-field dynamics. The model Hamiltonian used in the derivation involves separable effective interactions in the particle-particle and particl-hole channels. This initial Hamiltonian that forms the basis of the quasiparticle-phonon model at T = O is expressed in terms of thermal quasiparticles by means of two successive canonical transformations, i.e., by the conventional and thermal Bogolyubov transformations. The coefficients in the transformations are determined by minimizing the free-energy potential of a hot nucleus in the thermal vacuum state. The part that describes excitations of the hot nucleus in the random-phase approximation is then singled out in the resulting Hamiltonian at T {ne} O. The variational principle is used to derive equations for one-phonon excitations. If the Hamiltonian involves only residual particle-hole interaction, these equations coincide with those obtained earlier by means of Green`s functions and linearization of the equations of motion. The approach developed here can be used to extend the treatment beyond the random-phase approximation. 15 refs.
Coherent phonons in carbon nanotubes and graphene
Kim, J.-H.; Nugraha, A. R. T.; Booshehri, L. G.; Hároz, E. H.; Sato, K.; Sanders, G. D.; Yee, K.-J.; Lim, Y.-S.; Stanton, C. J.; Saito, R.; Kono, J.
2013-02-01
We review recent studies of coherent phonons (CPs) corresponding to the radial breathing mode (RBM) and G-mode in single-wall carbon nanotubes (SWCNTs) and graphene. Because of the bandgap-diameter relationship, RBM-CPs cause bandgap oscillations in SWCNTs, modulating interband transitions at terahertz frequencies. Interband resonances enhance CP signals, allowing for chirality determination. Using pulse shaping, one can selectively excite specific-chirality SWCNTs within an ensemble. G-mode CPs exhibit temperature-dependent dephasing via interaction with RBM phonons. Our microscopic theory derives a driven oscillator equation with a density-dependent driving term, which correctly predicts CP trends within and between (2n + m) families. We also find that the diameter can initially increase or decrease. Finally, we theoretically study the radial breathing like mode in graphene nanoribbons. For excitation near the absorption edge, the driving term is much larger for zigzag nanoribbons. We also explain how the armchair nanoribbon width changes in response to laser excitation.
Phonon bottleneck identification in disordered nanoporous materials
Romano, Giuseppe; Grossman, Jeffrey C.
2017-09-01
Nanoporous materials are a promising platform for thermoelectrics in that they offer high thermal conductivity tunability while preserving good electrical properties, a crucial requirement for high-efficiency thermal energy conversion. Understanding the impact of the pore arrangement on thermal transport is pivotal to engineering realistic materials, where pore disorder is unavoidable. Although there has been considerable progress in modeling thermal size effects in nanostructures, it has remained a challenge to screen such materials over a large phase space due to the slow simulation time required for accurate results. We use density functional theory in connection with the Boltzmann transport equation to perform calculations of thermal conductivity in disordered porous materials. By leveraging graph theory and regressive analysis, we identify the set of pores representing the phonon bottleneck and obtain a descriptor for thermal transport, based on the sum of the pore-pore distances between such pores. This approach provide a simple tool to estimate phonon suppression in realistic porous materials for thermoelectric applications and enhance our understanding of heat transport in disordered materials.
Thermal rectification based on phonon hydrodynamics and thermomass theory
Dong Yuan
2016-06-01
Full Text Available The thermal diode is the fundamental device for phononics. There are various mechanisms for thermal rectification, e.g. different temperature dependent thermal conductivity of two ends, asymmetric interfacial resistance, and nonlocal behavior of phonon transport in asymmetric structures. The phonon hydrodynamics and thermomass theory treat the heat conduction in a fluidic viewpoint. The phonon gas flowing through the media is characterized by the balance equation of momentum, like the Navier-Stokes equation for fluid mechanics. Generalized heat conduction law thereby contains the spatial acceleration (convection term and the viscous (Laplacian term. The viscous term predicts the size dependent thermal conductivity. Rectification appears due to the MFP supersession of phonons. The convection term also predicts rectification because of the inertia effect, like a gas passing through a nozzle or diffuser.
Heterobarrier for converting hot-phonon energy to electric potential
Shin, Seungha; Melnick, Corey; Kaviany, Massoud
2013-02-01
We show that hot phonons emitted in energy conversion or resistive processes can be converted to electric potential in heterobarrier structures. Using phonon and electron interaction kinetics and self-consistent ensemble Monte Carlo, we find the favorable conditions for unassisted absorption of hot phonons and design graded heterobarriers for their direct conversion into electric energy. Tandem barriers with nearly optical-phonon height allow for substantial potential gain without current loss. We find that 19% of hot phonons can be harvested with an optimized GaAs/AlxGa1-xAs barrier structure over a range of current and electron densities, thus enhancing the overall energy conversion efficiency and reducing waste heat.
Controlling elastic waves with small phononic crystals containing rigid inclusions
Peng, Pai
2014-05-01
We show that a two-dimensional elastic phononic crystal comprising rigid cylinders in a solid matrix possesses a large complete band gap below a cut-off frequency. A mechanical model reveals that the band gap is induced by negative effective mass density, which is affirmed by an effective medium theory based on field averaging. We demonstrate, by two examples, that such elastic phononic crystals can be utilized to design small devices to control low-frequency elastic waves. One example is a waveguide made of a two-layer anisotropic elastic phononic crystal, which can guide and bend elastic waves with wavelengths much larger than the size of the waveguide. The other example is the enhanced elastic transmission of a single-layer elastic phononic crystal loaded with solid inclusions. The effective mass density and reciprocal of the modulus of the single-layer elastic phononic crystal are simultaneously near zero. © CopyrightEPLA, 2014.
Suppression of phonon transport in molecular Christmas trees.
Lambert, Colin John; Famili, Marjan; Grace, Iain; Sadeghi, Hatef
2017-02-27
Minimising the phonon thermal conductance of self-assembled molecular films, whilst preserving their electrical properties, is highly desirable, both for thermal management at the nanoscale and for the design of high-efficiency thermoelectric materials. Here we highlight a new strategy for minimising the phonon thermal conductance of Christmas-tree-like molecules composed of a long trunk, along which phonons can propagate, attached to pendant molecular branches. We demonstrate that phonon transport along the trunk is suppressed by Fano resonances associated with internal vibrational modes of the branches and that thermal conductance is suppressed most-effectively in molecules with pendant branches of different lengths. As examples, we use density functional theory to demonstrate the reduction in phonon transport in tree-like molecules formed from alkane or acene trunks with various pendant branches.
Phononic Frequency Comb via Intrinsic Three-Wave Mixing
Ganesan, Adarsh; Do, Cuong; Seshia, Ashwin
2017-01-01
Optical frequency combs have resulted in significant advances in optical frequency metrology and found wide applications in precise physical measurements and molecular fingerprinting. A direct analogue of frequency combs in the phononic or acoustic domain has not been reported to date. In this Letter, we report the first clear experimental evidence for a phononic frequency comb. We show that the phononic frequency comb is generated through the intrinsic coupling of a driven phonon mode with an autoparametrically excited subharmonic mode. The experiments depict the comb generation process evidenced by a spectral response consisting of equally spaced discrete and phase coherent comb lines. Through systematic experiments at different drive frequencies and amplitudes, we portray the well-connected process of phononic frequency comb formation and define the attributes to control the features associated with comb formation in such a system. In addition to the demonstration of frequency comb, the interplay between the nonlinear resonances and the well-known Duffing phenomenon is also observed.
Mean free path dependent phonon contributions to interfacial thermal conductance
Tao, Yi; Liu, Chenhan; Chen, Weiyu; Cai, Shuang; Chen, Chen; Wei, Zhiyong; Bi, Kedong; Yang, Juekuan; Chen, Yunfei
2017-06-01
Interfacial thermal conductance as an accumulation function of the phonon mean free path is rigorously derived from the thermal conductivity accumulation function. Based on our theoretical model, the interfacial thermal conductance accumulation function between Si/Ge is calculated. The results show that the range of mean free paths (MFPs) for phonons contributing to the interfacial thermal conductance is far narrower than that for phonons contributing to the thermal conductivity. The interfacial thermal conductance is mainly contributed by phonons with shorter MFPs, and the size effects can be observed only for an interface constructed by nanostructures with film thicknesses smaller than the MFPs of those phonons mainly contributing to the interfacial thermal conductance. This is why most experimental measurements cannot detect size effects on interfacial thermal conductance. A molecular dynamics simulation is employed to verify our proposed model.
Quantum noise theory for phonon transport through nanostructures
Wan, Li; Huang, Yunmi; Huang, Changcheng
2017-04-01
We have developed a quantum noise approach to study the phonon transport through nanostructures. The nanostructures acting as phonon channels are attached to two phonon reservoirs. And the temperature drop between the two reservoirs drives the phonon transport through the channels. We have derived a quantum Langevin equation(QLE) to describe the phonon transport with the quantum noise originated from the thermal fluctuation of the reservoirs. Within the Markov approximation, the QLE is used to get the thermal conductivity κ of the nanostructures and the finite size effect of the κ then is studied. In this study, the advantage of the quantum noise approach lays on the fact that no any local temperature needs to be defined for the nanostructures in its non-equilibrium state.
Conceptual design of a quadrupole magnet for eRHIC
Witte, H. [Brookhaven National Lab. (BNL), Upton, NY (United States); Berg, J. S. [Brookhaven National Lab. (BNL), Upton, NY (United States)
2015-05-03
eRHIC is a proposed upgrade to the existing Relativistic Heavy Ion Collider (RHIC) hadron facility at Brookhaven National Laboratory, which would allow collisions of up to 21 GeV polarized electrons with a variety of species from the existing RHIC accelerator. eRHIC employs an Energy Recovery Linac (ERL) and an FFAG lattice for the arcs. The arcs require open-midplane quadrupole magnets of up to 30 T/m gradient of good field quality. In this paper we explore initial quadrupole magnet design concepts based on permanent magnetic material which allow to modify the gradient during operation.
Characterization and tuning of ultrahigh gradient permanent magnet quadrupoles
S. Becker
2009-10-01
Full Text Available The application of quadrupole devices with high field gradients and small apertures requires precise control over higher order multipole field components. We present a new scheme for performance control and tuning, which allows the illumination of most of the quadrupole device aperture because of the reduction of higher order field components. Consequently, the size of the aperture can be minimized to match the beam size achieving field gradients of up to 500 T m^{-1} at good imaging quality. The characterization method based on a Hall probe measurement and a Fourier analysis was confirmed using the high quality electron beam at the Mainz Microtron MAMI.
Quadrupole collectivity in silicon isotopes approaching neutron number N=28
Campbell, C. M.; Aoi, N.; Bazin, D.; Bowen, M. D.; Brown, B. A.; Cook, J. M.; Dinca, D.-C.; Gade, A.; Glasmacher, T.; Horoi, M.; Kanno, S.; Motobayashi, T.; Riley, L. A.; Sagawa, H.; Sakurai, H.; Starosta, K.; Suzuki, H.; Takeuchi, S.; Terry, J. R.; Yoneda, K.; Zwahlen, H.
2007-08-01
Quadrupole deformation parameters, |β|, have been deduced for 36,38,40Si from measured inelastic proton-scattering cross sections. Due to the strong Z=14 subshell gap, low-lying quadrupole collectivity in these nuclei is attributed to the excitation of valence neutrons. Enhanced collectivity at N=26 indicates a reduced N=28 shell gap at large neutron excess in this chain of isotopes. Data are compared to large-scale shell-model calculations and prior Coulomb excitation measurements on 36,38Si.
Low-frequency quadrupole impedance of undulators and wigglers
Blednykh, A.; Bassi, G.; Hidaka, Y.; Smaluk, V.; Stupakov, G.
2016-10-01
An analytical expression of the low-frequency quadrupole impedance for undulators and wigglers is derived and benchmarked against beam-based impedance measurements done at the 3 GeV NSLS-II storage ring. The adopted theoretical model, valid for an arbitrary number of electromagnetic layers with parallel geometry, allows to calculate the quadrupole impedance for arbitrary values of the magnetic permeability μr . In the comparison of the analytical results with the measurements for variable magnet gaps, two limit cases of the permeability have been studied: the case of perfect magnets (μr→∞ ), and the case in which the magnets are fully saturated (μr=1 ).
Extension of the Measurement Capabilities of the Quadrupole Resonator
Junginger, Tobias; Welsch, Carsten
2012-01-01
The Quadrupole Resonator, designed to measure the surface resistance of superconducting samples at 400 MHz has been refurbished. The accuracy of its RF-DC compensation measurement technique is tested by an independent method. It is shown that the device enables also measurements at 800 and 1200 MHz and is capable to probe the critical RF magnetic field. The electric and magnetic field configuration of the Quadrupole Resonator are dependent on the excited mode. It is shown how this can be used to distinguish between electric and magnetic losses.
Suppression of nonlinear phonon relaxation in Yb:YAG thin disk via zero phonon line pumping.
Smrž, Martin; Miura, Taisuke; Chyla, Michal; Nagisetty, Siva; Novák, Ondřej; Endo, Akira; Mocek, Tomáš
2014-08-15
A quantitative comparison of conventional absorption line (940 nm) pumping and zero phonon line (ZPL) (969 nm) pumping of a Yb:YAG thin disk laser is reported. Characteristics of an output beam profile, surface temperature, and deformation of a thin disk under the different pump wavelengths are evaluated. We found that a nonlinear phonon relaxation (NPR) of the excited state in Yb:YAG, which induces nonlinear temperature rise and large aspheric deformation, did not appear in the case of a ZPL pumped Yb:YAG thin disk. This means that the advantage of ZPL pumping is not only the reduction of quantum defect but also the suppression of NPR. The latter effect is more important for high power lasers.
Szczesniak, R. [Institute of Physics, Czestochowa University of Technology (Poland); Institute of Physics, Jan Dlugosz University in Czestochowa (Poland); Durajski, A.P.; Duda, A.M. [Institute of Physics, Czestochowa University of Technology (Poland)
2017-04-15
The properties of the superconducting and the anomalous normal state were described by using the Eliashberg method. The pairing mechanism was reproduced with the help of the Hamiltonian, which models the electron-phonon and the electron-electron-phonon interaction (EEPh). The set of the Eliashberg equations, which determines the order parameter function (φ), the wave function renormalization factor (Z), and the energy shift function (χ), was derived. It was proven that for the sufficiently large values of the EEPh potential, the doping dependence of the order parameter (φ/Z) has the analogous course to that observed experimentally in cuprates. The energy gap in the electron density of states is induced by Z and χ - the contribution from φ is negligible. The electron density of states possesses the characteristic asymmetric form and the pseudogap is observed above the critical temperature. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Measurement of an atomic quadrupole moment using dynamic decoupling
Akerman, Nitzan; Shaniv, Ravid; Ozeri, Roee
2016-05-01
Some of the best clocks today are ion-based optical clocks. These clocks are referenced to a narrow optical transition in a trapped ion. An example for such a narrow transition is the electric quadrupole E 2 transition between states with identical parity. An important systematic shift of such a transition is the quadrupole shift resulting from the electric field gradient inherent to the ion trap. We present a new dynamic decoupling method that rejects magnetic field noise while measuring the small quadrupole shift of the optical clock transition. Using our sequence we measured the quadrupole moment of the 4D5/2 level in a trapped 88 Sr+ ion to be 2 .973-0 . 033 + 0 . 026 ea02 , where e is the electron charge and a0 is the Bohr radius. Our measurement improves the uncertainty of this value by an order of magnitude and thus helps mitigate an important systematic uncertainty in 88 Sr+ based optical atomic clocks and verifies complicated many-body quantum calculations.
Third-Order Apochromatic Drift-Quadrupole Beamline
Balandin, V; Decking, W; Golubeva, N
2012-01-01
In this paper we present the design of a straight drift-quadrupole system which can transport certain beam ellipses (apochromatic beam ellipses) without influence of the second and of the third order chromatic and geometric aberrations of the beamline transfer map.
Prototype Superconducting Quadrupole for the ISR low-beta insertion
CERN PhotoLab
1977-01-01
The picture shows the cold mass of the Quadrupole with its outer aluminium alloy rings pre-compressing the superconducting coils via the magnetic yoke split in 4 parts.The end of the inner vacuum chamber,supporting the 6-pole correction windings, can also be seen as well as the electrical connections. See also photos 7702690X, 7702307.
Quadrupole moment of superdeformed bands in Tb-151
Finck, C; Stezowski, O; Beck, FA; Appelbe, DE; Byrski, T; Courtin, S; Cullen, DM; Curien, D; de France, G; Duchene, G; Erturk, S; Gall, BJP; Garg, U; Haas, B; Khadiri, N; Kharraja, B; Kintz, N; Nourreddine, A; Prevost, D; Rigollet, C; Savajols, H; Twin, PJ; Vivien, JP; Zuber, K
1998-01-01
The quadrupole moments of the first two superdeformed (SD) bands in the nucleus Tb-151 have been measured with the Doppler Shift Attenuation Method (DSAM) using the EUROGAM gamma-ray spectrometer, The first excited band (B2) is identical to the yrast SD band of Dy-152 in terms of dynamical moments o
ISR Superconducting Quadrupole Prototype:preparing the first test
1976-01-01
The photo shows the first prototype quadrupole (still with an adjustable stainless steel shrinking cylinder) being lifted to be inserted in a vertical cryostat for testing. It attained the design field gradient without any quench.The persons are Pierre Rey and Michel Bouvier. See also 7702690X.
Detection of quadrupole relaxation in an optically pumped cesium vapour
Bernabeu, E.; Tornos, J.
1985-10-01
The relaxation of quadrupole orientation induced by means of optical pumping in a cesium vapour is experimentally studied, and the results are compared to the theoretical predictions. The optical detection process of this type of orientation is also discussed as a function of the polarization and spectral profile of the detection light.
Alignment-to-orientation conversion and nuclear quadrupole resonance
Budker, D; Rochester, S M; Urban, J T
2003-01-01
The role of alignment-to-orientation conversion (AOC) in nuclear quadrupole resonance (NQR) is discussed. AOC is shown to be the mechanism responsible for the appearance of macroscopic orientation in a sample originally lacking any global polarization. Parallels are drawn between NQR and AOC in atomic physics.
Quadrupole moment of superdeformed bands in Tb-151
Finck, C; Stezowski, O; Beck, FA; Appelbe, DE; Byrski, T; Courtin, S; Cullen, DM; Curien, D; de France, G; Duchene, G; Erturk, S; Gall, BJP; Garg, U; Haas, B; Khadiri, N; Kharraja, B; Kintz, N; Nourreddine, A; Prevost, D; Rigollet, C; Savajols, H; Twin, PJ; Vivien, JP; Zuber, K
The quadrupole moments of the first two superdeformed (SD) bands in the nucleus Tb-151 have been measured with the Doppler Shift Attenuation Method (DSAM) using the EUROGAM gamma-ray spectrometer, The first excited band (B2) is identical to the yrast SD band of Dy-152 in terms of dynamical moments
Single mode phonon energy transmission in functionalized carbon nanotubes.
Lee, Jonghoon; Varshney, Vikas; Roy, Ajit K; Farmer, Barry L
2011-09-14
Although the carbon nanotube (CNT) features superior thermal properties in its pristine form, the chemical functionalization often required for many applications of CNT inevitably degrades the structural integrity and affects the transport of energy carriers. In this article, the effect of the side wall functionalization on the phonon energy transmission along the symmetry axis of CNT is studied using the phonon wave packet method. Three different functional groups are studied: methyl (-CH(3)), vinyl (-C(2)H(3)), and carboxyl (-COOH). We find that, near Γ point of the Brillouin zone, acoustic phonons show ideal transmission, while the transmission of the optical phonons is strongly suppressed. A positive correlation between the energy transmission coefficient and the phonon group velocity is observed for both acoustic and optical phonon modes. On comparing the transmission due to functional groups with equivalent point mass defects on CNT, we find that the chemistry of the functional group, rather than its molecular mass, has a dominant role in determining phonon scattering, hence the transmission, at the defect sites.
Geometrical tuning of thermal phonon spectrum in nanoribbons
Ramiere, Aymeric; Volz, Sebastian; Amrit, Jay
2016-03-01
Phonon spectral energy transmission in silicon nanoribbons is investigated using Monte-Carlo simulations in the boundary scattering regime by changing the length and width geometrical parameters. We show that the transition frequency from specular scattering to diffuse scattering is inversely proportional to the edge roughness σ with a geometry independent factor of proportionality. The increase of the length over width ratio \\zeta leads to a decrease of the energy transmission in the diffuse scattering regime which evolves as {{≤ft(1+{{\\zeta}0.59}\\right)}-1} . This trend is explained by developing a model of phonon energy transmission in the fully diffuse scattering regime which takes into account the probability for a diffusively scattered phonon to be directly transmitted from any position on the edge of the nanoribbon. This model establishes the importance of the solid angles in the energy transmission evolution with \\zeta . The transition from unity energy transmission in the specular scattering regime to reduced transmission in the diffuse scattering regime constitutes a low-pass frequency filter for phonons. Our simulations show an energy rejection rate better than 90% for high \\zeta , which paves the way for potential high performance filters. Filtering out high frequency phonons is of significant interest for phononic crystal applications, which use band engineering of phonons in the wave regime with low frequencies.
Double Dirac cones in phononic crystals
Li, Yan
2014-07-07
A double Dirac cone is realized at the center of the Brillouin zone of a two-dimensional phononic crystal (PC) consisting of a triangular array of core-shell-structure cylinders in water. The double Dirac cone is induced by the accidental degeneracy of two double-degenerate Bloch states. Using a perturbation method, we demonstrate that the double Dirac cone is composed of two identical and overlapping Dirac cones whose linear slopes can also be accurately predicted from the method. Because the double Dirac cone occurs at a relatively low frequency, a slab of the PC can be mapped onto a slab of zero refractive index material by using a standard retrieval method. Total transmission without phase change and energy tunneling at the double Dirac point frequency are unambiguously demonstrated by two examples. Potential applications can be expected in diverse fields such as acoustic wave manipulations and energy flow control.
Phonon hydrodynamics in two-dimensional materials.
Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola
2015-03-06
The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane.
Phonon-Mediated Nonclassical Interference in Diamond
England, Duncan G.; Fisher, Kent A. G.; MacLean, Jean-Philippe W.; Bustard, Philip J.; Heshami, Khabat; Resch, Kevin J.; Sussman, Benjamin J.
2016-08-01
Quantum interference of single photons is a fundamental aspect of many photonic quantum processing and communication protocols. Interference requires that the multiple pathways through an interferometer be temporally indistinguishable to within the coherence time of the photon. In this Letter, we use a diamond quantum memory to demonstrate interference between quantum pathways, initially temporally separated by many multiples of the optical coherence time. The quantum memory can be viewed as a light-matter beam splitter, mapping a THz-bandwidth single photon to a variable superposition of the output optical mode and stored phononic mode. Because the memory acts both as a beam splitter and as a buffer, the relevant coherence time for interference is not that of the photon, but rather that of the memory. We use this mechanism to demonstrate nonclassical single-photon and two-photon interference between quantum pathways initially separated by several picoseconds, even though the duration of the photons themselves is just ˜250 fs .
Multifunctional solid/solid phononic crystal
Swinteck, N.; Vasseur, J. O.; Hladky-Hennion, A. C.; Croënne, C.; Bringuier, S.; Deymier, P. A.
2012-07-01
A two-dimensional, solid/solid phononic crystal (PC) comprised a square array of steel cylinders in epoxy is shown to perform a variety of spectral, wave vector, and phase-space functions. Over a range of operating frequencies, the PC's elastic band structure shows uniquely shaped equifrequency contours that are only accessible to excitations of longitudinal polarization. Under this condition, the PC is shown to behave as (1) an acoustic wave collimator, (2) a defect-less wave guide, (3) a directional source for elastic waves, (4) an acoustic beam splitter, (5) a phase-control device, and (6) a k-space multiplexer. Wave vector diagrams and finite-difference time-domain simulations are employed to authenticate the above mentioned capabilities.
Structure of the phonon vacuum state
Mishev, S
2012-01-01
The action of the long-range residual force on the the expectation value of observables in the nuclear ground-states is evaluated by finding optimal values for the coefficients of the canonical transformation which connects the phonon vacuum state with the (quasi-)particle ground-state. After estimating the improvements over the predictions of the independent particle approximation we compare the ground-state wave functions obtained using the presented approach with those obtained using the conventional random phase approximation (RPA) and its extended version. The problem with overbinding of the nuclear ground state calculated using the RPA is shown to be removed if one sticks to the prescriptions of the present approach. The reason being that the latter conforms to the original variational formulation. Calculations are performed within the two-level Lipkin model in which we present results for the binding energies.
Targeted proteomic quantification on quadrupole-orbitrap mass spectrometer.
Gallien, Sebastien; Duriez, Elodie; Crone, Catharina; Kellmann, Markus; Moehring, Thomas; Domon, Bruno
2012-12-01
There is an immediate need for improved methods to systematically and precisely quantify large sets of peptides in complex biological samples. To date protein quantification in biological samples has been routinely performed on triple quadrupole instruments operated in selected reaction monitoring mode (SRM), and two major challenges remain. Firstly, the number of peptides to be included in one survey experiment needs to be increased to routinely reach several hundreds, and secondly, the degree of selectivity should be improved so as to reliably discriminate the targeted analytes from background interferences. High resolution and accurate mass (HR/AM) analysis on the recently developed Q-Exactive mass spectrometer can potentially address these issues. This instrument presents a unique configuration: it is constituted of an orbitrap mass analyzer equipped with a quadrupole mass filter as the front-end for precursor ion mass selection. This configuration enables new quantitative methods based on HR/AM measurements, including targeted analysis in MS mode (single ion monitoring) and in MS/MS mode (parallel reaction monitoring). The ability of the quadrupole to select a restricted m/z range allows one to overcome the dynamic range limitations associated with trapping devices, and the MS/MS mode provides an additional stage of selectivity. When applied to targeted protein quantification in urine samples and benchmarked with the reference SRM technique, the quadrupole-orbitrap instrument exhibits similar or better performance in terms of selectivity, dynamic range, and sensitivity. This high performance is further enhanced by leveraging the multiplexing capability of the instrument to design novel acquisition methods and apply them to large targeted proteomic studies for the first time, as demonstrated on 770 tryptic yeast peptides analyzed in one 60-min experiment. The increased quality of quadrupole-orbitrap data has the potential to improve existing protein
Research Update: Phonon engineering of nanocrystalline silicon thermoelectrics
Shiomi, Junichiro
2016-10-01
Nanocrystalline silicon thermoelectrics can be a solution to improve the cost-effectiveness of thermoelectric technology from both material and integration viewpoints. While their figure-of-merit is still developing, recent advances in theoretical/numerical calculations, property measurements, and structural synthesis/fabrication have opened up possibilities to develop the materials based on fundamental physics of phonon transport. Here, this is demonstrated by reviewing a series of works on nanocrystalline silicon materials using calculations of multiscale phonon transport, measurements of interfacial heat conduction, and synthesis from nanoparticles. Integration of these approaches allows us to engineer phonon transport to improve the thermoelectric performance by introducing local silicon-oxide structures.
The optical phonon spectrum of SmFeAsO
Marini, C.; Mirri, C.; Profeta, G.; Lupi, S.; Di Castro, D.; Sopracase, R.; Postorino, P.; Calvani, P.; Perucchi, A.; Massidda, S.; Tropeano, G. M.; Putti, M.; Martinelli, A.; Palenzona, A.; Dore, P.
2008-01-01
We measured the Raman and the Infrared phonon spectrum of SmFeAsO polycrystalline samples. We also performed Density Functional Theory calculations within the pseudopotential approximation to obtain the structural and dynamical lattice properties of both the SmFeAsO and the prototype LaFeAsO compounds. The measured Raman and Infrared phonon frequencies are well predicted by the optical phonon frequencies computed at the Gamma point, showing the capability of the employed ab-initio methods to ...
Spin-seebeck effect: a phonon driven spin distribution.
Jaworski, C M; Yang, J; Mack, S; Awschalom, D D; Myers, R C; Heremans, J P
2011-05-06
Here we report on measurements of the spin-Seebeck effect in GaMnAs over an extended temperature range alongside the thermal conductivity, specific heat, magnetization, and thermoelectric power. The amplitude of the spin-Seebeck effect in GaMnAs scales with the thermal conductivity of the GaAs substrate and the phonon-drag contribution to the thermoelectric power of the GaMnAs, demonstrating that phonons drive the spin redistribution. A phenomenological model involving phonon-magnon drag explains the spatial and temperature dependence of the measured spin distribution.
Lifetimes of confined acoustic phonons in ultrathin silicon membranes.
Cuffe, J; Ristow, O; Chávez, E; Shchepetov, A; Chapuis, P-O; Alzina, F; Hettich, M; Prunnila, M; Ahopelto, J; Dekorsy, T; Sotomayor Torres, C M
2013-03-01
We study the relaxation of coherent acoustic phonon modes with frequencies up to 500 GHz in ultrathin free-standing silicon membranes. Using an ultrafast pump-probe technique of asynchronous optical sampling, we observe that the decay time of the first-order dilatational mode decreases significantly from ~4.7 ns to 5 ps with decreasing membrane thickness from ~194 to 8 nm. The experimental results are compared with theories considering both intrinsic phonon-phonon interactions and extrinsic surface roughness scattering including a wavelength-dependent specularity. Our results provide insight to understand some of the limits of nanomechanical resonators and thermal transport in nanostructures.
Non-equilibrium phonon generation and detection in microstructure devices
Hertzberg, J. B.
2011-01-01
We demonstrate a method to excite locally a controllable, non-thermal distribution of acoustic phonon modes ranging from 0 to ∼200 GHz in a silicon microstructure, by decay of excited quasiparticle states in an attached superconducting tunnel junction (STJ). The phonons transiting the structure ballistically are detected by a second STJ, allowing comparison of direct with indirect transport pathways. This method may be applied to study how different phonon modes contribute to the thermal conductivity of nanostructures. © 2011 American Institute of Physics.
Confined and interface phonons in combined cylindrical nanoheterosystem
O.M.Makhanets
2006-01-01
Full Text Available The spectra of all types of phonons existing in a complicated combined nanoheterosystem consisting of three cylindrical quantum dots embedded into the cylindrical quantum wire placed into vacuum are studied within the dielectric continuum model. It is shown that there are confined optical (LO and interface phonons of two types: top surface optical (TSO and side surface optical (SSO modes of vibration in such a nanosystem. The dependences of phonon energies on the quasiwave numbers and geometrical parameters of quantum dots are investigated and analysed.
Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene
Gunst, Tue; Kaasbjerg, Kristen; Brandbyge, Mads
2017-01-01
Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry, yielding a coupling mechanism to the flexural phonons.......We examine the effect of the gate-induced one-phonon scattering on the mobility for several gate geometries and dielectric environments using first-principles calculations based on density functional theory and the Boltzmann equation. We demonstrate that this scattering mechanism can be a mobility...
Electron-phonon coupling in the rare-earth metals
Skriver, Hans Lomholt; Mertig, I.
1990-01-01
We have estimated the strength of the mass enhancement of the conduction electrons due to electron-phonon interaction in the rare metals Sc, Y, and La–Lu. The underlying self-consistent energy bands were obtained by means of the scalar relativistic linear-muffin-tin-orbital method, and the electron......-phonon parameters were calculated within the Gaspari-Gyorffy formulation. For the heavier rare earths Gd–Tm spin polarization was included both in the band-structure calculations and in the treatment of the electron-phonon coupling to take into account the spin splitting of the conduction electrons induced by the 4...
Quantum symmetries induced by phonons in the Hubbard model
Montorsi, Arianna; Rasetti, Mario
1994-03-01
We show how the addition of a phonon field to the Hubbard model deforms the superconducting su(2) part of the global symmetry Lie algebra su(2)⊗su(2)/openZ2, holding at half filling for the customary model, into a quantum [su(2)]q symmetry, holding for a filling which depends on the electron-phonon interaction strength. Such symmetry originates in the feature that in the presence of phonons the hopping amplitude turns out to depend on the coupling strength. The states generated by resorting to this q symmetry exhibit both off-diagonal long-range order and pairing.
Quantum symmetries induced by phonons in the Hubbard model
Montorsi, Arianna; Rasetti, Mario
1994-01-01
We show how the addition of a phonon field to the Hubbard model deforms the superconducting su(2) part of the global symmetry Lie algebra su(2)⊗su(2)/openZ2, holding at half filling for the customary model, into a quantum [su(2)]q symmetry, holding for a filling which depends on the electron-phonon interaction strength. Such symmetry originates in the feature that in the presence of phonons the hopping amplitude turns out to depend on the coupling strength. The states generated by resorting t...
Deterministic Single-Phonon Source Triggered by a Single Photon
Söllner, Immo; Lodahl, Peter
2016-01-01
We propose a scheme that enables the deterministic generation of single phonons at GHz frequencies triggered by single photons in the near infrared. This process is mediated by a quantum dot embedded on-chip in an opto-mechanical circuit, which allows for the simultaneous control of the relevant photonic and phononic frequencies. We devise new opto-mechanical circuit elements that constitute the necessary building blocks for the proposed scheme and are readily implementable within the current state-of-the-art of nano-fabrication. This will open new avenues for implementing quantum functionalities based on phonons as an on-chip quantum bus.
Single phase 3D phononic band gap material.
Warmuth, Franziska; Wormser, Maximilian; Körner, Carolin
2017-06-19
Phononic band gap materials are capable of prohibiting the propagation of mechanical waves in certain frequency ranges. Band gaps are produced by combining different phases with different properties within one material. In this paper, we present a novel cellular material consisting of only one phase with a phononic band gap. Different phases are modelled by lattice structure design based on eigenmode analysis. Test samples are built from a titanium alloy using selective electron beam melting. For the first time, the predicted phononic band gaps via FEM simulation are experimentally verified. In addition, it is shown how the position and extension of the band gaps can be tuned by utilizing knowledge-based design.
Bloch oscillations of THz acoustic phonons in coupled nanocavity structures.
Lanzillotti-Kimura, N D; Fainstein, A; Perrin, B; Jusserand, B; Mauguin, O; Largeau, L; Lemaître, A
2010-05-14
Nanophononic Bloch oscillations and Wannier-Stark ladders have been recently predicted to exist in specifically tailored structures formed by coupled nanocavities. Using pump-probe coherent phonon generation techniques we demonstrate that Bloch oscillations of terahertz acoustic phonons can be directly generated and probed in these complex nanostructures. In addition, by Fourier transforming the time traces we had access to the proper eigenmodes in the frequency domain, thus evidencing the related Wannier-Stark ladder. The observed Bloch oscillation dynamics are compared with simulations based on a model description of the coherent phonon generation and photoelastic detection processes.
Decoherence in semiconductor cavity QED systems due to phonon couplings
Nielsen, Per Kær; Mørk, Jesper
2014-01-01
We investigate the effect of electron-phonon interactions on the coherence properties of single photons emitted from a semiconductor cavity QED (quantum electrodynamics) system, i.e., a quantum dot embedded in an optical cavity. The degree of indistinguishability, governing the quantum mechanical...... interference between two single photons, is calculated as a function of important parameters describing the cavity QED system and the phonon reservoir, e.g., cavity quality factor, light-matter coupling strength, temperature, and phonon lifetime. We show that non-Markovian effects play an important role...
Phonon Quasidiffusion in Cryogenic Dark Matter Search Large Germanium Detectors
Leman, S W; McCarthy, K A; Pyle, M; Resch, R; Sadoulet, B; Sundqvist, K M; Brink, P L; Cherry, M; Silva, E Do Couto E; Figueroa-Feliciano, E; Mirabolfathi, N; Serfass, B; Tomada, A
2011-01-01
We present results on quasidiffusion studies in large, 3 inch diameter, 1 inch thick [100] high purity germanium crystals, cooled to 50 mK in the vacuum of a dilution refrigerator, and exposed with 59.5 keV gamma-rays from an Am-241 calibration source. We compare data obtained in two different detector types, with different phonon sensor area coverage, with results from a Monte Carlo. The Monte Carlo includes phonon quasidiffusion and the generation of phonons created by charge carriers as they are drifted across the detector by ionization readout channels.
PHONON SOFTENING IN INTERMEDIATE VALENT SmB6
Mörke, I.; Wachter, P.
1981-01-01
We have measured the Raman spectrum of a SmB6 single crystal and compared it to LaB6 and EuB6. Beside the three high energy Raman active phonons we found additional excitations in these compounds. Most prominent is a peak at 172 cm-1 for SmB6, 214 cm-1 for LaB6 and 220 cm-1 for EuB6. The spectra are analysed in terms of defect induced phonon scattering. The softening of the line in intermediate valent (IV) SmB6 is explained in analogy with the phonon anomalies found in other IV compounds.
Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites
Yang, Jianfeng; Wen, Xiaoming; Xia, Hongze; Sheng, Rui; Ma, Qingshan; Kim, Jincheol; Tapping, Patrick; Harada, Takaaki; Kee, Tak W.; Huang, Fuzhi; Cheng, Yi-Bing; Green, Martin; Ho-Baillie, Anita; Huang, Shujuan; Shrestha, Santosh; Patterson, Robert; Conibeer, Gavin
2017-01-01
The hot-phonon bottleneck effect in lead-halide perovskites (APbX3) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA+/MA+/Cs+, X=I−/Br−) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI3. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials. PMID:28106061
Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites
Yang, Jianfeng; Wen, Xiaoming; Xia, Hongze; Sheng, Rui; Ma, Qingshan; Kim, Jincheol; Tapping, Patrick; Harada, Takaaki; Kee, Tak W.; Huang, Fuzhi; Cheng, Yi-Bing; Green, Martin; Ho-Baillie, Anita; Huang, Shujuan; Shrestha, Santosh; Patterson, Robert; Conibeer, Gavin
2017-01-01
The hot-phonon bottleneck effect in lead-halide perovskites (APbX3) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA+/MA+/Cs+, X=I-/Br-) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI3. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials.
Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites.
Yang, Jianfeng; Wen, Xiaoming; Xia, Hongze; Sheng, Rui; Ma, Qingshan; Kim, Jincheol; Tapping, Patrick; Harada, Takaaki; Kee, Tak W; Huang, Fuzhi; Cheng, Yi-Bing; Green, Martin; Ho-Baillie, Anita; Huang, Shujuan; Shrestha, Santosh; Patterson, Robert; Conibeer, Gavin
2017-01-20
The hot-phonon bottleneck effect in lead-halide perovskites (APbX3) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA(+)/MA(+)/Cs(+), X=I(-)/Br(-)) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI3. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials.
Kuleev, I. I.; Bakharev, S. M.; Kuleev, I. G.; Ustinov, V. V.
2017-01-01
Effect of anisotropy of elastic energy on the phonon propagation in single-crystal nanowires made of Fe, Cu, MgO, InSb, and GaAs materials that are used to fabricate spintronics devices in the regime of the Knudsen flow of phonon gas has been studied. A new method of analyzing the focusing of quasi-transverse modes has been suggested, which made it possible to determine the average values of the densities of phonon states in the regions of focusing and defocusing slow and fast quasi-transverse modes. The effect of phonon focusing on the anisotropy of heat conductivity and lengths of the phonon free paths has been analyzed for all acoustic modes that exist in spintronics nanostructures. It has been shown that for all the nanowires investigated the angular dependences of the free paths of fast and slow transverse modes in the {100} and {110} planes correlate with the angular dependences of the densities of phonon states for these modes. Directions of the heat flux that ensure the maximum and minimum phonon heat conductivity in the nanowires have been determined.
Dimitropoulos, C.; Maglione, M.; Borsa, F.
1988-03-01
The nuclear-magnetic-resonance and nuclear-quadrupole-resonance (NQR-NMR) spectra of /sup 187/Re and /sup 185/Re in a powder of rhenium metal were measured in the temperature range 5--10 K both in zero field and with an external magnetic field. The zero-field NQR spectrum is severely broadened by a nonuniform distribution of quadrupole interactions. The average quadrupole coupling frequencies measured at 5 K are, for the two isotopes, ..nu../sub Q/ = 39 +- 0.2 MHz (/sup 187/Re) and ..nu../sub Q/ = 40.8 +- 0.3 MHz (/sup 185/Re). The spectra obtained in the presence of an external magnetic field can be interpreted satisfactorily in terms of transitions among the eigenstates of the full Hamiltonian (Zeeman plus quadrupolar). Measurements of relaxation rates yield T/sub 1/T = 0.03 sK, indicating a relaxation mechanism driven by the hyperfine interaction with the conduction electrons. The feasibility of NQR-NMR studies in small metal particles in the presence of strong inhomogeneous quadrupole interactions is assessed
Influence of anharmonic phonon decay on self-heating in Si nanowire transistors
Rhyner, Reto, E-mail: rhyner@iis.ee.ethz.ch; Luisier, Mathieu, E-mail: mluisier@iis.ee.ethz.ch [Integrated Systems Laboratory, ETH Zürich, Gloriastr. 35, 8092 Zürich (Switzerland)
2014-08-11
Anharmonic phonon-phonon scattering is incorporated into an electro-thermal quantum transport approach based on the nonequilibrium Green's function formalism. Electron-phonon and phonon-phonon interactions are taken into account through scattering self-energies solved in the self-consistent Born approximation. While studying self-heating effects in ultra-scaled Si nanowire transistors, it is found that the phonon decay process softens the artificial accumulation of high energy phonons caused by electron relaxations close to the drain region. This leads to an increase of the device current in the ON-state and a reduction of the effective lattice temperature.
Stability considerations of permanent magnet quadrupoles for CESR phase-III upgrade
W. Lou
1998-06-01
Full Text Available The Cornell electron storage ring (CESR phase-III upgrade plan includes very strong permanent magnet quadrupoles in front of the cryostat for the superconducting quadrupoles and physically as close as possible to the interaction point. Together with the superconducting quadrupoles, they provide tighter vertical focusing at the interaction point. The quadrupoles are built with neodymium iron boron (NdFeB material and operate inside the 15 kG solenoid field. Requirements on the field quality and stability of these quadrupoles are discussed and test results are presented.
Electron scale nested quadrupole Hall field in Cluster observations of magnetic reconnection
Jain, Neeraj
2014-01-01
This Letter presents the first evidence of a new and unique feature of spontaneous reconnection at multiple sites in electron current sheet, viz. nested quadrupole structure of Hall field at electron scales, in Cluster observations. The new nested quadrupole is a consequence of electron scale processes in reconnection. Whistler response of the upstream plasma to the interaction of electron flows from neighboring reconnection sites produces a large scale quadrupole Hall field enclosing the quadrupole fields of the multiple sites, thus forming a nested structure. Electron-magnetohydrodynamic simulations of an electron current sheet yields mechanism of the formation of nested quadrupole.
Phonon dispersion and electron-phonon coupling in MgB2 and AlB2.
Bohnen, K P; Heid, R; Renker, B
2001-06-18
We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the superconductor MgB2 and the isostructural AlB2 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. Complete phonon dispersion curves and Eliashberg functions alpha2F are calculated for both systems. The main differences are related to high frequency in-plane boron vibrations, which are strongly softened in MgB2 and exhibit an exceptionally strong electron-phonon coupling. We also report on Raman measurements, which support the theoretical findings. Implications for the superconducting transition temperature are briefly discussed.
B Ojha; P Nayak; S N Behera
2000-02-01
The electron–phonon interaction in the periodic Anderson model (PAM) is considered. The PAM incorporates the effect of onsite Coulomb interaction () between -electrons. The inﬂuence of Coulomb correlation on the phonon response of the system is studied by evaluating the phonon spectral function for various parameters of the model. The numerical evaluation of the spectral function is carried out in the long wavelength limit at ﬁnite temperatures keeping only linear terms in . The observed behaviour is found to agree well with the general features obtained experimentally for some heavy fermion (HF) systems.
The Electron-Phonon Interaction as Studied by Photoelectron Spectroscopy
D.W. Lynch
2004-09-30
With recent advances in energy and angle resolution, the effects of electron-phonon interactions are manifest in many valence-band photoelectron spectra (PES) for states near the Fermi level in metals.
Effect of pressure on the phonon properties of europium chalcogenides
U K Sakalle; P K Jha; S P Sanyal
2000-06-01
Lattice vibrational properties of europium chalcogenides have been investigated at high pressure by using a simple lattice dynamical model theory viz. the three-body force rigid ion model (TRIM) which includes long range three-body interaction arising due to charge transfer effects. The dispersion curves for the four Eu-chalcogenides agree reasonably well with the available experimental data. Variation of LO, TO, LA and TA phonons with pressure have also been studied at the symmetry points of the brillouin zone (BZ) for Euchalcogenides for the first time by using a lattice dynamical model theory. We have also calculated the one phonon density of states and compared them with the first order Raman scattering results. The calculation of one phonon density of states for Eu-chalcogenides has also been extended up to the phase transition pressure. We observed a pronounced shift in phonon spectrum as pressure is increased.
Phonon-assisted decoherence and tunneling in quantum dot molecules
Grodecka-Grad, Anna; Foerstner, Jens
2011-01-01
We study the influence of the phonon environment on the electron dynamics in a doped quantum dot molecule. A non-perturbative quantum kinetic theory based on correlation expansion is used in order to describe both diagonal and off-diagonal electron-phonon couplings representing real and virtual...... processes with relevant acoustic phonons. We show that the relaxation is dominated by phonon-assisted electron tunneling between constituent quantum dots and occurs on a picosecond time scale. The dependence of the time evolution of the quantum dot occupation probabilities on the energy mismatch between...... the quantum dots is studied in detail. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)...
Phonon-assisted electron emission from individual carbon nanotubes.
Wei, Xianlong; Golberg, Dmitri; Chen, Qing; Bando, Yoshio; Peng, Lianmao
2011-02-09
A question of how electrons can escape from one-atom-thick surfaces has seldom been studied and is still not properly answered. Herein, lateral electron emission from a one-atom-thick surface is thoroughly studied for the first time. We study electron emission from side surface of individual electrically biased carbon nanotubes (CNTs) both experimentally and theoretically and discover a new electron emission mechanism named phonon-assisted electron emission. A kinetic model based on coupled Boltzmann equations of electrons and optical phonons is proposed and well describes experimentally measured lateral electron emission from CNTs. It is shown that the electrons moving along a biased CNT can overflow from the one-atom-thick surface due to the absorption of hot forward-scattering optical phonons. A low working voltage, high emission density, and side emission character make phonon-assisted electron emission primarily promising in electron source applications.
Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene
Gunst, Tue; Kaasbjerg, Kristen; Brandbyge, Mads
2017-01-01
Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry, yielding a coupling mechanism to the flexural phonons. We examine the effect of the gate-induced one-phonon scattering on the mobility for several gate geometries and dielectric environments using first-principles calculations based on density functional theory and the Boltzmann equation. We demonstrate that this scattering mechanism can be a mobility-limiting factor, and show how the carrier density and temperature scaling of the mobility depends on the electrostatic environment. Our findings may explain the high deformation potential for in-plane acoustic phonons extracted from experiments and, furthermore, suggest a direct relation between device symmetry and resulting mobility.
Phonon transport in single-layer Boron nanoribbons
Zhang, Zhongwei; Peng, Qing; Chen, Yuanping
2016-01-01
Inspired by the successful synthesis of several allotropes, boron sheets have been one of the hottest spot areas of focus in various fields. Here, we study phonon transport in three types of boron nanoribbons with zigzag and armchair edges by using a non-equilibrium Green's function combined with first principles methods. Diverse transport properties are found in the nanoribbons. At the room temperature, their highest thermal conductance can be comparable with that of graphene, while the lowest thermal conductance is less than half of graphene's. The three boron sheets exhibit different anisotropic transport characteristics. Two of these sheets have stronger phonon transport abilities along the zigzag edges than the armchair edges, while in the case of the third, the results are reversed. With the analysis of phonon dispersion, bonding charge density, and simplified models of atomic chains, the mechanisms of the diverse phonon properties are discussed. Because all boron allotropes consists of hexagonal and tr...
Influence of mass contrast in alloy phonon scattering
Shiga, Takuma; Shiomi, Junichiro
2015-01-01
We have investigated the effect of mass contrast on alloy phonon scattering in mass-substituted Lennard-Jones crystals. By calculating the mass-difference phonon scattering rate using a modal analysis method based on molecular dynamics, we have identified the applicability and limits of the widely-used mass-difference perturbation model in terms of magnitude and sign of the mass difference. The result of a phonon -mode-dependent analysis reveals that the critical phonon frequency, above which the mass-difference perturbation theory fails, decreases with the magnitude of the mass difference independently of its sign. This gives rise to a critical mass contrast, above which the mass-difference perturbation model noticeably underestimates the lattice thermal conductivity.
On the Cauchy Problem Describing an Electron-Phonon Interaction
Jo(a)o-Paulo DIAS; Mário FIGUEIRA; Filipe OLIVEIRA
2011-01-01
In this paper, a model is derived to describe a quartic anharmonic interatomic interaction with an external potential involving a pair electron-phonon. The authors study the corresponding Cauchy Problem in the semilinear and quasilinear cases.
Phonons in Ge/Si superlattices with Ge quantum dots
Milekhin, A G; Pchelyakov, O P; Schulze, S; Zahn, D R T
2001-01-01
Ge/Si superlattices with Ge quantum dots obtained by means of molecular-beam epitaxy were investigated by means of light Raman scattering under resonance conditions. These structures are shown to have oscillation properties of both two-dimensional and zero-dimensional objects. Within spectrum low-frequency range one observes twisted acoustic phonons (up to 15 order) typical for planar superlattices. Lines of acoustic phonons are overlapped with a wide band of continuous emission. Analysis of frequencies of Ge and Ge-Si optical phonons shows that Ge quantum dots are pseudoamorphous ones and mixing of Ge and Si atoms is a negligible one. One detected low-frequency shift of longitudinal optical phonons at laser excitation energy increase (2.54-2.71 eV)
Electron-phonon relaxation time in ultrathin tungsten silicon film
Sidorova, M; Korneev, A; Chulkova, G; Korneeva, Yu; Mikhailov, M; Devizenko, Yu; Kozorezov, A; Goltsman, G
2016-01-01
Using amplitude-modulated absorption of sub-THz radiation (AMAR) method, we studied electron-phonon relaxation in thin disordered films of tungsten silicide. We found a response time ~ 800 ps at critical temperature Tc = 3.4 K, which scales as minus 3 in the temperature range from 1.8 to 3.4 K. We discuss mechanisms, which can result in a strong phonon bottle-neck effect in a few nanometers thick film and yield a substantial difference between the measured time, characterizing response at modulation frequency, and the inelastic electron-phonon relaxation time. We estimate the electron-phonon relaxation time to be in the range ~ 100-200 ps at 3.4 K.
Stochastic approach to phonon-assisted optical absorption
Zacharias, Marios; Patrick, Christopher E.; Giustino, Feliciano
2015-01-01
We develop a first-principles theory of phonon-assisted optical absorption in semiconductors and insulators which incorporates the temperature dependence of the electronic structure. We show that the Hall-Bardeen-Blatt theory of indirect optical absorption and the Allen-Heine theory of temperature-dependent band structures can be derived from the present formalism by retaining only one-phonon processes. We demonstrate this method by calculating the optical absorption coefficient of silicon us...
Phonon Hall Effect in Four-Terminal Junctions
Zhang, Lifa; Wang, Jian-Sheng; Li, Baowen
2009-01-01
Using an exact nonequilibrium Green's function formulism, the phonon Hall effect for paramagnetic dielectrics is studied in a four-terminal device setting. The temperature difference in the transverse direction of the heat current is calculated for two-dimensional models with the magnetic field perpendicular to the plane. We find a surprising result that the square lattice does not have the phonon Hall effect while a honeycomb lattice has. This can be explained by symmetry. The temperature di...
Long-time correlated quantum dynamics of phonon cooling
Carlig, Sergiu; Macovei, Mihai A.
2014-01-01
We investigate the steady-state cooling dynamics of vibrational degrees of freedom related to a nanomechanical oscillator coupled with a laser-pumped quantum dot in an optical resonator. Correlations between phonon-cooling and quantum-dot photon emission processes occur respectively when a photon laser absorption together with a vibrational phonon absorption is followed by photon emission in the optical resonator. Therefore, the detection of photons generated in the cavity mode concomitantly ...
Acoustic Bloch oscillations in a two-dimensional phononic crystal.
He, Zhaojian; Peng, Shasha; Cai, Feiyan; Ke, Manzhu; Liu, Zhengyou
2007-11-01
We report the observation of acoustic Bloch oscillations at megahertz frequency in a two-dimensional phononic crystal. By creating periodically arrayed cavities with a decreasing gradient in width along one direction in the phononic crystal, acoustic Wannier-Stark ladders are created in the frequency domain. The oscillatory motion of an incident Gaussian pulse inside the sample is demonstrated by both simulation and experiment.
Far infrared absorption by acoustic phonons in titanium dioxide nanopowders
Murray, Daniel B.; Netting, Caleb H.; Saviot, Lucien; Pighini, Catherine; Millot, Nadine; Aymes, Daniel; Liu, Hsiang-Lin
2006-01-01
We report spectral features of far infrared electromagnetic radiation absorption in anatase TiO2 nanopowders which we attribute to absorption by acoustic phonon modes of nanoparticles. The frequency of peak excess absorption above the background level corresponds to the predicted frequency of the dipolar acoustic phonon from continuum elastic theory. The intensity of the absorption cannot be accounted for in a continuum elastic dielectric description of the nanoparticle material. Quantum mech...
On-chip photonic-phononic emitter-receiver apparatus
Cox, Jonathan Albert; Jarecki, Jr., Robert L.; Rakich, Peter Thomas; Wang, Zheng; Shin, Heedeuk; Siddiqui, Aleem; Starbuck, Andrew Lea
2017-07-04
A radio-frequency photonic devices employs photon-phonon coupling for information transfer. The device includes a membrane in which a two-dimensionally periodic phononic crystal (PnC) structure is patterned. The device also includes at least a first optical waveguide embedded in the membrane. At least a first line-defect region interrupts the PnC structure. The first optical waveguide is embedded within the line-defect region.
A Comprehensive Approach to Phonon Control for Enhanced Device Performance
2006-07-12
that moving the power density in time domain experiments, it is possible to go from the renormalized frequency (at power P1) to the bare frequency (at...function in the infrared and, thereby, renormalizes the frequency of the optical modes; see the energy level diagram in Fig. 9(left). In particular, a...filled electronic trap with an allowed transition frequency larger than the bare optical phonon frequency, will push the effective optical phonon
On time-resolved approach for phonon assisted interband transitions
Klotins, E.
2015-03-01
Photoexcited dynamics of electrons and holes in two-band dielectric, with special emphasis on back reaction of phonons are developed by combining the quantum electrodynamics and Baker-Campbell-Hausdorff (BCH) canonical transformation. These methods create an explicit time-domain representation of photoinduced processes and contribute in unifying phonon-assisted description of distribution functions of electron and hole quasiparticles for the description of observable effects of photoinduced processes in dielectrics.
Mixed symmetry Wilson-loop interactions in the worldline formalism
Edwards, James P
2016-01-01
Using the worldline formalism of the Dirac field with a non-Abelian gauge symmetry we show how to describe the matter field transforming in an arbitrary representation of the gauge group. Colour degrees of freedom are carried on the worldline by auxiliary fields, responsible for providing path ordering and the Wilson-loop coupling. The Hilbert space of these fields is reducible but we make use of recent work in order to project onto a single, arbitrary, irreducible representation. By functionally quantising the resulting theory we show that this procedure correctly generates the Wilson-loop interaction between the gauge field and the matter field taken to transform in a chosen representation. This work has direct application to physical observables such as scattering amplitudes in the presence of such a matter multiplet and lifts the restriction on the type of matter that has previously featured in worldline calculations.
Wigner surmise for mixed symmetry classes in random matrix theory.
Schierenberg, Sebastian; Bruckmann, Falk; Wettig, Tilo
2012-06-01
We consider the nearest-neighbor spacing distributions of mixed random matrix ensembles interpolating between different symmetry classes or between integrable and nonintegrable systems. We derive analytical formulas for the spacing distributions of 2×2 or 4×4 matrices and show numerically that they provide very good approximations for those of random matrices with large dimension. This generalizes the Wigner surmise, which is valid for pure ensembles that are recovered as limits of the mixed ensembles. We show how the coupling parameters of small and large matrices must be matched depending on the local eigenvalue density.
Wigner surmise for mixed symmetry classes in random matrix theory
Schierenberg, Sebastian; Wettig, Tilo
2012-01-01
We consider the nearest-neighbor spacing distributions of mixed random matrix ensembles interpolating between different symmetry classes, or between integrable and non-integrable systems. We derive analytical formulas for the spacing distributions of 2x2 or 4x4 matrices and show numerically that they provide very good approximations for those of random matrices with large dimension. This generalizes the Wigner surmise, which is valid for pure ensembles that are recovered as limits of the mixed ensembles. We show how the coupling parameters of small and large matrices must be matched depending on the local eigenvalue density.
Decomposition model for phonon thermal conductivity of a monatomic lattice
Evteev, Alexander V.; Momenzadeh, Leila; Levchenko, Elena V.; Belova, Irina V.; Murch, Graeme E.
2014-12-01
An analytical treatment of decomposition of the phonon thermal conductivity of a crystal with a monatomic unit cell is developed on the basis of a two-stage decay of the heat current autocorrelation function observed in molecular dynamics simulations. It is demonstrated that the contributions from the acoustic short- and long-range phonon modes to the total phonon thermal conductivity can be presented in the form of simple kinetic formulas, consisting of products of the heat capacity and the average relaxation time of the considered phonon modes as well as the square of the average phonon velocity. On the basis of molecular dynamics calculations of the heat current autocorrelation function, this treatment allows for a self-consistent numerical evaluation of the aforementioned variables. In addition, the presented analysis allows, within the Debye approximation, for the identification of the temperature range where classical molecular dynamics simulations can be employed for the prediction of phonon thermal transport properties. As a case example, Cu is considered.
Phononic crystals with one-dimensional defect as sensor materials
Aly, Arafa H.; Mehaney, Ahmed
2017-09-01
Recently, sensor technology has attracted great attention in many fields due to its importance in many engineering applications. In the present work, we introduce a study using the innovative properties of phononic crystals in enhancing a new type of sensors based on the intensity of transmitted frequencies inside the phononic band gaps. Based on the transfer matrix method and Bloch theory, the expressions of the reflection coefficient and dispersion relation are presented. Firstly, the influences of filling fraction ratio and the angle of incidence on the band gap width are discussed. Secondly, the localization of waves inside band gaps is discussed by enhancing the properties of the defected phononic crystal. Compared to the periodic structure, localization modes involved within the band structure of phononic crystals with one and two defect layers are presented and compared. Trapped localized modes can be detected easily and provide more information about defected structures. Such method could increase the knowledge of manufacturing defects by measuring the intensity of propagated waves in the resonant cavities and waveguides. Moreover, several factors enhance the role of the defect layer on the transmission properties of defected phononic crystals are presented. The acoustic band gap can be used to detect or sense the type of liquids filling the defect layer. The liquids make specific resonant modes through the phononic band gaps that related to the properties of each liquid. The frequency where the maximum resonant modes occur is correlated to material properties and allows to determine several parameters such as the type of an unknown material.
Experimental studies of electron-phonon interactions in gallium nitride
Stanton, N M
2001-01-01
This thesis presents an experimental investigation of the electron-phonon interaction in GaN. Bulk epilayers, grown by MBE, and AIGaN/GaN heterostructure grown by MOCVD, have been studied. The energy relaxation rate for hot electrons has been measured over a wide range of temperatures, allowing both acoustic and optic phonon emission to be studied in GaN epilayers. Direct phonon measurements, both studying the emission and absorption processes, have been performed. Detection of phonons emitted when hot electrons relax their excess energy complements the measurements of relaxation rates. Absorption of acoustic phonons by the epilayers, using both fixed and extended metal film phonon sources, allowed investigation into the effectiveness of the 2k sub F cutoff in the low mobility layers. The experimental findings are compared with the predictions of theory. AIGaN/GaN heterostructures were characterised and measurements of the energy relaxation rate in the temperature range 4K-40K obtained. Excellent agreement wi...
Electron-phonon coupling in hybrid lead halide perovskites
Wright, Adam D.; Verdi, Carla; Milot, Rebecca L.; Eperon, Giles E.; Pérez-Osorio, Miguel A.; Snaith, Henry J.; Giustino, Feliciano; Johnston, Michael B.; Herz, Laura M.
2016-05-01
Phonon scattering limits charge-carrier mobilities and governs emission line broadening in hybrid metal halide perovskites. Establishing how charge carriers interact with phonons in these materials is therefore essential for the development of high-efficiency perovskite photovoltaics and low-cost lasers. Here we investigate the temperature dependence of emission line broadening in the four commonly studied formamidinium and methylammonium perovskites, HC(NH2)2PbI3, HC(NH2)2PbBr3, CH3NH3PbI3 and CH3NH3PbBr3, and discover that scattering from longitudinal optical phonons via the Fröhlich interaction is the dominant source of electron-phonon coupling near room temperature, with scattering off acoustic phonons negligible. We determine energies for the interacting longitudinal optical phonon modes to be 11.5 and 15.3 meV, and Fröhlich coupling constants of ~40 and 60 meV for the lead iodide and bromide perovskites, respectively. Our findings correlate well with first-principles calculations based on many-body perturbation theory, which underlines the suitability of an electronic band-structure picture for describing charge carriers in hybrid perovskites.
Phonon anharmonicity and negative thermal expansion in SnSe
Bansal, Dipanshu; Hong, Jiawang; Li, Chen W.; May, Andrew F.; Porter, Wallace; Hu, Michael Y.; Abernathy, Douglas L.; Delaire, Olivier
2016-08-01
The anharmonic phonon properties of SnSe in the P n m a phase were investigated with a combination of experiments and first-principles simulations. Using inelastic neutron scattering (INS) and nuclear resonant inelastic X-ray scattering (NRIXS), we have measured the phonon dispersions and density of states (DOS) and their temperature dependence, which revealed a strong, inhomogeneous shift and broadening of the spectrum on warming. First-principles simulations were performed to rationalize these measurements, and to explain the previously reported anisotropic thermal expansion, in particular the negative thermal expansion within the Sn-Se bilayers. Including the anisotropic strain dependence of the phonon free energy, in addition to the electronic ground state energy, is essential to reproduce the negative thermal expansion. From the phonon DOS obtained with INS and additional calorimetry measurements, we quantify the harmonic, dilational, and anharmonic components of the phonon entropy, heat capacity, and free energy. The origin of the anharmonic phonon thermodynamics is linked to the electronic structure.
Slow light and slow acoustic phonons in optophononic resonators
Villafañe, V.; Soubelet, P.; Bruchhausen, A. E.; Lanzillotti-Kimura, N. D.; Jusserand, B.; Lemaître, A.; Fainstein, A.
2016-11-01
Slow and confined light have been exploited in optoelectronics to enhance light-matter interactions. Here we describe the GaAs/AlAs semiconductor microcavity as a device that, depending on the excitation conditions, either confines or slows down both light and optically generated acoustic phonons. The localization of photons and phonons in the same place of space amplifies optomechanical processes. Picosecond laser pulses are used to study through time-resolved reflectivity experiments the coupling between photons and both confined and slow acoustic phonons when the laser is tuned either with the cavity (confined) optical mode or with the stop-band edge (slow) optical modes. A model that fully takes into account the modified propagation of the acoustic phonons and light in these resonant structures is used to describe the laser detuning dependence of the coherently generated phonon spectra and amplitude under these different modes of laser excitation. We observe that confined light couples only to confined mechanical vibrations, while slow light can generate both confined and slow coherent vibrations. A strong enhancement of the optomechanical coupling using confined photons and vibrations, and also with properly designed slow photon and phonon modes, is demonstrated. The prospects for the use of these optoelectronic devices in confined and slow optomechanics are addressed.
A moment model for phonon transport at room temperature
Mohammadzadeh, Alireza; Struchtrup, Henning
2017-01-01
Heat transfer in solids is modeled by deriving the macroscopic equations for phonon transport from the phonon-Boltzmann equation. In these equations, the Callaway model with frequency-dependent relaxation time is considered to describe the Resistive and Normal processes in the phonon interactions. Also, the Brillouin zone is considered to be a sphere, and its diameter depends on the temperature of the system. A simple model to describe phonon interaction with crystal boundary is employed to obtain macroscopic boundary conditions, where the reflection kernel is the superposition of diffusive reflection, specular reflection and isotropic scattering. Macroscopic moments are defined using a polynomial of the frequency and wave vector of phonons. As an example, a system of moment equations, consisting of three directional and seven frequency moments, i.e., 63 moments in total, is used to study one-dimensional heat transfer, as well as Poiseuille flow of phonons. Our results show the importance of frequency dependency in relaxation times and macroscopic moments to predict rarefaction effects. Good agreement with data reported in the literature is obtained.
Polar phonon mixing in magnetoelectric EuTiO3
Goian, V.; Kamba, S.; Hlinka, J.; Vaněk, P.; Belik, A. A.; Kolodiazhnyi, T.; Petzelt, J.
2009-10-01
Infrared reflectivity spectra of antiferromagnetic incipient ferroelectric EuTiO3 were investigated up to 600 K. Three polar phonons typical for the cubic perovskite Pmbar {3}m structure were observed. Analysis of phonon plasma frequencies showed that the lowest-energy TO1 phonon corresponds predominantly to the Slater mode describing vibration of Ti cations against the oxygen octahedra and the TO2 phonon expresses vibrations of the Eu cation against the TiO6 octahedra. The highest frequency TO4 phonon represents O-octahedra bending. Incipient ferroelectric behavior of the permittivity is caused by pronounced softening of the TO1 phonon, which is coupled to the TO2 mode. Although the Eu cations are not involved in the TO1 mode, the spin ordering of the 4f electrons at Eu cations has influence on the frequency of the TO1 mode due to Eu-O-Eu super-exchange interaction. This is probably responsible for the 7% change of the permittivity induced by the magnetic field in the antiferromagnetic phase, as reported by Katsufuji and Takagi [Phys. Rev. B 64, 054415 (2001)].
Phononic crystals with one-dimensional defect as sensor materials
Aly, Arafa H.; Mehaney, Ahmed
2017-04-01
Recently, sensor technology has attracted great attention in many fields due to its importance in many engineering applications. In the present work, we introduce a study using the innovative properties of phononic crystals in enhancing a new type of sensors based on the intensity of transmitted frequencies inside the phononic band gaps. Based on the transfer matrix method and Bloch theory, the expressions of the reflection coefficient and dispersion relation are presented. Firstly, the influences of filling fraction ratio and the angle of incidence on the band gap width are discussed. Secondly, the localization of waves inside band gaps is discussed by enhancing the properties of the defected phononic crystal. Compared to the periodic structure, localization modes involved within the band structure of phononic crystals with one and two defect layers are presented and compared. Trapped localized modes can be detected easily and provide more information about defected structures. Such method could increase the knowledge of manufacturing defects by measuring the intensity of propagated waves in the resonant cavities and waveguides. Moreover, several factors enhance the role of the defect layer on the transmission properties of defected phononic crystals are presented. The acoustic band gap can be used to detect or sense the type of liquids filling the defect layer. The liquids make specific resonant modes through the phononic band gaps that related to the properties of each liquid. The frequency where the maximum resonant modes occur is correlated to material properties and allows to determine several parameters such as the type of an unknown material.
Topological phononic insulator with robust pseudospin-dependent transport
Xia, Bai-Zhan; Liu, Ting-Ting; Huang, Guo-Liang; Dai, Hong-Qing; Jiao, Jun-Rui; Zang, Xian-Guo; Yu, De-Jie; Zheng, Sheng-Jie; Liu, Jian
2017-09-01
Topological phononic states, which facilitate unique acoustic transport around defects and disorders, have significantly revolutionized our scientific cognition of acoustic systems. Here, by introducing a zone folding mechanism, we realize the topological phase transition in a double Dirac cone of the rotatable triangular phononic crystal with C3 v symmetry. We then investigate the distinct topological edge states on two types of interfaces of our phononic insulators. The first one is a zigzag interface which simultaneously possesses a symmetric mode and an antisymmetric mode. Hybridization of the two modes leads to a robust pseudospin-dependent one-way propagation. The second one is a linear interface with a symmetric mode or an antisymmetric mode. The type of mode is dependent on the topological phase transition of the phononic insulators. Based on the rotatability of triangular phononic crystals, we consider several complicated contours defined by the topological zigzag interfaces. Along these contours, the acoustic waves can unimpededly transmit without backscattering. Our research develops a route for the exploration of the topological phenomena in experiments and provides an excellent framework for freely steering the acoustic backscattering-immune propagation within topological phononic structures.
Electron-phonon coupling in hybrid lead halide perovskites.
Wright, Adam D; Verdi, Carla; Milot, Rebecca L; Eperon, Giles E; Pérez-Osorio, Miguel A; Snaith, Henry J; Giustino, Feliciano; Johnston, Michael B; Herz, Laura M
2016-05-26
Phonon scattering limits charge-carrier mobilities and governs emission line broadening in hybrid metal halide perovskites. Establishing how charge carriers interact with phonons in these materials is therefore essential for the development of high-efficiency perovskite photovoltaics and low-cost lasers. Here we investigate the temperature dependence of emission line broadening in the four commonly studied formamidinium and methylammonium perovskites, HC(NH2)2PbI3, HC(NH2)2PbBr3, CH3NH3PbI3 and CH3NH3PbBr3, and discover that scattering from longitudinal optical phonons via the Fröhlich interaction is the dominant source of electron-phonon coupling near room temperature, with scattering off acoustic phonons negligible. We determine energies for the interacting longitudinal optical phonon modes to be 11.5 and 15.3 meV, and Fröhlich coupling constants of ∼40 and 60 meV for the lead iodide and bromide perovskites, respectively. Our findings correlate well with first-principles calculations based on many-body perturbation theory, which underlines the suitability of an electronic band-structure picture for describing charge carriers in hybrid perovskites.
Magnetic moments induce strong phonon renormalization in FeSi.
Krannich, S; Sidis, Y; Lamago, D; Heid, R; Mignot, J-M; Löhneysen, H v; Ivanov, A; Steffens, P; Keller, T; Wang, L; Goering, E; Weber, F
2015-11-27
The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron-phonon coupling is well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron-phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe-Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin-phonon coupling and multiple interaction paths.
A twin aperture resistive quadrupole for the LHC
Clark, G S; de Rijk, G; Racine, M
2000-01-01
The European Organization for Nuclear Research (CERN) is constructing the Large Hadron Collider (LHC). The LHC's cleaning insertions require 48 twin aperture resistive quadrupoles. These 3.1 m long magnets have a gradient of 35 T/m for an inscribed circle of 46 mm diameter and an aperture separation distance of 224 mm. This magnet project is part of the Canadian contribution to the LHC. A prototype magnet was delivered in May 1998 and measured at CERN. Design changes were made based on the results. Due to the small apertures and the complicated geometry, the mechanical precision of the laminations and stacks is the main issue in the production of these quadrupoles. Series production will start in October 1999. The design and the measurement results are described in this paper. (1 refs).
Performance of an Adjustable Strength Permanent Magnet Quadrupole
Gottschalk, Stephen C; Kangas, Kenneth; Spencer, Cherrill M; Volk, James T
2005-01-01
An adjustable strength permanent magnet quadrupole suitable for use in Next Linear Collider has been built and tested. The pole length is 42cm, aperture diameter 13mm, peak pole tip strength 1.03Tesla and peak integrated gradient * length (GL) is 68.7 Tesla. This paper describes measurements of strength, magnetic centerline and field quality made using an air bearing rotating coil system. The magnetic centerline stability during -20% strength adjustment proposed for beam based alignment was < 0.2 microns. Strength hysteresis was negligible. Thermal expansion of quadrupole and measurement parts caused a repeatable and easily compensated change in the vertical magnetic centerline. Calibration procedures as well as centerline measurements made over a wider tuning range of 100% to 20% in strength useful for a wide range of applications will be described. The impact of eddy currents in the steel poles on the magnetic field during strength adjustments will be reported.
Low-frequency quadrupole impedance of undulators and wigglers
A. Blednykh
2016-10-01
Full Text Available An analytical expression of the low-frequency quadrupole impedance for undulators and wigglers is derived and benchmarked against beam-based impedance measurements done at the 3 GeV NSLS-II storage ring. The adopted theoretical model, valid for an arbitrary number of electromagnetic layers with parallel geometry, allows to calculate the quadrupole impedance for arbitrary values of the magnetic permeability μ_{r}. In the comparison of the analytical results with the measurements for variable magnet gaps, two limit cases of the permeability have been studied: the case of perfect magnets (μ_{r}→∞, and the case in which the magnets are fully saturated (μ_{r}=1.
Nuclear quadrupole coupling interactions in the rotational spectrum of tryptamine
Alonso, J. L.; Cortijo, V.; Mata, S.; Pérez, C.; Cabezas, C.; López, J. C.; Caminati, W.
2011-09-01
Four conformers of tryptamine have been detected in a supersonic expansion and characterized by laser ablation molecular beam Fourier transform microwave spectroscopy LA-MB-FTMW in the 5-10 GHz frequency range. The quadrupole hyperfine structure originated by two 14N nuclei has been completely resolved for all conformers and used for their unambiguous identification. Nuclear quadrupole coupling constants of the nitrogen atom of the side chain have been used to determine the orientation of the amino group involved in N-H⋯π interactions: to the π electronic system of the pyrrole unit in the Gauche-Pyrrole conformers (GPy) or to the phenyl unit in the Gauche-Phenyl ones.
120-mm superconducting quadrupole for interaction regions of hadron colliders
Zlobin, A V; Mokhov, N V; Novitski, I
2012-01-01
Magnetic and mechanical designs of a Nb3Sn quadrupole magnet with 120-mm aperture suitable for interaction regions of hadron colliders are presented. The magnet is based on a two-layer shell-type coil and a cold iron yoke. Special spacers made of a low-Z material are implemented in the coil mid-planes to reduce the level of radiation heat deposition and radiation dose in the coil. The quadrupole mechanical structure is based on aluminum collars supported by an iron yoke and a stainless steel skin. Magnet parameters including maximum field gradient and field harmonics, Nb3Sn coil pre-stress and protection at the operating temperatures of 4.5 and 1.9 K are reported. The level and distribution of radiation heat deposition in the coil and other magnet components are discussed.
Chlorine Nuclear Quadrupole Hyperfine Structure in the Vinyl - Chloride Complex
Leung, Helen O.; Marshall, Mark D.; Messinger, Joseph P.
2015-06-01
The microwave spectrum of the vinyl chloride--hydrogen chloride complex, presented at last year's symposium, is greatly complicated by the presence of two chlorine nuclei as well as an observed, but not fully explained tunneling motion. Indeed, although it was possible at that time to demonstrate conclusively that the complex is nonplanar, the chlorine nuclear quadrupole hyperfine splitting in the rotational spectrum resisted analysis. With higher resolution, Balle-Flygare Fourier transform microwave spectra, the hyperfine structure has been more fully resolved, but appears to be perturbed for some rotational transitions. It appears that knowledge of the quadrupole coupling constants will provide essential information regarding the structure of the complex, specifically the location of the hydrogen atom in HCl. Our progress towards obtaining values for these constants will be presented.
Beta Function Measurement in the Tevatron Using Quadrupole Gradient Modulation
Jansson, Andreas; Volk, James T
2005-01-01
Early in Run2, there was an effort to compare the different emittance measurements in the Tevatron (flying wires and synchtotron light) and understand the origin of the observed differences. To measure the beta function at a few key locations near the instruments, air-core quadrupoles were installed. By modulating the gradient of these magents and measuring the effect on the tune, the lattice parameters can be extracted. Initially, the results seem to disagree with with other methods. At the time, the lattice was strongly coupled due to a skew component in the main dipoles, caused by sagging of the cryostat. After a large fraction of the superconducting magnets were shimmed to remove a strong skew quadrupole component, the results now agree with expectations, confirming that the beta function is not the major error source of discrepancy in the emittance measurement.
Quadrupole association and dissociation of hydrogen in the early Universe
Forrey, Robert C.
2016-10-01
Radiative association and photodissociation rates are calculated for quadrupole transitions of H2. A complete set of bound and unbound states are included in a self-consistent master equation to obtain steady-state concentrations for a dilute system of hydrogen atoms and molecules. Phenomenological rate constants computed from the steady-state concentrations satisfy detailed balance for any combination of matter and radiation temperature. Simple formulas are derived for expressing the steady-state distributions in terms of equilibrium distributions. The rate constant for radiative association is found to be generally small for all temperature combinations. The photodissociation rate constant for quadrupole transitions is found to dominate the rate constants for other H2 photodestruction mechanisms for {T}{{R}} ≤slant 3000 K. Implications for the formation and destruction of H2 in the early Universe are discussed.
Quadrupole association and dissociation of hydrogen in the early Universe
Forrey, Robert C
2016-01-01
Radiative association and photodissociation rates are calculated for quadrupole transitions of H2. A complete set of bound and unbound states are included in a self-consistent master equation to obtain steady-state concentrations for a dilute system of hydrogen atoms and molecules. Phenomenological rate constants computed from the steady-state concentrations satisfy detailed balance for any combination of matter and radiation temperature. Simple formulas are derived for expressing the steady-state distributions in terms of equilibrium distributions. The rate constant for radiative association is found to be generally small for all temperature combinations. The photodissociation rate constant for quadrupole transitions is found to dominate the rate constants for other H2 photodestruction mechanisms for radiation temperatures less than or equal to 3000 K. Implications for the formation and destruction of H2 in the early universe are discussed.
Prototype of Superconducting Quadrupole for ISR Low-Beta Insertion
1977-01-01
In colliders, smaller beam cross-section means higher luminosity. Beam-size being proportional to the square-root of the "beta function" value, a small beta means small beam size, hence high luminosity. The first p-p collision in the ISR occurred in January 1971 and in 1973 a study was launched on low-beta insertions, which focus beams to even smaller sizes at the beam crossing points. In 1976 the first prototype of a superconducting quadrupole was tested. Here we see Theodor Tortschanoff with a prototype of 1.25 m magnetic length. Manufacture of 8 quadrupoles (4 of L=1.15 m, 4 of L=0.65 m) began at Alsthom in 1978. They were installed at point 8 of the ISR, enhancing luminosity there until final low-beta operation in December 1983. For details see "Yellow Report" CERN 76-16.
Generating Low Beta Regions with Quadrupoles for Final Muon Cooling
Acosta, J. G. [Mississippi U.; Cremaldi, L. M. [Mississippi U.; Hart, T. L. [Mississippi U.; Oliveros, S. J. [Mississippi U.; Summers, D. J. [Mississippi U.; Neuffer, D. V. [Fermilab
2017-05-01
Muon beams and colliders are rich sources of new physics, if muons can be cooled. A normalized rms transverse muon emittance of 280 microns has been achieved in simulation with short solenoids and a betatron function of 3 cm. Here we use ICOOL, G4beamline, and MAD-X to explore using a 400 MeV/c muon beam and strong focusing quadrupoles to approach a normalized transverse emittance of 100 microns and finish 6D muon cooling. The low beta regions produced by the quadrupoles are occupied by dense, low Z absorbers, such as lithium hydride or beryllium, that cool the beam. Equilibrium transverse emittance is linearly proportional to the beta function. Reverse emittance exchange with septa and/or wedges is then used to decrease transverse emittance from 100 to 25 microns at the expense of longitudinal emittance for a high energy lepton collider. Work remains to be done on chromaticity correction.
High Gradient $Nb_3Sn$ Quadrupole Demonstrator MKQXF Engineering Design
Kokkinos, C; Karppinen, Mikko; CERN. Geneva. ATS Department
2016-01-01
A new mechanical design concept for the $Nb_3Sn$ quadrupoles has been developed with a goal of an accelerator quality magnet that can be industrially produced in large series. This concept can easily be extended to any length and applied on both 1-in-1 and 2-in-1 configurations. It is based on the pole-loading concept and collared coils using dipole-type collars. Detailed design optimisation of a demonstrator magnet based on present base-line HL-LHC IR quadrupole QXF coil geometry has been carried out including the end regions. This report describes the design concept and the fully parametric multi-physics finite element (FE) models that were used to determine the optimal assembly parameters including the effects of the manufacturing tolerances.
Wooden models of an AA quadrupole between bending magnets
1978-01-01
At two points in the AA lattice, a quadrupole (QDN, defocusing, narrow) was tightly wedged between two bending magnets (BST, short, wide). This picture of wooden models lets one imagine the strong interaction between their magnetic fields. There was no way one could calculate with the necessary accuracy the magnetic effects and their consequences for the machine optics. The necessary corrections were made after measurements with a circulating beam, in a tedious iterative procedure, with corrrection coils and shims.
Testing the Dipole and Quadrupole Moments of Galactic Models
Briggs, Michael S.; Paciesas, William S.; Pendleton, Geoffrey N.; Meegan, Charles A.; Fishman, Gerald J.; Horack, John M.; Kouveliotou, Chryssa; Hartmann, Dieter H.; Hakkila, Jon
1996-01-01
If gamma-ray bursts originate in the Galaxy, at some level there should be a galactic pattern in their distribution on the sky. We test published galactic models by comparing their dipole and quadrupole moments with the moments of the BATSE 3B catalog. While many models have moments that are too large, several models are in acceptable or good agreement with the data.
Electrostatic quadrupole focusing in the AGS g-2 storage ring
Bennett, G.; Larsen, R.; Morse, W.; Semertzidis, Y.; Yelk, J. [Brookhaven National Lab., Upton, NY (United States); Liu, Z. [Boston Univ., MA (United States). Dept. of Physics
1993-06-01
Electrostatic quadrupole focusing is to be used in the high precision measurement of the anomalous magnetic moment of the muon, AGS Experiment 821. The final design uses planar rather than hyperbolic electrodes, and the field is pulsed to minimize the effect of trapped electrons. The mechanical design is described. Performance in a 1.5T magnetic field at less than 10{sup {minus}6} Torr is reviewed.
Electrostatic quadrupole focusing in the AGS g-2 storage ring
Bennett, G.; Larsen, R.; Morse, W.; Semertzidis, Y.; Yelk, J. (Brookhaven National Lab., Upton, NY (United States)); Liu, Z. (Boston Univ., MA (United States). Dept. of Physics)
1993-01-01
Electrostatic quadrupole focusing is to be used in the high precision measurement of the anomalous magnetic moment of the muon, AGS Experiment 821. The final design uses planar rather than hyperbolic electrodes, and the field is pulsed to minimize the effect of trapped electrons. The mechanical design is described. Performance in a 1.5T magnetic field at less than 10[sup [minus]6] Torr is reviewed.
Active quadrupole stabilization for future linear particle colliders
Collette, Christophe; Kuzmin, Andrey; Janssens, Stef; Sylte, Magnus; Guinchard, Michael; Hauviller, Claude
2010-01-01
The future Compact LInear particle Collider (CLIC) under study at CERN will require to stabilize heavy electromagnets, and also to provide them some positioning capabilities. Firstly, this paper presents the concept adopted to address both requirements. Secondly, the control strategy adopted for the stabilization is studied numerically, showing that the quadrupole can be stabilized in both lateral and vertical direction. Finally, the strategy is validated experimentally on a single degree of freedom scaled test bench.
Permanent magnet quadrupoles for the CLIC Drive Beam decelerator
Shepherd, Ben; Collomb, Norbert
2012-01-01
STFC in collaboration with CERN has developed a new type of adjustable permanent magnet based quadrupole for the CLIC Drive Beam Decelerator. It uses vertical movement of the permanent magnets to achieve an integrated gradient range of 3.6-14.6T, which will allow it to be used for the first 60% of the decelerator line. Construction of a prototype of this magnet has begun; following this, it will be measured magnetically at CERN and Daresbury Laboratory.
Short quadrupole, first at the SC, then at LEAR
1982-01-01
Quadrupoles of this type were built for the beam lines of the 600 MeV Synchro-Cylclotron. Surplus ones were installed in the LEAR injection line. The particularity of these quads is that they are very short and that a special design, resembling the "Lambertson magnet", limits and linearizes their stray field. This was achieved by the iron between the poles extending beyond the poles.
General quadrupole shapes in the Interacting Boson Model
Leviatan, A.
1990-01-01
Characteristic attributes of nuclear quadrupole shapes are investigated within the algebraic framework of the Interacting Boson Model. For each shape the Hamiltonian is resolved into intrinsic and collective parts, normal modes are identified and intrinsic states are constructed and used to estimate transition matrix elements. Special emphasis is paid to new features (e.g. rigid triaxiality and coexisting deformed shapes) that emerge in the presence of the three-body interactions. 27 refs.
Determining gaseous composition of fluid inclusions with quadrupole mass spectrometer
朱和平; 王莉娟
2002-01-01
Quadrupole mass spectrometer (QMS) is an instrument for effectively determining gaseous composition of fluid inclusion. The gaseous component is extracted from inclusions with thermal decrepitation method and then determined with the sensitive QMS instrument. The method is characterized by high sensitivity and high accuracy with the relative standard deviation (RSD, n = 6) of less than 3%. It has been successfully used for analyzing fluid inclusions. The analytical re-sults meet the requirement of geological study.
Targeted Proteomic Quantification on Quadrupole-Orbitrap Mass Spectrometer*
Gallien, Sebastien; Duriez, Elodie; Crone, Catharina; Kellmann, Markus; Moehring, Thomas; Domon, Bruno
2012-01-01
There is an immediate need for improved methods to systematically and precisely quantify large sets of peptides in complex biological samples. To date protein quantification in biological samples has been routinely performed on triple quadrupole instruments operated in selected reaction monitoring mode (SRM), and two major challenges remain. Firstly, the number of peptides to be included in one survey experiment needs to be increased to routinely reach several hundreds, and secondly, the degr...
Mass Quadrupole as a Source of Naked Singularities
Quevedo, Hernando
2010-01-01
We investigate the gravitational field of a static mass with quadrupole moment in empty space. It is shown that in general this configuration is characterized by the presence of curvature singularities without a surrounding event horizon. These naked singularities generate an effective field of repulsive gravity which, in turn, drastically changes the behavior of test particles. As a possible consequence, the accretion disk around a naked singularity presents a particular discontinuous structure.
NMR Probe as a Field Marker in a Quadrupole
Caspers, Friedhelm; CERN. Geneva. SPS and LEP Division
1999-01-01
A study has started to improve the reproducibility of the focusing elements of the SPS for its operation as LHC injector. This note is a copy of the oral presentation to the IMMW11 seminar, which took place at Brookhaven National Laboratory in September 1999. It indicates the feasibility of the creation of a "G-Train" via a NMR probe used as a field marker in a reference quadrupole.
Longitudinal capture in the radio-frequency-quadrupole structure
Inagaki, S.
1980-03-01
The radio-frequency-quadrupole (RFQ) linac structure not only can attain easily transverse focusing in the low-beta region, but also can obtain very high capture efficiency because of its low beta-lambda and low-particle rigidity. An optimization study of the zero space-charge longitudinal capture in an RFQ linac that yields configurations with large capture efficiency is described.
Quadrupole Law and Steering Options in the Linac4 DTL
Stovall, J
2009-01-01
The Linac4 drift-tube linac (DTL) reference design has been modified to reduce the power consumption in tank 1 by adjusting the accelerating field and phase laws. In this note we investigate three options for the transverse focusing lattice, quadrupole law, and two options for beam steering. We use acceptance, sensitivity to alignment errors and the probabiity of beam loss as figures of merit for evaluating each option.
Analysis of lamination measurements for CERN's twin aperture quadrupoles
Clark, G S
2002-01-01
The European Organization for Nuclear Research (CERN) is constructing the Large Hadron Collider (LHC). The LHC's cleaning insertions require 48 twin aperture resistive quadrupoles. The laminations for these magnets are punched from low carbon steel sheet 1.5 mm thick. To check the quality of the laminations, samples are regularly collected and measured. This paper describes how these measurements are analyzed. This work is part of the Canadian contribution to the LHC. (5 refs).
MEASURING LOCAL GRADIENT AND SKEW QUADRUPOLE ERRORS IN RHIC IRS.
CARDONA,J.; PEGGS,S.; PILAT,R.; PTITSYN,V.
2004-07-05
The measurement of local linear errors at RHIC interaction regions using an ''action and phase'' analysis of difference orbits has already been presented. This paper evaluates the accuracy of this technique using difference orbits that were taken when known gradient errors and skew quadrupole errors were intentionally introduced. It also presents action and phase analysis of simulated orbits when controlled errors are intentionally placed in a RHIC simulation model.
Mesoscopic hydro-thermodynamics of phonons
Aurea R. Vasconcellos
2013-07-01
Full Text Available A generalized Hydrodynamics, referred to as Mesoscopic Hydro-Thermodynamics, of phonons in semiconductors is presented. It involves the descriptions of the motion of the quasi-particle density and of the energy density. The hydrodynamic equations, which couple both types of movement via thermo-elastic processes, are derived starting with a generalized Peierls-Boltzmann kinetic equation obtained in the framework of a Non-Equilibrium Statistical Ensemble Formalism, providing such Mesoscopic Hydro-Thermodynamics. The case of a contraction in first order is worked out in detail. The associated Maxwell times are derived and discussed. The densities of quasi-particles and of energy are found to satisfy coupled Maxwell-Cattaneo-like (hyperbolic equations. The analysis of thermo-elastic effects is done and applied to investigate thermal distortion in silicon mirrors under incidence of high intensity X-ray pulses in FEL facilities. The derivation of a generalized Guyer-Krumhansl equation governing the flux of heat and the associated thermal conductivity coefficient is also presented.
TOPICAL REVIEW: Photonic and phononic quasicrystals
Steurer, Walter; Sutter-Widmer, Daniel
2007-07-01
This review focuses on the peculiarities of quasiperiodic order for the properties of photonic and phononic (sonic) heterostructures. The most beneficial feature of quasiperiodicity is that it can combine perfectly ordered structures with purely point-diffractive spectra of arbitrarily high rotational symmetry. Both are prerequisites for the construction of isotropic band gap composites, in particular from materials with low index contrast, which are required for numerous applications. Another interesting property of quasiperiodic structures is their scaling symmetry, which may be exploited to create spectral gaps in the sub-wavelength regime. This review covers structure/property relationships of heterostructures based on one-dimensional (1D) substitutional sequences such as the Fibonacci, Thue Morse, period-doubling, Rudin Shapiro and Cantor sequence as well as on 1D modulated structures, further on 2D tilings with 8-, 10-, 12- and 14-fold symmetry as well as on the pinwheel tiling, the Sierpinski gasket and on curvilinear tilings and, finally, on the 3D icosahedral Penrose tiling.
Focusing Strength Measurements of the Main Quadrupoles for the LHC
Smirnov, N; Calvi, M; Deferne, G; Di Marco, J; Sammut, N; Sanfilippo, S
2006-01-01
More than 1100 quadrupole magnets of different types are needed for the Large Hadron Collider (LHC) which is in the construction stage at CERN. The most challenging parameter to measure on these quadrupoles is the integrated gradient (Gdl). An absolute accuracy of 0.1% is needed to control the beta beating. In this paper we briefly describe the whole set of equipment used for Gdl measurements: Automated Scanner system, Single Stretched Wire system and Twin Coils system, concentrating mostly on their absolute accuracies. Most of the possible inherent effects that can introduce systematic errors are discussed along with their preventive methods. In the frame of this qualification some of the magnets were tested with two systems. The results of the intersystem cross-calibrations are presented. In addition, the qualification of the measurement system used at the magnet manufacturer's is based on results of more than 40 quadrupole assemblies tested in cold conditions at CERN and in warm conditions at the vendor si...
In-situ Vibration Measurements of the CTF2 Quadrupoles
Coosemans, Williame
2004-01-01
The Compact LInear Collider (CLIC), presently under study at the European Organization for Nuclear Research (CERN), aims at colliding high energy âﾜnanobeamsâ at a luminosity of 1035 cm-2s-1. Vibrations of the lattice elements, if not properly corrected, can result in a loss in performance by creating both unacceptable emittance growth in the linear accelerator and relative beam-beam offsets at the interaction point. Of particular concern are the vibrations induced by the accelerator environment. For example, the circulating water used to cool the lattice quadrupoles will increase magnet vibration levels. In the framework of the CLIC stability study, in-situ measurements of quadrupole vibrations have been performed at the CLIC Test Facility 2 (CTF2) with all accelerator equipment switched on. Since the CTF2 quadrupoles and their alignment support structures are realistic prototypes of those to be used in the CLIC linac, the measurements provide a realistic estimate of the CLIC magnet vibrations in a...
Development of a $Nb_{3}$Sn quadrupole magnet model
Devred, Arnaud; Gourdin, C; Juster, F P; Peyrot, M; Rey, J M; Rifflet, J M; Streiff, J M; Védrine, P
2001-01-01
One possible application of Nb/sub 3/Sn, whose superconducting properties far exceed those of NbTi, is the fabrication of short and powerful quadrupole magnets for the crowded interaction regions of large particle accelerators. To learn about Nb/sub 3/Sn technology and to evaluate fabrication techniques, DAPNIA/STCM at CEA/Saclay has undertaken an R&D program aimed at designing and building a 1 m-long, 56 mm single-aperture quadrupole magnet model. The model relies on the same coil geometry as the LHC arc quadrupole magnets, but has no iron yoke. It is expected to produce a nominal field gradient of 211 T/m at 11870 A. The coils are wound from Rutherford-type cables insulated with quartz fiber tapes, before being heat-treated and vacuum-impregnated with epoxy resin. Laminated, austenitic collars, locked around the coil assembly by means of keys restrain the Lorentz forces. After reviewing the conceptual design of the magnet model, we report on the cable and cable insulation development programs and we pre...
Final 6D Muon Ionization Colling using Strong Focusing Quadrupoles
Hart, T. L. [Mississippi U.; Acosta, J. G. [Mississippi U.; Cremaldi, L. M. [Mississippi U.; Oliveros, S. J. [Mississippi U.; Summers, D. J. [Mississippi U.; Neuffer, D. V. [Fermilab
2016-11-15
Abstract Low emittance muon beam lines and muon colliders are potentially a rich source of BSM physics for future exper- imenters. A muon beam normalized emittance of ax,y,z = (280, 280, 1570)µm has been achieved in simulation with short solenoids and a betatron function of 3 cm. Here we use ICOOL and MAD-X to explore using a 400 MeV/c muon beam and strong focusing quadrupoles to achieve a normalized transverse emittance of 100 µm and complete 6D cooling. The low beta regions, as low as 5 mm, produced by the quadrupoles are occupied by dense, low Z absorbers, such as lithium hydride or beryllium, that cool the beam transversely. Equilibrium transverse emittance is linearly proportional to the transverse betatron function. Reverse emittance exchange with septa and/or wedges is then used to decrease transverse emittance from 100 to 25 µm at the expense of longitudinal emittance for a high energy lepton collider. Cooling challenges include chromaticity correction, ssband overlap, quadrupole acceptance, and staying in phase with RF.
Position Stability Monitoring of THEthe LCLS Undulator Quadrupoles
Nuhn, Heinz Dieter; Gassner, Georg; Peters, Franz; /SLAC
2012-03-26
X-ray FELs demand that the positions of undulator components be stable to less than 1 {mu}m per day. Simultaneously, the undulator length increases significantly in order to saturate at x-ray wavelengths. To minimize the impact of the outside environment, the Linac Coherent Light Source (LCLS) undulator is placed underground, but reliable data about ground motion inside such a tunnel was not available in the required stability range during the planning phase. Therefore, a new position monitor system had been developed and installed with the LCLS undulator. This system is capable of measuring x, y, roll, pitch and yaw of each of the 33 undulator quadrupoles with respect to stretched wires. Instrument resolution is about 10 nm and instrument drift is negligible. Position data of individual quadrupoles can be correlated along the entire 132-m long undulator. The system has been under continuous operation since 2009. This report describes long term experiences with the running system and the observed positional stability of the undulator quadrupoles.
Polarization dependent behavior of CdS around the first and second LO-phonon modes
Frausto-Reyes, C., E-mail: cfraus@cio.mx [Centro de Investigaciones en Optica AC, Unidad Aguascalientes, Prolong., Constitucion 607, Fracc. Reserva Loma Bonita, CP 20200, Apartado Postal 507, Ags. (Mexico); Molina-Contreras, J.R., E-mail: rmolina@correo.ita.mx [Departamento de Ingenieria Electrica y Electronica, Instituto Tecnologico de Aguascalientes, Av. Lopez Mateos 1081 Oriente, Fracc. Bonna Gens, CP 20256, Aguascalientes, Ags. (Mexico); Lopez-Alvarez, Y.F. [Departamento de Ingenieria Electrica y Electronica, Instituto Tecnologico de Aguascalientes, Av. Lopez Mateos 1081 Oriente, Fracc. Bonna Gens, CP 20256, Aguascalientes, Ags. (Mexico); Medel-Ruiz, C.I.; Perez Ladron de Guevara, H. [Universidad de Guadalajara, Centro Universitario de los Lagos, Av. Enrique Diaz de Leon s/n, Fracc. Paseos de la Montana, CP 47460, Lagos de Moreno, Jal. (Mexico); Ortiz-Morales, M. [Centro de Investigaciones en Optica AC, Unidad Aguascalientes, Prolong., Constitucion 607, Fracc. Reserva Loma Bonita, CP 20200, Apartado Postal 507, Ags. (Mexico)
2010-10-25
The present work report studies on resonant Raman experimental line shape for CdS around the first and second LO-phonon modes. The application of our method to the study of LO-phonon modes of CdS suggests that the scattered intensity is dominated by the surface and dependent on polarization. Results showed that the Raman spectra for CdS, roughly fall into three groups: a broad line-wing with apparent maxima around 194 cm{sup -1} in the range of 140 and 240 cm{sup -1} which can be ascribed to overtone scattering from acoustic phonons; a band near the 1LO phonon mode which can be attributed to a combination of one-phonon scattering and peak acoustic phonon and finally, a band near the 2LO phonon mode which can be attributed to a combination of two-phonon scattering and peak acoustic phonon.
Thermal characterization of nanoscale phononic crystals using supercell lattice dynamics
Davis, Bruce L.; Hussein, Mahmoud I.
2011-12-01
The concept of a phononic crystal can in principle be realized at the nanoscale whenever the conditions for coherent phonon transport exist. Under such conditions, the dispersion characteristics of both the constitutive material lattice (defined by a primitive cell) and the phononic crystal lattice (defined by a supercell) contribute to the value of the thermal conductivity. It is therefore necessary in this emerging class of phononic materials to treat the lattice dynamics at both periodicity levels. Here we demonstrate the utility of using supercell lattice dynamics to investigate the thermal transport behavior of three-dimensional nanoscale phononic crystals formed from silicon and cubic voids of vacuum. The periodicity of the voids follows a simple cubic arrangement with a lattice constant that is around an order of magnitude larger than that of the bulk crystalline silicon primitive cell. We consider an atomic-scale supercell which incorporates all the details of the silicon atomic locations and the void geometry. For this supercell, we compute the phonon band structure and subsequently predict the thermal conductivity following the Callaway-Holland model. Our findings dictate that for an analysis based on supercell lattice dynamics to be representative of the properties of the underlying lattice model, a minimum supercell size is needed along with a minimum wave vector sampling resolution. Below these minimum values, a thermal conductivity prediction of a bulk material based on a supercell will not adequately recover the value obtained based on a primitive cell. Furthermore, our results show that for the relatively small voids and void spacings we consider (where boundary scattering is dominant), dispersion at the phononic crystal unit cell level plays a noticeable role in determining the thermal conductivity.
Thermal characterization of nanoscale phononic crystals using supercell lattice dynamics
Bruce L. Davis
2011-12-01
Full Text Available The concept of a phononic crystal can in principle be realized at the nanoscale whenever the conditions for coherent phonon transport exist. Under such conditions, the dispersion characteristics of both the constitutive material lattice (defined by a primitive cell and the phononic crystal lattice (defined by a supercell contribute to the value of the thermal conductivity. It is therefore necessary in this emerging class of phononic materials to treat the lattice dynamics at both periodicity levels. Here we demonstrate the utility of using supercell lattice dynamics to investigate the thermal transport behavior of three-dimensional nanoscale phononic crystals formed from silicon and cubic voids of vacuum. The periodicity of the voids follows a simple cubic arrangement with a lattice constant that is around an order of magnitude larger than that of the bulk crystalline silicon primitive cell. We consider an atomic-scale supercell which incorporates all the details of the silicon atomic locations and the void geometry. For this supercell, we compute the phonon band structure and subsequently predict the thermal conductivity following the Callaway-Holland model. Our findings dictate that for an analysis based on supercell lattice dynamics to be representative of the properties of the underlying lattice model, a minimum supercell size is needed along with a minimum wave vector sampling resolution. Below these minimum values, a thermal conductivity prediction of a bulk material based on a supercell will not adequately recover the value obtained based on a primitive cell. Furthermore, our results show that for the relatively small voids and void spacings we consider (where boundary scattering is dominant, dispersion at the phononic crystal unit cell level plays a noticeable role in determining the thermal conductivity.
Mwakikunga, BW
2012-07-01
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Phonon transport in perovskite SrTiO3 from first principles
Feng, Lei; Shiomi, Junichiro
2015-01-01
We investigate phonon transport in perovskite strontium titanate (SrTiO3) which is stable above its phase transition temperature (~105 K) by using first-principles molecular dynamics and anharmonic lattice dynamics. Unlike conventional ground-state-based perturbation methods that give imaginary phonon frequencies, the current calculation reproduces stable phonon dispersion relations observed in experiments. We find the contribution of optical phonons to overall lattice thermal conductivity is larger than 60%, markedly different from the usual picture with dominant contribution from acoustic phonons. The mode- and pseudopotential-dependence analysis suggests the strong attenuation of acoustic phonons transport originated from strong anharmonic coupling with the transversely-polarized ferroelectric modes.
Temperature dependent magnon-phonon coupling in bcc Fe from theory and experiment.
Körmann, F; Grabowski, B; Dutta, B; Hickel, T; Mauger, L; Fultz, B; Neugebauer, J
2014-10-17
An ab initio based framework for quantitatively assessing the phonon contribution due to magnon-phonon interactions and lattice expansion is developed. The theoretical results for bcc Fe are in very good agreement with high-quality phonon frequency measurements. For some phonon branches, the magnon-phonon interaction is an order of magnitude larger than the phonon shift due to lattice expansion, demonstrating the strong impact of magnetic short-range order even significantly above the Curie temperature. The framework closes the previous simulation gap between the ferro- and paramagnetic limits.
ZHANG Li
2011-01-01
Within the framework of the macroscopic dielectric continuum model and Loudon's uniaxial crystal model,the phonon modes of a wurtzite/zinc-blende one-dimensional (ID) cylindrical nanowire (NW) are derived and studied.The analytical phonon states of phonon modes are given.It is found that there exist two types of polar phonon modes,i.e.interface optical (IO) phonon modes and the quasi-confined (QC) phonon modes existing in 1D wurtzite/zinc-blende NWs.Via the standard procedure of field quantization, the Frohlich electron-phonon interaction Hamiltonians are obtained.Numerical calculations of dispersive behavior of these phonon modes on a wurtzite/zinc-blende ZnO/MgO NW are performed.The frequency ranges of the I0 and QC phonon modes of the ZnO/MgO NWs are analyzed and discussed.It is found that the IO modes only exist in one frequency range, while QC modes may appear in three frequency ranges.The dispersive properties of the IO and QC modes on the free wave-number kz and the azimuthal quantum number m are discussed.The analytical Hamiltonians of electron-phonon interaction obtained here are quite useful for further investigating phonon influence on optoelectronics properties of wurtzite/zinc-blende 1D NW structures.
Hoffmann, Stanislaw K.; Lijewski, Stefan
2015-03-01
Electron spin-lattice relaxation rate is determined by electron spin echo method in temperature range 4-60 K. The Raman relaxation processes dominate and its theory is outlined in a form suitable for calculations of relaxation rate using real phonon spectrum. A few approximations have been considered: when phonon spectrum and Debye temperature are not available; when Debye temperature is available but phonon spectrum is not; and when spin-phonon coupling is known. All these approximations use the Debye model of phonons and give a non-satisfactory description the temperature dependence of the relaxation rate. A perfect description of experimental results is obtained when real phonon spectrum is considered. The value of the spin-phonon coupling parameter was determined as G = = 1362cm-1 . This value is discussed by a comparison with G-values published for various ions and crystals.
Xu, Zhi-Jie
2015-01-01
We first propose fundamental solutions of wave propagation in dispersive chain subject to a localized initial perturbation in the displacement. Analytical solutions are obtained for both second order nonlinear dispersive chain and homogenous harmonic chain using stationary phase approximation. Solution is also compared with numerical results from molecular dynamics (MD) simulations. Locally dominant phonon modes (k-space) are introduced based on these solutions. These locally defined spatially and temporally varying phonon modes k(x, t) are critical to the concept of the local thermodynamic equilibrium (LTE). Wave propagation accompanying with the nonequilibrium dynamics leads to the excitation of these locally defined phonon modes. It is found that the system energy is gradually redistributed among these excited phonons modes (k-space). This redistribution process is only possible with nonlinear dispersion and requires a finite amount of time to achieve a steady state distribution. This time scale is dependent on the spatial distribution (or frequency content) of the initial perturbation and the dispersion relation. Sharper and more concentrated perturbation leads to a faster energy redistribution and dissipation. This energy redistribution generates localized phonons with various frequencies that can be important for phonon-phonon interaction and energy dissipation in nonlinear systems. Depending on the initial perturbation and temperature, the time scale associated with this energy distribution can be critical for energy dissipation compared to the Umklapp scattering process. Ballistic type of heat transport along the harmonic chain reveals that at any given position, the lowest mode (k = 0) is excited first and gradually expanding to the highest mode (kmax(x,t)), where kmax(x,t) can only asymptotically approach the maximum mode kB of the first Brillouin zone (kmax(x,t) → kB). No energy distributed into modes with kmax(x,t) proportional to the sound speed
Larecki, Wieslaw; Banach, Zbigniew
2014-01-01
This paper analyzes the propagation of the waves of weak discontinuity in a phonon gas described by the four-moment maximum entropy phonon hydrodynamics involving a nonlinear isotropic phonon dispersion relation. For the considered hyperbolic equations of phonon gas hydrodynamics, the eigenvalue problem is analyzed and the condition of genuine nonlinearity is discussed. The speed of the wave front propagating into the region in thermal equilibrium is first determined in terms of the integral formula dependent on the phonon dispersion relation and subsequently explicitly calculated for the Dubey dispersion-relation model: |k|=ωc-1(1+bω2). The specification of the parameters c and b for sodium fluoride (NaF) and semimetallic bismuth (Bi) then makes it possible to compare the calculated dependence of the wave-front speed on the sample’s temperature with the empirical relations of Coleman and Newman (1988) describing for NaF and Bi the variation of the second-sound speed with temperature. It is demonstrated that the calculated temperature dependence of the wave-front speed resembles the empirical relation and that the parameters c and b obtained from fitting respectively the empirical relation and the original material parameters of Dubey (1973) are of the same order of magnitude, the difference being in the values of the numerical factors. It is also shown that the calculated temperature dependence is in good agreement with the predictions of Hardy and Jaswal’s theory (Hardy and Jaswal, 1971) on second-sound propagation. This suggests that the nonlinearity of a phonon dispersion relation should be taken into account in the theories aiming at the description of the wave-type phonon heat transport and that the Dubey nonlinear isotropic dispersion-relation model can be very useful for this purpose.
Reduction of thermal conductivity in phononic nanomesh structures
Yu, Jen-Kan
2010-07-25
Controlling the thermal conductivity of a material independently of its electrical conductivity continues to be a goal for researchers working on thermoelectric materials for use in energy applications1,2 and in the cooling of integrated circuits3. In principle, the thermal conductivity κ and the electrical conductivity σ may be independently optimized in semiconducting nanostructures because different length scales are associated with phonons (which carry heat) and electric charges (which carry current). Phonons are scattered at surfaces and interfaces, so κ generally decreases as the surface-to-volume ratio increases. In contrast, σ is less sensitive to a decrease in nanostructure size, although at sufficiently small sizes it will degrade through the scattering of charge carriers at interfaces. Here, we demonstrate an approach to independently controlling κ based on altering the phonon band structure of a semiconductor thin film through the formation of a phononic nanomesh film. These films are patterned with periodic spacings that are comparable to, or shorter than, the phonon mean free path. The nanomesh structure exhibits a substantially lower thermal conductivity than an equivalently prepared array of silicon nanowires, even though this array has a significantly higher surface-to-volume ratio. Bulk-like electrical conductivity is preserved. We suggest that this development is a step towards a coherent mechanism for lowering thermal conductivity. © 2010 Macmillan Publishers Limited. All rights reserved.
Soft phononic crystals with deformation-independent band gaps
2017-01-01
Soft phononic crystals have the advantages over their stiff counterparts of being flexible and reconfigurable. Normally, the band gaps of soft phononic crystals will be modified after deformation due to both geometric and constitutive nonlinearity. Indeed these are important properties that can be exploited to tune the dynamic properties of the material. However, in some instances, it may be that one wishes to deform the medium while retaining the band gap structure. A special class of soft phononic crystals is described here with band gaps that are independent or almost-independent of the imposed mechanical deformation, which enables the design of phononic crystals with robust performance. This remarkable behaviour originates from transformation elasticity theory, which leaves the wave equation and the eigenfrequencies invariant after deformation. The necessary condition to achieve such a property is that the Lagrangian elasticity tensor of the hyperelastic material should be constant, i.e. independent of deformation. It is demonstrated that incompressible neo-Hookean materials exhibit such a unique property. Semilinear materials also possess this property under special loading conditions. Phononic crystals composed of these two materials are studied theoretically and the predictions of invariance, or the manner in which the response deviates from invariance, are confirmed via numerical simulation. PMID:28484331
Functional crossover in the dispersion relations of magnons and phonons
Hoser, A.; Köbler, U.
2016-09-01
Experimental data are presented showing that the dispersion relations of magnons and acoustic phonons can consist of two sections with different functions of wave vector. In the low wave vector range a power function of wave vector often holds over a finite q-range while dispersions for larger wave vector values better approach the atomistic model predictions. In the magnon spectra ∼⃒qx power functions with exponents x=1.25, 1.5 and 2 are identified. The dispersion of the acoustic phonons can be a linear function of wave vector over a surprisingly large range of energy. Since the slope of the linear section agrees with the known sound velocities it can be concluded that the dispersion of the acoustic phonons has got attracted by the linear dispersion of the mass less Debye bosons (sound waves). Due to the different (translational) symmetries of bosons and atomistic excitations (magnons, phonons) the associated dispersions can attract each other. In the same way the different ∼⃒qx power functions in the magnon dispersions indicate that magnon dispersions are attracted by the dispersion of the bosons of the magnetic continuum (Goldstone bosons). This allows evaluation of the otherwise difficult to obtain dispersions of the Goldstone bosons from the known magnon dispersions. Interestingly, the dispersions of Goldstone bosons (Debye bosons) attract magnon dispersions (phonon dispersions) and not vice versa.
Thermally triggered phononic gaps in liquids at THz scale
Bolmatov, Dima; Zhernenkov, Mikhail; Zav'Yalov, Dmitry; Stoupin, Stanislav; Cunsolo, Alessandro; Cai, Yong Q.
2016-01-01
In this paper we present inelastic X-ray scattering experiments in a diamond anvil cell and molecular dynamic simulations to investigate the behavior of phononic excitations in liquid Ar. The spectra calculated using molecular dynamics were found to be in a good agreement with the experimental data. Furthermore, we observe that, upon temperature increases, a low-frequency transverse phononic gap emerges while high-frequency propagating modes become evanescent at the THz scale. The effect of strong localization of a longitudinal phononic mode in the supercritical phase is observed for the first time. The evidence for the high-frequency transverse phononic gap due to the transition from an oscillatory to a ballistic dynamic regimes of motion is presented and supported by molecular dynamics simulations. This transition takes place across the Frenkel line thermodynamic limit which demarcates compressed liquid and non-compressed fluid domains on the phase diagram and is supported by calculations within the Green-Kubo phenomenological formalism. These results are crucial to advance the development of novel terahertz thermal devices, phononic lenses, mirrors, and other THz metamaterials.
Investigation of phonon coherence and backscattering using silicon nanomeshes
Lee, Jaeho; Lee, Woochul; Wehmeyer, Geoff; Dhuey, Scott; Olynick, Deirdre L.; Cabrini, Stefano; Dames, Chris; Urban, Jeffrey J.; Yang, Peidong
2017-01-01
Phonons can display both wave-like and particle-like behaviour during thermal transport. While thermal transport in silicon nanomeshes has been previously interpreted by phonon wave effects due to interference with periodic structures, as well as phonon particle effects including backscattering, the dominant mechanism responsible for thermal conductivity reductions below classical predictions still remains unclear. Here we isolate the wave-related coherence effects by comparing periodic and aperiodic nanomeshes, and quantify the backscattering effect by comparing variable-pitch nanomeshes. We measure identical (within 6% uncertainty) thermal conductivities for periodic and aperiodic nanomeshes of the same average pitch, and reduced thermal conductivities for nanomeshes with smaller pitches. Ray tracing simulations support the measurement results. We conclude phonon coherence is unimportant for thermal transport in silicon nanomeshes with periodicities of 100 nm and higher and temperatures above 14 K, and phonon backscattering, as manifested in the classical size effect, is responsible for the thermal conductivity reduction. PMID:28051081
Bose-Einstein Condensation in an electro-pneumatically transformed quadrupole-Ioffe magnetic trap
Kumar, Sunil; Verma, Gunjan; Vishwakarma, Chetan; Noaman, Md; Rapol, Umakant
2014-01-01
We report a novel approach for preparing a Bose-Einstein condensate (BEC) of $^{87}$Rb atoms using electro-pneumatically driven transfer of atoms into a Quadrupole-Ioffe magnetic trap (QUIC Trap). More than 5$\\times$$10^{8}$ atoms from a Magneto-optical trap are loaded into a spherical quadrupole trap and then these atoms are transferred into an Ioffe trap by moving the Ioffe coil towards the center of the quadrupole coil, thereby, changing the distance between quadrupole trap center and the Ioffe coil. The transfer efficiency is more than 80 \\%. This approach is different from a conventional approach of loading the atoms into a QUIC trap wherein the spherical quadrupole trap is transformed into a QUIC trap by changing the currents in the quadrupole and the Ioffe coils. The phase space density is then increased by forced rf evaporative cooling to achieve the Bose-Einstein condensation having more than $10^{5}$ atoms.
Testing of Nb3Sn quadrupole coils using magnetic mirror structure
Zlobin, A.V.; Andreev, N.; Barzi, E.; Bossert, R.; Chlachidze, G.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.; Novitski, I.; Tartaglia, M.; Tompkins, J.C.; /Fermilab
2009-07-01
This paper describes the design and parameters of a quadrupole mirror structure for testing the mechanical, thermal and quench performance of single shell-type superconducting quadrupole coils at field, current and force levels similar to that of real magnet. The concept was experimentally verified by testing two quadrupole coils, previously used in quadrupole models, in the developed mirror structure in the temperature range from 4.5 to 1.9 K. The coils were instrumented with voltage taps, heaters, and strain gauges to monitor their mechanical and thermal properties and quench performance. A new quadrupole coil made of improved Nb{sub 3}Sn RRP-108/127 strand and cable insulation based on E-glass tape was also tested using this structure. The fabrication and test results of the quadrupole mirror models are reported and discussed.
Testing of Nb3Sn quadrupole coils using magnetic mirror structure
Zlobin, A.V.; Andreev, N.; Barzi, E.; Bossert, R.; Chlachidze, G.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.; Novitski, I.; Tartaglia, M.; Tompkins, J.C.; /Fermilab
2009-07-01
This paper describes the design and parameters of a quadrupole mirror structure for testing the mechanical, thermal and quench performance of single shell-type superconducting quadrupole coils at field, current and force levels similar to that of real magnet. The concept was experimentally verified by testing two quadrupole coils, previously used in quadrupole models, in the developed mirror structure in the temperature range from 4.5 to 1.9 K. The coils were instrumented with voltage taps, heaters, and strain gauges to monitor their mechanical and thermal properties and quench performance. A new quadrupole coil made of improved Nb{sub 3}Sn RRP-108/127 strand and cable insulation based on E-glass tape was also tested using this structure. The fabrication and test results of the quadrupole mirror models are reported and discussed.
S KH Mousavi
2015-09-01
Full Text Available In this paper the design and simulation of quadrupole magnets and electron beam optical of that by CST Studio code has been studied. Based on simulation result the magnetic quadrupole has been done for using in beam line of first Iranian powerful electron accelerator. For making the suitable magnetic field the effects of material and core geometry and coils current variation on quadrupole magnetic field have been studied. For test of quadrupole magnet the 10 MeV beam energy and 0.5 pi mm mrad emittance of input beam has been considered. We see the electron beam through the quadrupole magnet focus in one side and defocus in other side. The optimum of distance between two quadrupole magnets for low emittance have been achieved. The simulation results have good agreement with experimental results
Flach, B.
2000-01-01
This thesis has two topics: One is the investigation of an adsorbate induced phonon anomaly on W(110) and Mo{sub 1-x}Re{sub x}(110) (x = 5, 15, 25%) with inelastic helium atom scattering (HAS). The other one is the study of the growth, morphology and dynamics of ultra-thin lithium films deposited on W(110). In 1992 a giant phonon anomaly was found by J. Luedecke on the hydrogen saturated W(110) and Mo(110) surfaces. The anomaly consists of a deep and sharp indentation in the phonon dispersion curves in which the phonon energy nearly drops to zero ({omega}{sub 1}). In addition, a small and broad dip in the surface Rayleigh mode is observed ({omega}{sub 2}). The anomaly appears in the anti {gamma}-H- as well as in the anti {gamma}-S-direction of the surface Brillouin zone (SBZ). Since its first discovery, numerous other experimental and theoretical studies have followed. In the present work the effects is reinvestigated and experimental parameters, such as the crystal temperature and the incident energy, were changed in order to study their influence on the anomalous phonon behavior. In the case of H/Mo(110) the substrate was changed as well by alloying with small amounts of rhenium. In the present experiments a strong crystal temperature dependence of the {omega}{sub 2}-branch was found which leads to lower energies at the 'dip' for smaller temperatures, while the {omega}{sub 1}-anomaly remains unchanged. Such behavior agrees well with the picture that the {omega}{sub 2}-branch is due to a Kohn anomaly. (orig.)
Theory and experimental evidence of phonon domains and their roles in pre-martensitic phenomena
Jin, Yongmei M.; Wang, Yu U.; Ren, Yang
2015-12-01
Pre-martensitic phenomena, also called martensite precursor effects, have been known for decades while yet remain outstanding issues. This paper addresses pre-martensitic phenomena from new theoretical and experimental perspectives. A statistical mechanics-based Grüneisen-type phonon theory is developed. On the basis of deformation-dependent incompletely softened low-energy phonons, the theory predicts a lattice instability and pre-martensitic transition into elastic-phonon domains via 'phonon spinodal decomposition.' The phase transition lifts phonon degeneracy in cubic crystal and has a nature of phonon pseudo-Jahn-Teller lattice instability. The theory and notion of phonon domains consistently explain the ubiquitous pre-martensitic anomalies as natural consequences of incomplete phonon softening. The phonon domains are characterised by broken dynamic symmetry of lattice vibrations and deform through internal phonon relaxation in response to stress (a particular case of Le Chatelier's principle), leading to previously unexplored new domain phenomenon. Experimental evidence of phonon domains is obtained by in situ three-dimensional phonon diffuse scattering and Bragg reflection using high-energy synchrotron X-ray single-crystal diffraction, which observes exotic domain phenomenon fundamentally different from usual ferroelastic domain switching phenomenon. In light of the theory and experimental evidence of phonon domains and their roles in pre-martensitic phenomena, currently existing alternative opinions on martensitic precursor phenomena are revisited.
Quadrupole Moments of Rapidly Rotating Compact Objects in Dilatonic Einstein-Gauss-Bonnet Theory
Kleihaus, Burkhard; Mojica, Sindy
2014-01-01
We consider rapidly rotating black holes and neutron stars in dilatonic Einstein-Gauss-Bonnet (EGBd) theory and determine their quadrupole moments, which receive a contribution from the dilaton. The quadrupole moment of EGBd black holes can be considerably larger than the Kerr value. For neutron stars, the universality property of the $\\hat I$-$\\hat Q$ relation between the scaled moment of inertia and the scaled quadrupole moment appears to extend to EGBd theory.
Precision Alignments of Stripline BPMs with Quadrupole Magnets for TTF2
Priebe, G; Wendt, M; Werner, M
2004-01-01
We report on our alignment setup to calibrate beam position monitors (BPM) with respect to the magnetic axis of the quadrupole magnets used in the warm sections of the TESLA Test Facility (TTF2). The Stripline BPM's are fixed inside the quadrupole magnets. A streched wire measurement was used to calibrate the electrical axis of the BPM wrt. to the magnetic axis of the quadrupole.
Progress in the Development of Superconducting Quadrupoles forHeavy-ion Fusion
Faltens, A.; Lietzke, A.; Sabbi, G.; Seidl, P.; Lund, S.; Manahan, R.; Martovetsky, N.; Gung, C.; Minervini, J.; Schultz, J.; Myatt, L.; Meinke, R.
2002-08-19
The Heavy Ion Fusion program is developing single aperture superconducting quadrupoles based on NbTi conductor, for use in the High Current Experiment at Lawrence Berkeley National Laboratory. Following the fabrication and testing of prototypes using two different approaches, a baseline design has been selected and further optimized. A prototype cryostat for a quadrupole doublet, with features to accommodate induction acceleration modules, is being fabricated. The single aperture magnet was derived from a conceptual design of a quadrupole array magnet for multi-beam transport. Progress on the development of superconducting quadrupole arrays for future experiments is also reported.
Progress in the development of superconducting quadrupoles for heavy ion fusion
Faltens, A.; Lietzke, A.; Sabbi, G.; Seidl, P.; Lund, S.; Manahan, B.; Martovetsky, N.; Gung, C.; Minervini, J.; Schultz, J.; Myatt, L.; Meinke, R.
2002-05-24
The Heavy Ion Fusion program is developing single aperture superconducting quadrupoles based on NbTi conductor, for use in the High Current Experiment at Lawrence Berkeley National Laboratory. Following the fabrication and testing of prototypes using two different approaches, a baseline design has been selected and further optimized. A prototype cryostat for a quadrupole doublet, with features to accommodate induction acceleration modules, is being fabricated. The single aperture magnet was derived from a conceptual design of a quadrupole array magnet for multi-beam transport. Progress on the development of superconducting quadrupole arrays for future experiments is also reported.
Moloney, G.R.; Jamieson, D.N.; Legge, G.J.F. (School of Physics, Univ. of Melbourne, Parkville (Australia))
1991-03-01
Extensive, quantitative measurements of magnetic quadrupole lens fringe fields have been conducted. The fringe field region of magnetic quadrupole lenses has been shown to contain significant contamination by higher-order multipole fields. These multipole components will contribute to the aberration coefficients of the lens. One of the largest components is the duodecapole component, which contributes to the fifth-order geometric aberrations of the lens. The measured multipole profiles in the fringe field region of the Melbourne quadrupoles are presented. We also present the results of an investigation into the effect of modifying the quadrupole pole tip profile at the pole ends. (orig.).
Comparison of conventional and novel quadrupole drift tube magnets inspired by Klaus Halbach
Feinberg, B. [Lawrence Berkeley Lab., CA (United States)
1995-02-01
Quadrupole drift tube magnets for a heavy-ion linac provide a demanding application of magnet technology. A comparison is made of three different solutions to the problem of providing an adjustable high-field-strength quadrupole magnet in a small volume. A conventional tape-wound electromagnet quadrupole magnet (conventional) is compared with an adjustable permanent-magnet/iron quadrupole magnet (hybrid) and a laced permanent-magnet/iron/electromagnet (laced). Data is presented from magnets constructed for the SuperHILAC heavy-ion linear accelerator, and conclusions are drawn for various applications.
Rotational character change of the one-phonon and two-phonon $\\gamma$ vibration in odd-$A$ nuclei
Matsuzaki, Masayuki
2014-01-01
\\item[Background] The $\\gamma$ vibration is the most typical low-lying collective motion prevailing the nuclear chart. But only few one-phonon rotational bands in odd-$A$ nuclei have been known. Furthermore, two-phonon states, even the band head, have been observed in a very limited number of nuclides not only of odd-$A$ but even-even. \\item[Purpose] Among them, that in $^{105}$Mo is unique in that Coriolis effects are expected to be stronger than in $^{103}$Nb and $^{105}$Nb on which theoretical studies were reported. Then the purpose of the present work is to study $^{105}$Mo paying attention to rotational character change of the one-phonon and two-phonon bands in comparison with the present author's previous studies on $^{103}$Nb and $^{105}$Nb. \\item[Method] The particle-vibration coupling model based on the cranking model and the random-phase approximation is used to calculate the vibrational states in rotating odd-$A$ nuclei. \\item[Results] The present model reproduces the observed yrast zero-phonon and...
Integrated phononic crystal resonators based on adiabatically-terminated phononic crystal waveguides
Razi Dehghannasiri
2016-12-01
Full Text Available In this letter, we demonstrate a new design for integrated phononic crystal (PnC resonators based on confining acoustic waves in a heterogeneous waveguide-based PnC structure. In this architecture, a PnC waveguide that supports a single mode at the desired resonance frequencies is terminated by two waveguide sections with no propagating mode at those frequencies (i.e., have mode gap. The proposed PnC resonators are designed through combining the spatial-domain and the spatial-frequency domain (i.e., the k-domain analysis to achieve a smooth mode envelope. This design approach can benefit both membrane-based and surface-acoustic-wave-based architectures by confining the mode spreading in k-domain that leads to improved electromechanical excitation/detection coupling and reduced loss through propagating bulk modes.
Integrated phononic crystal resonators based on adiabatically-terminated phononic crystal waveguides
Dehghannasiri, Razi; Pourabolghasem, Reza; Eftekhar, Ali Asghar; Adibi, Ali
2016-12-01
In this letter, we demonstrate a new design for integrated phononic crystal (PnC) resonators based on confining acoustic waves in a heterogeneous waveguide-based PnC structure. In this architecture, a PnC waveguide that supports a single mode at the desired resonance frequencies is terminated by two waveguide sections with no propagating mode at those frequencies (i.e., have mode gap). The proposed PnC resonators are designed through combining the spatial-domain and the spatial-frequency domain (i.e., the k-domain) analysis to achieve a smooth mode envelope. This design approach can benefit both membrane-based and surface-acoustic-wave-based architectures by confining the mode spreading in k-domain that leads to improved electromechanical excitation/detection coupling and reduced loss through propagating bulk modes.
Cooling phonons with phonons: Acoustic reservoir engineering with silicon-vacancy centers in diamond
Kepesidis, K. V.; Lemonde, M.-A.; Norambuena, A.; Maze, J. R.; Rabl, P.
2016-12-01
We study a setup where a single negatively-charged silicon-vacancy center in diamond is magnetically coupled to a low-frequency mechanical bending mode and via strain to the high-frequency phonon continuum of a semiclamped diamond beam. We show that under appropriate microwave driving conditions, this setup can be used to induce a laser-cooling-like effect for the low-frequency mechanical vibrations, where the high-frequency longitudinal compression modes of the beam serve as an intrinsic low-temperature reservoir. We evaluate the experimental conditions under which cooling close to the quantum ground state can be achieved and describe an extended scheme for the preparation of a stationary entangled state between two mechanical modes. By relying on intrinsic properties of the mechanical beam only, this approach offers an interesting alternative for quantum manipulation schemes of mechanical systems, where otherwise efficient optomechanical interactions are not available.
Research Update: Phonon engineering of nanocrystalline silicon thermoelectrics
Junichiro Shiomi
2016-10-01
Full Text Available Nanocrystalline silicon thermoelectrics can be a solution to improve the cost-effectiveness of thermoelectric technology from both material and integration viewpoints. While their figure-of-merit is still developing, recent advances in theoretical/numerical calculations, property measurements, and structural synthesis/fabrication have opened up possibilities to develop the materials based on fundamental physics of phonon transport. Here, this is demonstrated by reviewing a series of works on nanocrystalline silicon materials using calculations of multiscale phonon transport, measurements of interfacial heat conduction, and synthesis from nanoparticles. Integration of these approaches allows us to engineer phonon transport to improve the thermoelectric performance by introducing local silicon-oxide structures.
Raman spectrum of Si nanowires: temperature and phonon confinement effects
Anaya, J.; Torres, A.; Hortelano, V.; Jiménez, J.; Prieto, A. C.; Rodríguez, A.; Rodríguez, T.; Rogel, R.; Pichon, L.
2014-03-01
The Raman spectrum of Si nanowires (NWs) is a matter of controversy. Usually, the one-phonon band appears broadened and shifted. This behaviour is interpreted in terms of phonon confinement; however, similar effects are observed for NWs with dimensions for which phonon confinement does not play any relevant role. In this context, the temperature increase induced by the laser beam is recognized to play a capital role in the shape of the spectrum. The analysis of the Raman spectrum, under the influence of the heating induced by the laser beam, is strongly dependent on the excitation conditions and the properties of the NWs. We present herein an analysis of the Raman spectrum of Si NWs based on a study of the interaction between the laser beam and the NWs, for both ensembles of NWs and individual NWs, taking account of the temperature increase in the NWs under the focused laser beam and the dimensions of the NWs.
Electron-phonon coupling in perovskites studied by Raman Scattering
Sathe, V. G.; Tyagi, S.; Sharma, G.
2016-10-01
Raman scattering is an unique technique for characterization and quantification of electron-phonon, spin-phonon and spin-lattice coupling in many of the currently prominent compounds like multiferroics and manganites. In manganites, it is understood now that a phase separated landscape with coexisting metallic and insulating regions exist in most of the compounds and application of small external perturbation causes an alteration in this landscape. In such scenario, local metallic regions grow suddenly at the expense of insulating regions below the magnetic ordering temperature. Such regions can be characterized effectively using Raman scattering measurements where delocalized electrons couple with the adjacent phonon peaks giving a Fano resonance in the form of asymmetric line shape.
Phonon band structures of the three dimensional latticed pentamode metamaterials
Guan Wang
2017-02-01
Full Text Available The artificially designed three-dimensional (3D pentamode metamaterials have such an extraordinary characteristic that the solid materials behave like liquids. Meanwhile, the ideal structure of the pentamode metamaterials arranges in the same way as that of the diamond crystals. In the present research, we regard three types of pentamode metamaterials derived from the 3D crystal lattices as research objects. The phonon band structures of the candidate pentamode structures are calculated by using the finite element method (FEM. We illustrate the relation between the ratio of the bulk modulus B and the shear modulus G of different combinations of D and d. Finally, we find out the relationship between the phonon band structure and the structure parameters. It is useful for generating the phonon band structure and controlling elastic wave propagation.
Classification of topological phonons in linear mechanical metamaterials.
Süsstrunk, Roman; Huber, Sebastian D
2016-08-16
Topological phononic crystals, alike their electronic counterparts, are characterized by a bulk-edge correspondence where the interior of a material dictates the existence of stable surface or boundary modes. In the mechanical setup, such surface modes can be used for various applications such as wave guiding, vibration isolation, or the design of static properties such as stable floppy modes where parts of a system move freely. Here, we provide a classification scheme of topological phonons based on local symmetries. We import and adapt the classification of noninteracting electron systems and embed it into the mechanical setup. Moreover, we provide an extensive set of examples that illustrate our scheme and can be used to generate models in unexplored symmetry classes. Our work unifies the vast recent literature on topological phonons and paves the way to future applications of topological surface modes in mechanical metamaterials.
Microwave-frequency electromechanical resonators incorporating phononic crystals
Satzinger, K. J.; Peairs, G.; Vainsencher, A.; Cleland, A. N.
Piezoelectric micromechanical resonators at gigahertz frequencies have been operated in the quantum limit, with quantum control and measurement achieved using superconducting qubits. However, experiments to date have been limited by mechanical dissipation, due to a combination of internal and radiative losses. In this talk, we explore the incorporation of phononic crystals into resonator designs. In phononic crystals, periodic patterning manipulates the acoustic band structure of the material. Through appropriately chosen geometries, these periodic patterns lead to full acoustic bandgaps which can be used to greatly reduce radiation losses from resonant structures. Alternatively, the crystal geometry can be manipulated to allow isolated modes within the bandgap, giving fine control over the spatial structure of the resonator modes. In this talk, we will describe the design, fabrication, and measurement of resonators with phononic crystals.
Temperature Dependent Variations of Phonon Interactions in Nanocrystalline Cerium Oxide
Sugandha Dogra Pandey
2015-01-01
Full Text Available The temperature dependent anharmonic behavior of the phonon modes of nanocrystalline CeO2 was investigated in the temperature range of 80–440 K. The anharmonic constants have been derived from the shift in phonon modes fitted to account for the anharmonic contributions as well as the thermal expansion contribution using the high pressure parameters derived from our own high pressure experimental data reported previously. The total anharmonicity has also been estimated from the true anharmonicity as well as quasiharmonic component. In the line-width variation analysis, the cubic anharmonic term was found to dominate the quartic term. Finally, the phonon lifetime also reflected the trend so observed.
Anomalous phonon behaviour in V sub 3 Si
Yethiraj, M
2002-01-01
In earlier studies of phonons in V sub 3 Si, a gradual softening of the (hh0) branch was observed and attributed to the martensitic transition in this compound, which precedes the onset of superconductivity by a few degrees K. In this work, the temperature dependence of the transverse acoustic (TA) branch along the hh0 direction was studied in greater detail and it is shown that while the TA hh0 mode starts to soften at relatively high temperatures (>200 K), an anomalous softening, which is rather localized in q, occurs just below T sub c. The intensity of this soft-phonon peak correlates extremely well with the onset of the superconducting phase and appears to vary as the order parameter with temperature and applied field. The similarities in the phonon softening and Fermi-surface anisotropy between this compound and the rare-earth nickel borocarbides suggest the existence of a common mechanism for the superconducting transition. (orig.)
Classification of topological phonons in linear mechanical metamaterials
Süsstrunk, Roman; Huber, Sebastian D.
2016-08-01
Topological phononic crystals, alike their electronic counterparts, are characterized by a bulk-edge correspondence where the interior of a material dictates the existence of stable surface or boundary modes. In the mechanical setup, such surface modes can be used for various applications such as wave guiding, vibration isolation, or the design of static properties such as stable floppy modes where parts of a system move freely. Here, we provide a classification scheme of topological phonons based on local symmetries. We import and adapt the classification of noninteracting electron systems and embed it into the mechanical setup. Moreover, we provide an extensive set of examples that illustrate our scheme and can be used to generate models in unexplored symmetry classes. Our work unifies the vast recent literature on topological phonons and paves the way to future applications of topological surface modes in mechanical metamaterials.
Dynamics of Phononic Dissipation at the Atomic Scale
Sevincli, Haldun; Mukhopadhay, Soma; Tugrul Senger, R.; Ciraci, Salim
2007-03-01
Dynamics of dissipation of a local phonon distribution to the bulk is a key issue in boundary lubrication and friction between sliding surfaces. We consider a highly excited molecule which interacts weakly with the substrate surface. We study different types of coupling and substrates having different types of dimensionality and phonon densities of states. We propose three different methods to solve the dynamics of the combined system, namely the equation of mation technique, Fano-Anderson method and the Green's function method. Using this theoretical framework we present an analysis of transient properties of energy dissipation via phonon discharge at the microscopic level. The methods allow the theoretical calculations to be extended to include any density of states for the substrate including experimental ones and any type of molecule that represent the lubricant or the asperity.
Reprint of : Absorbing/Emitting Phonons with one dimensional MOSFETs
Bosisio, Riccardo; Gorini, Cosimo; Fleury, Geneviève; Pichard, Jean-Louis
2016-08-01
We consider nanowires in the field effect transistor device configuration. Modeling each nanowire as a one dimensional lattice with random site potentials, we study the heat exchanges between the nanowire electrons and the substrate phonons, when electron transport is due to phonon-assisted hops between localized states. Shifting the nanowire conduction band with a metallic gate induces different behaviors. When the Fermi potential is located near the band center, a bias voltage gives rise to small local heat exchanges which fluctuate randomly along the nanowire. When it is located near one of the band edges, the bias voltage yields heat currents which flow mainly from the substrate towards the nanowire near one boundary of the nanowire, and in the opposite direction near the other boundary. This opens interesting perspectives for heat management at submicron scales: arrays of parallel gated nanowires could be used for a field control of phonon emission/absorption.
Electromagnetic excitation of phonons at C(001) surfaces
Perez-Sanchez, F L [Escuela de Ciencias, Universidad Autonoma ' Benito Juarez' de Oaxaca, Avenida Universidad S/N, Ex-Hacienda de Cinco Senores, Ciudad Universitaria, Oaxaca de Juarez, Oaxaca, 68120 (Mexico); Perez-Rodriguez, F, E-mail: fperez@sirio.ifuap.buap.m [Instituto de Fisica, Benemerita Universidad Autonoma de Puebla, Apartado Post. J-48, Puebla 72570 (Mexico)
2009-09-02
The photon-phonon coupling at C(001)-(2 x 1) surfaces and its manifestation in far-infrared reflectance anisotropy spectra (FIR-RAS) are theoretically investigated. We solve the coupled system of equations for the electromagnetic field and lattice vibrations, described within the adiabatic bond charge model (ABCM), with the method of expansion into bulk phonon and photon modes. The calculated FIR-RAS exhibit resonances associated with zone-center surface phonons in good agreement with available HREELS experiments and predictions of vibrational modes for diamond (001)-(2 x 1) surfaces from ABCM and ab initio calculations. Interestingly, the reflectance anisotropy spectra for a C(001)-(2 x 1) surface turn out to be qualitatively different from the spectra for a Si(001)-(2 x 1) surface, reported previously.
Photonic-phononic orbital angular momentum in Brillouin parametric conversion
Zhu, Zhihan; Mu, Chunyuan; Li, Hongwei
2014-01-01
Orbital angular momentum (OAM) is a fundamental photonic degree of freedom, showed by Allen and co-workers. Its most attractive feature is an inherently infinite dimensionality, which in recent years has obtained several ground-breaking demonstrations for high information-density communication and processing, both in classical and quantum. Here, by seeking the reason for photonic OAM non-conservation in stimulated Brillouin amplification, we report the first demonstration of the evolution law for OAM in Brillouin process. The parameter of OAM can conveniently transfer between the phonons and different polarized photons due to the photonic spin angular momentum conservation. Our results have revealed a parametric conversion mechanism of Brillouin process for Photonic-phononic OAM, demonstrated the role of phononic OAM and the vortex acoustic wave in this process, and suggested this mechanism may find important applications in OAM-based information communication and processing.
High temperature phonon dispersion in graphene using classical molecular dynamics
Anees, P., E-mail: anees@igcar.gov.in; Panigrahi, B. K. [Materials Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India); Valsakumar, M. C., E-mail: anees@igcar.gov.in [School of Engineering Sciences and Technology, University of Hyderabad, Hyderabad-500046 (India)
2014-04-24
Phonon dispersion and phonon density of states of graphene are calculated using classical molecular dynamics simulations. In this method, the dynamical matrix is constructed based on linear response theory by computing the displacement of atoms during the simulations. The computed phonon dispersions show excellent agreement with experiments. The simulations are done in both NVT and NPT ensembles at 300 K and found that the LO/TO modes are getting hardened at the Γ point. The NPT ensemble simulations capture the anharmonicity of the crystal accurately and the hardening of LO/TO modes is more pronounced. We also found that at 300 K the C-C bond length reduces below the equilibrium value and the ZA bending mode frequency becomes imaginary close to Γ along K-Γ direction, which indicates instability of the flat 2D graphene sheets.
Design, development, and acceleration trials of radio-frequency quadrupole
Rao, S. V. L. S.; Jain, Piyush; Pande, Rajni; Roy, Shweta; Mathew, Jose V.; Kumar, Rajesh; Pande, Manjiri; Krishnagopal, S.; Gupta, S. K.; Singh, P.
2014-04-01
A deuteron radio frequency quadrupole (RFQ) accelerator has been designed, fabricated, and tested at BARC, which will be used for neutron generation. The RFQ operates at a frequency of 350 MHz and needs an inter-vane voltage of 44 kV to accelerate the deuteron beam to 400 keV within a length of 1.03 m. The error analysis shows that the offset of two opposite vanes in the same direction by 100 μm leads to a change in resonant frequency by 1.3 MHz and a significant change of fields in the quadrants (˜±40% with respect to average field). From the 3D analysis, we have observed that the unwanted dipole mode frequencies are very near to the quadrupole mode frequency which will make structure sensitive to the perturbations. In order to move the dipole modes away from the quadrupole modes, we have used the dipole stabilizer rods. The 5 wire transmission line theory was used to study the perturbative analysis of the RFQ and based on this a computer program has been written to tune the cavity to get required field distribution. Based on these studies, a 1.03 m long RFQ made of OFE copper has been fabricated and tested. Even though the RFQ was designed for deuteron (D+) beam, we tested it by accelerating both the proton (H+) and D+ beams. The RFQ was operated in pulsed mode and accelerated both H+ and D+ beams to designed values of 200 and 400 keV, respectively. The measured parameters are in good agreement with the designed values validating our simulations and fabrication processes. In this paper, simulations, RF measurements, and beam commissioning results are presented.
Origin of coherent G -band phonon spectra in single-wall carbon nanotubes
Nugraha, A. R. T.; Hasdeo, E. H.; Sanders, G. D.; Stanton, C. J.; Saito, R.
2015-01-01
Coherent phonons in single-wall carbon nanotubes (SWNTs) are observed as oscillations of the differential absorption coefficient as a function of time by means of pump-probe spectroscopy. For the radial breathing mode (RBM) of a SWNT, the coherent phonon signal is understood to be a result of the modulated diameter-dependent energy gaps due to the coherent RBM phonon oscillations. However, this mechanism might not be the dominant contribution to other phonon modes in the SWNT. In particular, for the G -band phonons, which correspond to bond-stretching motions, we find that the modulation of the interatomic optical dipole (electron-photon) matrix element gives rise to a strong coherent G -band phonon intensity comparable to the coherent RBM phonon intensity. We also further discuss the dependence of coherent G -band and RBM phonon amplitudes on the laser excitation pulse width.
Small Aperture BPM to Quadrupole Assembly Tolerance Study
Fong, K. W.
2010-12-07
The LCLS injector and linac systems utilize a series of quadrupole magnets with a beam position monitor (BPM) captured in the magnet pole tips. The BPM measures the electron beam position by comparing the electrical signal from 4 electrodes and interpolating beam position from these signals. The manufacturing tolerances of the magnet and BPM are critical in determining the mechanical precision of the electrodes relative to the nominal electron beam Z-axis. This study evaluates the statistical uncertainty of the electrodes center axis relative to the nominal electron beam axis.
Superconducting focusing quadrupoles for heavy ion fusion experiments
Sabbi, G.L.; Faltens, A.; Leitner, M.; Lietzke, A.; Seidl, P.; Barnard, J.; Lund, S.; Martovetsky, N.; Gung, C.; Minervini, J.; Radovinsky, A.; Schultz, J.; Meinke, R.
2003-05-01
The Heavy Ion Fusion (HIF) Program is developing superconducting focusing magnets for both near-term experiments and future driver accelerators. In particular, single bore quadrupoles have been fabricated and tested for use in the High Current Experiment (HCX) at Lawrence Berkeley National Laboratory (LBNL). The next steps involve the development of magnets for the planned Integrated Beam Experiment (IBX) and the fabrication of the first prototype multi-beam focusing arrays for fusion driver accelerators. The status of the magnet R&D program is reported, including experimental requirements, design issues and test results.
Optimized Superconducting Quadrupole Arrays for Multiple Beam Transport
Meinke, Rainer, B.; Goodzeit, Carl, L.; Ball, Millicent, J.
2005-09-20
This research project advanced the development of reliable, cost-effective arrays of superconducting quadrupole magnets for use in multi-beam inertial fusion accelerators. The field in each array cell must be identical and meet stringent requirements for field quality and strength. An optimized compact array design using flat double-layer pancake coils was developed. Analytical studies of edge termination methods showed that it is feasible to meet the requirements for field uniformity in all cells and elimination of stray external field in several ways: active methods that involve placement of field compensating coils on the periphery of the array or a passive method that involves use of iron shielding.
Status of the LHC inner triplet quadrupole program at Fermilab
Andreev, N; Bauer, P; Bossert, R; Brandt, J; Carson, J; Caspi, S; Chichili, D R; Chiesa, L; Darve, C; Di Marco, J; Fehér, S; Ghosh, A; Glass, H; Huang, Y; Kerby, J S; Lamm, M J; Markarov, A A; McInturff, A D; Nicol, T H; Nobrega, A; Novitski, I; Ogitsu, T; Orris, D; Ozelis, J P; Page, T; Peterson, T; Rabehl, Roger Jon; Robotham, W; Sabbi, G L; Scanlan, R M; Schlabach, P; Sylvester, C D; Strait, J B; Tartaglia, M; Tompkins, J C; Velev, G V; Yadav, S; Zlobin, A V
2001-01-01
Fermilab, in collaboration with LBNL and BNL, is developing a quadrupole for installation in the interaction region inner triplets of the LHC. This magnet is required to have an operating gradient of 215 T/m across a 70 mm coil bore, and operates in superfluid helium at 1.9 K. A 2 m magnet program addressing mechanical, magnetic, quench protection, and thermal issues associated with the design was completed earlier this year, and production of the first full length, cryostatted prototype magnet is underway. This paper summarizes the conclusions of the 2 m program, and the design and status of the first full-length prototype magnet. (11 refs).
Beam acceleration through proton radio frequency quadrupole accelerator in BARC
Bhagwat, P. V.; Krishnagopal, S.; Mathew, J. V.; Singh, S. K.; Jain, P.; Rao, S. V. L. S.; Pande, M.; Kumar, R.; Roychowdhury, P.; Kelwani, H.; Rama Rao, B. V.; Gupta, S. K.; Agarwal, A.; Kukreti, B. M.; Singh, P.
2016-05-01
A 3 MeV proton Radio Frequency Quadrupole (RFQ) accelerator has been designed at the Bhabha Atomic Research Centre, Mumbai, India, for the Low Energy High Intensity Proton Accelerator (LEHIPA) programme. The 352 MHz RFQ is built in 4 segments and in the first phase two segments of the LEHIPA RFQ were commissioned, accelerating a 50 keV, 1 mA pulsed proton beam from the ion source, to an energy of 1.24 MeV. The successful operation of the RFQ gave confidence in the physics understanding and technology development that have been achieved, and indicate that the road forward can now be traversed rather more quickly.
Cool Down Analysis of a Cryocooler Based Quadrupole Magnet Cryostat
Choudhury, A.; Kar, S.; Chacko, J.; Kumar, M.; Babu, S.; Sahu, S.; Kumar, R.; Antony, J.; Datta, T. S.
A superconducting quadrupole doublet magnet with cold superferric iron cover for the Hybrid Recoil Mass Analyzer (HYRA) beam line has been commissioned. The total cold mass of the helium vessel with iron yoke and pole is 2 ton. A set of two Sumitomo cryocoolers take care of various heat loads to the cryostat. The first successful cool down of the cryostat has been completed recently, magnets have been powered and magnetic field profiling has been done inside theroom temperature beam tube. This paper will highlight the cryostat details along with the cool down and operational test results obtained from the first cool down.
Kick velocity induced by magnetic dipole and quadrupole radiation
Kojima, Yasufumi
2010-01-01
We examine the recoil velocity induced by the superposition of the magnetic dipole and quadrupole radiation from a pulsar/magnetar born with rapid rotation. The resultant velocity depends on not the magnitude, but rather the ratio of the two moments and their geometrical configuration. The model does not necessarily lead to high spatial velocity for a magnetar with a strong magnetic field, which is consistent with the recent observational upper bound. The maximum velocity predicted with this model is slightly smaller than that of observed fast-moving pulsars.
2-MV electrostatic quadrupole injector for heavy-ion fusion
Bieniosek, F.M.; Celata, C.M.; Henestroza, E.; Kwan, J.W.; Prost, L.; Seidl, P.A.
2004-11-10
High current and low emittance are principal requirements for heavy-ion injection into a linac driver for inertial fusion energy. An electrostatic quadrupole (ESQ) injector is capable of providing these high charge density and low emittance beams. We have modified the existing 2-MV Injector to reduce beam emittance and to double the pulse length. We characterize the beam delivered by the modified injector to the High Current Transport Experiment (HCX) and the effects of finite rise time of the extraction voltage pulse in the diode on the beam head. We demonstrate techniques for mitigating aberrations and reducing beam emittance growth in the injector.
Quadrupole collectivity in Si isotopes around N=20
Rodríguez-Guzman, R R; Robledo, L M
2001-01-01
The angular momentum projected Generator Coordinate Method using the quadrupole moment as collective coordinate and the Gogny force as the effective interaction is used to describe the properties of the ground state and low-lying excited states of the neutron rich light nuclei 32,34,36Si. It is found that the ground state of the nucleus 34Si is spherical. However, this is not only due to the N=20 shell closure as the ground state of 34Si contains a significant amount of the intruder f7/2 neutron orbital. On the other hand, rather good agreement with experimental data for many observables is obtained.
Electrostatic quadrupole accelerator for the heavy ion fusion project
Henestroza, E.; Yu, S.; Eylon, S.
1994-07-01
A full scale (2 MeV, 800 mA, K{sup +}), low emittance injector for the Heavy Ion Fusion Project has been built at LBL It consists of a 750 key diode pre-injector followed by an electrostatic quadrupole accelerator (ESQ) which provide strong (alternating gradient) focusing for the space-charge dominated beam and simultaneously accelerates the ions to 2 MeV. The actual operation of this new machine has exceeded design parameters. Design of the accelerator, report on experiments performed in connection with the evaluation and characterization of the ESQ and corresponding 3D Particle in Cell simulations will be presented.
Low-lying quadrupole collectivity in {sup 136}Xe
Stahl, Christian; Leske, Joerg; Pietralla, Norbert; Reese, Michael [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Bazzacco, Dino; Farnea, Enrico [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova (Italy); Gadea, Andres [Instituto de Fisica Corpuscular, CSIC-Universitat de Valencia, Valencia (Spain); Gottardo, Andrea [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro (Italy); Dipartimento di Fisica e Astronomia dell' Universita degli Studi di Padova, Padova (Italy); John, Philipp Rudolf; Michelagnoli, Caterina [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova (Italy); Dipartimento di Fisica e Astronomia dell' Universita degli Studi di Padova, Padova (Italy); Valiente-Dobon, Jose Javier [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro (Italy)
2015-07-01
We present recent results from our investigation of low-lying quadrupole collectivity in the semi-magic N=82 nucleus {sup 136}Xe. An experiment was performed at the Legnaro National Laboratory employing the AGATA demonstrator. Level-lifetimes and B(E2, 0{sup +}{sub 1}→2{sup +}{sub i})-values were determined from Coulomb excitation and by the continuous-angle DSA method exploiting AGATA's position resolution. 2{sup +}{sub i} - states up to i=7 were excited and analyzed.
Nuclear quadrupole resonance of boron in borate glasses
Gravina, Samuel J.; Bray, Phillip J.
A continuous wave nuclear quadrupole resonance spectrometer that has a high sensitivity even at low frequencies has been built. Boron and aluminum NQR has been detected in the region 200 kHz to 1.4 MHz. For the first time, boron NQR has been detected in a glass. The NQR spectrum of pure B 20 3 glass is consistent with 85 ± 2% of the boron atoms belonging to boroxol rings. In sodium borate glasses, the number of borons in boroxol rings decreases with increasing sodium content, until when sodium oxide comprises 20 mol% of the glass less than 2% of the borons are in boroxol rings.
Photons, phonons, and plasmons with orbital angular momentum in plasmas
Chen, Qiang; Liu, Jian
2016-01-01
Exact eigen modes with orbital angular momentum (OAM) in the complex media of unmagnetized homogeneous plasma are studied. Three exact eigen modes with OAM are discovered, i.e., photons, phonons, and plasmons. It is found that an OAM photon can be excited by two familiar Bessel modes without OAM. For the phonons and plasmons, their OAM are carried by the electrons and ions. The OAM modes in plasmas and their characteristics can be explored for various potential applications in plasma physics and accelerator physics.
Time Resolved Phonon Spectroscopy, Version 1.0
2016-12-22
TRPS code was developed for the project "Time Resolved Phonon Spectroscopy". Routines contained in this piece of software were specially created to model phonon generation and tracking within materials that interact with ionizing radiation, particularly applicable to the modeling of cryogenic radiation detectors for dark matter and neutrino research. These routines were created to link seamlessly with the open source Geant4 framework for the modeling of radiation transport in matter, with the explicit intent of open sourcing them for eventual integration into that code base.
YPHON: A package for calculating phonons of polar materials
Wang, Yi; Chen, Long-Qing; Liu, Zi-Kui
2014-11-01
In our recent works, we have developed a mixed-space approach within the framework of direct method for the first-principle calculation of phonon properties. It makes full use of the accuracy of the force constants calculated in the real space and the dipole-dipole interactions in the reciprocal space, making the accurate phonon calculation possible with the direct method for polar materials. In this paper, an efficient C++ implementation of the mixed-space approach, YPHON, is provided as open source, including demos and Linux scripts for extracting input data to YPHON from the output of VASP.5. The functions of the current package include the calculations of: (1) the phonon dispersions; (2) the phonon density of states; (3) the neutron scattering section weighted phonon density of state; (4) the phonons of the high symmetry structure using the force constants from low symmetry structure; (5) the phonon dispersions of random alloys; and (6) the analysis of the vibrational modes using the point group theory. Catalogue identifier: AETS_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETS_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 567815 No. of bytes in distributed program, including test data, etc.: 9763594 Distribution format: tar.gz Programming language: C++, Linux scripts. Computer: Linux systems with a g++ or C++ compiler. Operating system: Linux. RAM: Ranges from a few Mbytes to a few Gbytes, dynamically depending on the system size. Classification: 7.8. External routines: GSL-the GNU Scientific Library (GSL) is a numerical library for C and C++ programmers. VASP.5 or later for the calculations of force constants and dielectric constants and Born effective charge for polar materials. Nature of problem: This package has the purpose of computing
Band structures and localization properties of aperiodic layered phononic crystals
Yan Zhizhong, E-mail: zzyan@bit.edu.cn [Department of Applied Mathematics, Beijing Institute of Technology, Beijing 100081 (China); Zhang Chuanzeng [Department of Civil Engineering, University of Siegen, D-57078 Siegen (Germany)
2012-03-15
The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on Thue-Morse and Rudin-Shapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper.
Band structures and localization properties of aperiodic layered phononic crystals
Yan, Zhi-Zhong; Zhang, Chuanzeng
2012-03-01
The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on Thue-Morse and Rudin-Shapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper.
Homogenization of Two-Dimensional Phononic Crystals at Low Frequencies
NI Qing; CHENG Jian-Chun
2005-01-01
@@ Effective velocities of elastic waves propagating in two-dimensional phononic crystal at low frequencies are analysed theoretically, and exact analytical formulas for effective velocities of elastic waves are derived according to the method presented by Krokhin et al. [Phys. Rev. Lett. 91 (2003) 264302]. Numerical calculations for phononic crystals consisted of array of Pb cylinders embedded in epoxy show that the composites have distinct anisotropy at low filling fraction. The anisotropy increases as the filling fraction increases, while as the filling fraction closes to the limitation, the anisotropy decreases.
The inverted pendulum, interface phonons and optic Tamm states
Combe, Nicolas
2011-01-01
The propagation of waves in periodic media is related to the parametric oscillators. We transpose the possibility that a parametric pendulum oscillates in the vicinity of its unstable equilibrium positions to the case of waves in lossless unidimensional periodic media. This concept formally applies to any kind of wave. We apply and develop it to the case of phonons in realizable structures and evidence new classes of phonons. Discussing the case of electromagnetic waves, we show that our concept is related to optic Tamm states one but extends it to periodic Optic Tamm state.
Electron-phonon interaction in high temperature superconductors
H. Khosroabadi
2006-09-01
Full Text Available We explore the important role of the strong electron-phonon interaction in high temperature superconductivity through the study of the results of some important experiments, such as inelastic neutron and X-ray scattering, angle resolved photoemission spectroscopy, and isotope effects. We also present our computational results of the eigenvalues and eigenvectors of the Ag Raman modes, and the ionic displacement dependence of the electronic band structure by density functional theory. It is clearly evident that the role of phonons in the mechanism behind the high-temperature superconducting state should be seriously considered.
Phonon Softening and Dispersion in EuTiO3
Ellis, David S.; UCHIYAMA, Hiroshi; Tsutsui, Satoshi; Sugimoto, Kunihisa; Kato, Kenichi; Ishikawa, Daisuke; Baron, Alfred Q. R.
2012-01-01
We measured phonon dispersion in single crystal EuTiO$_3$ using inelastic x-ray scattering. A structural transition to an antiferrodistortive phase was found at a critical temperature $T_0$=287$\\pm$1 K using powder and single-crystal x-ray diffraction. Clear softening of the zone boundary \\emph{R}-point \\textbf{q}=(0.5 0.5 0.5) acoustic phonon shows this to be a displacive transition. The mode energy plotted against reduced temperature could be seen to nearly overlap that of $\\rm SrTiO_3$, su...
Electron-phonon equilibration in laser-heated gold films
White, T. G.; Mabey, P.; Gericke, D. O.; Hartley, N. J.; Doyle, H. W.; McGonegle, D.; Rackstraw, D. S.; Higginbotham, A.; Gregori, G.
2014-07-01
By irradiating a thin metal foil with an intense short-pulse laser, we have created a uniform system far from equilibrium. The deposited energy is initially deposited only within the electronic subsystem, and the subsequent evolution of the system is determined by the details of the electron-phonon coupling. Here, we measure the time evolution of the lattice parameter through multilayer Bragg diffraction and compare the result to classical molecular dynamic simulations to determine the lattice temperature. The electron-ion coupling constant for gold is then determined by comparison with the evolution of a two-temperature electron-phonon system.
Coherent phonon coupling to individual Bloch states in photoexcited bismuth.
Papalazarou, E; Faure, J; Mauchain, J; Marsi, M; Taleb-Ibrahimi, A; Reshetnyak, I; van Roekeghem, A; Timrov, I; Vast, N; Arnaud, B; Perfetti, L
2012-06-22
We investigate the temporal evolution of the electronic states at the bismuth (111) surface by means of time- and angle-resolved photoelectron spectroscopy. The binding energy of bulklike bands oscillates with the frequency of the A(1g) phonon mode, whereas surface states are insensitive to the coherent displacement of the lattice. A strong dependence of the oscillation amplitude on the electronic wave vector is correctly reproduced by ab initio calculations of electron-phonon coupling. Besides these oscillations, all the electronic states also display a photoinduced shift towards higher binding energy whose dynamics follows the evolution of the electronic temperature.
Optical Conductivity of Graphene Sheet Including Electron-Phonon Interaction
Hamze Mousavi
2012-01-01
Using an expression of optical conductivity, based on the linear response theory, the Green＇s function technique and within the Holstein Hamiltonian model, the effect of electron-phonon interaction on the optical conductivity of graphene plane is studied. It is found that the electron-phonon coupling increases the optical conductivity of graphene sheet in the low frequency region due to decreasing quasiparticle weight of electron excitation while the optical conductivity reduces in the high frequency region. The latter is due to role of electrical field＇s frequency.
Phonon heat capacity of graphene nanofilms and nanotubes
Gospodarev, I. A.; Grishaev, V. I.; Manzhelii, E. V.; Syrkin, E. S.; Feodosyev, S. B.; Minakova, K. A.
2017-02-01
Based on calculations conducted on a microscopic level, the phonon heat capacity of ultrathin graphene nanofilms such as bigraphene and trigraphene, and single-wall graphene nanotubes, is quantitatively described. The nature of the flexural stiffness of graphene monolayers is analyzed, and the temperature intervals at which the shape of the temperature dependence of heat capacity is determined by contributions made by flexural vibrations are identified. The contribution to the phonon heat capacity derived from graphene nanotube flexural waves that propagate along the surface thereof is analyzed, as are the bending vibrations of the tube as a whole one-dimensional object, and the contribution from torsional vibrations.
Reconfigurable long-range phonon dynamics in optomechanical arrays
Xuereb, André; Pupillo, Guido; Paternostro, Mauro; Dantan, Aurélien
2013-01-01
We investigate periodic optomechanical arrays as reconfigurable platforms for engineering the coupling between multiple mechanical and electromagnetic modes and for exploring many-body phonon dynamics. Exploiting structural resonances in the coupling between light fields and collective motional modes of the array, we show that tunable effective long-range interactions between mechanical modes can be achieved. This paves the way towards the implementation of controlled phononic walks and heat transfer on densely-connected graphs as well as the coherent transfer of excitations between distant elements of optomechanical arrays.
Evidences of evanescent Bloch waves in Phononic Crystals
Romero-García, V; Castiñeira-Ibáñez, S; Garcia-Raffi, L M
2010-01-01
We show both experimentally and theoretically the evanescent behaviour of modes in the Band Gap (BG) of finite Phononic Crystal (PC). Based on experimental and numerical data we obtain the imaginary part of the wave vector in good agreement with the complex band structures obtained by the Extended Plane Wave Expansion (EPWE). The calculated and measured acoustic field of a localized mode out of the point defect inside the PC presents also evanescent behaviour. The correct understanding of evanescent modes is fundamental for designing narrow filters and wave guides based on Phononic Crystals with defects.
Dynamical Cooper pairing in nonequilibrium electron-phonon systems
Knap, Michael; Babadi, Mehrtash; Refael, Gil; Martin, Ivar; Demler, Eugene
2016-12-01
We analyze Cooper pairing instabilities in strongly driven electron-phonon systems. The light-induced nonequilibrium state of phonons results in a simultaneous increase of the superconducting coupling constant and the electron scattering. We demonstrate that the competition between these effects leads to an enhanced superconducting transition temperature in a broad range of parameters. Our results may explain the observed transient enhancement of superconductivity in several classes of materials upon irradiation with high intensity pulses of terahertz light, and may pave new ways for engineering high-temperature light-induced superconducting states.
Phonon thermal transport in metallic glasses below 100 K
Matey, James Regis
1978-01-01
Measurements of the phonon thermal conductivity of a variety of metallic glasses were made. In each case, the temperature dependence and magnitude of the phonon thermal conductivity of the glassy metal was very similar to that characteristic of nonmetallic glasses. Variation of sound velocity measurements were made on a glassy palladium silicon alloy and a qualitative similarity was found between its behavior and the behavior of nonmetallic glasses. These findings and results from other laboratories have led to the conclusion that the localized excitations responsible for the anomalous behavior of nonmetallic glasses are also present in the metallic glasses.
Unraveling the acoustic electron-phonon interaction in graphene
Kaasbjerg, Kristen; Thygesen, Kristian S.; Jacobsen, Karsten W.
2012-01-01
Using a first-principles approach we calculate the electron-phonon couplings in graphene for the transverse and longitudinal acoustic phonons. Analytic forms of the coupling matrix elements valid in the long-wavelength limit are found to give an almost quantitative description of the first...... that the intrinsic effective acoustic deformation potential of graphene is Ξeff=6.8 eV and that the temperature dependence of the mobility μ~T-α in the Bloch-Gru¨neisen regime increases beyond an α=4 dependence even in the absence of screening when the true coupling matrix elements are considered. The α>4...
Photons, phonons, and plasmons with orbital angular momentum in plasmas
Chen, Qiang; Qin, Hong; Liu, Jian
2017-01-01
Exact eigen modes with orbital angular momentum (OAM) in the complex media of unmagnetized homogeneous plasmas are studied. Three exact eigen modes with OAM are derived, i.e., photons, phonons, and plasmons. The OAM of different plasma components are closely related to the charge polarities. For photons, the OAM of electrons and ions are of the same magnitude but opposite direction, and the total OAM is carried by the field. For the phonons and plasmons, their OAM are carried by the electrons and ions. The OAM modes in plasmas and their characteristics can be explored for potential applications in plasma physics and accelerator physics. PMID:28164998
Temperature dependence of the Raman-active phonon frequencies in indium sulfide
Gasanly, N. M.; Özkan, H.; Aydinli, A.; Yilmaz, İ.
1999-03-01
The temperature dependence of the Raman-active mode frequencies in indium sulfide was measured in the range from 10 to 300 K. The analysis of the temperature dependence of the A g intralayer optical modes show that Raman frequency shift results from the change of harmonic frequency with volume expansion and anharmonic coupling to phonons of other branches. The pure-temperature contribution (phonon-phonon coupling) is due to three- and four-phonon processes.
Theoretical study of the transverse acoustic phonons of GaSb at high pressure
S Shinde; M Talati; Prafulla K Jha; S P Sanyal
2004-08-01
We have investigated the phonon dispersion curves and one-phonon density of states up to the pressure of 8 GPa using a theoretical model, namely the rigid ion model. The transverse acoustic phonons as a function of pressure have been compared with the recently measured inelastic neutron scattering data which show a strong softening near the zone boundaries. The calculated one-phonon density of states show pronounced shift in the peak positions with the increase in pressure.
Phonon dilatation, dressed vibrons and two-vibron bound states localization in an adsorbed nanowire
Pouthier, Vincent,
2006-01-01
A special attention is paid to characterize the two-vibron bound state dynamics of an anharmonic molecular nanostructure coupled with a set of optical phonons. It is shown that the vibron-phonon coupling is responsible for a new dressing mechanism. The vibrons are accompanied by virtual phonons which account for the scaling of each phonon coordinate and for the dilatation of the corresponding wave function. As a result, the dynamics of the dressed vibrons is governed by an effective Hamiltoni...
Nielsen, Per Kær; Nielsen, Torben Roland; Lodahl, P.
2012-01-01
of the physics and emphasize the important role played by the effective phonon density, describing the availability of phonons for scattering, in quantum dot decay dynamics. Based on the analytical expressions, we present the parameter regimes where phonon effects are expected to be important. Also, we include...
Two-phonon capture processes into quantum dots: The role of intermediate states
Magnúsdóttir, Ingibjörg; Uskov, A. V.; Bischoff, Svend;
2003-01-01
We present a study of carrier capture into quantum dots via emission of longitudinal optical phonons. Two-phonon capture times are found to be of the order of some picoseconds at carrier densities 10^1^7cm^-^3 in situations where single-phonon capture processes are energetically prohibited. The i...
The Influence of Surface Phonons on Polaron States in Quantum Dots
Maslov, A. Yu.; Proshina, O. V.; Rusina, A. N.
2007-04-01
The influence of the surface phonons on the polaron effect in a quantum dot is investigated. We consider the polar quantum dot embedded into the polar matrix. The polaron energy shift for the electron and hole ground states is calculated. It is shown that the contribution of the surface phonons may exceed the bulk phonon contribution.
Relaxation between electrons and surface phonons of a homogeneously photoexcited metal film
Navinder Singh
2004-11-01
The energy relaxation between the hot degenerate electrons of a homogeneously photoexcited metal film and the surface phonons (phonon wave vectors in two dimensions) is considered under Debye approximation. The state of electrons and phonons is described by equilibrium Fermi and Bose functions with different temperatures. Two cases for electron scattering by the metal surface, namely specular and diffuse scattering, are considered.
Non-Markovian phonon dephasing of a quantum dot in a photonic-crystal nanocavity
Madsen, Kristian Høeg; Nielsen, Per Kær; Kreiner-Møller, Asger
2012-01-01
) is introduced, which determines the rate of phonon-assisted spontaneous emission. If, e.g., the QD is blue-detuned from the cavity mode, the QD can emit a photon into the cavity mode by emitting the residual energy as a phonon [3]. Our microscopic model allows us to extract the effective phonon DOS, that turns...
Performance of a Nb(3)Sn Quadrupole Under High Stress
Felice, H; Ferracin, P; De Rijk, G; Bajko, M; Caspi, S; Bingham, B; Giloux, C; Bordini, B; Milanese, A; Bottura, L; Sabbi, G L; Hafalia, R; Godeke, A; Dietderich, D
2011-01-01
Future upgrades of the Large Hadron Collider (LHC) will require large aperture and high gradient quadrupoles. Nb(3)Sn is the most viable option for this application but is also known for its strain sensitivity. In high field magnets, with magnetic fields above 12 T, the Lorentz forces will generate mechanical stresses that may exceed 200 MPa in the windings. The existing measurements of critical current versus strain of Nb(3)Sn strands or cables are not easily applicable to magnets. In order to investigate the impact of high mechanical stress on the quench performance, a series of tests was carried out within a LBNL/CERN collaboration using the magnet TQS03 (a LHC Accelerator Research Program (LARP) 1-meter long, 90-mm aperture Nb(3)Sn quadrupole). The magnet was tested four times at CERN under various pre-stress conditions. The average mechanical compressive azimuthal pre-stress on the coil at 4.2 K ranged from 120 MPa to 200 MPa. This paper reports on the magnet performance during the four tests focusing on...
Chaotic motion in axially symmetric potentials with oblate quadrupole deformation
Letelier, Patricio S. [Departamento de Matematica Aplicada, IMECC, Universidade Estadual de Campinas, 13083-859, Campinas, SP (Brazil); Ramos-Caro, Javier, E-mail: javier@ime.unicamp.br [Departamento de Matematica Aplicada, IMECC, Universidade Estadual de Campinas, 13083-859, Campinas, SP (Brazil); Lopez-Suspes, Framsol, E-mail: framsol@gmail.com [Facultad de Telecomunicaciones, Universidad Santo Tomas and Escuela de Fisica, Universidad Industrial de Santander, Bucaramanga (Colombia)
2011-10-03
By computing the Poincare's surfaces of section and Lyapunov exponents, we study the effect of introducing an oblate quadrupole in the dynamics associated with two generic spherical potentials of physical interest: the central monopole and the isotropic harmonic oscillator. In the former case we find saddle points in the effective potential, in contrast to the statements presented by Gueron and Letelier in [E. Gueron, P.S. Letelier, Phys. Rev. E 63 (2001) 035201]. The results we show in the second case have application in nuclear or atomic physics. In particular, we find values of oblate deformation leading to a disappearance of shell structure in the single-particle spectrum. -- Highlights: → We find chaotic motion around a monopole with oblate quadrupole deformation. → This corrects the statements introduced in [E. Gueron, P.S. Letelier, Phys. Rev. E 63 (2001) 035201]. → We present an alternative model for the potential due to an oblate deformed nuclei. → This leads to stochastic regions in the phase space of classical orbits. → It suggests that the shell structure of single-particle spectrum tends to disappear.
VIBRATION MEASUREMENTS IN A RHIC QUADRUPOLE AT CRYOGENIC TEMPERATURES.
JAIN, A.; AYDIN, S.; HE, P.; ANERELLA, M.; GANETIS, G.; HARRISON, M.; PARKER, B.; PLATE, S.
2005-10-17
One of the concerns in using compact superconducting magnets in the final focus region of the ILC is the influence of the cryogen flow on the vibration characteristics. As a first step towards characterizing such motion at nanometer levels, a project was undertaken at BNL to measure the vibrations in a spare RHIC quadrupole under cryogenic conditions. Given the constraints of cryogenic operation, and limited space available, it was decided to use a dual head laser Doppler vibrometer for this work. The performance of the laser vibrometer was tested in a series of room temperature tests and compared with results from Mark L4 geophones. The laser system was then used to measure the vibration of the cold mass of the quadrupole with respect to the outside warm enclosure. These measurements were carried out both with and without the flow of cold helium through the magnet. The results indicate only a minor increase in motion in the horizontal direction (where the cold mass is relatively free to move).
Extracting the Omega- electric quadrupole moment from lattice QCD data
Ramalho, G
2010-01-01
The Omega- has an extremely long lifetime, and is the most stable of the baryons with spin 3/2. Therefore the Omega- magnetic moment is very accurately known. Nevertheless, its electric quadrupole moment was never measured, although estimates exist in different formalisms. In principle, lattice QCD simulations provide at present the most appropriate way to estimate the Omega- form factors, as function of the square of the transferred four-momentum, Q2, since it describes baryon systems at the physical mass for the strange quark. However, lattice QCD form factors, and in particular GE2, are determined at finite Q2 only, and the extraction of the electric quadrupole moment, Q_Omega= GE2(0) e/(2 M_Omega), involves an extrapolation of the numerical lattice results. In this work we reproduce the lattice QCD data with a covariant spectator quark model for Omega- which includes a mixture of S and two D states for the relative quark-diquark motion. Once the model is calibrated, it is used to determine Q_Omega. Our pr...
Busbar studies for the LHC interaction region quadrupoles
Bauer, P; Fehér, S; Kerby, J S; Lamm, M J; Orris, D; Sylvester, C D; Tompkins, J C; Zlobin, A V
2001-01-01
Fermilab (FNAL) and the Japanese high energy physics lab (KEK) are developing the superconducting quadrupole magnets for the interaction regions (IR) of the Large Hadron Collider (LHC). These magnets have a nominal field gradient of 215 T/m in a 70 mm bore and operate in superfluid helium at 1.9 K. The IR magnets are electrically interconnected with superconducting busbars, which need to be protected in the event of a quench. Experiments to determine the most suitable busbar design for the LHC IR magnets and the analysis of the data are presented. The main purpose of the study was to find a design that allows the inclusion of the superconducting busbars in the magnet quench protection scheme, thus avoiding additional quench protection circuitry. A proposed busbar design that was tested in these experiments consists of a superconducting cable, which is normally used for the inner layer of the Fermilab IR quadrupoles, soldered to similar Rutherford type cables as a stabilizer. A series of prototypes with varyin...
Low-frequency nuclear quadrupole resonance with a dc SQUID
Chang, J.W.
1991-07-01
Conventional pure nuclear quadrupole resonance (NQR) is a technique well suited for the study of very large quadrupolar interactions. Numerous nuclear magnetic resonance (NMR) techniques have been developed for the study of smaller quadrupolar interactions. However, there are many nuclei which have quadrupolar interactions of intermediate strength. Quadrupolar interactions in this region have traditionally been difficult or unfeasible to detect. This work describes the development and application of a SQUID NQR technique which is capable of measuring intermediate strength quadrupolar interactions, in the range of a few hundred kilohertz to several megahertz. In this technique, a dc SQUID (Superconducting QUantum Interference Device) is used to monitor the longitudinal sample magnetization, as opposed to the transverse magnetization, as a rf field is swept in frequency. This allows the detection of low-frequency nuclear quadrupole resonances over a very wide frequency range with high sensitivity. The theory of this NQR technique is discussed and a description of the dc SQUID system is given. In the following chapters, the spectrometer is discussed along with its application to the study of samples containing half-odd-integer spin quadrupolar nuclei, in particular boron-11 and aluminum-27. The feasibility of applying this NQR technique in the study of samples containing integer spin nuclei is discussed in the last chapter. 140 refs., 46 figs., 6 tabs.