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Sample records for anomalous hall effect

  1. Nonlocal Anomalous Hall Effect

    Science.gov (United States)

    Zhang, Steven S.-L.; Vignale, Giovanni

    2016-04-01

    The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect—the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt /YIG structures.

  2. Anomalous Hall effect

    Czech Academy of Sciences Publication Activity Database

    Nagaosa, N.; Sinova, Jairo; Onoda, S.; MacDonald, A. H.; Ong, N. P.

    2010-01-01

    Roč. 82, č. 2 (2010), s. 1539-1592. ISSN 0034-6861 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 51.695, year: 2010

  3. The quantum anomalous Hall effect

    OpenAIRE

    LIU, CHAO-XING; Zhang, Shou-Cheng; Qi, Xiao-Liang

    2015-01-01

    The quantum anomalous Hall effect is defined as a quantized Hall effect realized in a system without external magnetic field. Quantum anomalous Hall effect is a novel manifestation of topological structure in many-electron systems, and may have potential applications in future electronic devices. In recent years, quantum anomalous Hall effect has been proposed theoretically and realized experimentally. In this review article, we provide a systematic overview of the theoretical and experimenta...

  4. Anomalous Hall effect in polycrystalline Ni films

    KAUST Repository

    Guo, Zaibing

    2012-02-01

    We systematically studied the anomalous Hall effect in a series of polycrystalline Ni films with thickness ranging from 4 to 200 nm. It is found that both the longitudinal and anomalous Hall resistivity increased greatly as film thickness decreased. This enhancement should be related to the surface scattering. In the ultrathin films (46 nm thick), weak localization corrections to anomalous Hall conductivity were studied. The granular model, taking into account the dominated intergranular tunneling, has been employed to explain this phenomenon, which can explain the weak dependence of anomalous Hall resistivity on longitudinal resistivity as well. © 2011 Elsevier Ltd. All rights reserved.

  5. Anomalous Hall effect for semiclassical chiral fermions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Pengming, E-mail: zhpm@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Horváthy, P.A., E-mail: horvathy@lmpt.univ-tours.fr [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Laboratoire de Mathématiques et de Physique Théorique, Université de Tours (France)

    2015-03-06

    Semiclassical chiral fermions manifest the anomalous spin-Hall effect: when put into a pure electric field they suffer a side jump, analogous to what happens to their massive counterparts in non-commutative mechanics. The transverse shift is consistent with the conservation of the angular momentum. In a pure magnetic field, instead, spiraling motion is found. Motion in Hall-type perpendicular electric and magnetic fields is also studied. - Highlights: • Chiral fermions exhibit an anomalous spin-Hall effect. • Transverse shift appears in a pure electric field. • In a pure magnetic field spiraling motion is found.

  6. Anomalous Hall Effect for chiral fermions

    CERN Document Server

    Zhang, P -M

    2014-01-01

    Semiclassical chiral fermions manifest the anomalous spin-Hall effect: when put into a pure electric field, they suffer a side jump, analogous to what happens to their massive counterparts in non-commutative mechanics. The transverse shift is consistent with the conservation of the angular momentum. In a pure magnetic field a cork-screw-like, spiraling motion is found.

  7. Anomalous Hall effect in disordered multiband metals

    Czech Academy of Sciences Publication Activity Database

    Kovalev, A.A.; Sinova, Jairo; Tserkovnyak, Y.

    2010-01-01

    Roč. 105, č. 3 (2010), 036601/1-036601/4. ISSN 0031-9007 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.621, year: 2010

  8. Anomalous Hall effect in Weyl superconductors

    Science.gov (United States)

    Bednik, G.; Zyuzin, A. A.; Burkov, A. A.

    2016-08-01

    We present a theory of the anomalous Hall effect in a topological Weyl superconductor with broken time reversal symmetry. Specifically, we consider a ferromagnetic Weyl metal with two Weyl nodes of opposite chirality near the Fermi energy. In the presence of inversion symmetry, such a metal experiences a weak-coupling Bardeen–Cooper–Schrieffer instability, with pairing of parity-related eigenstates. Due to the nonzero topological charge, carried by the Weyl nodes, such a superconductor is necessarily topologically nontrivial, with Majorana surface states coexisting with the Fermi arcs of the normal Weyl metal. We demonstrate that, surprisingly, the anomalous Hall conductivity of such a superconducting Weyl metal coincides with that of a nonsuperconducting one, under certain conditions, in spite of the nonconservation of charge in a superconductor. We relate this to the existence of an extra (nearly) conserved quantity in a Weyl metal, the chiral charge.

  9. Anomalous Josephson Hall effect in magnet/triplet superconductor junctions

    OpenAIRE

    Yokoyama, Takehito

    2015-01-01

    We investigate anomalous Hall effect in a magnet coupled to a triplet superconductor under phase gradient. It is found that the anomalous Hall supercurrent arises from non-trivial structure of the magnetization. The magnetic structure manifested in the Hall supercurrent is characterized by even order terms of the exchange coupling, essentially different from that discussed in the context of anomalous Hall effect, reflecting the disspationless nature of supercurrent. We also discuss a possible...

  10. Anomalous Hall effect in YIG$|$Pt bilayers

    OpenAIRE

    Meyer, Sibylle; Schlitz, Richard; Geprägs, Stephan; Opel, Matthias; Huebl, Hans; Gross, Rudolf; Goennenwein, Sebastian T. B.

    2015-01-01

    We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet$|$platinum (YIG$|$Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall like signature in Pt, sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing ...

  11. Localization corrections to the anomalous Hall effect in a ferromagnet

    OpenAIRE

    Dugaev, V. K.; Crepieux, A.; Bruno, P

    2001-01-01

    We calculate the localization corrections to the anomalous Hall conductivity related to the contribution of spin-orbit scattering into the current vertex (side-jump mechanism). We show that in contrast to the ordinary Hall effect, there exists a nonvanishing localization correction to the anomalous Hall resistivity. The correction to the anomalous Hall conductivity vanishes in the case of side-jump mechanism, but is nonzero for the skew scattering. The total correction to the nondiagonal cond...

  12. Photoinduced Anomalous Hall Effects in Weyl Semimetals

    Science.gov (United States)

    Chan, Ching-Kit; Lee, Patrick A.; Burch, Kenneth S.; Han, Jung Hoon; Ran, Ying

    We examine theoretically the interplay between chiral photons and chiral electrons in Weyl semimetals. Owing to its monopole nature, a three-dimensional Weyl node is topologically-robust against a circularly polarized light. A driven Weyl system exhibits node shifts in the momentum space, in sharp contrast to the gap opening in a driven two-dimensional Dirac system. We show that the node shift leads to a change of the Chern vector which gives arise to a net photoinduced anomalous Hall conductivity, in the plane perpendicular to the light propagation. We shall describe the basic idea behind this generic photoinduced Hall effect, illustrate it with a concrete microscope model, and estimate its feasibility based on current optical experimental techniques.

  13. Anomalous Hall Effect in non-commutative mechanics

    OpenAIRE

    Horvathy, P. A.

    2006-01-01

    The anomalous velocity term in the semiclassical model of a Bloch electron deviates the trajectory from the conventional one. When the Berry curvature (alias noncommutative parameter) is a monopole in momentum space as found recently in some ferromagnetic semiconductors while observing the anomalous Hall effect, we get a transverse shift, similar to that in the optical Hall effect.

  14. Anomalous Hall effect in YIG|Pt bilayers

    International Nuclear Information System (INIS)

    We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet|platinum (YIG|Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall effect like voltage in Pt, which is sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing conductance Gi plays a crucial role in YIG|Pt bilayers. In particular, our data suggest a sign change in Gi between 10 K and 300 K. Additionally, we report a higher order Hall effect contribution, which appears in thin Pt films on YIG at low temperatures

  15. Anomalous Hall effect in YIG|Pt bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Sibylle, E-mail: sibylle.meyer@wmi.badw.de; Schlitz, Richard [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany); Geprägs, Stephan; Opel, Matthias [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Huebl, Hans; Goennenwein, Sebastian T. B. [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Nanosystems Initiative Munich, 80799 München (Germany); Gross, Rudolf [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany); Nanosystems Initiative Munich, 80799 München (Germany)

    2015-03-30

    We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet|platinum (YIG|Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall effect like voltage in Pt, which is sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing conductance G{sub i} plays a crucial role in YIG|Pt bilayers. In particular, our data suggest a sign change in G{sub i} between 10 K and 300 K. Additionally, we report a higher order Hall effect contribution, which appears in thin Pt films on YIG at low temperatures.

  16. Quantized Anomalous Hall Effect in Magnetic Topological Insulators

    Institute of Scientific and Technical Information of China (English)

    YU Rui

    2011-01-01

    @@ The Hall effect, the anomalous Hall effect (AHE) and the spin Hall effect are fundamental transport processes in solids arising from the Lorentz force and the spin-orbit coupling respectively.The AHE, in which a voltage transverse to the electric current appears even in the absence of an external magnetic field, was first detected in ferromagnetic (FM) metals in 1881 and later found to arise from the spin-orbit coupling (SOC) between the current and magnetic moments.Recent progress on the mechanism of AHE has established a link between the AHE and the topological nature of the Hall current by adopting the Berry-phase concepts in close analogy to the intrinsic spin Hall effect.Given the experimental discovery of the quantum Hall and the quantum spin Hall effects, it is natural to ask whether the AHE can also be quantized.In a quantized anomalous Hall (QAH) insulator, spontaneous magnetic moments and spin-orbit coupling combine to give rise to a topologically non-trivial electronic structure, leading to the quantized Hall effect without any external magnetic field.

  17. Quantized Anomalous Hall Effect in Magnetic Topological Insulators

    Institute of Scientific and Technical Information of China (English)

    YU Rui

    2011-01-01

    The Hall effect, the anomalous Hall effect (AHE) and the spin Hall effect are thndamental transport processes in solids arising from the Lorentz force and the spin-orbit coupling respectively. The AHE, in which a voltage transverse to the electric current appears even in the absence of an external magnetic field, was first detected in ferromagnetic (FM) metals in 1881 and later found to arise from the spin-orbit coupling (SOC) between the current and magnetic moments.

  18. Quantum Anomalous Hall Effect in Magnetic Insulator Heterostructure

    OpenAIRE

    Xu, Gang; Jing WANG; FELSER, CLAUDIA; Qi, Xiao-Liang; Zhang, Shou-Cheng

    2014-01-01

    Based on ab initio calculations, we predict that a monolayer of Cr-doped (Bi,Sb)2Te3 and GdI2 heterostructure is a quantum anomalous Hall insulator with a non-trivial band gap up to 38 meV. The principle behind our prediction is that the band inversion between two topologically trivial ferromagnetic insulators can result in a non-zero Chern number, which offers a better way to realize the quantum anomalous Hall state without random magnetic doping. In addition, a simple effective model is pre...

  19. Anomalous Hall Effect in a 2D Rashba Ferromagnet.

    Science.gov (United States)

    Ado, I A; Dmitriev, I A; Ostrovsky, P M; Titov, M

    2016-07-22

    Skew scattering on rare impurity configurations is shown to dominate the anomalous Hall effect in a 2D Rashba ferromagnet. The mechanism originates in scattering on rare impurity pairs separated by distances of the order of the Fermi wavelength. The corresponding theoretical description goes beyond the conventional noncrossing approximation. The mechanism provides the only contribution to the anomalous Hall conductivity in the most relevant metallic regime and strongly modifies previously obtained results for lower energies in the leading order with respect to impurity strength. PMID:27494487

  20. Inverse Spin Hall Effect and Anomalous Hall Effect in a Two-Dimensional Electron Gas

    OpenAIRE

    Schwab, Peter; Raimondi, Roberto; Gorini, Cosimo

    2010-01-01

    We study the coupled dynamics of spin and charge currents in a two-dimensional electron gas in the transport diffusive regime. For systems with inversion symmetry there are established relations between the spin Hall effect, the anomalous Hall effect and the inverse spin Hall effect. However, in two-dimensional electron gases of semiconductors like GaAs, inversion symmetry is broken so that the standard arguments do not apply. We demonstrate that in the presence of a Rashba type of spin-orbit...

  1. Quantum anomalous Hall effect in magnetic topological insulators

    OpenAIRE

    Jing WANG; Lian, Biao; Zhang, Shou-Cheng

    2014-01-01

    The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimension (2D) and three-dimension (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magn...

  2. Anomalous Hall Effect in a Feromagnetic Rare-Earth Cobalite

    Science.gov (United States)

    Samoilov, A. V.; Yeh, N. C.; Vasquez, R. P.

    1996-01-01

    Rare-Earth manganites and cobalites with the perovskite structure have been a subject of great recent interest because their electrical resistance changes significantly when a magnetic field is applied...we have studied the Hall effect in thin film La(sub 0.5)Ca(sub 0.5)CoO(sub 3) material and have obtained convincing evidence fo the so called anomalous Hall effect, typical for magnetic metals...Our results suggest that near the ferromagnetic ordering temperature, the dominant electron scattering mechanism is the spin fluctuation.

  3. Quantum anomalous Hall effect in topological insulator memory

    Energy Technology Data Exchange (ETDEWEB)

    Jalil, Mansoor B. A., E-mail: elembaj@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); Tan, S. G. [Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117576 (Singapore); Siu, Z. B. [Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore (Singapore)

    2015-05-07

    We theoretically investigate the quantum anomalous Hall effect (QAHE) in a magnetically coupled three-dimensional-topological insulator (3D-TI) system. We apply the generalized spin-orbit coupling Hamiltonian to obtain the Hall conductivity σ{sup xy} of the system. The underlying topology of the QAHE phenomenon is then analyzed to show the quantization of σ{sup xy} and its relation to the Berry phase of the system. Finally, we analyze the feasibility of utilizing σ{sup xy} as a memory read-out in a 3D-TI based memory at finite temperatures, with comparison to known magnetically doped 3D-TIs.

  4. Quantum anomalous Hall effect in topological insulator memory

    International Nuclear Information System (INIS)

    We theoretically investigate the quantum anomalous Hall effect (QAHE) in a magnetically coupled three-dimensional-topological insulator (3D-TI) system. We apply the generalized spin-orbit coupling Hamiltonian to obtain the Hall conductivity σxy of the system. The underlying topology of the QAHE phenomenon is then analyzed to show the quantization of σxy and its relation to the Berry phase of the system. Finally, we analyze the feasibility of utilizing σxy as a memory read-out in a 3D-TI based memory at finite temperatures, with comparison to known magnetically doped 3D-TIs

  5. Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators

    OpenAIRE

    Daniel Guterding; Jeschke, Harald O.; Roser Valentí

    2015-01-01

    Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice M...

  6. Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators.

    Science.gov (United States)

    Guterding, Daniel; Jeschke, Harald O; Valentí, Roser

    2016-01-01

    Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions. PMID:27185665

  7. Nonlinear dynamics induced anomalous Hall effect in topological insulators

    Science.gov (United States)

    Wang, Guanglei; Xu, Hongya; Lai, Ying-Cheng

    2016-01-01

    We uncover an alternative mechanism for anomalous Hall effect. In particular, we investigate the magnetisation dynamics of an insulating ferromagnet (FM) deposited on the surface of a three-dimensional topological insulator (TI), subject to an external voltage. The spin-polarised current on the TI surface induces a spin-transfer torque on the magnetisation of the top FM while its dynamics can change the transmission probability of the surface electrons through the exchange coupling and hence the current. We find a host of nonlinear dynamical behaviors including multistability, chaos, and phase synchronisation. Strikingly, a dynamics mediated Hall-like current can arise, which exhibits a nontrivial dependence on the channel conductance. We develop a physical understanding of the mechanism that leads to the anomalous Hall effect. The nonlinear dynamical origin of the effect stipulates that a rich variety of final states exist, implying that the associated Hall current can be controlled to yield desirable behaviors. The phenomenon can find applications in Dirac-material based spintronics.

  8. Anomalous Hall Effect in Geometrically Frustrated Magnets

    Directory of Open Access Journals (Sweden)

    D. Boldrin

    2012-01-01

    space mechanism based on spin chirality that was originally applied to the pyrochlore Nd2Mo2O7 appears unsatisfactory. Recently, an orbital description based on the Aharonov-Bohm effect has been proposed and applied to both the ferromagnetic pyrochlores Nd2Mo2O7 and Pr2Ir2O7; the first of which features long-ranged magnetic order while the latter is a chiral spin liquid. Two further examples of geometrically frustrated conducting magnets are presented in this paper—the kagome-like Fe3Sn2 and the triangular PdCrO2. These possess very different electronic structures to the 3-dimensional heavy-metal pyrochlores and provide new opportunities to explore the different origins of the AHE. This paper summarises the experimental findings in these materials in an attempt to unite the conflicting theoretical arguments.

  9. Effects of surface and interface scattering on anomalous Hall effect in Co/Pd multilayers

    KAUST Repository

    Guo, Z. B.

    2012-09-27

    In this paper, we report the results of surface and interface scattering on anomalous Hall effect in Co/Pd multilayers with perpendicular magnetic anisotropy. The surface scattering effect has been extracted from the total anomalous Hall effect. By scaling surface scattering contribution with ρAHs∼ργss, the exponent γ has been found to decrease with the increase of surface scattering resistivity, which could account for the thickness-dependent anomalous Hall effect. Interface diffusion induced by rapid thermal annealing modifies not only the magnetization and longitudinal resistivity but also the anomalous Hall effect; a large exponent γ ∼ 5.7 has been attributed to interface scattering-dominated anomalous Hall effect.

  10. Precise quantization of anomalous Hall effect near zero magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Bestwick, A. J. [Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Fox, E. J. [Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Kou, Xufeng [Univ. of California, Los Angeles, CA (United States); Pan, Lei [Univ. of California, Los Angeles, CA (United States); Wang, Kang L. [Univ. of California, Los Angeles, CA (United States); Goldhaber-Gordon, D. [Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-05-04

    In this study, we report a nearly ideal quantum anomalous Hall effect in a three-dimensional topological insulator thin film with ferromagnetic doping. Near zero applied magnetic field we measure exact quantization in the Hall resistance to within a part per 10,000 and a longitudinal resistivity under 1 Ω per square, with chiral edge transport explicitly confirmed by nonlocal measurements. Deviations from this behavior are found to be caused by thermally activated carriers, as indicated by an Arrhenius law temperature dependence. Using the deviations as a thermometer, we demonstrate an unexpected magnetocaloric effect and use it to reach near-perfect quantization by cooling the sample below the dilution refrigerator base temperature in a process approximating adiabatic demagnetization refrigeration.

  11. Anomalous Hall effect in Fe/Au multilayers

    KAUST Repository

    Zhang, Q.

    2016-07-22

    To understand the interfacial scattering effect on the anomalous Hall effect (AHE), we prepared multilayers of (Fe(36/n)nm/Au(12/n)nm)n using an e-beam evaporator. This structure design allowed us to investigate the effect of interfacial scattering on the AHE, while keeping the samples\\' thickness and composition unchanged. We measured the (magneto)transport properties of the samples in a wide temperature range (10–310 K) with magnetic fields up to 50 kOe. We found that the scaling between the anomalous Hall resistivity (ρAHE) and longitudinal resistivity (ρxx) can be roughly described by ρAHE∼ργxx with γ=2.65±0.10 and 1.90 ± 0.04 for samples from n=1 to n=4 and samples from n=4 to n=12, respectively. Our quantitative analysis results showed that the interfacial scattering suppresses the contribution of the intrinsic mechanism and gives rise to a side-jump contribution.

  12. Anomalous Hall effect in Fe/Gd bilayers

    KAUST Repository

    Xu, W. J.

    2010-04-01

    Non-monotonic dependence of anomalous Hall resistivity on temperature and magnetization, including a sign change, was observed in Fe/Gd bilayers. To understand the intriguing observations, we fabricated the Fe/Gd bilayers and single layers of Fe and Gd simultaneously. The temperature and field dependences of longitudinal resistivity, Hall resistivity and magnetization in these films have also been carefully measured. The analysis of these data reveals that these intriguing features are due to the opposite signs of Hall resistivity/or spin polarization and different Curie temperatures of Fe and Gd single-layer films. Copyright (C) EPLA, 2010

  13. Quantum anomalous Hall effect in magnetic topological insulators

    Science.gov (United States)

    Wang, Jing; Lian, Biao; Zhang, Shou-Cheng

    2015-12-01

    The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimensions (2D) and three-dimensions (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magnetic order opens up a gap for the topological surface states, and chiral edge state has been predicted to exist on the magnetic domain walls. We present the phase diagram in thin films of a magnetic topological insulator and review the basic mechanism of ferromagnetic order in magnetically doped topological insulators. We also review the recent experimental observation of the QAH effect. We discuss more recent theoretical work on the coexistence of the helical and chiral edge states, multi-channel chiral edge states, the theory of the plateau transition, and the thickness dependence in the QAH effect.

  14. Stacking order dependence of inverse spin Hall effect and anomalous Hall effect in spin pumping experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang-Il; Seo, Min-Su; Park, Seung-Young, E-mail: parksy@kbsi.re.kr [Division of Materials Science, Korea Basic Science Institute, Daejeon 305-806 (Korea, Republic of); Kim, Dong-Jun; Park, Byong-Guk [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of)

    2015-05-07

    The dependence of the measured DC voltage on the non-magnetic material (NM) in NM/CoFeB and CoFeB/NM bilayers is studied under ferromagnetic resonance conditions in a TE{sub 011} resonant cavity. The directional change of the inverse spin Hall effect (ISHE) voltage V{sub ISHE} for the stacking order of the bilayer can separate the pure V{sub ISHE} and the anomalous Hall effect (AHE) voltage V{sub AHE} utilizing the method of addition and subtraction. The Ta and Ti NMs show a broad deviation of the spin Hall angle θ{sub ISH}, which originates from the AHE in accordance with the high resistivity of NMs. However, the Pt and Pd NMs show that the kinds of NMs with low resistivity are consistent with the previously reported θ{sub ISH} values. Therefore, the characteristics that NM should simultaneously satisfy to obtain a reasonable V{sub ISHE} value in bilayer systems are large θ{sub ISH} and low resistivity.

  15. Anomalous Hall effect on the surface of topological Kondo insulators

    Science.gov (United States)

    König, E. J.; Ostrovsky, P. M.; Dzero, M.; Levchenko, A.

    2016-07-01

    We calculate the anomalous Hall conductivity σx y of the surface states in cubic topological Kondo insulators. We consider a generic model for the surface states with three Dirac cones on the (001) surface. The Fermi velocity, the Fermi momentum, and the Zeeman energy in different Dirac pockets may be unequal. The microscopic impurity potential mediates mixed intra- and interband extrinsic scattering processes. Our calculation of σx y is based on the Kubo-Streda diagrammatic approach. It includes diffractive skew scattering contributions originating from the rare two-impurity complexes. Remarkably, these contributions yield anomalous Hall conductivity that is independent of impurity concentration, and thus is of the same order as other known extrinsic side jump and skew scattering terms. We discuss various special cases of our results and the experimental relevance of our study in the context of the recent hysteretic magnetotransport data in SmB6 samples.

  16. Localization correction to the anomalous Hall effect in amorphous CoFeB thin films

    Institute of Scientific and Technical Information of China (English)

    丁进军; 吴少兵; 杨晓非; 朱涛

    2015-01-01

    An obvious weak localization correction to anomalous Hall conductance (AHC) in very thin CoFeB film is reported. We find that both the weak localization to AHC and the mechanism of anomalous Hall effect are related to the CoFeB thickness. When the film is thicker than 3 nm, the side jump mechanism dominates and the weak localization to AHC vanishes. For very thin CoFeB films, both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect, and the weak localization correction to AHC is observed.

  17. Unconventional scaling of the anomalous Hall effect accompanying electron localization correction in the dirty regime

    KAUST Repository

    Lu, Y. M.

    2013-03-05

    Scaling of the anomalous Hall conductivity to longitudinal conductivity σAH∝σ2xx has been observed in the dirty regime of two-dimensional weak and strong localization regions in ultrathin, polycrystalline, chemically disordered, ferromagnetic FePt films. The relationship between electron transport and temperature reveals a quantitatively insignificant Coulomb interaction in these films, while the temperature dependent anomalous Hall conductivity experiences quantum correction from electron localization. At the onset of this correction, the low-temperature anomalous Hall resistivity begins to be saturated when the thickness of the FePt film is reduced, and the corresponding Hall conductivity scaling exponent becomes 2, which is above the recent unified theory of 1.6 (σAH∝σ1.6xx). Our results strongly suggest that the correction of the electron localization modulates the scaling exponent of the anomalous Hall effect.

  18. Carrier-independent ferromagnetism and giant anomalous Hall effect in magnetic topological insulator

    OpenAIRE

    Chang, Cui-Zu; Zhang, Jin-song; Liu, Min-Hao; Zhang, Zuo-Cheng; Feng, Xiao; Li, Kang; Wang, Li-Li; Chen, Xi; Dai, Xi; Fang, Zhong; Qi, Xiao-Liang; Zhang, Shou-Cheng; Wang, Yayu; He, Ke; Ma, Xu-Cun

    2011-01-01

    Breaking the time-reversal symmetry of a topological insulator (TI) by ferromagnetism can induce exotic magnetoelectric phenomena such as quantized anomalous Hall (QAH) effect. Experimental observation of QAH effect in a magnetically doped TI requires ferromagnetism not relying on the charge carriers. We have realized the ferromagnetism independent of both polarity and density of carriers in Cr-doped BixSb2-xTe3 thin films grown by molecular beam epitaxy. Meanwhile, the anomalous Hall effect ...

  19. Magnetic Topological Insulators and Quantum Anomalous Hall Effect

    Science.gov (United States)

    Kou, Xufeng

    The engineering of topological surface states is a key to realize applicable devices based on topological insulators (TIs). Among various proposals, introducing magnetic impurities into TIs has been proven to be an effective way to open a surface gap and integrate additional ferromagnetism with the original topological order. In this Dissertation, we study both the intrinsic electrical and magnetic properties of the magnetic TI thin films grown by molecular beam epitaxy. By doping transition element Cr into the host tetradymite-type V-VI semiconductors, we achieve robust ferromagnetic order with a strong perpendicular magnetic anisotropy. With additional top-gating capability, we realize the electric-field-controlled ferromagnetism in the magnetic TI systems, and demonstrate such magneto-electric effects can be effectively manipulated, depending on the interplays between the band topology, magnetic exchange coupling, and structural engineering. Most significantly, we report the observation of quantum anomalous Hall effect (QAHE) in the Cr-doped (BiSb)2Te3 samples where dissipationless chiral edge conduction is realized in the macroscopic millimeter-size devices without the presence of any external magnetic field, and the stability of the quantized Hall conductance of e2/h is well-maintained as the film thickness varies across the 2D hybridization limit. With additional quantum confinement, we discover the metal-to-insulator switching between two opposite QAHE states, and reveal the universal QAHE phase diagram in the thin magnetic TI samples. In addition to the uniform magnetic TIs, we further investigate the TI/Cr-doped TI bilayer structures prepared by the modulation-doped growth method. By controlling the magnetic interaction profile, we observe the Dirac hole-mediated ferromagnetism and develop an effective way to manipulate its strength. Besides, the giant spin-orbit torque in such magnetic TI-based heterostructures enables us to demonstrate the current

  20. Large anomalous Hall effect in a non-collinear antiferromagnet at room temperature.

    Science.gov (United States)

    Nakatsuji, Satoru; Kiyohara, Naoki; Higo, Tomoya

    2015-11-12

    In ferromagnetic conductors, an electric current may induce a transverse voltage drop in zero applied magnetic field: this anomalous Hall effect is observed to be proportional to magnetization, and thus is not usually seen in antiferromagnets in zero field. Recent developments in theory and experiment have provided a framework for understanding the anomalous Hall effect using Berry-phase concepts, and this perspective has led to predictions that, under certain conditions, a large anomalous Hall effect may appear in spin liquids and antiferromagnets without net spin magnetization. Although such a spontaneous Hall effect has now been observed in a spin liquid state, a zero-field anomalous Hall effect has hitherto not been reported for antiferromagnets. Here we report empirical evidence for a large anomalous Hall effect in an antiferromagnet that has vanishingly small magnetization. In particular, we find that Mn3Sn, an antiferromagnet that has a non-collinear 120-degree spin order, exhibits a large anomalous Hall conductivity of around 20 per ohm per centimetre at room temperature and more than 100 per ohm per centimetre at low temperatures, reaching the same order of magnitude as in ferromagnetic metals. Notably, the chiral antiferromagnetic state has a very weak and soft ferromagnetic moment of about 0.002 Bohr magnetons per Mn atom (refs 10, 12), allowing us to switch the sign of the Hall effect with a small magnetic field of around a few hundred oersted. This soft response of the large anomalous Hall effect could be useful for various applications including spintronics--for example, to develop a memory device that produces almost no perturbing stray fields. PMID:26524519

  1. Thickness Dependence of the Quantum Anomalous Hall Effect in Magnetic Topological Insulator Films.

    Science.gov (United States)

    Feng, Xiao; Feng, Yang; Wang, Jing; Ou, Yunbo; Hao, Zhenqi; Liu, Chang; Zhang, Zuocheng; Zhang, Liguo; Lin, Chaojing; Liao, Jian; Li, Yongqing; Wang, Li-Li; Ji, Shuai-Hua; Chen, Xi; Ma, Xucun; Zhang, Shou-Cheng; Wang, Yayu; He, Ke; Xue, Qi-Kun

    2016-08-01

    The evolution of the quantum anomalous Hall effect with the thickness of Cr-doped (Bi,Sb)2 Te3 magnetic topological insulator films is studied, revealing how the effect is caused by the interplay of the surface states, band-bending, and ferromagnetic exchange energy. Homogeneity in ferromagnetism is found to be the key to high-temperature quantum anomalous Hall material. PMID:27166762

  2. Theory of the anomalous Hall effect from the Kubo formula and the Dirac equation

    OpenAIRE

    Crépieux, A.; Bruno, P

    2001-01-01

    A model to treat the anomalous Hall effect is developed. Based on the Kubo formalism and on the Dirac equation, this model allows the simultaneous calculation of the skew-scattering and side-jump contributions to the anomalous Hall conductivity. The continuity and the consistency with the weak-relativistic limit described by the Pauli Hamiltonian is shown. For both approaches, Dirac and Pauli, the Feynman diagrams, which lead to the skew-scattering and the side-jump contributions, are underli...

  3. Field-effect modulation of anomalous Hall effect in diluted ferromagnetic topological insulator epitaxial films

    Science.gov (United States)

    Chang, CuiZu; Liu, MinHao; Zhang, ZuoCheng; Wang, YaYu; He, Ke; Xue, QiKun

    2016-03-01

    High quality chromium (Cr) doped three-dimensional topological insulator (TI) Sb2Te3 films are grown via molecular beam epitaxy on heat-treated insulating SrTiO3 (111) substrates. We report that the Dirac surface states are insensitive to Cr doping, and a perfect robust long-range ferromagnetic order is unveiled in epitaxial Sb2- x Cr x Te3 films. The anomalous Hall effect is modulated by applying a bottom gate, contrary to the ferromagnetism in conventional diluted magnetic semiconductors (DMSs), here the coercivity field is not significantly changed with decreasing carrier density. Carrier-independent ferromagnetism heralds Sb2- x Cr x Te3 films as the base candidate TI material to realize the quantum anomalous Hall (QAH) effect. These results also indicate the potential of controlling anomalous Hall voltage in future TI-based magneto-electronics and spintronics.

  4. Anomalous Hall effect of heavy holes in Ⅲ-Ⅴ semiconductor quantum wells

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Gang; Zhang Ping

    2007-01-01

    The anomalous Hall effect of heavy holes in semiconductor quantum wells is studied in the intrinsic transport regime, where the Berry curvature governs the Hall current properties. Based on the first-order perturbation of wave function the expression of the Hall conductivity the same as that from the semiclassical equation of motion of the Bloch particles is derived. The dependence of Hall conductivity on the system parameters is shown. The amplitude of Hall conductivity is found to be balanced by a competition between the Zeeman splitting and the spin-orbit splitting.

  5. Artificial ferroelectricity due to anomalous Hall effect in magnetic tunnel junctions

    OpenAIRE

    Vedyayev, A.; Ryzhanova, N.; Strelkov, N.; Dieny, B

    2012-01-01

    We theoretically investigated Anomalous Hall Effect (AHE) and Spin Hall Effect (SHE) transversally to the insulating spacer O, in magnetic tunnel junctions of the form F/O/F where F are ferromagnetic layers and O represents a tunnel barrier. We considered the case of purely ballistic (quantum mechanical) transport, taking into account the assymetric scattering due to spin-orbit interaction in the tunnel barrier. AHE and SHE in the considered case have a surface nature due to proximity effect....

  6. Anomalous Hall effect from vortex motion in high-Tc superconductors

    International Nuclear Information System (INIS)

    In this work, the unusual Seebeck effect is taken into consideration in explaining the possible origin of the anomalous Hall effect for high-Tc superconductors. Combining Maki's theory of transport entropy and Tinkham's theory of resistive transition, we explain why the anomalous Hall effect can be observed in high-Tc superconductors, but is absent in most conventional superconductors. The behavior of ρxy(H,T) in our theory is qualitatively consistent with experiments. In addition, our theory not only predicts that ρxy will become positive from ρxyxy|∝ρxx2 in the region of ρxyxy will diminish with increasing defect concentration

  7. Spontaneous magnetization and anomalous Hall effect in an emergent Dice lattice

    Science.gov (United States)

    Dutta, Omjyoti; Przysiężna, Anna; Zakrzewski, Jakub

    2015-06-01

    Ultracold atoms in optical lattices serve as a tool to model different physical phenomena appearing originally in condensed matter. To study magnetic phenomena one needs to engineer synthetic fields as atoms are neutral. Appropriately shaped optical potentials force atoms to mimic charged particles moving in a given field. We present the realization of artificial gauge fields for the observation of anomalous Hall effect. Two species of attractively interacting ultracold fermions are considered to be trapped in a shaken two dimensional triangular lattice. A combination of interaction induced tunneling and shaking can result in an emergent Dice lattice. In such a lattice the staggered synthetic magnetic flux appears and it can be controlled with external parameters. The obtained synthetic fields are non-Abelian. Depending on the tuning of the staggered flux we can obtain either anomalous Hall effect or its quantized version. Our results are reminiscent of Anomalous Hall conductivity in spin-orbit coupled ferromagnets.

  8. Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; /Stanford U., Phys. Dept.; Dai, Xi; Fang, Zhong; /Beijing, Inst. Phys.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{sub 1-y}Mn{sub y}Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices.

  9. Scaling of anomalous hall effect in amorphous CoFeB Films with accompanying quantum correction

    KAUST Repository

    Zhang, Yan

    2015-05-08

    Scaling of anomalous Hall effect in amorphous CoFeB films with thickness ranging from 2 to 160 nm have been investigated. We have found that the scaling relationship between longitudinal (ρxx) and anomalous Hall (ρAH) resistivity is distinctly different in the Bloch and localization regions. For ultrathin CoFeB films, the sheet resistance (Rxx) and anomalous Hall conductance (GAH) received quantum correction from electron localization showing two different scaling relationships at different temperature regions. In contrast, the thicker films show a metallic conductance, which have only one scaling relationship in the entire temperature range. Furthermore, in the dirty regime of localization regions, an unconventional scaling relationship View the MathML sourceσAH∝σxxα with α=1.99 is found, rather than α=1.60 predicted by the unified theory.

  10. Quantum Anomalous Hall Effect in Hg$_{1-y}$Mn$_{y}$Te Quantum Wells

    OpenAIRE

    Liu, Chao-Xing; Qi, Xiao-Liang; Dai, Xi; Fang, Zhong; Zhang, Shou-Cheng

    2008-01-01

    The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg$_{1-y}$Mn$_{y}$Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the $Mn$ atoms, and the quantized Hall conductance is predi...

  11. 3d Transition Metal Adsorption Induced Vally-polarized Anomalous Hall Effect in Germanene

    OpenAIRE

    Zhou, P; Sun, L. Z.

    2015-01-01

    Based on DFT+U and Berry curvature calculations, we study the electronic structures and topological properties of 3d transition metal (TM) atom (from Ti to Co) adsorbed germanene (TM-germanene). We find that valley-polarized anomalous hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn, or Co atom on its surface. A finite valley hall voltage can be easily detected in its nanoribbon, which is important for valleytronics devices. Moreover, different valley-polarized current and ...

  12. The effect of interfacial intermixing on magnetization and anomalous Hall effect in Co/Pd multilayers

    KAUST Repository

    Guo, Zaibing

    2015-05-01

    The effect of interfacial intermixing on magnetization and anomalous Hall effect (AHE) in Co/Pd multilayers is studied by using rapid thermal annealing to enhance the interfacial diffusion. The dependence of saturation magnetization and coercivity on the temperature of rapid thermal annealing at 5 K is discussed. It is found that AHE is closely related to the relative thickness of the Co and Pd layers. Localized paramagnetism has been observed which destroys AHE, while AHE can be enhanced by annealing.

  13. 3d Transition Metal Adsorption Induced the valley-polarized Anomalous Hall Effect in Germanene

    Science.gov (United States)

    Zhou, P.; Sun, L. Z.

    2016-06-01

    Based on DFT + U and Berry curvature calculations, we study the electronic structures and topological properties of 3d transition metal (TM) atom (from Ti to Co) adsorbed germanene (TM-germanene). We find that valley-polarized anomalous Hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn, or Co atoms on its surface. A finite valley Hall voltage can be easily detected in their nanoribbon, which is important for valleytronics devices. Moreover, different valley-polarized current and even reversible valley Hall voltage can be archived by shifting the Fermi energy of the systems. Such versatile features of the systems show potential in next generation electronics devices.

  14. Switching field distribution of arrays of Co-Pt Nanodots determined by anomalous hall effect measurements

    NARCIS (Netherlands)

    Delalande, M.; Engelen, J.B.C.; Febre, le A.J.; Abelmann, L.; Lodder, J.C.

    2008-01-01

    Anomalous Hall Effect (AHE) measurements have previously been used to measure the magnetization of L10-FePt [1] and Co/Pt multilayer nanodots [2]. The high sensitivity allows us to measure the magnetization reversal behaviour of sub-100-nm dots. In this work, we investigate the magnetization reversa

  15. Anomalous Hall effects in pseudo-single-crystal γ'-Fe4N thin films

    Science.gov (United States)

    Kabara, Kazuki; Tsunoda, Masakiyo; Kokado, Satoshi

    2016-05-01

    The anomalous Hall effects (AHE) were investigated at various temperatures for the pseudo-single-crystal Fe4N films, deposited on MgO substrates with changing the degree of order (S) of the nitrogen site. Both the anomalous Hall resistivity and the longitudinal resistivity simply decrease with lowering temperature for all the specimens. The AHE of the Fe4N films is presumed to arise from an intrinsic mechanism because of the relationship between the anomalous Hall resistivity and longitudinal resistivity. The anomalous Hall conductivity, σAH, exhibits a specific behavior at low temperature. In the case of the film with S = 0.93, the σAH drastically drops below 50 K, while it simply increases with lowering temperature in the range of 50-300 K. This low-temperature anomaly decays with decreasing S of the film and nearly vanishes in the films with low S. The threshold temperature and the dependence on S of the low-temperature anomaly of the σAH well correspond to those of the anisotropic magnetoresistance effects in the Fe4N films, reported in the literatures. From these results, it is suggested that the low-temperature anomaly of the σAH originates from the crystal field effect which reflects the structural transformation from a cubic to a tetragonal symmetry below 50 K and provides a modulation of the orbital angular momentum of the 3d orbitals at the Fermi level.

  16. Giant Anomalous Hall Effect in the Chiral Antiferromagnet Mn3Ge

    Science.gov (United States)

    Kiyohara, Naoki; Tomita, Takahiro; Nakatsuji, Satoru

    2016-06-01

    The external field control of antiferromagnetism is a significant subject both for basic science and technological applications. As a useful macroscopic response to detect magnetic states, the anomalous Hall effect (AHE) is known for ferromagnets, but it has never been observed in antiferromagnets until the recent discovery in Mn3Sn . Here we report another example of the AHE in a related antiferromagnet, namely, in the hexagonal chiral antiferromagnet Mn3Ge . Our single-crystal study reveals that Mn3Ge exhibits a giant anomalous Hall conductivity |σx z|˜60 Ω-1 cm-1 at room temperature and approximately 380 Ω-1 cm-1 at 5 K in zero field, reaching nearly half of the value expected for the quantum Hall effect per atomic layer with Chern number of unity. Our detailed analyses on the anisotropic Hall conductivity indicate that in comparison with the in-plane-field components |σx z| and |σz y|, which are very large and nearly comparable in size, we find |σy x| obtained in the field along the c axis to be much smaller. The anomalous Hall effect shows a sign reversal with the rotation of a small magnetic field less than 0.1 T. The soft response of the AHE to magnetic field should be useful for applications, for example, to develop switching and memory devices based on antiferromagnets.

  17. From magnetically doped topological insulator to the quantum anomalous Hall effect

    Institute of Scientific and Technical Information of China (English)

    He Ke; Ma Xu-Cun; Chen Xi; Lü Li; Wang Ya-Yu; Xue Qi-Kun

    2013-01-01

    Quantum Hall effect (QHE),as a class of quantum phenomena that occur in macroscopic scale,is one of the most important topics in condensed matter physics.It has long been expected that QHE may occur without Landau levels so that neither extemal magnetic field nor high sample mobility is required for its study and application.Such a QHE free of Landau levels,can appear in topological insulators (TIs) with ferromagnetism as the quantized version of the anomalous Hall effect,i.e.,quantum anomalous Hall (QAH) effect.Here we review our recent work on experimental realization of the QAH effect in magnetically doped TIs.With molecular beam epitaxy,we prepare thin films of Cr-doped (Bi,Sb)2Te3 TIs with wellcontrolled chemical potential and long-range ferromagnetic order that can survive the insulating phase.In such thin films,we eventually observed the quantization of the Hall resistance at h/e2 at zero field,accompanied by a considerable drop in the longitudinal resistance.Under a strong magnetic field,the longitudinal resistance vanishes,whereas the Hall resistance remains at the quantized value.The realization of the QAH effect provides a foundation for many other novel quantum phenomena predicted in TIs,and opens a route to practical applications of quantum Hall physics in low-power-consumption electronics.

  18. Charge transport in manganites: Hopping conduction, the anomalous Hall effect, and universal scaling

    International Nuclear Information System (INIS)

    The low-temperature Hall resistivity ρxy of La2/3A1/3MnO3 single crystals (where A stands for Ca, Pb, and Ca, or Sr) can be separated into ordinary and anomalous contributions, giving rise to ordinary and anomalous Hall effects, respectively. However, no such decomposition is possible near the Curie temperature which, in these systems, is close to metal-to-insulator transition. Rather, for all of these compounds and to a good approximation, the ρxy data at various temperatures and magnetic fields collapse (up to an overall scale), on to a single function of the reduced magnetization m(equivalent to)M/Msat, the extremum of this function lying at m∼0.4. A mechanism for the anomalous Hall effect in the inelastic hopping regime, which reproduces these scaling curves, is identified. This mechanism, which is an extension of Holstein's model for the ordinary Hall effect in the hopping regime, arises from the combined effects of the double-exchange-induced quantal phase in triads of Mn ions and spin-orbit interactions. We identify processes that lead to the anomalous Hall effect for localized carriers and, along the way, analyze issues of quantum interference in the presence of phonon-assisted hopping. Our results suggest that, near the ferromagnet-to-paramagnet transition, it is appropriate to describe transport in manganites in terms of carrier hopping between states that are localized due to the combined effect of magnetic and nonmagnetic disorder. We attribute the qualitative variations in resistivity characteristics across manganite compounds to the differing strengths of their carrier self-trapping, and conclude that both disorder-induced localization and self-trapping effects are important for transport

  19. Quantized topological magnetoelectric effect of the zero-plateau quantum anomalous Hall state

    OpenAIRE

    Jing WANG; Lian, Biao; Qi, Xiao-Liang; Zhang, Shou-Cheng

    2015-01-01

    Topological magnetoelectric effect in a three-dimensional topological insulator is a novel phenomenon, where an electric field induces a magnetic field in the same direction, with a universal coefficient of proportionality quantized in units of $e^2/2h$. Here we propose that the topological magnetoelectric effect can be realized in the zero-plateau quantum anomalous Hall state of magnetic topological insulators or ferromagnet-topological insulator heterostructure. The finite-size effect is al...

  20. Measurement of the intrinsic anomalous Hall effect in a 2D hole system with Rashba spin-orbit coupling

    International Nuclear Information System (INIS)

    The anomalous Hall effect of two-dimensional holes in a GaAs/AlGaAs heterostructure was measured under a slightly tilted-from-parallel magnetic field (B). In addition to the dominant ordinary Hall resistivity, which is linear in B, there is a small anomalous Hall resistivity correlated with the perpendicular spin magnetization of the holes due to the subband depopulation. When the anomalous Hall conductivity (σAxy) is extracted from the experimental data, it exhibits a nonmonotonic dependence on B, a behavior expected for the intrinsic anomalous Hall effect in the 2D Rashba model. If σAxy is plotted as a function of the longitudinal conductivity (σxx), an intrinsic region in which σAxy is almost constant and is several tenths of e2/h for σxx of several tens of e2/h is identified.

  1. Anomalous Hall effect studies on Tb-Fe thin films

    Science.gov (United States)

    Rajasekhar, P.; Deepak Kumar, K.; Markandeyulu, G.

    2016-08-01

    Tbx Fe100-x (with x=11, 25, 31 and 44) thin films were prepared with the substrates kept at a temperature of 300 °C and the Hall resistivities and electrical resistivities were investigated in the temperature range 25-300 K. The sign of Hall resistivity is found to change from positive for x=31 to negative for x=44 film at temperatures 25 K and 300 K, reflecting the compensation of Tb and Fe magnetic moments between these two compositions. Perpendicular magnetic anisotropy was observed in the films of x=25 and 31 at 25 K as well as at 300 K. The Hall resistivity is seen to increase for the films of x=11 and 31 with increasing temperature, while it decreases for the films of x=25 and 44 with increasing temperature. The temperature coefficients of electrical resistivities of these films are seen to be positive. The presence of perpendicular magnetic anisotropy (refers to magnetic anisotropy, in this paper) in the temperature range 25-300 K in Tb25Fe75 and Tb31Fe69 and their metallic nature are indicators that the Tb-Fe films deposited at higher temperatures are more suitable for magneto optic data storage applications than their amorphous counterparts, due to the stability of the former.

  2. Large anomalous Hall effect driven by a nonvanishing Berry curvature in the noncolinear antiferromagnet Mn3Ge.

    Science.gov (United States)

    Nayak, Ajaya K; Fischer, Julia Erika; Sun, Yan; Yan, Binghai; Karel, Julie; Komarek, Alexander C; Shekhar, Chandra; Kumar, Nitesh; Schnelle, Walter; Kübler, Jürgen; Felser, Claudia; Parkin, Stuart S P

    2016-04-01

    It is well established that the anomalous Hall effect displayed by a ferromagnet scales with its magnetization. Therefore, an antiferromagnet that has no net magnetization should exhibit no anomalous Hall effect. We show that the noncolinear triangular antiferromagnet Mn3Ge exhibits a large anomalous Hall effect comparable to that of ferromagnetic metals; the magnitude of the anomalous conductivity is ~500 (ohm·cm)(-1) at 2 K and ~50 (ohm·cm)(-1) at room temperature. The angular dependence of the anomalous Hall effect measurements confirms that the small residual in-plane magnetic moment has no role in the observed effect except to control the chirality of the spin triangular structure. Our theoretical calculations demonstrate that the large anomalous Hall effect in Mn3Ge originates from a nonvanishing Berry curvature that arises from the chiral spin structure, and that also results in a large spin Hall effect of 1100 (ħ/e) (ohm·cm)(-1), comparable to that of platinum. The present results pave the way toward the realization of room temperature antiferromagnetic spintronics and spin Hall effect-based data storage devices. PMID:27152355

  3. Hysteretic magnetoresistance and unconventional anomalous Hall effect in the frustrated magnet TmB4

    Science.gov (United States)

    Sunku, Sai Swaroop; Kong, Tai; Ito, Toshimitsu; Canfield, Paul C.; Shastry, B. Sriram; Sengupta, Pinaki; Panagopoulos, Christos

    2016-05-01

    We study TmB4, a frustrated magnet on the Archimedean Shastry-Sutherland lattice, through magnetization and transport experiments. The lack of anisotropy in resistivity shows that TmB4 is an electronically three-dimensional system. The magnetoresistance (MR) is hysteretic at low temperature even though a corresponding hysteresis in magnetization is absent. The Hall resistivity shows unconventional anomalous Hall effect (AHE) and is linear above saturation despite a large MR. We propose that complex structures at magnetic domain walls may be responsible for the hysteretic MR and may also lead to the AHE.

  4. Weak localization and Anomalous Hall Effect in Chemically Disordered L10-Mn1.5Ga

    OpenAIRE

    Zhu, L. J.; Pan, D.; J. H. Zhao

    2013-01-01

    The anomalous Hall effect (AHE) in perpendicularly magnetized L10-Mn1.5Ga single-crystalline films is investigated as a function of degree of long-range chemical ordering and temperature. Our results provide firm evidence that weak localization, phonons and magnons have negligibly smaller effect on skew scattering contributions to AHE resistivity than defects, the overlook of which in conventional scaling laws results in significant discrepancies and exponent n beyond 2 when fitting the data....

  5. 3d Transition Metal Adsorption Induced the valley-polarized Anomalous Hall Effect in Germanene.

    Science.gov (United States)

    Zhou, P; Sun, L Z

    2016-01-01

    Based on DFT + U and Berry curvature calculations, we study the electronic structures and topological properties of 3d transition metal (TM) atom (from Ti to Co) adsorbed germanene (TM-germanene). We find that valley-polarized anomalous Hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn, or Co atoms on its surface. A finite valley Hall voltage can be easily detected in their nanoribbon, which is important for valleytronics devices. Moreover, different valley-polarized current and even reversible valley Hall voltage can be archived by shifting the Fermi energy of the systems. Such versatile features of the systems show potential in next generation electronics devices. PMID:27312176

  6. Giant gap quantum spin Hall effect and valley-polarized quantum anomalous Hall effect in cyanided bismuth bilayers

    Science.gov (United States)

    Ji, Wei-xiao; Zhang, Chang-wen; Ding, Meng; Zhang, Bao-min; Li, Ping; Li, Feng; Ren, Miao-juan; Wang, Pei-ji; Zhang, Run-wu; Hu, Shu-jun; Yan, Shi-shen

    2016-08-01

    Bismuth (Bi) has attracted a great deal of attention for its strongest spin–orbit coupling (SOC) strength among main group elements. Although quantum anomalous Hall (QAH) state is predicted in half-hydrogenated Bi honeycomb monolayers Bi2H, the experimental results are still missing. Halogen atoms (X = F, Cl and Br) were also frequently used as modifications, but Bi2X films show a frustrating metallic character that masks the QAH effects. Here, first-principle calculations are performed to predict the full-cyanided bismuthene (Bi2(CN)2) as 2D topological insulator supporting quantum spin Hall state with a record large gap up to 1.10 eV, and more importantly, half-cyanogen saturated bismuthene (Bi2(CN)) as a Chern insulator supporting a valley-polarized QAH state, with a Curie temperature to be 164 K, as well as a large gap reaching 0.348 eV which could be further tuned by bi-axial strain and SOC strength. Our findings provide an appropriate and flexible material family candidate for spintronic and valleytronic devices.

  7. Origin of enhanced anomalous Hall effect in ultrathin Pt/permalloy bilayers

    Directory of Open Access Journals (Sweden)

    Y. Q. Zhang

    2016-02-01

    Full Text Available There are two mechanisms which could enhance spin-dependent scattering in a low dimensional Pt/Ferromagnetic metal structure. One is magnetic proximity effect. The other is spin orbit coupling proximity effect which was suggested recently. This work demonstrates that, through a series of experiments on anomalous Hall effect, the spin orbit coupling proximity effect dominates the enhancement in very thin Pt/Permalloy bilayers. It may help to find a way to optimize magnetic transport property of spintronics devices in which the spin orbit coupling is deeply involved.

  8. Intrinsic quantum spin Hall and anomalous Hall effects in h-Sb/Bi epitaxial growth on a ferromagnetic MnO2 thin film

    Science.gov (United States)

    Zhou, Jian; Sun, Qiang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

    2016-05-01

    Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large band gap quantum spin Hall state and a nearly quantized anomalous Hall state which can be tuned by adjusting the Fermi level. Our findings provide an efficient way to realize both quantized intrinsic spin Hall conductivity and anomalous Hall conductivity in a single material.Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large

  9. Resonant cavity mode dependence of anomalous and inverse spin Hall effect

    International Nuclear Information System (INIS)

    The direct current electric voltage induced by the Inverse Spin Hall Effect (ISHE) and Anomalous Hall Effect (AHE) was investigated in the TE011 and TE102 cavities. The ISHE and AHE components were distinguishable through the fitting of the voltage spectrum. The unwanted AHE was minimized by placing the DUT (Device Under Test) at the center of both the TE011 and TE102 cavities. The voltage of ISHE in the TE011 cavity was larger than that in the TE102 cavity due to the higher quality factor of the former. Despite optimized centering, AHE voltage from TE011 cavity was also higher. The reason was attributed to the E-field distribution inside the cavity. In the case of the TE011 cavity, the DUT was easily exposed to the E-field in all directions. Therefore, the parasitic AHE voltage in the TE102 cavity was less sensitive than that in the TE011 cavity to decentering problem

  10. Scaling of Anomalous Hall Effects in Facing-Target Reactively Sputtered Fe4N Films

    KAUST Repository

    Zhang, Yan

    2015-05-13

    Anomalous Hall effect (AHE) in the reactively sputtered epitaxial and polycrystalline γ′-Fe4N films is investigated systematically. The Hall resistivity is positive in the entire temperature range. The magnetization, carrier density and grain boundaries scattering have a major impact on the AHE scaling law. The scaling exponent γ in the conventional scaling of is larger than 2 in both the epitaxial and polycrystalline γ′-Fe4N films. Although γ>2 has been found in heterogeneous systems due to the effects of the surface and interface scattering on AHE, γ>2 is not expected in homogenous epitaxial systems. We demonstrated that γ>2 results from residual resistivity (ρxx0) in γ′-Fe4N films. Furthermore, the side-jump and intrinsic mechanisms are dominant in both epitaxial and polycrystalline samples according to the proper scaling relation.

  11. Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators

    Science.gov (United States)

    Chang, Cui-Zu; Li, Mingda

    2016-03-01

    The quantum anomalous Hall effect (QAHE), the last member of Hall family, was predicted to exhibit quantized Hall conductivity {σyx}=\\frac{{{e}2}}{h} without any external magnetic field. The QAHE shares a similar physical phenomenon with the integer quantum Hall effect (QHE), whereas its physical origin relies on the intrinsic topological inverted band structure and ferromagnetism. Since the QAHE does not require external energy input in the form of magnetic field, it is believed that this effect has unique potential for applications in future electronic devices with low-power consumption. More recently, the QAHE has been experimentally observed in thin films of the time-reversal symmetry breaking ferromagnetic (FM) topological insulators (TI), Cr- and V- doped (Bi,Sb)2Te3. In this topical review, we review the history of TI based QAHE, the route to the experimental observation of the QAHE in the above two systems, the current status of the research of the QAHE, and finally the prospects for future studies.

  12. Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators.

    Science.gov (United States)

    Chang, Cui-Zu; Li, Mingda

    2016-03-31

    The quantum anomalous Hall effect (QAHE), the last member of Hall family, was predicted to exhibit quantized Hall conductivity σ(yx) = e2/h without any external magnetic field. The QAHE shares a similar physical phenomenon with the integer quantum Hall effect (QHE), whereas its physical origin relies on the intrinsic topological inverted band structure and ferromagnetism. Since the QAHE does not require external energy input in the form of magnetic field, it is believed that this effect has unique potential for applications in future electronic devices with low-power consumption. More recently, the QAHE has been experimentally observed in thin films of the time-reversal symmetry breaking ferromagnetic (FM) topological insulators (TI), Cr- and V- doped (Bi,Sb)2Te3. In this topical review, we review the history of TI based QAHE, the route to the experimental observation of the QAHE in the above two systems, the current status of the research of the QAHE, and finally the prospects for future studies. PMID:26934535

  13. The anomalous Hall conductivity due to the vector spin chirality

    OpenAIRE

    Taguchi, Katsuhisa; Tatara, Gen

    2008-01-01

    We study theoretically the anomalous Hall effect due to the vector spin chirality carried by the local spins in the $s$-$d$ model. We will show that the vector spin chirality indeed induces local Hall effect in the presence of the electron spin polarization, while the global Hall effect vanishes if electron transport is homogeneous. This anomalous Hall effect can be interpreted in terms of the rotational component of the spin current associated with the vector chirality.

  14. Anomalous Hall effect in the prospective spintronic material Eu1‑x Gd x O integrated with Si

    Science.gov (United States)

    Parfenov, Oleg E.; Averyanov, Dmitry V.; Tokmachev, Andrey M.; Taldenkov, Alexander N.; Storchak, Vyacheslav G.

    2016-06-01

    Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm‑1 in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies.

  15. Anomalous Hall effect in the prospective spintronic material Eu1-x Gd x O integrated with Si.

    Science.gov (United States)

    Parfenov, Oleg E; Averyanov, Dmitry V; Tokmachev, Andrey M; Taldenkov, Alexander N; Storchak, Vyacheslav G

    2016-06-01

    Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm(-1) in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies. PMID:27165844

  16. Large anomalous Hall effect in Pt interfaced with perpendicular anisotropy ferrimagnetic insulator

    Science.gov (United States)

    Tang, Chi; Sellappan, Pathikumar; Liu, Yawen; Garay, Javier; Shi, Jing; Shines Team

    We demonstrate the strain induced perpendicular magnetic anisotropy (PMA) in a ferrimagnetic insulator (FMI), Tm3Fe5O12 (TIG) and the first observation of large anomalous Hall effect (AHE) in TIG/Pt bilayers. Atomically flat TIG films were deposited by a laser molecular beam epitaxy system on (111)-orientated substituted gadolinium gallium garnet substrates. The strength of PMA could be effectively tuned by controlling the oxygen pressure during deposition. Sharp squared anomalous Hall hysteresis loops were observed in bilayers of TIG/Pt over a range of thicknesses of Pt, with the maximum AHE conductivity reaching 1 S/cm at room temperature. The AHE vanishes when a 5 nm Cu layer was inserted between Pt and TIG, strongly indicating the proximity-induced ferromagnetism in Pt. The large AHE in the bilayer structures demonstrates a potential use of PMA-FMI related heterostructures in spintronics. This work was supported as part of the SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # SC0012670.

  17. Anomalous Hall conductivity: Local orbitals approach

    Czech Academy of Sciences Publication Activity Database

    Středa, Pavel

    2010-01-01

    Roč. 82, č. 4 (2010), 045115/1-045115/9. ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * Berry phase correction * orbital polarization momentum Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.772, year: 2010

  18. Anomalous Hall Effect in SnMnEuTe and SnMnErTe mixed crystals

    OpenAIRE

    Racka, K.; Kuryliszyn, I.; Arciszewska, M.; Dobrowolski, W.; Broto, J. -M.; Goiran, M.; Portugall, O.; Rakoto, H.; Raquet, B.; Dugaev, V.; Slynko, E. I.; Slynko, V. E.

    2002-01-01

    The Anomalous Hall Effect was investigated in IV-VI ferromagnetic semimagnetic semiconductors of Sn1-xMnxTe codoped with either Eu or Er. The analysis of experimental data: Hall resisitivity and magnetization showed that AHE coefficient RS depends on temperature, its value decreases with the temperature increase. We observe that above ferromagnet-paramagnet transition temperature RS changes sign. We discuss the possible physical mechanisms responsible for observed temperature dependence of RS...

  19. Local orbitals approach to the anomalous Hall and Nernst effects in itinerant ferromagnets

    Directory of Open Access Journals (Sweden)

    Středa Pavel

    2014-07-01

    Full Text Available Linear response of the orbital momentum to the gradient of the chemical potential is used to obtain anomalous Hall conductivity. Transition from the ideal Bloch system for which the conductivity is determined by the Berry phase curvatures to the case of strong disorder for which the conductivity becomes dependent on the relaxation time is analysed. Presented tight-binding model reproduces experimentally observed qualitative features of the anomalous Hall conductivity and the transverse Peltier coefficient in the so called bad-metal and scattering-independent regimes.

  20. Tuning giant anomalous Hall resistance ratio in perpendicular Hall balance

    International Nuclear Information System (INIS)

    Anomalous Hall effect at room temperature in perpendicular Hall balance with a core structure of [Pt/Co]4/NiO/[Co/Pt]4 has been tuned by functional CoO layers, where [Pt/Co]4 multilayers exhibit perpendicular magnetic anisotropy. A giant Hall resistance ratio up to 69 900% and saturation Hall resistance (RSP) up to 2590 mΩ were obtained in CoO/[Pt/Co]4/NiO/[Co/Pt]4/CoO system, which is 302% and 146% larger than that in the structure without CoO layers, respectively. Transmission electron microscopy shows highly textured [Co/Pt]4 multilayers and oxide layers with local epitaxial relations, indicating that the crystallographic structure has significant influence on spin dependent transport properties

  1. Tuning giant anomalous Hall resistance ratio in perpendicular Hall balance

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J. Y.; Yang, G. [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, S. G., E-mail: sgwang@iphy.ac.cn, E-mail: ghyu@mater.ustb.edu.cn [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Liu, J. L. [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Wang, R. M. [Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Amsellem, E.; Kohn, A. [Department of Materials Engineering, Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Yu, G. H., E-mail: sgwang@iphy.ac.cn, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-04-13

    Anomalous Hall effect at room temperature in perpendicular Hall balance with a core structure of [Pt/Co]{sub 4}/NiO/[Co/Pt]{sub 4} has been tuned by functional CoO layers, where [Pt/Co]{sub 4} multilayers exhibit perpendicular magnetic anisotropy. A giant Hall resistance ratio up to 69 900% and saturation Hall resistance (R{sub S}{sup P}) up to 2590 mΩ were obtained in CoO/[Pt/Co]{sub 4}/NiO/[Co/Pt]{sub 4}/CoO system, which is 302% and 146% larger than that in the structure without CoO layers, respectively. Transmission electron microscopy shows highly textured [Co/Pt]{sub 4} multilayers and oxide layers with local epitaxial relations, indicating that the crystallographic structure has significant influence on spin dependent transport properties.

  2. Anomalous Hall effect and magnetoresistance behavior in Co/Pd1−xAgx multilayers

    KAUST Repository

    Guo, Z. B.

    2013-02-13

    In this paper, we report anomalous Hall effect (AHE) correlated with the magnetoresistance behavior in [Co/Pd1-xAg x]n multilayers. For the multilayers with n = 6, the increase in Ag content from x = 0 to 0.52 induces the change in AHE sign from negative surface scattering-dominated AHE to positive interface scattering-dominated AHE, which is accompanied with the transition from anisotropy magnetoresistance (AMR) dominated transport to giant magnetoresistance (GMR) dominated transport. For n = 80, scaling analysis with Rs ∝ρ xx γ yields γ ∼ 3.44 for x = 0.52 which presents GMR-type transport, in contrast to γ ∼ 5.7 for x = 0 which presents AMR-type transport. © 2013 American Institute of Physics.

  3. Theory for the anomalous electron transport in Hall effect thrusters. II. Kinetic model

    Science.gov (United States)

    Lafleur, T.; Baalrud, S. D.; Chabert, P.

    2016-05-01

    In Paper I [T. Lafleur et al., Phys. Plasmas 23, 053502 (2016)], we demonstrated (using particle-in-cell simulations) the definite correlation between an anomalously high cross-field electron transport in Hall effect thrusters (HETs), and the presence of azimuthal electrostatic instabilities leading to enhanced electron scattering. Here, we present a kinetic theory that predicts the enhanced scattering rate and provides an electron cross-field mobility that is in good agreement with experiment. The large azimuthal electron drift velocity in HETs drives a strong instability that quickly saturates due to a combination of ion-wave trapping and wave-convection, leading to an enhanced mobility many orders of magnitude larger than that expected from classical diffusion theory. In addition to the magnetic field strength, B0, this enhanced mobility is a strong function of the plasma properties (such as the plasma density) and therefore does not, in general, follow simple 1 /B02 or 1 /B0 scaling laws.

  4. Theory of Multifarious Quantum Phases and Large Anomalous Hall Effect in Pyrochlore Iridate Thin Films

    Science.gov (United States)

    Hwang, Kyusung; Kim, Yong Baek

    2016-01-01

    We theoretically investigate emergent quantum phases in the thin film geometries of the pyrochore iridates, where a number of exotic quantum ground states are proposed to occur in bulk materials as a result of the interplay between electron correlation and strong spin-orbit coupling. The fate of these bulk phases as well as novel quantum states that may arise only in the thin film platforms, are studied via a theoretical model that allows layer-dependent magnetic structures. It is found that the magnetic order develop in inhomogeneous fashions in the thin film geometries. This leads to a variety of magnetic metal phases with modulated magnetic ordering patterns across different layers. Both the bulk and boundary electronic states in these phases conspire to promote unusual electronic properties. In particular, such phases are akin to the Weyl semimetal phase in the bulk system and they would exhibit an unusually large anomalous Hall effect. PMID:27418293

  5. Theory of Multifarious Quantum Phases and Large Anomalous Hall Effect in Pyrochlore Iridate Thin Films.

    Science.gov (United States)

    Hwang, Kyusung; Kim, Yong Baek

    2016-01-01

    We theoretically investigate emergent quantum phases in the thin film geometries of the pyrochore iridates, where a number of exotic quantum ground states are proposed to occur in bulk materials as a result of the interplay between electron correlation and strong spin-orbit coupling. The fate of these bulk phases as well as novel quantum states that may arise only in the thin film platforms, are studied via a theoretical model that allows layer-dependent magnetic structures. It is found that the magnetic order develop in inhomogeneous fashions in the thin film geometries. This leads to a variety of magnetic metal phases with modulated magnetic ordering patterns across different layers. Both the bulk and boundary electronic states in these phases conspire to promote unusual electronic properties. In particular, such phases are akin to the Weyl semimetal phase in the bulk system and they would exhibit an unusually large anomalous Hall effect. PMID:27418293

  6. Quantum anomalous Hall effect in atomic crystal layers from in-plane magnetization

    Science.gov (United States)

    Ren, Yafei; Zeng, Junjie; Deng, Xinzhou; Yang, Fei; Pan, Hui; Qiao, Zhenhua

    2016-08-01

    We theoretically demonstrate that with in-plane magnetization, the quantum anomalous Hall effect (QAHE) can be realized in two-dimensional atomic crystal layers with preserved inversion symmetry but broken out-of-plane mirror reflection symmetry. By taking the honeycomb lattice system as an example, we find that the low-buckled structure satisfying the symmetry criteria is crucial to induce QAHE. The topologically nontrivial bulk gap carrying a Chern number of C =±1 opens in the vicinity of the saddle points M , where the band dispersion exhibits strong anisotropy. We further show that the QAHE with electrically tunable Chern number can be achieved in Bernal-stacked multilayer systems, and the applied interlayer potential differences can dramatically decrease the critical magnetization to make the QAHE experimentally feasible.

  7. Extrinsic anomalous Hall effect in epitaxial Mn{sub 4}N films

    Energy Technology Data Exchange (ETDEWEB)

    Meng, M.; Wu, S. X., E-mail: wushx3@mail.sysu.edu.cn; Ren, L. Z.; Zhou, W. Q.; Wang, Y. J.; Wang, G. L.; Li, S. W., E-mail: stslsw@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2015-01-19

    Anomalous Hall effect (AHE) in ferrimagnetic Mn{sub 4}N epitaxial films grown by molecular-beam epitaxy is investigated. The longitudinal conductivity σ{sub xx} is within the superclean regime, indicating Mn{sub 4}N is a highly conducting material. We further demonstrate that the AHE signal in 40-nm-thick films is mainly due to the extrinsic contributions based on the analysis fitted by ρ{sub AH}=a′ρ{sub xx0}+bρ{sub xx}{sup 2} and σ{sub AH}∝σ{sub xx}. Our study not only provide a strategy for further theoretical work on antiperovskite manganese nitrides but also shed promising light on utilizing their extrinsic AHE to fabricate spintronic devices.

  8. The temperature dependent anomalous Hall effect in La-Ca-Mn-O films

    International Nuclear Information System (INIS)

    The colossal magnetoresistance of La1-xCaxMnO3 has been reported in many experiments. The authors present their study of the anomalous Hall effect in epitaxial La0.67Ca0.33MnO3 thin films. They have measured the temperature dependence of resistivity, magnetization and AHE coefficients between 300K and 5K for the samples grown on different substrates. From these studies, the relation between the resistivity and AHE coefficient as well as the temperature dependence of AHE coefficient are explored. The results show that the direction of AHE is reversed below approximately 100K. This sign reversal is discussed in term of the change of band structure and the co-existence of hole-like and electron-like conduction

  9. Magnetoresistance and Anomalous Hall Effect of InSb Doped with Mn

    Directory of Open Access Journals (Sweden)

    A.V. Kochura

    2013-12-01

    Full Text Available Transport properties of polycrystalline (In, MnSb samples are investigated. Behavior of the temperature and magnetic field dependencies of the resistivity, anomalous Hall coefficient and magnetoresistivity at low temperatures points out the influence of Mn complexes, Mn ions and nano- and microsizes MnSb precipitates on charge transport.

  10. Testing dependence of anomalous Hall effect on resistivity in SrRuO3 by its increase with electron irradiation

    NARCIS (Netherlands)

    Haham, N.; Konczykowski, M.; Kuiper, B.; Koster, G.; Klein, L.

    2013-01-01

    We measure the anomalous Hall effect (AHE) in several patterns of the itinerant ferromagnet SrRuO 3 before and after the patterns are irradiated with electrons. The irradiation increases the resistivity of the patterns due to the introduction of point defects and we find that the AHE coefficient R

  11. Magnetoresistance and anomalous Hall effect of reactive sputtered polycrystalline Ti1 - XCrxN films

    KAUST Repository

    Duan, Xiaofei

    2013-09-01

    The reactive-sputtered polycrystalline Ti1 - xCrxN films with 0.17 ≤ x ≤ 0.51 are ferromagnetic and at x = 0.47 the Curie temperature TC shows a maximum of ~ 120 K. The films are metallic at 0 ≤ x ≤ 0.47, while the films with x = 0.51 and 0.78 are semiconducting-like. The upturn of resistivity below 70 K observed in the films with 0.10 ≤ x ≤ 0.47 is from the effects of the electron-electron interaction and weak localization. The negative magnetoresistance (MR) of the films with 0.10 ≤ x ≤ 0.51 is dominated by the double-exchange interaction, while at x = 0.78, MR is related to the localized magnetic moment scattering at the grain boundaries. The scaling ρxyA/n ∝ ρxx2.19 suggests that the anomalous Hall effect in the polycrystalline Ti1 - xCrxN films is scattering-independent. © 2013 Elsevier B.V. All rights reserved.

  12. Effect of band filling on anomalous Hall conductivity and magneto-crystalline anisotropy in NiFe epitaxial thin films

    International Nuclear Information System (INIS)

    The anomalous Hall effect (AHE) and magneto-crystalline anisotropy (MCA) are investigated in epitaxial NixFe1−x thin films grown on MgO (001) substrates. The scattering independent term b of anomalous Hall conductivity shows obvious correlation with cubic magneto-crystalline anisotropy K1. When nickel content x decreasing, both b and K1 vary continuously from negative to positive, changing sign at about x = 0.85. Ab initio calculations indicate NixFe1−x has more abundant band structures than pure Ni due to the tuning of valence electrons (band fillings), resulting in the increased b and K1. This remarkable correlation between b and K1 can be attributed to the effect of band filling near the Fermi surface

  13. Room-temperature anomalous Hall effect and magnetroresistance in (Ga, Co)-codoped ZnO diluted magnetic semiconductor films

    Institute of Scientific and Technical Information of China (English)

    Liu Xue-Chao; Chen Zhi-Zhan; Shi Er-Wei; Liao Da-Qian; Zhou Ke-Jin

    2011-01-01

    This paper reports that the (Ga, Co)-codoped ZnO thin films have been grown by inductively coupled plasma enhanced physical vapour deposition. Room-temperature ferromagnetism is observed for the as-grown thin films. The x-ray absorption fine structure characterization reveals that Co2+ and Ga3+ ions substitute for Zn2+ ions in the ZnO lattice and exclude the possibility of extrinsic ferromagnetism origin. The ferromagnetic (Ga, Co)-codoped ZnO thin films exhibit carrier concentration dependent anomalous Hall effect and positive magnetoresistance at room temperature. The mechanism of anomalous Hall effect and magneto-transport in ferromagnetic ZnO-based diluted magnetic semiconductors is discussed.

  14. Effect of band filling on anomalous Hall conductivity and magneto-crystalline anisotropy in NiFe epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Zhong; Jiang, Hang-Yu; Zhou, Shi-Ming, E-mail: shiming@tongji.edu.cn [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology & Pohl Institute of Solid State Physics, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Hou, Yan-Liang; Ye, Quan-Lin [Department of Physics, Hangzhou Normal University, Hangzhou 310036 (China); Su Si, Ming [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

    2016-01-15

    The anomalous Hall effect (AHE) and magneto-crystalline anisotropy (MCA) are investigated in epitaxial Ni{sub x}Fe{sub 1−x} thin films grown on MgO (001) substrates. The scattering independent term b of anomalous Hall conductivity shows obvious correlation with cubic magneto-crystalline anisotropy K{sub 1}. When nickel content x decreasing, both b and K{sub 1} vary continuously from negative to positive, changing sign at about x = 0.85. Ab initio calculations indicate Ni{sub x}Fe{sub 1−x} has more abundant band structures than pure Ni due to the tuning of valence electrons (band fillings), resulting in the increased b and K{sub 1}. This remarkable correlation between b and K{sub 1} can be attributed to the effect of band filling near the Fermi surface.

  15. Effect of band filling on anomalous Hall conductivity and magneto-crystalline anisotropy in NiFe epitaxial thin films

    Directory of Open Access Journals (Sweden)

    Zhong Shi

    2016-01-01

    Full Text Available The anomalous Hall effect (AHE and magneto-crystalline anisotropy (MCA are investigated in epitaxial NixFe1−x thin films grown on MgO (001 substrates. The scattering independent term b of anomalous Hall conductivity shows obvious correlation with cubic magneto-crystalline anisotropy K1. When nickel content x decreasing, both b and K1 vary continuously from negative to positive, changing sign at about x = 0.85. Ab initio calculations indicate NixFe1−x has more abundant band structures than pure Ni due to the tuning of valence electrons (band fillings, resulting in the increased b and K1. This remarkable correlation between b and K1 can be attributed to the effect of band filling near the Fermi surface.

  16. Magnetic modulation doping in topological insulators toward higher-temperature quantum anomalous Hall effect

    Energy Technology Data Exchange (ETDEWEB)

    Mogi, M., E-mail: mogi@cmr.t.u-tokyo.ac.jp; Yoshimi, R.; Yasuda, K.; Kozuka, Y. [Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan); Tsukazaki, A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0075 (Japan); Takahashi, K. S. [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Kawasaki, M.; Tokura, Y. [Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan)

    2015-11-02

    Quantum anomalous Hall effect (QAHE), which generates dissipation-less edge current without external magnetic field, is observed in magnetic-ion doped topological insulators (TIs) such as Cr- and V-doped (Bi,Sb){sub 2}Te{sub 3}. The QAHE emerges when the Fermi level is inside the magnetically induced gap around the original Dirac point of the TI surface state. Although the size of gap is reported to be about 50 meV, the observable temperature of QAHE has been limited below 300 mK. We attempt magnetic-Cr modulation doping into topological insulator (Bi,Sb){sub 2}Te{sub 3} films to increase the observable temperature of QAHE. By introducing the rich-Cr-doped thin (1 nm) layers at the vicinity of both the surfaces based on non-Cr-doped (Bi,Sb){sub 2}Te{sub 3} films, we have succeeded in observing the QAHE up to 2 K. The improvement in the observable temperature achieved by this modulation-doping appears to be originating from the suppression of the disorder in the surface state interacting with the rich magnetic moments. Such a superlattice designing of the stabilized QAHE may pave a way to dissipation-less electronics based on the higher-temperature and zero magnetic-field quantum conduction.

  17. Magnetic modulation doping in topological insulators toward higher-temperature quantum anomalous Hall effect

    International Nuclear Information System (INIS)

    Quantum anomalous Hall effect (QAHE), which generates dissipation-less edge current without external magnetic field, is observed in magnetic-ion doped topological insulators (TIs) such as Cr- and V-doped (Bi,Sb)2Te3. The QAHE emerges when the Fermi level is inside the magnetically induced gap around the original Dirac point of the TI surface state. Although the size of gap is reported to be about 50 meV, the observable temperature of QAHE has been limited below 300 mK. We attempt magnetic-Cr modulation doping into topological insulator (Bi,Sb)2Te3 films to increase the observable temperature of QAHE. By introducing the rich-Cr-doped thin (1 nm) layers at the vicinity of both the surfaces based on non-Cr-doped (Bi,Sb)2Te3 films, we have succeeded in observing the QAHE up to 2 K. The improvement in the observable temperature achieved by this modulation-doping appears to be originating from the suppression of the disorder in the surface state interacting with the rich magnetic moments. Such a superlattice designing of the stabilized QAHE may pave a way to dissipation-less electronics based on the higher-temperature and zero magnetic-field quantum conduction

  18. Influence of defects and disorder on anomalous Hall effect and spin Seebeck effect on permalloy and Heusler compounds

    Energy Technology Data Exchange (ETDEWEB)

    Vilanova Vidal, Enrique

    2012-09-19

    In this work Heusler thin films have been prepared and their transport properties have been studied. Of particularly interest is the anomalous Hall effect (AHE). The effect is a long known but still not fully understood transport effect. Most theory papers focus on the influence of one particular contribution to the AHE. Actual measured experimental data, however, often are not in accordance with idealized assumptions. This thesis discusses the data analysis for materials with low residual resistivity ratios. As prototypical materials, half metallic Heusler compounds are studied. Here, the influence of defects and disorder is apparent in a material with a complex topology of the Fermi surface. Using films with different degrees of disorder, the different scattering mechanisms can be separated. For Co{sub 2}FeSi{sub 0.6}Al{sub 0.4} and Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5}, the AHE induced by B2-type disorder and temperature-dependent scattering is positive, while DO{sub 3}-type disorder and possible intrinsic contributions possess a negative sign. For these compounds, magneto-optical Kerr effects (MOKE) are investigated. First order contributions as a function of intrinsic and extrinsic parameters are qualitatively analyzed. The relation between the crystalline ordering and the second order contributions to the MOKE signal is studied. In addition, sets of the Heusler compound Co{sub 2}MnAl thin films were grown on MgO(100) and Si(100) substrates by radio frequency magnetron sputtering. Composition, magnetic and transport properties were studied systematically for samples deposited at different conditions. In particular, the anomalous Hall effect resistivity presents an extraordinarily temperature independent behavior in a moderate magnetic field range from 0 to 0.6 T. The off-diagonal transport at temperatures up to 300 C was analyzed. The data show the suitability of the material for Hall sensors working well above room temperature. Recently, the spin Seebeck effect

  19. Anomalous Hall effect in the Co-based Heusler compounds Co2FeSi and Co2FeAI

    Science.gov (United States)

    Imort, I.-M.; Thomas, P.; Reiss, G.; Thomas, A.

    2012-04-01

    The anomalous Hall effect (AHE) in the Heusler compounds Co2FeSi and Co2FeAl is studied in dependence of the annealing temperature to achieve a general comprehension of its origin. We have demonstrated that the crystal quality affected by annealing processes is a significant control parameter to tune the electrical resistivity ρxx as well as the anomalous Hall resistivity ρahe. Analyzing the scaling behavior of ρahe in terms of ρxx points to a temperature-dependent skew scattering as the dominant mechanism in both Heusler compounds.

  20. Transport theory for disordered multiple-band systems: Anomalous Hall effect and anisotropic magnetoresistance

    Czech Academy of Sciences Publication Activity Database

    Kovalev, A.A.; Tserkovnyak, Y.; Výborný, Karel; Sinova, J.

    2009-01-01

    Roč. 79, č. 19 (2009), 19529/1-19529/19. ISSN 1098-0121 R&D Projects: GA MŠk LC510; GA AV ČR KJB100100802 Institutional research plan: CEZ:AV0Z10100521 Keywords : ferromagnetic materials * Hall effect * magnetoresistance * quasiparticles * spin-orbit interactions * two-dimensional electron gas Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.475, year: 2009 http://link.aps.org/doi/10.1103/PhysRevB.79.195129

  1. Ferromagnetism, variable range hopping, and the anomalous Hall effect in epitaxial Co:ZnO thin film

    Institute of Scientific and Technical Information of China (English)

    Bai Hong-Liang; Chen Yan-Xue; Mei Liang-Mo; He Shu-Min; Xu Tong-Shuai; Liu Guo-Lei; Yan Shi-Shen; Zhu Da-Peng; Dai Zheng-Kun; Yang Feng-Fan; Dai You-Yong

    2012-01-01

    A series of high quality single crystalline epitaxial Zn0.95Co0.05O thin films is prepared by molecular beam epitaxy.Superparamagnetism and ferromagnetism are observed when the donor density is manipulated in a range of 1018 cm-3- 1020 cm-3 by changing the oxygen partial pressure during film growth.The conduction shows variable range hopping at low temperature and thermal activation conduction at high temperature.The ferromagnetism can be maintained up to room temperature.However,the anomalous Hall effect is observed only at low temperature and disappears above 160 K.This phenomenon can be attributed to the local ferromagnetism and the decreased optimal hopping distance at high temperatures.

  2. Anomalous Integer Quantum Hall Effect in the Ballistic Regime with Quantum Point Contacts

    NARCIS (Netherlands)

    Wees, B.J. van; Willems, E.M.M.; Harmans, C.J.P.M.; Beenakker, C.W.J.; Houten, H. van; Williamson, J.G.; Foxon, C.T.; Harris, J.J.

    1989-01-01

    The Hall conductance of a wide two-dimensional electron gas has been measured in a geometry in which two quantum point contacts form controllable current and voltage probes, separated by less than the transport mean free path. Adjustable barriers in the point contacts allow selective population and

  3. Fermi surface versus Fermi sea contributions to intrinsic anomalous and spin Hall effects of multiorbital metals in the presence of Coulomb interaction and spin-Coulomb drag

    Science.gov (United States)

    Arakawa, Naoya

    2016-06-01

    Anomalous Hall effect (AHE) and spin Hall effect (SHE) are fundamental phenomena, and their potential for application is great. However, we understand the interaction effects unsatisfactorily, and should have clarified issues about the roles of the Fermi sea term and Fermi surface term of the conductivity of the intrinsic AHE or SHE of an interacting multiorbital metal and about the effects of spin-Coulomb drag on the intrinsic SHE. Here, we resolve the first issue and provide the first step about the second issue by developing a general formalism in the linear response theory with appropriate approximations and using analytic arguments. The most striking result is that even without impurities, the Fermi surface term, a non-Berry-curvature term, plays dominant roles at high or slightly low temperatures. In particular, this Fermi surface term causes the temperature dependence of the dc anomalous Hall or spin Hall conductivity due to the interaction-induced quasiparticle damping and the correction of the dc spin Hall conductivity due to the spin-Coulomb drag. Those results revise our understanding of the intrinsic AHE and SHE. We also find that the differences between the dc anomalous Hall and longitudinal conductivities arise from the difference in the dominant multiband excitations. This not only explains why the Fermi sea term such as the Berry-curvature term becomes important in clean and low-temperature case only for interband transports, but also provides the useful principles on treating the electron-electron interaction in an interacting multiorbital metal for general formalism of transport coefficients. Several correspondences between our results and experiments are finally discussed.

  4. Quantum anomalous Hall effect and a nontrivial spin-texture in ultra-thin films of magnetic topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Duong, Le Quy; Das, Tanmoy; Feng, Y. P.; Lin, Hsin, E-mail: nilnish@gmail.com [Graphene Research Centre and Department of Physics, National University of Singapore, Singapore 117546 (Singapore)

    2015-05-07

    We study the evolution of quantum anomalous Hall (QAH) effect for a Z{sub 2} topological insulator (TI) thin films in a proximity induced magnetic phase by a realistic layered k·p model with interlayer coupling. We examine three different magnetic configurations in which ferromagnetic (FM) layer(s) is added either from one side (FM-TI), from both sides (FM-TI-FM), or homogeneously distributed (magnetically doped) in a TI slab. We map out the thickness-dependent topological phase diagram under various experimental conditions. The critical magnetic exchange energy for the emergence of QAH effect in the latter two cases decreases monotonically with increasing number of quintuple layers (QLs), while it becomes surprisingly independent of the film thickness in the former case. The gap size of the emergent QAH insulator depends on the non-magnetic “parent” gap of the TI thin film and is tuned by the FM exchange energy, opening a versatile possibility to achieve room-temperature QAH insulator in various topological nanomaterials. Finally, we find that the emergent spin-texture in the QAH effect is very unconventional, non-“hedgehog” type; and it exhibits a chiral out-of-plane spin-flip texture within the same valence band which is reminiscent of dynamical “skyrmion” pattern, except our results are in the momentum space.

  5. Scattering mechanisms in textured FeGe thin films: magnetoresistance and the anomalous Hall effect

    OpenAIRE

    Porter, N. A.; Gartside, J. C.; Marrows, C. H.

    2014-01-01

    A textured thin film of FeGe was grown by magnetron sputtering with a helimagnetic ordering temperature of TN = 276 +/- 2 K. From 5 K to room temperature a variety of scattering processes contribute towards the overall longitudinal and Hall resistivities. These were studied by combining magnetometry and magnetotransport measurements. The high-field magnetoresistance (MR) displays three clear temperature regimes: Lorentz force MR dominates at low temperatures, above T ~ 80 K scattering from sp...

  6. Anomalous Hall effect suppression in anatase Co:TiO2 by the insertion of an interfacial TiO2 buffer layer

    NARCIS (Netherlands)

    Lee, Y.J.; Jong, de M.P.; Wiel, van der W.G.; Kim, Y.; Brock, J.D.

    2010-01-01

    We present the effect of introducing a TiO2 buffer layer at the SrTiO3/Co:TiO2 interface on the magnetic and structural properties of anatase Co:TiO2 (1.4 at. % Co). Inserting the buffer layer leads to suppression of the room-temperature anomalous Hall effect, accompanied by a reduced density of Co

  7. Magnetoresistance and anomalous Hall effect of reactive sputtered polycrystalline Ti1−xCrxN films

    International Nuclear Information System (INIS)

    The reactive-sputtered polycrystalline Ti1−xCrxN films with 0.17 ≤ x ≤ 0.51 are ferromagnetic and at x = 0.47 the Curie temperature TC shows a maximum of ∼ 120 K. The films are metallic at 0 ≤ x ≤ 0.47, while the films with x = 0.51 and 0.78 are semiconducting-like. The upturn of resistivity below 70 K observed in the films with 0.10 ≤ x ≤ 0.47 is from the effects of the electron–electron interaction and weak localization. The negative magnetoresistance (MR) of the films with 0.10 ≤ x ≤ 0.51 is dominated by the double-exchange interaction, while at x = 0.78, MR is related to the localized magnetic moment scattering at the grain boundaries. The scaling ρxyA/n ∝ ρxx2.19 suggests that the anomalous Hall effect in the polycrystalline Ti1−xCrxN films is scattering-independent. - Highlights: • The reactive-sputtered polycrystalline Ti1−xCrxN films are ferromagnetic. • The highest Curie temperature TC of ∼ 120 K appears at x = 0.47. • The negative magnetoresistance is dominated by the double-exchange interaction. • The scaling ρxyA/n ∝ ρxx2.19 was observed

  8. Theory of the Dirac half metal and quantum anomalous Hall effect in Mn-intercalated epitaxial graphene

    Science.gov (United States)

    Li, Yuanchang; West, Damien; Huang, Huaqing; Li, Jia; Zhang, S. B.; Duan, Wenhui

    2015-11-01

    The prospect of a Dirac half metal, a material which is characterized by a band structure with a gap in one spin channel but a Dirac cone in the other, is of both fundamental interest and a natural candidate for use in spin-polarized current applications. However, while the possibility of such a material has been reported based on model calculations [H. Ishizuka and Y. Motome, Phys. Rev. Lett. 109, 237207 (2012), 10.1103/PhysRevLett.109.237207], it remains unclear what material system might realize such an exotic state. Using first-principles calculations, we show that the experimentally accessible Mn-intercalated epitaxial graphene on SiC(0001) transits to a Dirac half metal when the coverage is >1 /3 monolayer. This transition results from an orbital-selective breaking of quasi-two-dimensional inversion symmetry, leading to symmetry breaking in a single spin channel which is robust against randomness in the distribution of Mn intercalates. Furthermore, the inclusion of spin-orbit interaction naturally drives the system into the quantum anomalous Hall (QAH) state. Our results thus not only demonstrate the practicality of realizing the Dirac half metal beyond a toy model, but also open up an avenue to the realization of the QAH effect.

  9. Theory for the anomalous electron transport in Hall effect thrusters. I. Insights from particle-in-cell simulations

    Science.gov (United States)

    Lafleur, T.; Baalrud, S. D.; Chabert, P.

    2016-05-01

    Using a 1D particle-in-cell simulation with perpendicular electric, E0, and magnetic, B0, fields, and modelling the azimuthal direction (i.e., the E0 × B0 direction), we study the cross-field electron transport in Hall effect thrusters (HETs). For low plasma densities, the electron transport is found to be well described by classical electron-neutral collision theory, but at sufficiently high densities (representative of typical HETs), a strong instability is observed to significantly enhance the electron mobility, even in the absence of electron-neutral collisions. This instability is associated with correlated high-frequency (of the order of MHz) and short-wavelength (of the order of mm) fluctuations in both the electric field and the plasma density, which are shown to be the cause of the anomalous transport. Saturation of the instability is observed to occur due to a combination of ion-wave trapping in the E0 × B0 direction, and convection in the E0 direction.

  10. Anomalous Hall effect in ZnxFe3-xO4: Universal scaling law and electron localization below the Verwey transition

    Science.gov (United States)

    Jedrecy, N.; Hamieh, M.; Hebert, C.; Escudier, M.; Becerra, L.; Perriere, J.

    2016-08-01

    We show that the well-established universal scaling σxyAHE ˜ σxx1.6 between anomalous Hall and longitudinal conductivities in the low conductivity regime (σxx evolution of the anomalous Hall resistivity suggests the existence of spin polarons whose size would decrease below Tv.

  11. Large power factor and anomalous Hall effect and their correlation with observed linear magneto resistance in Co-doped Bi2Se3 3D topological insulator.

    Science.gov (United States)

    Singh, Rahul; Shukla, K K; Kumar, A; Okram, G S; Singh, D; Ganeshan, V; Lakhani, Archana; Ghosh, A K; Chatterjee, Sandip

    2016-09-21

    Magnetoresistance (MR), thermo power, magnetization and Hall effect measurements have been performed on Co-doped Bi2Se3 topological insulators. The undoped sample shows that the maximum MR as a destructive interference due to a π-Berry phase leads to a decrease of MR. As the Co is doped, the linearity in MR is increased. The observed MR of Bi2Se3 can be explained with the classical model. The low temperature MR behavior of Co doped samples cannot be explained with the same model, but can be explained with the quantum linear MR model. Magnetization behavior indicates the establishment of ferromagnetic ordering with Co doping. Hall effect data also supports the establishment of ferromagnetic ordering in Co-doped Bi2Se3 samples by showing the anomalous Hall effect. Furthermore, when spectral weight suppression is insignificant, Bi2Se3 behaves as a dilute magnetic semiconductor. Moreover, the maximum power factor is observed when time reversal symmetry (TRS) is maintained. As the TRS is broken the power factor value is decreased, which indicates that with the rise of Dirac cone above the Fermi level the anomalous Hall effect and linearity in MR increase and the power factor decreases. PMID:27419361

  12. Large power factor and anomalous Hall effect and their correlation with observed linear magneto resistance in Co-doped Bi2Se3 3D topological insulator

    Science.gov (United States)

    Singh, Rahul; Shukla, K. K.; Kumar, A.; Okram, G. S.; Singh, D.; Ganeshan, V.; Lakhani, Archana; Ghosh, A. K.; Chatterjee, Sandip

    2016-09-01

    Magnetoresistance (MR), thermo power, magnetization and Hall effect measurements have been performed on Co-doped Bi2Se3 topological insulators. The undoped sample shows that the maximum MR as a destructive interference due to a π-Berry phase leads to a decrease of MR. As the Co is doped, the linearity in MR is increased. The observed MR of Bi2Se3 can be explained with the classical model. The low temperature MR behavior of Co doped samples cannot be explained with the same model, but can be explained with the quantum linear MR model. Magnetization behavior indicates the establishment of ferromagnetic ordering with Co doping. Hall effect data also supports the establishment of ferromagnetic ordering in Co-doped Bi2Se3 samples by showing the anomalous Hall effect. Furthermore, when spectral weight suppression is insignificant, Bi2Se3 behaves as a dilute magnetic semiconductor. Moreover, the maximum power factor is observed when time reversal symmetry (TRS) is maintained. As the TRS is broken the power factor value is decreased, which indicates that with the rise of Dirac cone above the Fermi level the anomalous Hall effect and linearity in MR increase and the power factor decreases.

  13. Hall effects on anomalous heat, particle and helicity transports through tearing-mode turbulence

    International Nuclear Information System (INIS)

    The helicity transport in a current-carrying plasma results in heat and particle transports in the direction opposite to the helicity flux. Tearing-mode turbulence produces helicity flux that is proportional to the gradient of equilibrium parallel current. The helicity flux is a consequence of a fluctuating electric field with a circularly polarized component, which also causes a nonlinear parallel current (primarily an electron flux) and a nonlinear polarization current (primarily an ion flux). Such anomalous heat and particle fluxes are driven by the free-energy associated with the perturbed magnetic field in the tearing-mode turbulence, and are typically directed inward to the plasma. Both fluxes becomes large when the gradient of the equilibrium current is large. 12 refs

  14. Metal-to-insulator switching in quantum anomalous Hall states

    Science.gov (United States)

    Pan, Lei; Kou, Xufeng; Wang, Jing; Fan, Yabin; Choi, Eun Sang; Shao, Qiming; Zhang, Shou Cheng; Wang, Kang Lung

    Quantum anomalous Hall effect (QAHE) was recently achieved in magnetic topological insulator films as a form of dissipationless transport without external magnetic field. However, the universal phase diagram of QAHE and its relation with quantum Hall effect (QHE) remain to be investigated. Here, we report the experimental observation of the giant longitudinal resistance peak and zero Hall conductance plateau at the coercive field in the six quintuple-layer (Cr0.12Bi0.26Sb0.62)2 Te3 film, and demonstrate the metal-to-insulator switching between two opposite QAHE plateau states up to 0.3 K. The universal QAHE phase diagram is further confirmed through the angle-dependent measurements. Our results address that the quantum phase transitions in both QAHE and QHE regimes are in the same universality class, yet the microscopic details are different.

  15. Superparamagnetism, magnetoresistance and anomalous Hall effect in amorphous Mn{sub x}Si{sub 1−x} semiconductor films

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ai-chun; Zhang, Kun; Yan, Shi-shen; Kang, Shi-shou [School of Physics, National Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China); Qin, Yu-feng [Department of Applied Physics, School of Information Science and Engineering, Shandong Agricultural University, Taian, Shandong 271018 (China); Pei, Juan; He, Li-min; Li, Huan-huan; Dai, You-yong; Xiao, Shu-qin; Tian, Yu-feng [School of Physics, National Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong 250100 (China)

    2015-02-25

    Graphical abstract: (a) The Hall resistivity ρ{sub xy}(H) measured at different temperatures and the M(H) hysteresis loops at 5 K for the Mn{sub 0.48}Si{sub 0.52} film with a thickness of 20 nm. (b) The relationship between ρ{sub xy} and M obtained by using the data in Figs. 4(a) and 2(a). (c) The relationship between the anomalous Hall coefficient R{sub s} and the longitudinal resistivity ρ{sub xx.} - Highlights: • Magnetic and transport properties of Mn{sub x}Si{sub 1−x} films are systematically studied. • Superparamagnetism is observed in Mn{sub 0.48}Si{sub 0.52} above 17 K. • Small negative magnetoresistance indicates that spin-dependent scattering is weak. • Remarkable anomalous Hall effect is observed in the whole temperature range. • Electron–electron and electron–phonon interactions dominate the conductivity. - Abstract: A systematic study focusing on the magnetic and transport properties of Mn{sub 0.48}Si{sub 0.52} semiconductor films is performed. The Mn{sub 0.48}Si{sub 0.52} films show superparamagnetism above 17 K. The temperature dependence of the electrical transport reveals that electron–electron and electron–phonon interactions dominate the conductivity of weakly localized carriers. Very small negative magnetoresistance suggests that spin-dependent scattering between conductive carriers and local magnetic moments of Mn atoms is rather weak. On the contrary, the anomalous Hall effect due to the skew scattering is observed in the whole temperature range, indicating the spin–orbit coupling of the conducting carriers is significantly strong.

  16. Electrically tunable spin polarization of chiral edge modes in a quantum anomalous Hall insulator

    Science.gov (United States)

    Zhang, Rui-Xing; Hsu, Hsiu-Chuan; Liu, Chao-Xing

    2016-06-01

    In the quantum anomalous Hall effect, chiral edge modes are expected to conduct spin polarized current without dissipation and thus hold great promise for future electronics and spintronics with low energy consumption. However, spin polarization of chiral edge modes has never been established in experiments. In this work, we theoretically study spin polarization of chiral edge modes in the quantum anomalous Hall effect, based on both the effective model and more realistic tight-binding model constructed from first-principles calculations. We find that spin polarization can be manipulated by tuning either a local gate voltage or the Fermi energy. We also propose to extract spin information of chiral edge modes by contacting the quantum anomalous Hall insulator to a ferromagnetic lead. The establishment of spin polarization of chiral edge modes, as well as the manipulation and detection in a fully electrical manner, will pave the way to the applications of the quantum anomalous Hall effect in spintronics.

  17. Anomalous Hall effect in anatase Co:TiO2 ferromagnetic semiconductor

    NARCIS (Netherlands)

    Ramaneti, R.; Lodder, J.C.; Jansen, R.

    2007-01-01

    We have investigated the effects of modification of the SrTiO3 /Co interface as well as the SrTiO3 barrier on the tunnel magnetoresistance TMR of La0.67Sr0.33MnO3 /SrTiO3 /Co junctions. Modification was realized by the introduction of one atomic layer of either TiO2 or SrO at the SrTiO3 /Co interfac

  18. Hall Voltage with the Spin Hall Effect

    OpenAIRE

    Pershin, Yu. V.; Di Ventra, M.

    2007-01-01

    The spin Hall effect does not generally result in a charge Hall voltage. We predict that in systems with inhomogeneous electron density in the direction perpendicular to main current flow, the spin Hall effect is instead accompanied by a Hall voltage. Unlike the ordinary Hall effect, we find that this Hall voltage is quadratic in the longitudinal electric field for a wide range of parameters accessible experimentally. We also predict spin accumulation in the bulk and sharp peaks of spin-Hall ...

  19. The (Anomalous) Hall Magnetometer as an Analysis Tool for High Density Recording Media

    NARCIS (Netherlands)

    Haan, de S.; Lodder, J.C.

    1991-01-01

    In this work an evaluation tool for the characterization of high-density recording thin film media is discussed. The measurement principles are based on the anomalous and the planar Hall effect. We used these Hall effects to characterize ferromagnetic Co-Cr films and Co/Pd multilayers having perpend

  20. Anomalous enhancement of spin Hall conductivity in superconductor/normal metal junction

    OpenAIRE

    Hikino, S.; Yunoki, S.

    2011-01-01

    We propose a spin Hall device to induce a large spin Hall effect in a superconductor/normal metal (SN) junction. The side jump and skew scattering mechanisms are both taken into account to calculate the extrinsic spin Hall conductivity in the normal metal. We find that both contributions are anomalously enhanced when the voltage between the superconductor and the normal metal approaches to the superconducting gap. This enhancement is attributed to the resonant increase of the density of state...

  1. Dirac spin gapless semiconductors: Ideal platforms for massless and dissipationless spintronics and new (quantum) anomalous spin Hall effects

    OpenAIRE

    Wang, Xiao-lin

    2016-01-01

    It is proposed that the new generation of spintronics should be ideally massless and dissipationless for the realization of ultra-fast and ultra-low-power spintronic devices. We demonstrate that the spin-gapless materials with linear energy dispersion are unique materials that can realize these massless and dissipationless states. Furthermore, we propose four new types of spin Hall effects which consist of spin accumulation of equal numbers of electrons and holes having the same or opposite s...

  2. Evolution of anomalous Hall behavior in thin Pt/Co/Pt trilayers

    Science.gov (United States)

    Sun, Niu-yi; Zhang, Yan-qing; Che, Wen-ru; Shan, Rong; Zhu, Zhen-gang

    2016-05-01

    In this work, through controlling spin scattering mechanisms, anomalous Hall behaviors exhibit a series of evolutions in thin Pt/Co/Pt trilayers. The shape of Hall resistivity over longitudinal resistivity (ρAH /ρxx versus ρxx) curve turns from bending to linear and then bending again in most trilayers. This kind of evolution cannot be explained by the conventional linear scaling of anomalous Hall effect. It should be ascribed to the contribution of spin-phonon skew scattering. Our research may help to understand spin scattering behavior in low-dimensional systems more deeply and build a proper synergy between theory and experiment on the research of anomalous Hall effect.

  3. Quantum Hall effect

    OpenAIRE

    Taylor, Simon

    2015-01-01

    The main goal of this project was to write a review about different quantum Hall effects. This review focuses on the integer and relativistic quantum Hall effect in graphene. The quantum Hall effect is a newly discovered phenomena that was experimentally observed in 1980 and relativistic quantum Hall effect in graphene was observed in 2005. This project takes a theoretical approach to describe the quantum Hall effects and graphene itself. Experiments has shown that for very strong magnetic fi...

  4. The (Anomalous) Hall Magnetometer as an Analysis Tool for High Density Recording Media

    OpenAIRE

    Haan; Lodder, J. C.

    1991-01-01

    In this work an evaluation tool for the characterization of high-density recording thin film media is discussed. The measurement principles are based on the anomalous and the planar Hall effect. We used these Hall effects to characterize ferromagnetic Co-Cr films and Co/Pd multilayers having perpendicular anisotropy. The measurements set-up that was built has a sensitivity capable of measuring the hysteresis loops of 0.2x0.2 mm2 Hall structures in Co-Cr and jumps were observed in the Hall vol...

  5. Charge-Induced Spin Torque in Anomalous Hall Ferromagnets

    Science.gov (United States)

    Nomura, Kentaro; Kurebayashi, Daichi

    2015-09-01

    We demonstrate that spin-orbit coupled electrons in a magnetically doped system exert a spin torque on the local magnetization, without a flowing current, when the chemical potential is modulated in a magnetic field. The spin torque is proportional to the anomalous Hall conductivity, and its effective field strength may overcome the Zeeman field. Using this effect, the direction of the local magnetization is switched by gate control in a thin film. This charge-induced spin torque is essentially an equilibrium effect, in contrast to the conventional current-induced spin-orbit torque, and, thus, devices using this operating principle possibly have higher efficiency than the conventional ones. In addition to a comprehensive phenomenological derivation, we present a physical understanding based on a model of a Dirac-Weyl semimetal, possibly realized in a magnetically doped topological insulator. The effect might be realized also in nanoscale transition materials, complex oxide ferromagnets, and dilute magnetic semiconductors.

  6. Anomalous Suppression of the Vortex Hall Current in Underdoped YBa2Cu3Ox

    Institute of Scientific and Technical Information of China (English)

    许祝安; 黄有兴; 赵彦立; 张宣嘉; 焦正宽

    2001-01-01

    The transport properties of underdoped YBa2 Cu3 Ox (YBCO) crystals with x = 6.95, 6.80 and 6.66 were measured and the effect of the pseudogap on the Hall conductivity was studied. In the normal state, the Hall angle remains unperturbed at the crossover temperature of resistivity for the underdoped samples. An anomalous suppression of the vortex Hall current was observed near Tc and the contribution of the vortices to the Hall current is absent above 40 K in 60 K YBCO (x = 6.66).

  7. Spin Hall effects

    Science.gov (United States)

    Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.

    2015-10-01

    Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical

  8. Temperature dependence of the perpendicular magnetic anisotropy in Ta/Co2FeAl/MgO structures probed by Anomalous Hall Effect

    Science.gov (United States)

    Gabor, M. S.; Petrisor, T.; Pop, O.; Colis, S.; Tiusan, C.

    2015-10-01

    We report a detailed study of the temperature dependence of the magnetic anisotropy in Ta/Co2FeAl/MgO structures by means of Anomalous Hall Effect measurements. The volume magnetic anisotropy, although negligible at room temperature, shows a non-negligible value at low temperatures and favors an in-plane easy magnetization axis. The surface magnetic anisotropy, which promotes the perpendicular magnetic easy axis, shows an increase from 0.76 ± 0.05 erg /cm2 at 300 K, up to 1.08 ± 0.04 erg /cm2 at 5 K, attributed to the evolution of the Co2FeAl layer saturation magnetization with temperature.

  9. Ferromagnetism in reactive sputtered Cu0.96Fe 0.04O1-δ nanocrystalline films evidenced by anomalous Hall effect

    KAUST Repository

    Mi, Wenbo

    2011-03-14

    Cu0.96Fe0.04O1-δ nanocrystalline films were fabricated using reactive sputtering at different oxygen partial pressures (PO2). The electrical transport properties of the films were measured in a broad temperature range (10-300 K) under magnetic fields of up to 5T. Anomalous Hall effect (AHE) of up to 0.4μΩ cm was observed at 10 K and decreased to 0.2μΩ cm at 300 K. The characteristic AHE clearly indicated the existence of ferromagnetism in these materials. The AHE weakened as PO2 increased because the increasing PO2 reduced the fraction of Fe2+ ions, and consequently weakened the double exchange coupling between Fe2+-O2--Cu2+ in the materials. © 2011 The Japan Society of Applied Physics.

  10. Oxygen atom diffusion-driven anomalous Hall behavior in Co/Pt multilayers

    International Nuclear Information System (INIS)

    Anomalous Hall effect (AHE) studies have been carried out in Co/Pt multilayers prepared by magnetron sputtering under annealing. The AHE behavior can be deteriorated by annealing in Pt/[Co/Pt]3/Pt thin films, while saturation anomalous Hall resistivity in MgO/[Co/Pt]3/MgO multilayers after annealing at 623 K for 30 min is 124% larger than that in the as-deposited films. The X-ray photoelectron spectroscopy analysis exhibits that the increased AHE is primarily ascribed to annealing dependent oxygen atom diffusion at the Co/MgO interface. - Highlights: • The electronic transport properties in Co/Pt multilayers were studied. • The chemical states were investigated by X-ray photoelectron spectroscopy. • Oxygen atom diffusion has an effect on anomalous Hall effect in Co/Pt multilayers

  11. Disorder-induced anomalously signed Hall effect in crystalline GeTe/Sb{sub 2}Te{sub 3} superlattice-like materials

    Energy Technology Data Exchange (ETDEWEB)

    Tong, H.; Yu, N. N.; Yang, Z.; Cheng, X. M.; Miao, X. S., E-mail: miaoxs@mail.hust.edu.cn [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2015-08-21

    Opposite to the almost persistent p-type conductivity of the crystalline chalcogenides along the GeTe-Sb{sub 2}Te{sub 3} tie line, n-type Hall mobility is observed in crystalline GeTe/Sb{sub 2}Te{sub 3} superlattice-like material (SLL) with a short period length. We suggest that this unusual carrier characteristic originates from the structural disorder introduced by the lattice strain and dangling bonds at the SLL interfaces, which makes the crystalline SLLs behave like the amorphous chalcogenides. Detailed structural disorder in crystalline SLL has been studied by Raman scattering, X-ray photoelectron spectroscopy, as well as Variable-energy positron annihilation spectroscopy measurements. First-principles calculations results show that this structural disorder gives rise to three-site junctions that dominate the charge transport as the period length decreases and result in the anomalously signed Hall effect in the crystalline SLL. Our findings indicate a similar tetrahedral structure in the amorphous and crystalline states of SLLs, which can significantly reduce the entropy difference. Due to the reduced entropy loss and increased resistivity of crystalline phase introduced by disorder, it is not surprising that the SLLs exhibit extremely lower RESET current and power consumption.

  12. Topological Spin Hall Effect

    OpenAIRE

    Yin, Gen; Liu, Yizhou; Barlas, Yafis; Zang, Jiadong; Lake, Roger K.

    2015-01-01

    The intrinsic spin Hall effect (SHE) originates from the topology of the Bloch bands in momentum space. The duality between real space and momentum space calls for a spin Hall effect induced from a real space topology in analogy to the topological Hall effect (THE) of skyrmions. We theoretically demonstrate the topological spin Hall effect (TSHE) in which a pure transverse spin current is generated from a skyrmion spin texture.

  13. Scaling of the anomalous Hall current in Fe100−x(SiO2)x films

    KAUST Repository

    Xu, W. J.

    2011-05-20

    To study the origin of the anomalous Hall effect, Fe100−x(SiO2)x granular films with a volume fraction of SiO2 (0 ⩽ x ⩽ 40.51) were fabricated using cosputtering. Hall and longitudinal resistivities were measured in the temperature range of 5–350 K with magnetic fields up to 5 T. As x increased from 0 to 40.51, the anomalous Hall resistivity and longitudinal resistivity increased by about four and three orders in magnitude, respectively. Analysis of the results revealed that the normalized anomalous Hall conductivity is a constant for all of the samples, which may suggest a scattering-independent anomalous Hall conductivity in Fe.

  14. Noncommutative Hall Effect

    OpenAIRE

    Kokado, Akira; OKAMURA, TAKASHI; Saito, Takesi

    2002-01-01

    When coordinates are noncommutative, the Hall effect is reinvestigated. The Hall conductivity is expressed with noncommutative parameters, so that in the commutative limit it tends to the conventional result.

  15. Intrinsic Spin Hall Effect

    OpenAIRE

    Murakami, Shuichi

    2005-01-01

    A brief review is given on the spin Hall effect, where an external electric field induces a transverse spin current. It has been recognized over 30 years that such effect occurs due to impurities in the presence of spin-orbit coupling. Meanwhile, it was proposed recently that there is also an intrinsic contribution for this effect. We explain the mechanism for this intrinsic spin Hall effect. We also discuss recent experimental observations of the spin Hall effect.

  16. Geometric Hall effects in topological insulator heterostructures

    Science.gov (United States)

    Yasuda, K.; Wakatsuki, R.; Morimoto, T.; Yoshimi, R.; Tsukazaki, A.; Takahashi, K. S.; Ezawa, M.; Kawasaki, M.; Nagaosa, N.; Tokura, Y.

    2016-06-01

    Geometry, both in momentum and in real space, plays an important role in the electronic dynamics of condensed matter systems. Among them, the Berry phase associated with nontrivial geometry can be an origin of the transverse motion of electrons, giving rise to various geometric effects such as the anomalous, spin and topological Hall effects. Here, we report two unconventional manifestations of Hall physics: a sign-reversal of the anomalous Hall effect, and the emergence of a topological Hall effect in magnetic/non-magnetic topological insulator heterostructures, Crx(Bi1-ySby)2-xTe3/(Bi1-ySby)2Te3. The sign-reversal in the anomalous Hall effect is driven by a Rashba splitting at the bulk bands, which is caused by the broken spatial inversion symmetry. Instead, the topological Hall effect arises in a wide temperature range below the Curie temperature, in a region where the magnetic-field dependence of the Hall resistance largely deviates from the magnetization. Its origin is assigned to the formation of a Néel-type skyrmion induced by the Dzyaloshinskii-Moriya interaction.

  17. Quantum Spin Hall Effect

    Energy Technology Data Exchange (ETDEWEB)

    Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-01-15

    The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.

  18. Characteristics of anomalous Hall effect in spin-polarized two-dimensional electron gases in the presence of both intrinsic, extrinsic, and external electric-field induced spin-orbit couplings

    Institute of Scientific and Technical Information of China (English)

    Liu Song; Yan Yu-Zhen; Hu Liang-Bin

    2012-01-01

    The various competing contributions to the anomalous Hall effect in spin-polarized two-dimensional electron gases in the presence of both intrinsic,extrinsic and external electric-field induced spin-orbit coupling were investigated theoretically.Based on a unified semiclassical theoretical approach,it is shown that the total anomalous Hall conductivity can be expressed as the sum of three distinct contributions in the presence of these competing spin-orbit interactions,namely an intrinsic contribution determined by the Berry curvature in the momentum space,an extrinsic contribution determined by the modified Bloch band group velocity and an extrinsic contribution determined by spin-orbit-dependent impurity scattering.The characteristics of these competing contributions are discussed in detail in the paper.

  19. The quantum hall effect

    International Nuclear Information System (INIS)

    Transport phenomena in two dimensional semiconductors have revealed unusual properties. In this thesis these systems are considered and discussed. The theories explain the Integral Quantum Hall Effect (IQHE) and the Fractional Quantum Hall Effect (FQHE). The thesis is composed of five chapters. The first and the second chapters lay down the theory of the IQHE, the third and fourth consider the theory of the FQHE. Chapter five deals with the statistics of particles in two dimension. (author). Refs

  20. Quantum Hall Effects

    OpenAIRE

    Goerbig, M. O.

    2009-01-01

    These lecture notes yield an introduction to quantum Hall effects both for non-relativistic electrons in conventional 2D electron gases (such as in semiconductor heterostructures) and relativistic electrons in graphene. After a brief historical overview in chapter 1, we discuss in detail the kinetic-energy quantisation of non-relativistic and the relativistic electrons in a strong magnetic field (chapter 2). Chapter 3 is devoted to the transport characteristics of the integer quantum Hall eff...

  1. Tuning anomalous Hall conductivity in L1[sub 0] FePt films by long range chemical ordering

    KAUST Repository

    Chen, M.

    2011-02-24

    For L10 FePt films, the anomalous Hall conductivity σ xy=-a σxx-b, where a=a0f(T), b=b 0f(T), and f (T) is the temperature dependence factor of the spontaneous magnetization. With increasing chemical long range ordering S, a0 changes its sign accompanied by a reduction of its magnitude and b0 increases monotonically. The spin-orbit coupling strength is suggested to increase with increasing S. As an approach, the long range chemical ordering can be used to control the anomalous Hall effect in ferromagnetic alloy films. © 2011 American Institute of Physics.

  2. The quantized Hall effect

    International Nuclear Information System (INIS)

    The quantized Hall effect is theoretically explained in detail as are its basic properties. The explanation is completed with the pertinent mathematical relations and illustrative figures. Experimental data are critically assessed obtained by quantum transport measurement in a magnetic field on two-dimensional systems. The results are reported for a MOSFET silicon transistor and for GaAs-AlxGa1-xAs heterostructures. The application is discussed of the quantized Hall effect in determining the fine structure constant or in implementing the resistance standard. (M.D.). 27 figs., 57 refs

  3. AlO x /LiF composite protection layer for Cr-doped (Bi,Sb)2Te3 quantum anomalous Hall films

    Science.gov (United States)

    Ou, Yunbo; Feng, Yang; Feng, Xiao; Hao, Zhenqi; Zhang, Liguo; Liu, Chang; Wang, Yayu; He, Ke; Ma, Xucun; Xue, Qikun

    2016-08-01

    We have realized robust quantum anomalous Hall samples by protecting Cr-doped (Bi,Sb)2Te3 topological insulator films with a combination of LiF and AlO x capping layers. The AlO x /LiF composite capping layer well keeps the quantum anomalous Hall states of Cr-doped (Bi,Sb)2Te3 films and effectively prevent them from degradation induced by ambient conditions. The progress is a key step towards the realization of the quantum phenomena in heterostructures and devices based on quantum anomalous Hall system. Project supported by the National Natural Science Foundation of China (Grant No. 11325421).

  4. Hall Effect in Quasicrystals

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xiang; HU Cheng-zheng; GONG Ping; WANG Ai-jun

    2005-01-01

    The relations between Hall effect and symmetry are discussed for all 2- and 3 dimensional quasicrystals with crystallographically forbidden symmetries. The results show that the numbers of independent components of the Hall coefficient (RH) are one for 3-dimensional quasicrystals, two for those 2 dimensional quasicrystals whose symmetry group is non-Abelian, and three for those 2-dimensional quasicrystals whose symmetry group is Abelian, respectively. The quasicrystals with the same number of independent components have the same form of the components of RH.

  5. Hall Effect in a Plasma.

    Science.gov (United States)

    Kunkel, W. B.

    1981-01-01

    Describes an apparatus and procedure for conducting an undergraduate laboratory experiment to quantitatively study the Hall effect in a plasma. Includes background information on the Hall effect and rationale for conducting the experiment. (JN)

  6. The Fractional Quantum Hall Effect

    OpenAIRE

    Rao, Sumathi

    1999-01-01

    We give a brief introduction to the phenomenon of the Fractional Quantum Hall effect, whose discovery was awarded the Nobel prize in 1998. We also explain the composite fermion picture which describes the fractional quantum Hall effect as the integer quantum Hall effect of composite fermions.

  7. Prediction of a quantum anomalous Hall state in Co-decorated silicene

    KAUST Repository

    Kaloni, Thaneshwor P.

    2014-01-09

    Based on first-principles calculations, we demonstrate that Co-decorated silicene can host a quantum anomalous Hall state. The exchange field induced by the Co atoms combined with the strong spin-orbit coupling of the silicene opens a nontrivial band gap at the K point. As compared to other transition metals, Co-decorated silicene is unique in this respect, since usually hybridization and spin-polarization induced in the silicene suppress a quantum anomalous Hall state.

  8. Inverse spin Hall effect by spin injection

    Science.gov (United States)

    Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.

    2007-09-01

    Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.

  9. Prediction of Quantum Anomalous Hall Insulator in half-fluorinated GaBi Honeycomb

    Science.gov (United States)

    Chen, Sung-Ping; Huang, Zhi-Quan; Crisostomo, Christian P.; Hsu, Chia-Hsiu; Chuang, Feng-Chuan; Lin, Hsin; Bansil, Arun

    2016-08-01

    Using first-principles electronic structure calculations, we predict half-fluorinated GaBi honeycomb under tensile strain to harbor a quantum anomalous Hall (QAH) insulator phase. We show that this QAH phase is driven by a single inversion in the band structure at the Γ point. Moreover, we have computed the electronic spectrum of a half-fluorinated GaBi nanoribbon with zigzag edges, which shows that only one edge band crosses the Fermi level within the band gap. Our results suggest that half-fluorination of the GaBi honeycomb under tensile strain could provide a new platform for developing novel spintronics devices based on the QAH effect.

  10. Spin Hall effect

    Czech Academy of Sciences Publication Activity Database

    Sinova, Jairo; Valenzuela, O.V.; Wunderlich, Joerg; Back, C.H.; Jungwirth, Tomáš

    2015-01-01

    Roč. 87, č. 4 (2015), s. 1213-1259. ISSN 0034-6861 R&D Projects: GA MŠk(CZ) LM2011026; GA ČR GB14-37427G EU Projects: European Commission(XE) 268066 - 0MSPIN Institutional support: RVO:68378271 Keywords : spin Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 29.604, year: 2014

  11. Spin Hall effect transistor

    Czech Academy of Sciences Publication Activity Database

    Wunderlich, Joerg; Park, B.G.; Irvine, A.C.; Zarbo, Liviu; Rozkotová, E.; Němec, P.; Novák, Vít; Sinova, Jairo; Jungwirth, Tomáš

    2010-01-01

    Roč. 330, č. 6012 (2010), s. 1801-1804. ISSN 0036-8075 R&D Projects: GA AV ČR KAN400100652; GA MŠk LC510 Grant ostatní: EU FP7 SemiSpinNet(XE) 215368 Institutional research plan: CEZ:AV0Z10100521 Keywords : spin Hall effect * spintronics * spin transistor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 31.364, year: 2010

  12. Spin Hall effect devices

    Czech Academy of Sciences Publication Activity Database

    Jungwirth, Tomáš; Wunderlich, Joerg; Olejník, Kamil

    2012-01-01

    Roč. 11, č. 5 (2012), s. 382-390. ISSN 1476-1122 EU Projects: European Commission(XE) 215368 - SemiSpinNet Grant ostatní: FP7 - ERC Advanced Grant 0MSPIN(XE) 268066; AVČR(CZ) Premium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : spin Hall effect * spintronic s * spin transistor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 35.749, year: 2012

  13. Anomalous Hall voltage rectification and quantized spin-wave excitation induced by the simultaneous dc- and rf-current application in Ni81Fe19 wire

    OpenAIRE

    A. Yamaguchi; Motoi, K.; Hirohata, A.; Miyajima, H.

    2008-01-01

    An anomalous Hall effect and rectification of a Hall voltage are observed by applying a radio-frequency (rf) current through a single-layered ferromagnetic wire located on a coplanar waveguide. The components of the magnetization precession, both in and perpendicular to the plane, can be detected via the Hall voltage rectification of the rf current by incorporating an additional direct (dc) current. In this paper, we propose a phenomenological model, which describes the time-dependent anisotr...

  14. Electric-field manipulation of coercivity in FePt/Pb(Mg1/3Nb2/3)O3-PbTiO3 heterostructures investigated by anomalous Hall effect measurement

    Science.gov (United States)

    Liu, Mingfeng; Hao, Liang; Jin, Tianli; Cao, Jiangwei; Bai, Jianmin; Wu, Dongping; Wang, Ying; Wei, Fulin

    2015-06-01

    The effect of electric field (E-field) on the magnetism of FePt thin films in FePt/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) heterostructures was investigated by anomalous Hall effect measurement. For FePt films of different thicknesses, the coercivity vs E-field curves show a typical butterfly-like loop behavior. Further results indicate that the coercivity variation is composed of the volatile symmetrical butterfly-like loop and nonvolatile hysteresis loop-like parts, which originate from the volatile and nonvolatile strains induced by the E-field in the PMN-PT(001) substrate, respectively. No significant difference has been observed after inserting a 2 nm W interlayer, suggesting that the charge-mediated coercivity variation is negligible in FePt/PMN-PT heterostructures.

  15. The Microwave Hall Effect

    OpenAIRE

    Coppock, J. E.; Anderson, J R; Johnson, W. B.

    2015-01-01

    This paper describes a simple microwave apparatus to measure the Hall effect in semiconductor wafers. The advantage of this technique is that it does not require contacts on the sample or the use of a resonant cavity. Our method consists of placing the semiconductor wafer into a slot cut in an X-band (8 - 12 GHz) waveguide series tee, injecting microwave power into the two opposite arms of the tee, and measuring the microwave output at the third arm. A magnetic field applied perpendicular to ...

  16. Hall Effect in spinor condensates

    OpenAIRE

    Taillefumier, Mathieu; Dahl, Eskil K.; Brataas, Arne; Hofstetter, Walter

    2009-01-01

    We consider a neutral spinor condensate moving in a periodic magnetic field. The spatially dependent magnetic field induces an effective spin dependent Lorentz force which in turn gives rise to a spin dependent Hall effect. Simulations of the Gross-Pitaevskii equation quantify the Hall effect. We discuss possible experimental realizations.

  17. Towards Hall effect spintronics

    International Nuclear Information System (INIS)

    Major efforts in the current exploration of spintronics are focused on the giant magnetoresistance (GMR) phenomenon in metallic, semiconducting and tunnel junction magnetic heterostructures. I wish to present a different approach based on the extraordinary Hall effect (EHE). Since its discovery more than a century ago, the EHE was not considered seriously for technological applications because of its relatively small value in bulk magnetic materials. Several techniques were recently developed to significantly enhance the effect. Field sensitivity of tens to hundreds Ω/T has been obtained. We argue that EHE-based sensors and memory devices promise a number of valuable advantages, including high sensitivity, thermal stability and simplicity and low cost manufacture, and can become an alternative to the GMR

  18. Terahertz spectroscopy on Faraday and Kerr rotations in a quantum anomalous Hall state.

    Science.gov (United States)

    Okada, Ken N; Takahashi, Youtarou; Mogi, Masataka; Yoshimi, Ryutaro; Tsukazaki, Atsushi; Takahashi, Kei S; Ogawa, Naoki; Kawasaki, Masashi; Tokura, Yoshinori

    2016-01-01

    Electrodynamic responses from three-dimensional topological insulators are characterized by the universal magnetoelectric term constituent of the Lagrangian formalism. The quantized magnetoelectric coupling, which is generally referred to as topological magnetoelectric effect, has been predicted to induce exotic phenomena including the universal low-energy magneto-optical effects. Here we report the experimental indication of the topological magnetoelectric effect, which is exemplified by magneto-optical Faraday and Kerr rotations in the quantum anomalous Hall states of magnetic topological insulator surfaces by terahertz magneto-optics. The universal relation composed of the observed Faraday and Kerr rotation angles but not of any material parameters (for example, dielectric constant and magnetic susceptibility) well exhibits the trajectory towards the fine structure constant in the quantized limit. PMID:27436710

  19. Anomalous Nernst Effect of Perpendicularly Magnetic Anisotropy TbFeCo Thin Films

    Science.gov (United States)

    Ando, Ryo; Komine, Takashi; Hasegawa, Yasuhiro

    2016-07-01

    In this study, we investigated anomalous Nernst effect (ANE) of perpendicularly magnetized TbFeCo thin films with various Tb content, and especially studied the relation between ANE and anomalous Hall effect. As a result, the hysteresis of anomalous Nernst coefficient showed the same behavior as that of anomalous Hall resistivity, and the sign of anomalous Nernst coefficient was consistent with that of anomalous Hall voltage in any Tb content, whereas the Seebeck coefficient and the resistivity were almost constant even if the applied magnetic field was varied. Taking into account of thermoelectric coefficient tensor, it was revealed that the off-diagonal thermopower corresponding to the ANE in TbFeCo thin films is the product of Hall angle and Seebeck coefficient.

  20. Holographic duality between $(2+1)$-d quantum anomalous Hall state and $(3+1)$-d topological insulators

    CERN Document Server

    Gu, Yingfei; Wen, Xueda; Cho, Gil Young; Ryu, Shinsei; Qi, Xiao-Liang

    2016-01-01

    In this paper, we study $(2+1)$-dimensional quantum anomalous Hall states, i.e. band insulators with quantized Hall conductance, using the exact holographic mapping. The exact holographic mapping is an approach to holographic duality which maps the quantum anomalous Hall state to a different state living in $(3+1)$-dimensional hyperbolic space. By studying topological response properties and the entanglement spectrum, we demonstrate that the holographic dual theory of a quantum anomalous Hall state is a $(3+1)$-dimensional topological insulator. The dual description enables a new characterization of topological properties of a system by the quantum entanglement between degrees of freedom at different length scales.

  1. A Small Modular Laboratory Hall Effect Thruster

    Science.gov (United States)

    Lee, Ty Davis

    Electric propulsion technologies promise to revolutionize access to space, opening the door for mission concepts unfeasible by traditional propulsion methods alone. The Hall effect thruster is a relatively high thrust, moderate specific impulse electric propulsion device that belongs to the class of electrostatic thrusters. Hall effect thrusters benefit from an extensive flight history, and offer significant performance and cost advantages when compared to other forms of electric propulsion. Ongoing research on these devices includes the investigation of mechanisms that tend to decrease overall thruster efficiency, as well as the development of new techniques to extend operational lifetimes. This thesis is primarily concerned with the design and construction of a Small Modular Laboratory Hall Effect Thruster (SMLHET), and its operation on argon propellant gas. Particular attention was addressed at low-cost, modular design principles, that would facilitate simple replacement and modification of key thruster parts such as the magnetic circuit and discharge channel. This capability is intended to facilitate future studies of device physics such as anomalous electron transport and magnetic shielding of the channel walls, that have an impact on thruster performance and life. Preliminary results demonstrate SMLHET running on argon in a manner characteristic of Hall effect thrusters, additionally a power balance method was utilized to estimate thruster performance. It is expected that future thruster studies utilizing heavier though more expensive gases like xenon or krypton, will observe increased efficiency and stability.

  2. Quantum Hall effect in bilayer system with array of antidots

    Science.gov (United States)

    Pagnossin, I. R.; Gusev, G. M.; Sotomayor, N. M.; Seabra, A. C.; Quivy, A. A.; Lamas, T. E.; Portal, J. C.

    2007-04-01

    We have studied the Quantum Hall effect in a bilayer system modulated by gate-controlled antidot lattice potential. The Hall resistance shows plateaus which are quantized to anomalous multiplies of h/e2. We suggest that this complex behavior is due to the nature of the edge-states in double quantum well (DQW) structures coupled to an array of antidots: these plateaus may be originated from the coexistence of normal and counter-rotating edge-states in different layers.

  3. Spin Hall Effect

    OpenAIRE

    Schliemann, John

    2006-01-01

    It is proposed that when a charge current circulates in a paramagnetic metal a transverse spin imbalance will be generated, giving rise to a 'spin Hall voltage'. Similarly, that when a spin current circulates a transverse charge imbalance will be generated, hence a Hall voltage, in the absence of charge current and magnetic field. Based on these principles we propose an experiment to generate and detect a spin current in a paramagnetic metal.

  4. Spin-charge separation and anomalous correlation functions in the edge states of quantum hall liquids

    CERN Document Server

    Lee, H C

    1998-01-01

    First, we have investigated chiral edges of a quantum Hall liquids at filling factor nu=2. The separation of spin and charge degrees of freedom becomes manifest in the presence of long- range Coulomb interaction. Due to the spin-charge separation the tunneling density of states takes the form D(omega) approx ( -lnl omega l) sup 1 sup / sup 2. Experimentally, the spin-charge separation can be revealed in the temperature and voltage dependence of the tunneling current into Fermi liquid reservoir. Second, the charge and spin correlation functions of partially spin-polarized edge electrons of a quantum Hall bar are studied using effective Hamiltonian and bosonization techniques. In the presence of the Coulomb interaction between the edges with opposite chirality we find a different crossover behavior in spin and charge correlation functions. The crossover of the spin correlation function in the Coulomb dominated regime is characterized by an anomalous exponent, which originates from the finite value of the effect...

  5. Large anomalous Nernst effect in a skyrmion crystal

    Science.gov (United States)

    Mizuta, Yo Pierre; Ishii, Fumiyuki

    2016-06-01

    Thermoelectric properties of a model skyrmion crystal were theoretically investigated, and it was found that its large anomalous Hall conductivity, corresponding to large Chern numbers induced by its peculiar spin structure leads to a large transverse thermoelectric voltage through the anomalous Nernst effect. This implies the possibility of finding good thermoelectric materials among skyrmion systems, and thus motivates our quests for them by means of the first-principles calculations as were employed in this study.

  6. Multilayer thin film Hall effect device

    Science.gov (United States)

    Peters, Palmer N. (Inventor); Sisk, R. Charles (Inventor)

    1994-01-01

    A Hall effect device and a method of obtaining a magnetic field map of a magnetic body with the Hall effect device are presented. The device comprises: (1) a substrate, (2) a first layer having a first Hall coefficient deposited over the substrate, and (3) a second layer having a second Hall coefficient deposited over the first layer, the first and second layers cooperating to create, in the Hall effect device, a third Hall coefficient different from the first and second Hall coefficients. Creation of the third Hall coefficient by cooperation of the first and second layers allows use of materials for the first and second layers that were previously unavailable for Hall effect devices due to their relatively weak Hall coefficient.

  7. Quantum Dualities and Quantum Anomalous Hall Phases with Arbitrary Large Chern Numbers

    OpenAIRE

    Chern, Tong

    2016-01-01

    Quantum duality is a far reaching concept in contemporary theoretical physics. In the present paper, we reveal the quantum dualities in quantum anomalous Hall (QAH) phases through concrete two bands Hamiltonian models. Our models can realize QAH phases with arbitrary large Chern numbers. In real materials these models may be realized by stacked $n$ layer systems of $c_1=1$ QAH insulators. The topological phase transitions that can change the Chern numbers are studied. And we investigate the g...

  8. Thermally stable anomalous Hall behavior in perpendicular Co/Pt multilayers sandwiched by HfO2 layers

    Science.gov (United States)

    Jiang, Shao-Long; Li, Xu-Jing; Liu, Yi-Wei; Chen, Xi; Liu, Qian-Qian; Han, Gang; Yang, Guang; Wang, Dong-Wei; Zhang, Jing-Yan; Teng, Jiao; Yu, Guang-Hua

    2016-01-01

    The effect of annealing on the anomalous Hall effect (AHE) in perpendicular Co/Pt multilayers sandwiched by HfO2 layers has been studied. It was found that thermally stable AHE features can be obtained in perpendicular Co/Pt multilayers with the introduction of two Co/HfO2 interfaces, leading to the improvement of the skew scattering contribution to the AHE after annealing. On the contrary, thermally stable AHE behavior cannot be observed in Co/Pt multilayers sandwiched by Pt layers or MgO layers because of Co-Pt interdiffusion during annealing.

  9. Breaking time reversal symmetry, quantum anomalous Hall state and dissipationless chiral conduction in topological insulators

    Science.gov (United States)

    Moodera, Jagadeesh

    Breaking time reversal symmetry (TRS) in a topological insulator (TI) with ferromagnetic perturbation can lead to many exotic quantum phenomena exhibited by Dirac surface states including the quantum anomalous Hall (QAH) effect and dissipationless quantized Hall transport. The realization of the QAH effect in realistic materials requires ferromagnetic insulating materials and topologically non-trivial electronic band structures. In a TI, the ferromagnetic order and TRS breaking is achievable by conventional way, through doping with a magnetic element, or by ferromagnetic proximity coupling. Our experimental studies by both approaches will be discussed. In doped TI van Vleck ferromagnetism was observed. The proximity induced magnetism at the interface was stable, beyond the expected temperature range. We shall describe in a hard ferromagnetic TI system a robust QAH state and dissipationless edge current flow is achieved,1,2 a major step towards dissipationless electronic applications with no external fields, making such devices more amenable for metrology and spintronics applications. Our study of the gate and temperature dependences of local and nonlocal magnetoresistance, may elucidate the causes of the dissipative edge channels and the need for very low temperature to observe QAH. In close collaboration with: CuiZu Chang,2,3 Ferhat Katmis, 1 . 2 , 3 Peng Wei. 1 , 2 , 3 ; From Nuclear Eng. Dept. MIT, M. Li, J. Li; From Penn State U, W-W. Zhao, D. Y. Kim, C-x. Liu, J. K. Jain, M. H. W. Chan; From Oakridge National Lab, V. Lauter; From Northeastern U., B. A. Assaf, M. E. Jamer, D. Heiman; From Argonne Lab, J. W. Freeland; From Ruhr-Universitaet Bochum (Germany), F. S. Nogueira, I. Eremin; From Saha Institute of Nuclear Physics (India), B. Satpati. Work supported by NSF Grant DMR-1207469, the ONR Grant N00014-13-1-0301, and the STC Center for Integrated Quantum Materials under NSF Grant DMR-1231319.

  10. Spin Hall Effect in Noncommutative Coordinates

    OpenAIRE

    Dayi, O. F.; Elbistan, M.

    2008-01-01

    A semiclassical constrained Hamiltonian system which was established to study dynamical systems of matrix valued non-Abelian gauge fields is employed to formulate spin Hall effect in noncommuting coordinates at the first order in the constant noncommutativity parameter theta . The method is first illustrated by studying the Hall effect on the noncommutative plane in a gauge independent fashion. Then, the Drude model type and the Hall effect type formulations of spin Hall effect are considered...

  11. Effective actions for anomalous hydrodynamics

    International Nuclear Information System (INIS)

    We argue that an effective field theory of local fluid elements captures the constraints on hydrodynamic transport stemming from the presence of quantum anomalies in the underlying microscopic theory. Focussing on global current anomalies for an arbitrary flavour group, we derive the anomalous constitutive relations in arbitrary even dimensions. We demonstrate that our results agree with the constraints on anomaly governed transport derived hitherto using a local version of the second law of thermodynamics. The construction crucially uses the anomaly inflow mechanism and involves a novel thermofield double construction. In particular, we show that the anomalous Ward identities necessitate non-trivial interaction between the two parts of the Schwinger-Keldysh contour

  12. Enhancement in anomalous Hall resistivity of Co/Pd multilayer and CoPd alloy by Ga+ ion irradiation

    KAUST Repository

    Guo, Zaibing

    2014-02-01

    In this paper, we report the effect of Ga+ ion irradiation on anomalous Hall effect (AHE) and longitudinal resistivity (ρxx) in [Co(3 Å)/Pd(5 Å)]80 multilayer and Co 42Pd58 alloy. 4- and 2-fold increases in anomalous Hall resistivity (ρAH) in the Co/Pd multilayer and CoPd alloy have been observed after irradiations at doses of 2.4 × 1015 and 3.3×10 15 ions/cm2, respectively. Skew scattering and side jump contributions to AHE have been analyzed based on the scaling relationship ρAH = aρxx + bρ2xx. For the Co/Pd multilayer, AHE is mainly affected by ion irradiation-induced interface diffusion and defects. For the CoPd alloy, the increase in doses above 1.5 × 1015 ions/cm2 induces a sign change in skew scattering, followed by the skew scattering contribution to AHE overwhelming the side jump contribution, this phenomenon should be attributed to irradiation-induced defects and modifications in chemical ordering. © Copyright EPLA, 2014.

  13. New insight into the Hall effect

    OpenAIRE

    Huang, X. Q.

    2009-01-01

    In this paper, we develop a unified theory for describing Hall effect in various electronic systems based on a pure electron picture (without the hole concept). We argue that the Hall effect is the magnetic field induced symmetry breaking of the charge carrier's spatial distribution. Due to the interaction of the charge carriers and the ion lattice, there are two possible symmetry breaking mechanisms which cause different signs of Hall coefficient in a Hall material. The scenario provides an ...

  14. Topological Nature of the Phonon Hall Effect

    OpenAIRE

    Zhang, Lifa; Ren, Jie; Wang, Jian-Sheng; Li, Baowen

    2010-01-01

    We provide a topological understanding on phonon Hall effect in dielectrics with Raman spinphonon coupling. A general expression for phonon Hall conductivity is obtained in terms of the Berry curvature of band structures. We find a nonmonotonic behavior of phonon Hall conductivity as a function of magnetic field. Moreover, we observe a phase transition in phonon Hall effect, which corresponds to the sudden change of band topology, characterized by the altering of integer Chern numbers. This c...

  15. Optical Hall effect-model description: tutorial.

    Science.gov (United States)

    Schubert, Mathias; Kühne, Philipp; Darakchieva, Vanya; Hofmann, Tino

    2016-08-01

    The optical Hall effect is a physical phenomenon that describes the occurrence of magnetic-field-induced dielectric displacement at optical wavelengths, transverse and longitudinal to the incident electric field, and analogous to the static electrical Hall effect. The electrical Hall effect and certain cases of the optical Hall effect observations can be explained by extensions of the classic Drude model for the transport of electrons in metals. The optical Hall effect is most useful for characterization of electrical properties in semiconductors. Among many advantages, while the optical Hall effect dispenses with the need of electrical contacts, electrical material properties such as effective mass and mobility parameters, including their anisotropy as well as carrier type and density, can be determined from the optical Hall effect. Measurement of the optical Hall effect can be performed within the concept of generalized ellipsometry at an oblique angle of incidence. In this paper, we review and discuss physical model equations, which can be used to calculate the optical Hall effect in single- and multiple-layered structures of semiconductor materials. We define the optical Hall effect dielectric function tensor, demonstrate diagonalization approaches, and show requirements for the optical Hall effect tensor from energy conservation. We discuss both continuum and quantum approaches, and we provide a brief description of the generalized ellipsometry concept, the Mueller matrix calculus, and a 4×4 matrix algebra to calculate data accessible by experiment. In a follow-up paper, we will discuss strategies and approaches for experimental data acquisition and analysis. PMID:27505654

  16. Planar Hall effect bridge magnetic field sensors

    DEFF Research Database (Denmark)

    Henriksen, A.D.; Dalslet, Bjarke Thomas; Skieller, D.H.;

    2010-01-01

    Until now, the planar Hall effect has been studied in samples with cross-shaped Hall geometry. We demonstrate theoretically and experimentally that the planar Hall effect can be observed for an exchange-biased ferromagnetic material in a Wheatstone bridge topology and that the sensor signal can...... be significantly enhanced by a geometric factor. For the samples in the present study, we demonstrate an enhancement of the sensor output by a factor of about 100 compared to cross-shaped sensors. The presented construction opens a new design and application area of the planar Hall effect, which we term planar...... Hall effect bridge sensors....

  17. Phase Diagram of Integer Quantum Hall Effect

    OpenAIRE

    Sheng, D. N.; Weng, Z. Y.

    1999-01-01

    The phase diagram of integer quantum Hall effect is numerically determined in the tight-binding model, which can account for overall features of recently obtained experimental phase diagram. In particular, the quantum Hall plateaus are terminated by two distinct insulating phases, characterized by the Hall resistance with classic and quantized values, respectively, which is also in good agreement with experiments.

  18. The Other Hall Effect: College Board Physics

    Science.gov (United States)

    Sheppard, Keith; Gunning, Amanda M.

    2013-01-01

    Edwin Herbert Hall (1855-1938), discoverer of the Hall effect, was one of the first winners of the AAPT Oersted Medal for his contributions to the teaching of physics. While Hall's role in establishing laboratory work in high schools is widely acknowledged, his position as chair of the physics section of the Committee on College Entrance…

  19. Hall effect in NS and SNS junctions

    OpenAIRE

    Zhou, F.; Spivak, B.

    1997-01-01

    Hall effect in SN and SNS junctions is considered. It is shown that at small temperature the Hall voltage is significantly suppressed as compared to its normal metal value. The time dependence of the Hall voltage in SNS junctions has a form of narrow pulses with the Josephson frequency.

  20. Automated Micro Hall Effect measurements

    DEFF Research Database (Denmark)

    Petersen, Dirch Hjorth; Henrichsen, Henrik Hartmann; Lin, Rong;

    2014-01-01

    With increasing complexity of processes and variety of materials used for semiconductor devices, stringent control of the electronic properties is becoming ever more relevant. Collinear micro four-point probe (M4PP) based measurement systems have become high-end metrology methods for characteriza...... characterization and monitoring of sheet resistance as well as sheet carrier density and mobility via the Micro Hall Effect (MHE) method....

  1. Phenomenological Spin Transport Theory Driven by Anomalous Nernst Effect

    Science.gov (United States)

    Taniguchi, Tomohiro

    2016-07-01

    Several experimental efforts such as material investigation and structure improvement have been made recently to find a large anomalous Nernst effect in ferromagnetic metals. Here, we develop a theory of spin transport driven by the anomalous Nernst effect in a diffusive ferromagnetic/nonmagnetic multilayer. Starting from a phenomenological formula of a spin-dependent electric current, the theoretical formulas of electric voltage and spin torque generated by the anomalous Nernst effect are derived. The magnitude of the electric voltage generated from the spin current via the inverse spin Hall effect is on the order of 0.1 µV for currently available experimental parameter values. The temperature gradient necessary to switch the magnetization is quite larger than the typical experimental value. The separation of the contributions of the Seebeck and transverse spin Seebeck effects is also discussed.

  2. The anti-ordinary Hall effect in NiPt thin films

    OpenAIRE

    Golod, Taras; Rydh, Andreas; Svedlindh, Peter; Krasnov, Vladimir M.

    2012-01-01

    We study the anomalous Hall effect in binary alloys between the group-10 elements Ni and Pt. It is observed that the ordinary Hall effect is negative (electron-like) at any composition of the alloy. The extraordinary Hall effect is also negative except in the vicinity of the ferromagnetic quantum critical point. Close to the critical point the sign of the extraordinary Hall effect can be changed to positive (hole-like) by tuning either the temperature or the composition of the alloy. We attri...

  3. On The Quantum Theory of Hall Effect

    OpenAIRE

    Ghaboussi, F.

    1996-01-01

    We discuss a model of both classical and integer quantum Hall-effect which is based on a semi-classical Schroedinger-Chern-Simons-action, where the Ohm-equations result as equations of motion. The quantization of the classical Chern-Simons-part of action under typical quantum Hall conditions results in the quantized Hall conductivity. We show further that the classical Hall-effect is described by a theory which arises as the classical limit of a theory of quantum Hall-effect. The model explai...

  4. Effect of the pseudogap on the Hall conductivity in underdoped YBa_2Cu_3O_6+x

    OpenAIRE

    Xu, Z. A.; Zhang, Y.; Ong, N. P.

    1999-01-01

    In underdoped YBa_2Cu_3O_x (YBCO) with x = 6.63, the opening of the pseudogap at T^* ~ 160 K has a strong effect on the Hall angle tan(theta). While the Hall response is significantly reduced, the diagonal current is relatively unaffected. The Hall conductivity suppression continues deep into the flux-flow state (from T_c to 40 K), as an anomalous suppression of the vortex Hall current.

  5. Observation of topological Hall effect in Mn2RhSn films

    Science.gov (United States)

    Rana, K. G.; Meshcheriakova, O.; Kübler, J.; Ernst, B.; Karel, J.; Hillebrand, R.; Pippel, E.; Werner, P.; Nayak, A. K.; Felser, C.; Parkin, S. S. P.

    2016-08-01

    Recently non-collinear magnetic structures have attracted renewed attention due to the novel Hall effects that they display. In earlier work evidence for a non-collinear magnetic structure has been reported for the ferromagnetic Heusler compound Mn2RhSn. Using sputtering techniques we have prepared high quality epitaxial thin films of Mn2RhSn by high temperature growth on MgO (001) substrates. The films are tetragonally distorted with an easy magnetization axis along the c-axis. Moreover, we find evidence for an anomalous Hall effect whose magnitude increases strongly below the Curie temperature that is near room temperature. Consistent with theoretical calculations of the anomalous Hall conductivity that we have carried out by deriving the Berry curvature from the electronic structure of perfectly ordered Mn2RhSn, the sign of the anomalous Hall conductivity is negative, although the measured value is considerably smaller than the calculated value. We attribute this difference to small deviations in stoichiometry and chemical ordering. We also find evidence for a topological Hall resistivity of about 50 nΩ cm, which is ∼5% of the anomalous Hall effect, for temperatures below 100 K. The topological Hall effect signifies the presence of a chiral magnetic structure that evolves from the non-collinear magnetic structure that Mn2RhSn is known to exhibit.

  6. Fractional quantum Hall effect revisited

    Energy Technology Data Exchange (ETDEWEB)

    Jacak, J., E-mail: janusz.jacak@pwr.edu.pl; Łydżba, P., E-mail: patrycja.lydzba@pwr.edu.pl; Jacak, L., E-mail: lucjan.jacak@pwr.edu.pl

    2015-10-15

    The topology-based explanation of the fractional quantum Hall effect (FQHE) is summarized. The cyclotron braid subgroups crucial for this approach are introduced in order to identify the origin of the Laughlin correlations in 2D (two-dimensional) Hall systems. Flux-tubes and vortices for composite fermions in their standard constructions are explained in terms of cyclotron braids. The derivation of the hierarchy of the FQHE is proposed by mapping onto the integer effect within the topology-based approach. The experimental observations of the FQHE supporting the cyclotron braid picture are reviewed with a special attention paid to recent experiments with a suspended graphene. The triggering role of a carrier mobility for organization of the fractional state in Hall configuration is emphasized. The prerequisites for the FQHE are indicated including topological conditions substantially increasing the previously accepted set of physical necessities. The explanation of numerical studies by exact diagonalizations of the fractional Chern insulator states is formulated in terms of the topology condition applied to the Berry field flux quantization. Some new ideas withz regard to the synthetic fractional states in the optical lattices are also formulated.

  7. Intrinsic spin Hall effect in noncubic crystals

    OpenAIRE

    Chudnovsky, E. M.

    2009-01-01

    We study the dependence of the intrinsic spin Hall effect on the crystal symmetry and geometry of experiment. The spin current is obtained and the Hall voltage caused by the polarization of the electron spins is computed. The unique dependence of the effect on the crystal symmetry permits the choice of geometry in which the spin Hall effect can be unambiguously distinguished from the effects due to the orbital motion of charge carriers and due to the magnetic field generated by the transport ...

  8. Spin Hall effect by surface roughness

    KAUST Repository

    Zhou, Lingjun

    2015-01-08

    The spin Hall and its inverse effects, driven by the spin orbit interaction, provide an interconversion mechanism between spin and charge currents. Since the spin Hall effect generates and manipulates spin current electrically, to achieve a large effect is becoming an important topic in both academia and industries. So far, materials with heavy elements carrying a strong spin orbit interaction, provide the only option. We propose here a new mechanism, using the surface roughness in ultrathin films, to enhance the spin Hall effect without heavy elements. Our analysis based on Cu and Al thin films suggests that surface roughness is capable of driving a spin Hall angle that is comparable to that in bulk Au. We also demonstrate that the spin Hall effect induced by surface roughness subscribes only to the side-jump contribution but not the skew scattering. The paradigm proposed in this paper provides the second, not if only, alternative to generate a sizable spin Hall effect.

  9. Anomalous transport phenomena in px+i py superconductors

    Science.gov (United States)

    Li, Songci; Andreev, A. V.; Spivak, B. Z.

    2015-09-01

    Spontaneous breaking of time-reversal symmetry in superconductors with the px+i py symmetry of the order parameter allows for a class of effects which are analogous to the anomalous Hall effect in ferromagnets. These effects exist below the critical temperature, T effects. In particular, we consider anomalous Hall thermal conductivity, the polar Kerr effect, the anomalous Hall effect, and the anomalous photo- and acousto-galvanic effects.

  10. Large extrinsic spin Hall effect in Au-Cu alloys by extensive atomic disorder scattering

    Science.gov (United States)

    Zou, L. K.; Wang, S. H.; Zhang, Y.; Sun, J. R.; Cai, J. W.; Kang, S. S.

    2016-01-01

    Spin Hall angle, which denotes the conversion efficiency between spin and charge current, is a key parameter in the pure spin current phenomenon. The search for materials with large spin Hall angle is indeed important for scientific interest and potential application in spintronics. Here the large enhanced spin Hall effect (SHE) of Au-Cu alloy is reported by investigating the spin Seebeck effect, spin Hall anomalous Hall effect, and spin Hall magnetoresistance of the Y3F e5O12 (YIG)/A uxC u1 -x hybrid structure over the full composition. At the near equiatomic Au-Cu composition with maximum atomic disorder scattering, the spin Hall angle of the Au-Cu alloy increases by two to three times together with a moderate spin diffusion length in comparison with Au. The longitudinal spin Seebeck voltage and the spin Hall magnetoresistance ratio also increase by two to three times. More importantly, no evidence of anomalous Hall effect is observed in all YIG/Au-Cu samples, in contrast to the cases of other giant SHE materials Pt(Pd), Ta, and W. This behavior makes Au-Cu free from any suspicion of the magnetic proximity effect involved in the hybrid structure, and thus the Au-Cu alloy can be an ideal material for pure spin current study.

  11. Lectures on the Quantum Hall Effect

    CERN Document Server

    Tong, David

    2016-01-01

    The purpose of these lectures is to describe the basic theoretical structures underlying the rich and beautiful physics of the quantum Hall effect. The focus is on the interplay between microscopic wavefunctions, long-distance effective Chern-Simons theories, and the modes which live on the boundary. The notes are aimed at graduate students in any discipline where $\\hbar=1$. A working knowledge of quantum field theory is assumed. Contents: 1. The Basics (Landau levels and Berry phase). 2. The Integer Quantum Hall Effect. 3. The Fractional Quantum Hall Effect. 4. Non-Abelian Quantum Hall States. 5. Chern-Simons Theories. 6. Edge Modes.

  12. A new method to calculate Berry phase in one-dimensional quantum anomalous Hall insulator

    Science.gov (United States)

    Liao, Yi

    2016-08-01

    Based on the residue theorem and degenerate perturbation theory, we derive a new, simple and general formula for Berry phase calculation in a two-level system for which the Hamiltonian is a real symmetric matrix. The special torus topology possessed by the first Brillouin zone (1 BZ) of this kind of systems ensures the existence of a nonzero Berry phase. We verify the correctness of our formula on the Su-Schrieffer-Heeger (SSH) model. Then the Berry phase of one-dimensional quantum anomalous Hall insulator (1DQAHI) is calculated analytically by applying our method, the result being -π/2 -π/4 sgn (B) [ sgn (Δ - 4 B) + sgn (Δ) ]. Finally, illuminated by this idea, we investigate the Chern number in the two-dimensional case, and find a very simple way to determine the parameter range of the non-trivial Chern number in the phase diagram.

  13. Honeycomb lattice with multiorbital structure: Topological and quantum anomalous Hall insulators with large gaps

    Science.gov (United States)

    Zhang, Gu-Feng; Li, Yi; Wu, Congjun

    2015-03-01

    We construct a minimal four-band model for the two-dimensional topological insulators and quantum anomalous Hall insulators based on the px- and py-orbital bands in the honeycomb lattice. The multiorbital structure allows the atomic spin-orbit coupling which lifts the degeneracy between two sets of on-site Kramers doublets jz = +/-3/2 and jz = +/-1/2 . Because of the orbital angular momentum structure of Bloch-wave states at Γ and K (K') points, topological gaps are equal to the atomic spin-orbit coupling strengths, which are much larger than those based on the mechanism of the s - p band inversion.The energy spectra and eigen wave functions are solved analytically based on Clifford algebra. The competition among spin-orbit coupling λ, sublattice asymmetry m, and the Néel exchange field n results in band crossings at Γ and K (K') points, which leads to various topological band structure transitions. The quantum anomalous Hall state is reached under the condition that three gap parameters λ, m, and n satisfy the triangle inequality. Flat bands also naturally arise which allow a local construction of eigenstates. The above mechanism is related to several classes of solid state semiconductor. G.F.Z. and C.W. are supported by the NSF DMR-1410375 and AFOSR FA9550-11-1-0067(YIP). Y.L. thanks the Inamori Fellowship and the support at the Princeton Center for Theoretical Science. C.W. acknowledges financial support from the National Natural Science.

  14. Bound values for Hall conductivity of heterogeneous medium under quantum Hall effect conditions

    Indian Academy of Sciences (India)

    V E Arkhincheev

    2008-02-01

    Bound values for Hall conductivity under quantum Hall effect (QHE) conditions in inhomogeneous medium has been studied. It is shown that bound values for Hall conductivity differ from bound values for metallic conductivity. This is due to the unusual character of current percolation under quantum Hall effect conditions.

  15. Route towards Localization for Quantum Anomalous Hall Systems with Chern Number 2.

    Science.gov (United States)

    Song, Zhi-Gang; Zhang, Yan-Yang; Song, Jun-Tao; Li, Shu-Shen

    2016-01-01

    The quantum anomalous Hall system with Chern number 2 can be destroyed by sufficiently strong disorder. During its process towards localization, it was found that the electronic states will be directly localized to an Anderson insulator (with Chern number 0), without an intermediate Hall plateau with Chern number 1. Here we investigate the topological origin of this phenomenon, by calculating the band structures and Chern numbers for disordered supercells. We find that on the route towards localization, there exists a hidden state with Chern number 1, but it is too short and too fluctuating to be practically observable. This intermediate state cannot be stabilized even after some "smart design" of the model and this should be a universal phenomena for insulators with high Chern numbers. By performing numerical scaling of conductances, we also plot the renormalization group flows for this transition, with Chern number 1 state as an unstable fixed point. This is distinct from known results, and can be tested by experiments and further theoretical analysis. PMID:26743996

  16. Two-Dimensional π-Conjugated Covalent-Organic Frameworks as Quantum Anomalous Hall Topological Insulators.

    Science.gov (United States)

    Dong, Liang; Kim, Youngkuk; Er, Dequan; Rappe, Andrew M; Shenoy, Vivek B

    2016-03-01

    The quantum anomalous Hall (QAH) insulator is a novel topological state of matter characterized by a nonzero quantized Hall conductivity without an external magnetic field. Using first-principles calculations, we predict the QAH state in monolayers of covalent-organic frameworks based on the newly synthesized X_{3}(C_{18}H_{12}N_{6})_{2} structure where X represents 5d transition metal elements Ta, Re, and Ir. The π conjugation between X d_{xz} and d_{yz} orbitals, mediated by N p_{z} and C p_{z} orbitals, gives rise to a massive Dirac spectrum in momentum space with a band gap of up to 24 meV due to strong spin-orbit coupling. We show that the QAH state can appear by chemically engineering the exchange field and the Fermi level in the monolayer structure, resulting in nonzero Chern numbers. Our results suggest a reliable pathway toward the realization of a QAH phase at temperatures between 100 K and room temperature in covalent-organic frameworks. PMID:26991189

  17. Two-Dimensional π -Conjugated Covalent-Organic Frameworks as Quantum Anomalous Hall Topological Insulators

    Science.gov (United States)

    Dong, Liang; Kim, Youngkuk; Er, Dequan; Rappe, Andrew M.; Shenoy, Vivek B.

    2016-03-01

    The quantum anomalous Hall (QAH) insulator is a novel topological state of matter characterized by a nonzero quantized Hall conductivity without an external magnetic field. Using first-principles calculations, we predict the QAH state in monolayers of covalent-organic frameworks based on the newly synthesized X3(C18H12N6) 2 structure where X represents 5 d transition metal elements Ta, Re, and Ir. The π conjugation between X dx z and dy z orbitals, mediated by N pz and C pz orbitals, gives rise to a massive Dirac spectrum in momentum space with a band gap of up to 24 meV due to strong spin-orbit coupling. We show that the QAH state can appear by chemically engineering the exchange field and the Fermi level in the monolayer structure, resulting in nonzero Chern numbers. Our results suggest a reliable pathway toward the realization of a QAH phase at temperatures between 100 K and room temperature in covalent-organic frameworks.

  18. Route towards Localization for Quantum Anomalous Hall Systems with Chern Number 2

    Science.gov (United States)

    Song, Zhi-Gang; Zhang, Yan-Yang; Song, Jun-Tao; Li, Shu-Shen

    2016-01-01

    The quantum anomalous Hall system with Chern number 2 can be destroyed by sufficiently strong disorder. During its process towards localization, it was found that the electronic states will be directly localized to an Anderson insulator (with Chern number 0), without an intermediate Hall plateau with Chern number 1. Here we investigate the topological origin of this phenomenon, by calculating the band structures and Chern numbers for disordered supercells. We find that on the route towards localization, there exists a hidden state with Chern number 1, but it is too short and too fluctuating to be practically observable. This intermediate state cannot be stabilized even after some “smart design” of the model and this should be a universal phenomena for insulators with high Chern numbers. By performing numerical scaling of conductances, we also plot the renormalization group flows for this transition, with Chern number 1 state as an unstable fixed point. This is distinct from known results, and can be tested by experiments and further theoretical analysis.

  19. Influence of complex disorder on skew-scattering Hall effects in L 10 -ordered FePt alloy

    Science.gov (United States)

    Zimmermann, Bernd; Long, Nguyen H.; Mavropoulos, Phivos; Blügel, Stefan; Mokrousov, Yuriy

    2016-08-01

    We show by first-principles calculations that the skew-scattering anomalous Hall and spin Hall angles of L 10 -ordered FePt drastically depend on different types of disorder. A different sign of the anomalous Hall angle is obtained when slightly deviating from the stoichiometric ratio towards the Fe-rich side as compared to the Pt-rich side. For stoichiometric samples, short-range ordering of defects has a profound effect on the Hall angles and can change them by a factor of 2 as compared to the case of uncorrelated disorder. This might explain the vast range of anomalous Hall angles measured in experiments, which undergo different preparation procedures and thus might differ in their crystallographic quality.

  20. Metal-Film Hall-Effect Devices

    Science.gov (United States)

    Peters, Palmer N.

    1994-01-01

    Large positive and negative Hall coefficients achievable. Family of Hall-effect devices made from multilayer metal films instead of semiconductor materials. Metal films easier to fabricate; formed by deposition on variety of substrates, and leads readily attached to them. Fabricated with larger areas, potentially more reliable, and less affected by impurities. Also used to measure magnetic fields. Devices especially useful at low temperatures.

  1. Quantum Hall Effect in Quantum Electrodynamics

    OpenAIRE

    Penin, Alexander A.

    2008-01-01

    We consider the quantum Hall effect in quantum electrodynamics and find a deviation from the quantum mechanical prediction for the Hall conductivity due to radiative antiscreening of electric charge in an external magnetic field. A weak universal dependence of the von Klitzing constant on the magnetic field strength, which can possibly be observed in a dedicated experiment, is predicted.

  2. Observation of spin Hall effective field

    Science.gov (United States)

    Fan, Xin; Wu, Jun; Chen, Yunpeng; Jerry, Matthew; Zhang, Huaiwu; Xiao, John

    2013-03-01

    Recent development in spin Hall driven spin transfer torque has attracted intensive interests1. Liu et. al. has shown that the spin transfer torque induced by the spin Hall effect in a normal metal-ferromagnetic metal bilayer can switch the magnetization of the ferromagnetic layer, which may be a potential candidate for magnetic random access memory2. The switching of the magnetization was primarily attributed to the Slonczewski torque3. We show that besides the Slonczewski torque, the spin Hall effect also produces an effective field that can also facilitate the magnetization reversal. This effective field persists even with a Cu spacer layer, and reduces quickly with the increase of the ferromagnetic layer thickness. The observation of the spin Hall effective field shall have ramification on the understanding of both spin transfer torque and spin Hall effect. 1. K. Ando et. al., Electric manipulation of spin relaxation using the spin Hall effect, Physical Review Letters, 101, 036601 (2008). 2. L. Liu et. al., Spin-Torque Switching with the Giant Spin Hall Effect of Tantalum. Science 336, 555-558 (2012). 3. J. Slonczewski, Current-driven excitation of magnetic multilayers. Journal of Magnetism and Magnetic Materials, 159, L1-L7 (1996).

  3. Theory of spin Hall effect

    OpenAIRE

    Chudnovsky, Eugene M.

    2007-01-01

    An extension of Drude model is proposed that accounts for spin and spin-orbit interaction of charge carriers. Spin currents appear due to combined action of the external electric field, crystal field and scattering of charge carriers. The expression for spin Hall conductivity is derived for metals and semiconductors that is independent of the scattering mechanism. In cubic metals, spin Hall conductivity $\\sigma_s$ and charge conductivity $\\sigma_c$ are related through $\\sigma_s = [2 \\pi \\hbar...

  4. Topological Hall Effect in Inhomogeneous Superconductors

    OpenAIRE

    Fujimoto, Satoshi

    2010-01-01

    We propose a possible mechanism of topological Hall effect in inhomogeneous superconducting states. In our scenario, the Berry phase effect associated with spatially modulated superconducting order parameter gives rise to a fictitious Lorentz force acting on quasiparticles. In the case of the Fulde-Ferrell-Larkin-Ovchinnikov state, the topological Hall effect is detected by applying an electromagnetic wave with a tuned wave number on a surface of the system.

  5. Quantum Hall effect in momentum space

    Science.gov (United States)

    Ozawa, Tomoki; Price, Hannah M.; Carusotto, Iacopo

    2016-05-01

    We theoretically discuss a momentum-space analog of the quantum Hall effect, which could be observed in topologically nontrivial lattice models subject to an external harmonic trapping potential. In our proposal, the Niu-Thouless-Wu formulation of the quantum Hall effect on a torus is realized in the toroidally shaped Brillouin zone. In this analogy, the position of the trap center in real space controls the magnetic fluxes that are inserted through the holes of the torus in momentum space. We illustrate the momentum-space quantum Hall effect with the noninteracting trapped Harper-Hofstadter model, for which we numerically demonstrate how this effect manifests itself in experimental observables. Extension to the interacting trapped Harper-Hofstadter model is also briefly considered. We finally discuss possible experimental platforms where our proposal for the momentum-space quantum Hall effect could be realized.

  6. Spin Hall effect, Hall effect and spin precession in diffusive normal metals

    OpenAIRE

    Shchelushkin, R. V.; Brataas, Arne

    2005-01-01

    We study transport in normal metals in an external magnetic field. This system exhibits an interplay between a transverse spin imbalance (spin Hall effect) caused by the spin-orbit interaction, a Hall effect via the Lorentz force, and spin precession due to the Zeeman effect. Diffusion equations for spin and charge flow are derived. The spin and charge accumulations are computed numerically in experimentally relevant thin film geometries. The out-of-plane spin Hall potential is suppressed whe...

  7. Hall viscosity from effective field theory

    OpenAIRE

    Nicolis, Alberto; Son, Dam Thanh

    2011-01-01

    For two-dimensional non-dissipative fluids with broken parity, we show via effective field theory methods that the infrared dynamics generically exhibit Hall viscosity--a conservative form of viscosity compatible with two-dimensional isotropy. The equality between the Hall viscosity coefficient and the ground state's intrinsic angular momentum density follows straightforwardly from their descending from the same Lagrangian term of the low-energy effective action. We show that for such fluids ...

  8. Piezo Voltage Controlled Planar Hall Effect Devices

    Science.gov (United States)

    Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K. W.; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

    2016-06-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials.

  9. Quantum Hall effect in higher dimensions

    International Nuclear Information System (INIS)

    Following recent work on the quantum Hall effect on S4, we solve the Landau problem on the complex projective spaces CPk and discuss quantum Hall states for such spaces. Unlike the case of S4, a finite spatial density can be obtained with a finite number of internal states for each particle. We treat the case of CP2 in some detail considering both Abelian and nonabelian background fields. The wavefunctions are obtained and incompressibility of the Hall states is shown. The case of CP3 is related to the case of S4

  10. Observation of a superfluid Hall effect

    OpenAIRE

    LeBlanc, Lindsay J.; Jiménez-García, Karina; Williams, Ross A.; Beeler, Matthew C.; Perry, Abigail R.; Phillips, William D.; Spielman, Ian B.

    2012-01-01

    Measurement techniques based upon the Hall effect are invaluable tools in condensed matter physics. When an electric current flows perpendicular to a magnetic field, a Hall voltage develops in the direction transverse to both the current and the field. In semiconductors, this behaviour is routinely used to measure the density and charge of the current carriers (electrons in conduction bands or holes in valence bands) -- internal properties of the system that are not accessible from measuremen...

  11. Boundary Effective Action for Quantum Hall States

    Science.gov (United States)

    Gromov, Andrey; Jensen, Kristan; Abanov, Alexander G.

    2016-03-01

    We consider quantum Hall states on a space with boundary, focusing on the aspects of the edge physics which are completely determined by the symmetries of the problem. There are four distinct terms of Chern-Simons type that appear in the low-energy effective action of the state. Two of these protect gapless edge modes. They describe Hall conductance and, with some provisions, thermal Hall conductance. The remaining two, including the Wen-Zee term, which contributes to the Hall viscosity, do not protect gapless edge modes but are instead related to the local boundary response fixed by symmetries. We highlight some basic features of this response. It follows that the coefficient of the Wen-Zee term can change across an interface without closing a gap or breaking a symmetry.

  12. Unusual Properties of Anisotropic Hall Gas: Implication to Metrology of the Integer Quantum Hall Effect

    OpenAIRE

    Ishikawa, K; Maeda, N.

    2001-01-01

    Physical properties of anisotropic compressible quantum Hall states and their implications to integer quantum Hall effect are studied based on a mean field theory on the von Neumann lattice. It is found that the Hall gas has unusual thermodynamic properties such as negative pressure and negative compressibility and unusual transport properties. Transport properties and density profile of Hall gas states at half fillings agree with those of anisotropic states discovered experimentally in highe...

  13. Quantum spin Hall effect in 2D topological insulators

    OpenAIRE

    Sonin, E. B.

    2011-01-01

    The original motivation of great interest to topological insulators was the hope to observe the quantum spin Hall effect. Therefore if a material is in the topological insulator state they frequently call it the quantum spin Hall state. However, despite impressive experimental results confirming the existence of the quantum spin Hall state, the quantum spin Hall effect has not yet been detected. After a short overview of what was originally suggested as the quantum spin Hall effect (quantum s...

  14. Extrinsic spin Hall effect in graphene

    Science.gov (United States)

    Rappoport, Tatiana

    The intrinsic spin-orbit coupling in graphene is extremely weak, making it a promising spin conductor for spintronic devices. In addition, many applications also require the generation of spin currents in graphene. Theoretical predictions and recent experimental results suggest one can engineer the spin Hall effect in graphene by greatly enhancing the spin-orbit coupling in the vicinity of an impurity. The extrinsic spin Hall effect then results from the spin-dependent skew scattering of electrons by impurities in the presence of spin-orbit interaction. This effect can be used to efficiently convert charge currents into spin-polarized currents. I will discuss recent experimental results on spin Hall effect in graphene decorated with adatoms and metallic cluster and show that a large spin Hall effect can appear due to skew scattering. While this spin-orbit coupling is small if compared with what it is found in metals, the effect is strongly enhanced in the presence of resonant scattering, giving rise to robust spin Hall angles. I will present our single impurity scattering calculations done with exact partial-wave expansions and complement the analysis with numerical results from a novel real-space implementation of the Kubo formalism for tight-binding Hamiltonians. The author acknowledges the Brazilian agencies CNPq, CAPES, FAPERJ and INCT de Nanoestruturas de Carbono for financial support.

  15. Charge carrier coherence and Hall effect in organic semiconductors.

    Science.gov (United States)

    Yi, H T; Gartstein, Y N; Podzorov, V

    2016-01-01

    Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor. PMID:27025354

  16. Charge carrier coherence and Hall effect in organic semiconductors

    Science.gov (United States)

    Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

    2016-03-01

    Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.

  17. Partially split Hall bar: Tunneling in the bosonic integer quantum Hall effect

    OpenAIRE

    Mulligan, Michael; Fisher, Matthew P. A.

    2014-01-01

    We study point-contact tunneling in the integer quantum Hall state of bosons. This symmetry-protected topological state has electrical Hall conductivity equal to 2e^2/h and vanishing thermal Hall conductivity. In contrast to the integer quantum Hall state of fermions, a point contact can have a dramatic effect on the low-energy physics. In the absence of disorder, a point contact generically leads to a partially split Hall bar geometry. We describe the resulting intermediate fixed point via t...

  18. The Partially-Split Hall Bar: Tunneling in the Bosonic Integer Quantum Hall Effect

    OpenAIRE

    Mulligan, Michael; Fisher, Matthew P. A.

    2013-01-01

    We study point-contact tunneling in the integer quantum Hall state of bosons. This symmetry-protected topological state has electrical Hall conductivity equal to $2 e^2/h$ and vanishing thermal Hall conductivity. In contrast to the integer quantum Hall state of fermions, a point contact can have a dramatic effect on the low energy physics. In the absence of disorder, a point contact generically leads to a partially-split Hall bar geometry. We describe the resulting intermediate fixed point vi...

  19. The hall effect in magnetic reconnection: Hybrid versus Hall-less hybrid simulations

    Science.gov (United States)

    Malakit, K.; Cassak, P. A.; Shay, M. A.; Drake, J. F.

    2009-04-01

    To understand the role of the Hall effect during fast magnetic reconnection, hybrid simulations with and without the Hall term in the generalized Ohm's Law are compared, as done originally by Karimabadi et al. (2004). It is found that reconnection with the Hall term is fast, but reconnection in the so-called Hall-less hybrid simulations is Sweet-Parker like (slow) when the resistivity is constant and uniform. These results re-affirm the importance of the Hall term in allowing fast reconnection in the hybrid model.

  20. Theory of fractional quantum Hall effect

    International Nuclear Information System (INIS)

    A theory of the fractional quantum Hall effect is constructed by introducing 3-particle interactions breaking the symmetry for ν=1/3 according to a degeneracy theorem proved here. An order parameter is introduced and a gap in the single particle spectrum is found. The critical temperature, critical filling number and critical behaviour are determined as well as the Ginzburg-Landau equation coefficients. A first principle calculation of the Hall current is given. 3, 5, 7 electron tunneling and Josephson interference effects are predicted. (author)

  1. Charge-Hall effect driven by spin force: reciprocal of the spin-Hall effect

    OpenAIRE

    zhang, ping; Niu, Qian

    2004-01-01

    A new kind of charge-Hall effect is shown. Unlike in the usual Hall effect, the driving force in the longitudinal direction is a spin force, which may originate from the gradient of a Zeeman field or a spin-dependent chemical potential. The transverse force is provided by a Berry curvature in a mixed position-momentum space. We can establish an Onsager relation between this effect and the spin-Hall effect provided the spin current in the latter is modified by a torque dipole contribution. Thi...

  2. Mesoscopic effects in the quantum Hall regime

    Indian Academy of Sciences (India)

    R N Bhatt; Xin Wan

    2002-02-01

    We report results of a study of (integer) quantum Hall transitions in a single or multiple Landau levels for non-interacting electrons in disordered two-dimensional systems, obtained by projecting a tight-binding Hamiltonian to the corresponding magnetic subbands. In finite-size systems, we find that mesoscopic effects often dominate, leading to apparent non-universal scaling behavior in higher Landau levels. This is because localization length, which grows exponentially with Landau level index, exceeds the system sizes amenable to the numerical study at present. When band mixing between multiple Landau levels is present, mesoscopic effects cause a crossover from a sequence of quantum Hall transitions for weak disorder to classical behavior for strong disorder. This behavior may be of relevance to experimentally observed transitions between quantum Hall states and the insulating phase at low magnetic fields.

  3. Spin Hall Effect in Doped Semiconductor Structures

    Science.gov (United States)

    Tse, Wang-Kong; Das Sarma, Sankar

    2006-03-01

    We present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump (SJ) and skew-scattering (SS) contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show their effects scale as σxy^SJ/σxy^SS ˜(/τ)/ɛF, where τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n-doped and p-doped 3D and 2D GaAs structures, obtaining analytical formulas for the SJ and SS contributions. Moreover, the ratio of the spin Hall conductivity to longitudinal conductivity is found as σs/σc˜10-3-10-4, in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)] in n-doped 3D GaAs system.

  4. Quantum Hall effect, Quillen metric and holomorphic anomaly

    CERN Document Server

    Klevtsov, Semyon; Marinescu, George; Wiegmann, Paul

    2015-01-01

    We study the generating functional, the adiabatic curvature and the adiabatic phase for the integer quantum Hall effect (QHE) on a compact Riemann surface. For the generating functional we derive its asymptotic expansion for the large flux of the magnetic field, i.e., for the large degree k of the positive Hermitian line bundle $L^k$. The expansion consists of the anomalous and exact terms. The anomalous terms are the leading terms of the expansion. This part is responsible for the quantization of the adiabatic transport coefficients in QHE. We then identify the anomalous part of the expansion with the Quillen metric on the determinant line bundle, and the subleading exact part with the asymptotics of the regularized spectral determinant of the Laplacian for the line bundle $L^k$, at large k. Finally, we show how the generating functional of the integer QHE is related to the gauge and gravitational (2+1)d Chern-Simons functionals. We observe the relation between the Bismut-Gillet-Soul\\'e curvature formula for...

  5. The Hall effect in star formation

    CERN Document Server

    Braiding, Catherine R

    2011-01-01

    Magnetic fields play an important role in star formation by regulating the removal of angular momentum from collapsing molecular cloud cores. Hall diffusion is known to be important to the magnetic field behaviour at many of the intermediate densities and field strengths encountered during the gravitational collapse of molecular cloud cores into protostars, and yet its role in the star formation process is not well-studied. We present a semianalytic self-similar model of the collapse of rotating isothermal molecular cloud cores with both Hall and ambipolar diffusion, and similarity solutions that demonstrate the profound influence of the Hall effect on the dynamics of collapse. The solutions show that the size and sign of the Hall parameter can change the size of the protostellar disc by up to an order of magnitude and the protostellar accretion rate by fifty per cent when the ratio of the Hall to ambipolar diffusivities is varied between -0.5 <= eta_H / eta_A <= 0.2. These changes depend upon the orien...

  6. The Two-Dimensional MnO2/Graphene Interface: Half-metallicity and Quantum Anomalous Hall State

    KAUST Repository

    Gan, Li-Yong

    2015-10-07

    We explore the electronic properties of the MnO2/graphene interface by first-principles calculations, showing that MnO2 becomes half-metallic. MnO2 in the MnO2/graphene/MnO2 system provides time-reversal and inversion symmetry breaking. Spin splitting by proximity occurs at the Dirac points and a topologically nontrivial band gap is opened, enabling a quantum anomalous Hall state. The half-metallicity, spin splitting, and size of the band gap depend on the interfacial interaction, which can be tuned by strain engineering.

  7. Unusual field and temperature dependence of Hall effect in graphene

    OpenAIRE

    Falkovsky, L. A.

    2006-01-01

    We calculate the classic Hall conductivity and mobility of the undoped and doped (or in the gate voltage) graphene as a function of temperature, magnetic field, and carrier concentration. Carrier collisions with defects and acoustic phonons are taken into account. The Hall resistivity varies almost linearly with temperature. The magnetic field dependence of resistivity and mobility is anomalous in weak magnetic fields. There is the square root contribution from the field in the resistivity. T...

  8. Piezo Voltage Controlled Planar Hall Effect Devices.

    Science.gov (United States)

    Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K W; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

    2016-01-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials. PMID:27329068

  9. Quantum Hall effect in a system with an electron reservoir

    Science.gov (United States)

    Dorozhkin, S. I.

    2016-04-01

    Precise measurements of the magnetic-field and gate-voltage dependences of the capacitance of a field-effect transistor with an electron system in a wide GaAs quantum well have been carried out. It has been found that the capacitance minima caused by the gaps in the Landau spectrum of the electron system become anomalously wide when two size-quantization subbands are occupied. The effect is explained by retention of the chemical potential in the gap between the Landau levels of one of the subbands owing to redistribution of electrons between the subbands under a change in the magnetic field. The calculation taking into account this redistribution has been performed in a model of the electron system formed by two two-dimensional electron layers. The calculation results describe both the wide capacitance features and the observed disappearance of certain quantum Hall effect states.

  10. Charge carrier coherence and Hall effect in organic semiconductors

    OpenAIRE

    Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

    2016-01-01

    Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experimen...

  11. Topological quantum numbers in the Hall effect

    OpenAIRE

    Avron, J. E.; Osadchy, D.; Seiler, R.

    2003-01-01

    Topological quantum numbers account for the precise quantization that occurs in the integer Hall effect. In this theory, Kubo's formula for the conductance acquires a topological interpretation in terms of Chern numbers and their non-commutative analog, the Fredholm Indices.

  12. Fractional Quantization of the Hall Effect

    Science.gov (United States)

    Laughlin, R. B.

    1984-02-27

    The Fractional Quantum Hall Effect is caused by the condensation of a two-dimensional electron gas in a strong magnetic field into a new type of macroscopic ground state, the elementary excitations of which are fermions of charge 1/m, where m is an odd integer. A mathematical description is presented.

  13. Quantization and hall effect: necessities and difficulties

    International Nuclear Information System (INIS)

    The quantization procedure is a necessary tool for a proper understanding of many interesting quantum phenomena in modern physics. In this note, we focus on geometrical framework for such procedures, particularly the group-theoretic approach and their difficulties. Finally we look through the example of Hall effect as a quantized macroscopic phenomenon with group-theoretic quantization approach. (author)

  14. Influence of the Hall effect on convection in plasmas

    International Nuclear Information System (INIS)

    The influence of the Hall effect on stationary convection in shearless current-carrying plasma columns is considered. It is shown that the Hall effect can inhibit the formation of convection cells generated by viscosity and resistivity

  15. Neutral-current Hall effects in disordered graphene

    OpenAIRE

    Wang, Yilin; Cai, Xinghan; Reutt-Robey, Janice; Fuhrer, Michael S.

    2015-01-01

    A non-local Hall bar geometry is used to detect neutral-current Hall effects in graphene on silicon dioxide. Disorder is tuned by the addition of Au or Ir adatoms in ultra-high vacuum. A reproducible neutral-current Hall effect is found in both as-fabricated and adatom-decorated graphene. The Hall angle exhibits a complex but reproducible dependence on gate voltage and disorder, and notably breaks electron-hole symmetry. An exponential dependence on length between Hall and inverse-Hall probes...

  16. High-Efficiency Cooper-Pair Splitter in Quantum Anomalous Hall Insulator Proximity-Coupled with Superconductor.

    Science.gov (United States)

    Zhang, Ying-Tao; Deng, Xinzhou; Sun, Qing-Feng; Qiao, Zhenhua

    2015-01-01

    The quantum entanglement between two qubits is crucial for applications in the quantum communication. After the entanglement of photons was experimentally realized, much effort has been taken to exploit the entangled electrons in solid-state systems. Here, we propose a Cooper-pair splitter, which can generate spatially-separated but entangled electrons, in a quantum anomalous Hall insulator proximity-coupled with a superconductor. After coupling with a superconductor, the chiral edge states of the quantum anomalous Hall insulator can still survive, making the backscattering impossible. Thus, the local Andreev reflection becomes vanishing, while the crossed Andreev reflection becomes dominant in the scattering process. This indicates that our device can serve as an extremely high-efficiency Cooper-pair splitter. Furthermore, because of the chiral characteristic, our Cooper-pair splitter is robust against disorders and can work in a wide range of system parameters. Particularly, it can still function even if the system length exceeds the superconducting coherence length. PMID:26450824

  17. Spin Hall effect on a noncommutative space

    International Nuclear Information System (INIS)

    We study the spin-orbital interaction and the spin Hall effect of an electron moving on a noncommutative space under the influence of a vector potential A(vector sign). On a noncommutative space, we find that the commutator between the vector potential A(vector sign) and the electric potential V1(r(vector sign)) of the lattice induces a new term, which can be treated as an effective electric field, and the spin Hall conductivity obtains some correction. On a noncommutative space, the spin current and spin Hall conductivity have distinct values in different directions, and depend explicitly on the noncommutative parameter. Once this spin Hall conductivity in different directions can be measured experimentally with a high level of accuracy, the data can then be used to impose bounds on the value of the space noncommutativity parameter. We have also defined a new parameter, σ=ρθ (ρ is the electron concentration, θ is the noncommutativity parameter), which can be measured experimentally. Our approach is based on the Foldy-Wouthuysen transformation, which gives a general Hamiltonian of a nonrelativistic electron moving on a noncommutative space.

  18. Improved Hall-Effect Sensors For Magnetic Memories

    Science.gov (United States)

    Wu, Jiin-Chuan; Stadler, Henry L.; Katti, Romney R.; Chen, Y. C.; Bhattacharya, Pallab K.

    1993-01-01

    High-electron-mobility sensor films deposited on superlattice buffer (strain) layers. Improved Hall-effect sensors offer combination of adequate response and high speed needed for use in micromagnet/Hall-effect random-access memories. Hall-effect material chosen for use in sensors is InAs.

  19. Orbital angular momentum driven intrinsic spin Hall effect

    OpenAIRE

    Jung, Wonsig; Go, Dongwook; Lee, Hyun-Woo; Kim, Changyoung

    2014-01-01

    We propose a mechanism of intrinsic spin Hall effect (SHE). In this mechanism, local orbital angular momentum (OAM) induces electron position shift and couples with the bias electric field to generate orbital Hall effect (OHE). SHE then emerges as a concomitant effect of OHE through the atomic spin-orbit coupling. Spin Hall conductivity due to this mechanism is estimated to be comparable to experimental values for heavy metals. This mechanism predicts the sign change of the spin Hall conducti...

  20. Parallel Hall effect from 3D single-component metamaterials

    OpenAIRE

    Kern, Christian; Kadic, Muamer; Wegener, Martin

    2015-01-01

    We propose a class of three-dimensional metamaterial architectures composed of a single doped semiconductor (e.g., n-Si) in air or vacuum that lead to unusual effective behavior of the classical Hall effect. Using an anisotropic structure, we numerically demonstrate a Hall voltage that is parallel---rather than orthogonal---to the external static magnetic-field vector ("parallel Hall effect"). The sign of this parallel Hall voltage can be determined by a structure parameter. Together with the...

  1. Intrinsic spin Hall effect in silicene: transition from spin Hall to normal insulator

    OpenAIRE

    Dyrdal, A.; Barnas, J.

    2012-01-01

    Intrinsic contribution to the spin Hall effect in a two-dimensional silicene is considered theoretically within the linear response theory and Green function formalism. When an external voltage normal to the silicene plane is applied, the spin Hall conductivity is shown to reveal a transition from the spin Hall insulator phase at low voltages to the conventional insulator phase at higher voltages. This transition resembles recently reported phase transition in a bilayer graphene. The spin-orb...

  2. Improved Readout For Micromagnet/Hall-Effect Memories

    Science.gov (United States)

    Wu, Jiin-Chuan; Stadler, Henry L.; Katti, Romney R.

    1993-01-01

    Two improved readout circuits for micromagnet/Hall-effect random-access memories designed to eliminate current shunts introducing errors into outputs of older readout circuits. Incorporate additional switching transistors to isolate Hall sensors as needed.

  3. Origin of Spin Hall Effect (Reply to Comment)

    OpenAIRE

    Chudnovsky, E. M.

    2008-01-01

    Conceptual framework behind the intrinsic spin Hall effect in three-dimensional conductors is discussed. Theory suggests how the spin Hall current should depend on symmetry and orientation of the crystal.

  4. Destruction of the Fractional Quantum Hall Effect by Disorder

    Science.gov (United States)

    Laughlin, R. B.

    1985-07-01

    It is suggested that Hall steps in the fractional quantum Hall effect are physically similar to those in the ordinary quantum Hall effect. This proposition leads to a simple scaling diagram containing a new type of fixed point, which is identified with the destruction of the fractional states by disorder. 15 refs., 3 figs.

  5. Flux State in von Neumann lattice and Fractional Hall Effect

    OpenAIRE

    Ishikawa, Kenzo; Maeda, Nobuki

    1996-01-01

    Formulation of quantum Hall dynamics using von Neumann lattice of guiding center coordinates is presented. A topological invariant expression of the Hall conductance is given and a new mean field theory of the fractional Hall effect based on flux condensation is proposed. Because our mean field Hamiltonian has the same form as Hofstadter Hamiltonian, it is possible to understand characteristic features of the fractional Hall effect from Hofstadter's spectrum. Energy gap and other physical qua...

  6. Intrinsic Spin and Orbital-Angular-Momentum Hall Effect

    OpenAIRE

    S. Zhang; Yang, Z.

    2004-01-01

    A generalized definition of intrinsic and extrinsic transport coefficients is introduced. We show that transport coefficients from the intrinsic origin are solely determined by local electronic structure, and thus the intrinsic spin Hall effect is not a transport phenomenon. The intrinsic spin Hall current is always accompanied by an equal but opposite intrinsic orbital-angular-momentum Hall current. We prove that the intrinsic spin Hall effect does not induce a spin accumulation at the edge ...

  7. Theory of Phonon Hall Effect in Paramagnetic Dielectrics

    OpenAIRE

    Sheng, L.; Sheng, D. N.; Ting, C. S.

    2006-01-01

    Based upon spin-lattice interaction, we propose a theoretical model for the phonon Hall effect in paramagnetic dielectrics. The thermal Hall conductivity is calculated by using the Kubo formula. Our theory reproduces the essential experimental features of the phonon Hall effect discovered recently in ionic dielectric Tb$_3$Ga$_5$O$_{12}$, including the sign, magnitude and linear magnetic field dependence of the thermal Hall conductivity.

  8. Hall Effect Sensors Design, Integration and Behavior Analysis

    Directory of Open Access Journals (Sweden)

    Maher Kayal

    2013-02-01

    Full Text Available The present paper focuses on various aspects regarding Hall Effect sensors’ design, integration, and behavior analysis. In order to assess their performance, different Hall Effect geometries were tested for Hall voltage, sensitivity, offset, and temperature drift. The residual offset was measured both with an automated measurement setup and by manual switching of the individual phases. To predict Hall sensors performance prior to integration, three-dimensional physical simulations were performed.

  9. Hall Effect Sensors Design, Integration and Behavior Analysis

    OpenAIRE

    Maher Kayal; Maria-Alexandra Paun; Jean-Michel Sallese

    2013-01-01

    The present paper focuses on various aspects regarding Hall Effect sensors’ design, integration, and behavior analysis. In order to assess their performance, different Hall Effect geometries were tested for Hall voltage, sensitivity, offset, and temperature drift. The residual offset was measured both with an automated measurement setup and by manual switching of the individual phases. To predict Hall sensors performance prior to integration, three-dimensional physical simulations were perfor...

  10. Physical principles underlying the quantum Hall effect

    OpenAIRE

    Bieri, Samuel; Froehlich, Juerg

    2010-01-01

    In this contribution, we present an introduction to the physical principles underlying the quantum Hall effect. The field theoretic approach to the integral and fractional effect is sketched, with some emphasis on the mechanism of electromagnetic gauge anomaly cancellation by chiral degrees of freedom living on the edge of the sample. Applications of this formalism to the design and theoretical interpretation of interference experiments are outlined.

  11. Accurate micro Hall effect measurements on scribe line pads

    DEFF Research Database (Denmark)

    Østerberg, Frederik Westergaard; Petersen, Dirch Hjorth; Wang, Fei;

    2009-01-01

    Hall mobility and sheet carrier density are important parameters to monitor in advanced semiconductor production. If micro Hall effect measurements are done on small pads in scribe lines, these parameters may be measured without using valuable test wafers. We report how Hall mobility can be extra......Hall mobility and sheet carrier density are important parameters to monitor in advanced semiconductor production. If micro Hall effect measurements are done on small pads in scribe lines, these parameters may be measured without using valuable test wafers. We report how Hall mobility can...... be extracted from micro four-point measurements performed on a rectangular pad. The dimension of the investigated pad is 400 × 430 ¿m2, and the probe pitches range from 20 ¿m to 50 ¿m. The Monte Carlo method is used to find the optimal way to perform the Hall measurement and extract Hall mobility most...

  12. Anomalous magnetic field effects on graphene

    International Nuclear Information System (INIS)

    Full text: Graphene exhibits anomalous properties in externally applied magnetic field. The orbital susceptibility of graphene has a singularity expressed as a delta function in Fermi energy EF, which diverges at Dirac point (EF =0) and vanishes otherwise. The singular diamagnetism is modified by various external factors such as the disorder potential [1], and the band gap opening [2,3], the finite-size effect [4] and the multilayer stacking [5], and studying those effects give deeper insights into the origin of the diamagnetic singularity of Dirac electron. The delta-function singularity is generally weakened by the electronic coupling between different graphene layers. In usual AB-stacked multilayer graphite, the interlayer coupling changes monlayer's linear band to quadratic, and then the susceptibility peak is broadened into a less singular logarithmic curve [5]. In a turbostratic (randomly-stacked) graphene multilayer, on the other hand, the diamagnetism generally becomes much stronger than in AB-stacked graphite, because the interlayer coupling is significantly reduced in misoriented lattice structure. There the external magnetic field is significantly screened inside the sample in low temperatures, and even a perfect screening is achieved at zero temperature in an ideal sample [4]. When the stacking angle between two graphene layers becomes as small as a few degree, the electronic structure is strongly modified by the long-period lattice structure with a Moire pattern. In increasing magnetic field, the spectrum gradually evolves into a fractal band structure called Hofstadter's butterfly, where the Hall conductivity exhibits a nonmonotonic behavior as a function of Fermi energy [6]. In finite-sized graphene system such as graphene ribbon and graphene nano-islands, the finite-size effect also changes the singular diamagnetism.[4] At T=0, the susceptibility χ(EF) oscillates between diamagnetism and paramagnetism in accordance with the subband structure formed

  13. Hall viscosity from effective field theory

    CERN Document Server

    Nicolis, Alberto

    2011-01-01

    For two-dimensional non-dissipative fluids with broken parity, we show via effective field theory methods that the infrared dynamics generically exhibit Hall viscosity--a conservative form of viscosity compatible with two-dimensional isotropy. The equality between the Hall viscosity coefficient and the ground state's intrinsic angular momentum density follows straightforwardly from their descending from the same Lagrangian term of the low-energy effective action. We show that for such fluids sound waves are not purely longitudinal, but acquire an elliptical polarization, with transverse-to-longitudinal aspect ratio proportional to frequency. Our analysis is fully relativistic, thus providing a natural description of (2+1) dimensional relativistic fluids with broken parity.

  14. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    International Nuclear Information System (INIS)

    The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE

  15. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    Energy Technology Data Exchange (ETDEWEB)

    Miao, B. F., E-mail: bfmiao@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Huang, S. Y. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Qu, D.; Chien, C. L., E-mail: clchien@jhu.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

    2016-01-15

    The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.

  16. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    Science.gov (United States)

    Miao, B. F.; Huang, S. Y.; Qu, D.; Chien, C. L.

    2016-01-01

    The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.

  17. Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG

    Directory of Open Access Journals (Sweden)

    B. F. Miao

    2016-01-01

    Full Text Available The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE, inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.

  18. Precision of single-engage micro Hall effect measurements

    DEFF Research Database (Denmark)

    Henrichsen, Henrik Hartmann; Hansen, Ole; Kjær, Daniel;

    2014-01-01

    Recently a novel microscale Hall effect measurement technique has been developed to extract sheet resistance (RS), Hall sheet carrier density (NHS) and Hall mobility (μH) from collinear micro 4-point probe measurements in the vicinity of an insulating boundary [1]. The technique measures in less...

  19. Multipole expansion in the quantum hall effect

    Science.gov (United States)

    Cappelli, Andrea; Randellini, Enrico

    2016-03-01

    The effective action for low-energy excitations of Laughlin's states is obtained by systematic expansion in inverse powers of the magnetic field. It is based on the W- infinity symmetry of quantum incompressible fluids and the associated higher-spin fields. Besides reproducing the Wen and Wen-Zee actions and the Hall viscosity, this approach further indicates that the low-energy excitations are extended objects with dipolar and multipolar moments.

  20. Generic superweak chaos induced by Hall effect

    Science.gov (United States)

    Ben-Harush, Moti; Dana, Itzhack

    2016-05-01

    We introduce and study the "kicked Hall system" (KHS), i.e., charged particles periodically kicked in the presence of uniform magnetic (B ) and electric (E ) fields that are perpendicular to each other and to the kicking direction. We show that for resonant values of B and E and in the weak-chaos regime of sufficiently small nonintegrability parameter κ (the kicking strength), there exists a generic family of periodic kicking potentials for which the Hall effect from B and E significantly suppresses the weak chaos, replacing it by "superweak" chaos (SWC). This means that the system behaves as if the kicking strength were κ2 rather than κ . For E =0 , SWC is known to be a classical fingerprint of quantum antiresonance, but it occurs under much less generic conditions, in particular only for very special kicking potentials. Manifestations of SWC are a decrease in the instability of periodic orbits and a narrowing of the chaotic layers, relative to the ordinary weak-chaos case. Also, for global SWC, taking place on an infinite "stochastic web" in phase space, the chaotic diffusion on the web is much slower than the weak-chaos one. Thus, the Hall effect can be relatively stabilizing for small κ . In some special cases, the effect is shown to cause ballistic motion for almost all parameter values. The generic global SWC on stochastic webs in the KHS appears to be the two-dimensional closest analog to the Arnol'd web in higher dimensional systems.

  1. Enhanced inverse spin-Hall voltage in (001) oriented Fe4N/Pt polycrystalline films without contribution of planar-Hall effect

    Science.gov (United States)

    Isogami, Shinji; Tsunoda, Masakiyo

    2016-04-01

    In this study, the output DC electric voltage (V out) generated by a Pt-capped Fe4N bilayer film (Fe4N/Pt) under ferromagnetic resonance conditions at room temperature was assessed. The contributions from the inverse spin-Hall effect (ISHE), the planar-Hall effect (PHE) and the anomalous-Hall effect (AHE) were separated from the output voltage by analysis of V out values determined at varying external field polar angles. The results showed that the polarity of the ISHE (V ISHE) component of V out was opposite to that of the PHE (V PHE). As a result, the magnitude of the intrinsic V ISHE was beyond V out by as much as the magnitude of V PHE. The X-ray diffraction structural analysis revealed the polycrystal of the Fe4N/Pt with (001) orientation, which might be one of the possible mechanisms for enhanced intrinsic V ISHE.

  2. Parallel Hall effect from 3D single-component metamaterials

    CERN Document Server

    Kern, Christian; Wegener, Martin

    2015-01-01

    We propose a class of three-dimensional metamaterial architectures composed of a single doped semiconductor (e.g., n-Si) in air or vacuum that lead to unusual effective behavior of the classical Hall effect. Using an anisotropic structure, we numerically demonstrate a Hall voltage that is parallel---rather than orthogonal---to the external static magnetic-field vector ("parallel Hall effect"). The sign of this parallel Hall voltage can be determined by a structure parameter. Together with the previously demonstrated positive or negative orthogonal Hall voltage, we demonstrate four different sign combinations

  3. Integer quantum Hall effect and correlated disorder

    International Nuclear Information System (INIS)

    The effect of the form of the random potential of impurities and defects on the longitudinal σxx and Hall σxy components of conductivity in the mode of the integer quantum Hall effect is theoretically investigated. It is shown that the width of the Hall conductivity plateau as well as the peak values of the longitudinal conductivity heavily depend on the ratio λ/aH between the random potential correlation length and the magnetic length. For the first time, it is established that in the case of the short-wavelength potential λ H, the peak values of σxx(N) are directly proportional to the Landau level number N ≥ 1, σxx = 0.5Ne2/h, whereas the peak values of σxx(N) are independent of the Landau level number in the case of the long-wavelength potential λ >> aH, and their magnitude is much lower than 0.5e2/h. The obtained results are in good agreement with the available experimental data

  4. Anomalous sequence of quantum Hall liquids revealing a tunable Lifshitz transition in bilayer graphene.

    Science.gov (United States)

    Varlet, Anastasia; Bischoff, Dominik; Simonet, Pauline; Watanabe, Kenji; Taniguchi, Takashi; Ihn, Thomas; Ensslin, Klaus; Mucha-Kruczyński, Marcin; Fal'ko, Vladimir I

    2014-09-12

    Bilayer graphene is a unique system where both the Fermi energy and the low-energy electron dispersion can be tuned. This is brought about by an interplay between trigonal warping and the band gap opened by a transverse electric field. Here, we drive the Lifshitz transition in bilayer graphene to experimentally controllable carrier densities by applying a large transverse electric field to a h-BN-encapsulated bilayer graphene structure. We perform magnetotransport measurements and investigate the different degeneracies in the Landau level spectrum. At low magnetic fields, the observation of filling factors -3 and -6 quantum Hall states reflects the existence of three maxima at the top of the valence-band dispersion. At high magnetic fields, all integer quantum Hall states are observed, indicating that deeper in the valence band the constant energy contours are singly connected. The fact that we observe ferromagnetic quantum Hall states at odd-integer filling factors testifies to the high quality of our sample. This enables us to identify several phase transitions between correlated quantum Hall states at intermediate magnetic fields, in agreement with the calculated evolution of the Landau level spectrum. The observed evolution of the degeneracies, therefore, reveals the presence of a Lifshitz transition in our system. PMID:25259994

  5. Anomalous Sequence of Quantum Hall Liquids Revealing a Tunable Lifshitz Transition in Bilayer Graphene

    Science.gov (United States)

    Varlet, Anastasia; Bischoff, Dominik; Simonet, Pauline; Watanabe, Kenji; Taniguchi, Takashi; Ihn, Thomas; Ensslin, Klaus; Mucha-Kruczyński, Marcin; Fal'ko, Vladimir I.

    2014-09-01

    Bilayer graphene is a unique system where both the Fermi energy and the low-energy electron dispersion can be tuned. This is brought about by an interplay between trigonal warping and the band gap opened by a transverse electric field. Here, we drive the Lifshitz transition in bilayer graphene to experimentally controllable carrier densities by applying a large transverse electric field to a h-BN-encapsulated bilayer graphene structure. We perform magnetotransport measurements and investigate the different degeneracies in the Landau level spectrum. At low magnetic fields, the observation of filling factors -3 and -6 quantum Hall states reflects the existence of three maxima at the top of the valence-band dispersion. At high magnetic fields, all integer quantum Hall states are observed, indicating that deeper in the valence band the constant energy contours are singly connected. The fact that we observe ferromagnetic quantum Hall states at odd-integer filling factors testifies to the high quality of our sample. This enables us to identify several phase transitions between correlated quantum Hall states at intermediate magnetic fields, in agreement with the calculated evolution of the Landau level spectrum. The observed evolution of the degeneracies, therefore, reveals the presence of a Lifshitz transition in our system.

  6. Composite particle and field theory in atomic quantum Hall effect

    Institute of Scientific and Technical Information of China (English)

    Zhao Bo; Chen Zeng-Bing

    2005-01-01

    In this paper, we explore the composite particle description of the atomic quantum Hall (QH) effect. We further give the Chern-Simon-Gross-Pitaevskii (CSGP) effective theory for the atomic Hall liquid, which is the counterpart of Chern-Simon theory in electron Hall effect. What we obtained is equivalent to the Laughlin wavefunction approach.Our results show that in terms of composite particles, the atomic Hall effect is really the same as the electronic QH effect. The CSGP effective theory would shed new light on the atomic QH effect.

  7. Excitons in the Fractional Quantum Hall Effect

    Science.gov (United States)

    Laughlin, R. B.

    1984-09-01

    Quasiparticles of charge 1/m in the Fractional Quantum Hall Effect form excitons, which are collective excitations physically similar to the transverse magnetoplasma oscillations of a Wigner crystal. A variational exciton wavefunction which shows explicitly that the magnetic length is effectively longer for quasiparticles than for electrons is proposed. This wavefunction is used to estimate the dispersion relation of these excitons and the matrix elements to generate them optically out of the ground state. These quantities are then used to describe a type of nonlinear conductivity which may occur in these systems when they are relatively clean.

  8. 量子霍尔效应的研究及进展%The Research and Progress of The Quantum Hall Effect

    Institute of Scientific and Technical Information of China (English)

    张琳; 米斌周

    2014-01-01

    对霍尔效应、量子霍尔效应、量子反常霍尔效应等霍尔效应家族一系列成员进行了介绍,并给出了各效应的应用或应用前景,首次综述了霍尔效应家族的发展史。%A series of the Hall Effect family ,such as Hall Effect , Quantum Hall Effect, Quantum Anomalous Hall Effect and so on, are introduced.The effect of application or application prospect for the series of Hall Effect are given.The development history of Hall Effect family is reviewed for the first time.

  9. Hall effect of Ce(Ru1−xFex)2Al10 single crystal

    International Nuclear Information System (INIS)

    The Hall resistivity ρH has been measured between 2 K and 300 K for pseudoternary compounds Ce(Ru1−xFex)2Al10 (x=0.375, 0.625, 1) single crystals up to 7 T. The ρH shows linear dependence against magnetic field except low temperatures. We calculated Hall coefficient RH by the gradient of ρH under the field between 5 T and 7 T, where the anomalous Hall effect expected to be small. While RH for CeRu2Al10 drastically increases below mysterious antiferromagnetic ordering temperature (T0 ∼ 27 K), RH decreases by replacing Ru with Fe. The RH becomes negative at lowest temperatures for x = 0.375, x = 0.625 and x = 1. The reversal of the sign suggests that Ce(Ru1−xFex)2Al10 is in a multicarrier system.

  10. Integer quantum Hall effect and related phenomena

    International Nuclear Information System (INIS)

    Experimental and theoretical research on the integer quantum Hall effect is reviewed, together with other transport phenomena in a two-dimensional electron gas in a quantizing magnetic field. Particular emphasis is placed on primary experimental data, on the comparison of experimental and theoretical results, and on the analysis of theoretical predictions from the point of view of their experimental verification. Among experiments conducted in recent years, those that have raised questions to be resolved are highlighted. Possible directions of further research are suggested. (reviews of topical problems)

  11. Faster Hall-Effect Current-Measuring Circuit

    Science.gov (United States)

    Sullender, Craig C.; Johnson, Daniel D.; Walker, Daniel D.

    1993-01-01

    Current-measuring circuit operates on Hall-effect-sensing and magnetic-field-nulling principles similar to those described in article, "Nulling Hall-Effect Current-Measuring Circuit" (LEW-15023), but simpler and responds faster. Designed without feedback loop, and analog pulse-width-modulated output indicates measured current. Circuit measures current at frequency higher than bandwidth of its Hall-effect sensor.

  12. Commemorative Symposium on the Hall Effect and its Applications

    CERN Document Server

    Westgate, C

    1980-01-01

    In 1879, while a graduate student under Henry Rowland at the Physics Department of The Johns Hopkins University, Edwin Herbert Hall discovered what is now universally known as the Hall effect. A symposium was held at The Johns Hopkins University on November 13, 1979 to commemorate the lOOth anniversary of the discovery. Over 170 participants attended the symposium which included eleven in­ vited lectures and three speeches during the luncheon. During the past one hundred years, we have witnessed ever ex­ panding activities in the field of the Hall effect. The Hall effect is now an indispensable tool in the studies of many branches of condensed matter physics, especially in metals, semiconductors, and magnetic solids. Various components (over 200 million!) that utilize the Hall effect have been successfully incorporated into such devices as keyboards, automobile ignitions, gaussmeters, and satellites. This volume attempts to capture the important aspects of the Hall effect and its applications. It includes t...

  13. Unified description of intrinsic spin-Hall effect mechanisms

    International Nuclear Information System (INIS)

    The intrinsic spin-Hall effects (SHEs) in p-doped semiconductors (Murakami et al Science 301 1348) and two-dimensional electron gases with Rashba spin-orbit coupling (Sinova et al 2004 Phys. Rev. Lett. 92 126603) have been the subject of many theoretical studies, but their driving mechanisms have yet to be described in a unified manner. The former effect arises from the adiabatic topological curvature of momentum space, from which holes acquire a spin-dependent anomalous velocity. The SHE in Rashba systems, on the other hand, results from momentum-dependent spin dynamics in the presence of an external electric field. Our motivation in this paper is to address the disparity between the two mechanisms and, in particular, to clarify whether there is any underlying link between the two effects. In this endeavor, we consider the explicit time dependence of SHE systems starting with a general spin-orbit model in the presence of an electric field. We find that by performing a gauge transformation of the general model with respect to time, a well-defined gauge field appears in time space which has the physical significance of an effective magnetic field. This magnetic field is shown to precisely account for the SHE in the Rashba system in the adiabatic limit. Remarkably, by applying the same limit to the equations of motion of the general model, this magnetic field is also found to be the underlying origin of the anomalous velocity due to the momentum-space curvature. Thus, our study unifies the two seemingly disparate intrinsic SHEs under a common adiabatic framework.

  14. The quantum Hall effect branches out

    International Nuclear Information System (INIS)

    It is surprising when five theoretical papers all concerned with a single experimental result appear in the same journal. It is perhaps even more surprising when the topic is the quantum Hall effect - a phenomenon that is now over two decades old and has already yielded two Nobel prizes. The great excitement stems from the fact that this experiment and the new theories elegantly intertwine the quantum Hall effect with ferromagnetism, Bose condensation, superfluidity and the Josephson effect. Last year our group at the California Institute of Technology teamed up with Loren Pfeiffer and Ken West of Bell Labs to study how electrons tunnel between two parallel 2-D electron gases. These electrons reside in a semiconductor heterostructure consisting of two thin layers of gallium arsenide separated by a barrier layer of aluminium gallium arsenide. Surprisingly, we observed a huge enhancement in the tunnelling current when just the right magnetic field was applied perpendicular to the 2-D planes in which the electrons were confined (I B Spielman et al. 2000 Phys. Rev. Lett. 84 5808). In the June issue of Physics World, James P Eisenstein of the California Institute of Technology, USA, describes the experiment and explains where it may lead. (U.K.)

  15. Anomalous electrical resistivity and Hall constant of Anderson lattice with finite f-band width

    CERN Document Server

    Panwar, S S

    2002-01-01

    We study here an extension of the periodic Anderson model by considering finite f-band width. A variational method is used to study the temperature dependence of electronic transport properties of Anderson lattice for different values of the f-band width. The electrical resistivity rho(T) and Hall constant R sub H (T) calculated show qualitatively the features experimentally observed in heavy fermion materials. We find that as f-band width increases, the low temperature peak in rho(T) disappears, while the low-temperature peak in R sub H (T) becomes sharper. (author)

  16. Anomalous electrical resistivity and Hall constant of Anderson lattice with finite f-band width

    International Nuclear Information System (INIS)

    We study here an extension of the periodic Anderson model by considering finite f-band width. A variational method is used to study the temperature dependence of electronic transport properties of Anderson lattice for different values of the f-band width. The electrical resistivity ρ(T) and Hall constant RH(T) calculated show qualitatively the features experimentally observed in heavy fermion materials. We find that as f-band width increases, the low temperature peak in ρ(T) disappears, while the low-temperature peak in RH(T) becomes sharper. (author)

  17. Estimates of Quantities in a Hall Effect Geodynamo Theory

    Directory of Open Access Journals (Sweden)

    Annraoi M de Paor

    2008-01-01

    Full Text Available Currents, resistances, dynamo constant, Hall voltage coefficient and inductances are estimated for the author’s geodynamo theory incorporating the Hall Effect. It is concluded that the Hall Coefficient in the bulk liquid core of the Earth is approximately 1.512x10-1, orders of magnitude greater than in normal liquid metals. The ordering effect of enormous pressure is a possible cause.

  18. Hybrid Spin Noise Spectroscopy and the Spin Hall Effect

    OpenAIRE

    Slipko, V. A.; Sinitsyn, N. A.; Pershin, Y. V.

    2013-01-01

    Here we suggest a novel hybrid spin noise spectroscopy technique, which is sensitive to the spin Hall effect. It is shown that, while the standard spin-spin correlation function is not sensitive to the spin Hall effect, spin-transverse voltage and transverse voltage-voltage correlation functions provide the missing sensitivity being linear and quadratic in the spin Hall coefficient, respectively. The correlation between transverse voltage and spin fluctuations appears as a result of spin-char...

  19. Mesoscopic Hall effect driven by chiral spin order

    OpenAIRE

    Ohe, Jun-ichiro; Ohtsuki, Tomi; Kramer, Bernhard

    2006-01-01

    A Hall effect due to spin chirality in mesoscopic systems is predicted. We consider a 4-terminal Hall system including local spins with geometry of a vortex domain wall, where strong spin chirality appears near the center of vortex. The Fermi energy of the conduction electrons is assumed to be comparable to the exchange coupling energy where the adiabatic approximation ceases to be valid. Our results show a Hall effect where a voltage drop and a spin current arise in the transverse direction....

  20. Estimates of Quantities in a Hall Effect Geodynamo Theory

    OpenAIRE

    Annraoi M de Paor

    2008-01-01

    Currents, resistances, dynamo constant, Hall voltage coefficient and inductances are estimated for the author’s geodynamo theory incorporating the Hall Effect. It is concluded that the Hall Coefficient in the bulk liquid core of the Earth is approximately 1.512x10-1, orders of magnitude greater than in normal liquid metals. The ordering effect of enormous pressure is a possible cause.

  1. Inverse Spin Hall Effect Driven by Spin Motive Force

    OpenAIRE

    Shibata, Junya; Kohno, Hiroshi

    2008-01-01

    The spin Hall effect is a phenomenon that an electric field induces a spin Hall current. In this Letter, we examine the inverse effect that, in a ferromagnetic conductor, a charge Hall current is induced by a spin motive force, or a spin-dependent effective ` electric' field ${\\bm E}_{\\rm s}$, arising from the time variation of magnetization texture. By considering skew-scattering and side-jump processes due to spin-orbit interaction at impurities, we obtain the Hall current density as $\\sigm...

  2. Inertial-Hall effect: the influence of rotation on the Hall conductivity

    Directory of Open Access Journals (Sweden)

    Julio E. Brandão

    2015-01-01

    Full Text Available Inertial effects play an important role in classical mechanics but have been largely overlooked in quantum mechanics. Nevertheless, the analogy between inertial forces on mass particles and electromagnetic forces on charged particles is not new. In this paper, we consider a rotating non-interacting planar two-dimensional electron gas with a perpendicular uniform magnetic field and investigate the effects of the rotation in the Hall conductivity. The rotation introduces a shift and a split in the Landau levels. As a consequence of the break of the degeneracy, the counting of the states fully occupied below the Fermi energy increases, tuning the Hall quantization steps. The rotation also changes the quantum Hall plateau widths. Additionally, we find the Hall quantization steps as a function of rotation at a fixed value of the magnetic field.

  3. Quantum Hall fluctuations and evidence for charging in the quantum Hall effect

    OpenAIRE

    Cobden, David H.; Barnes, C H W; Ford, C. J. B.

    1999-01-01

    We find that mesoscopic conductance fluctuations in the quantum Hall regime in silicon MOSFETs display simple and striking patterns. The fluctuations fall into distinct groups which move along lines parallel to loci of integer filling factor in the gate voltage-magnetic field plane. Also, a relationship appears between the fluctuations on quantum Hall transitions and those found at low densities in zero magnetic field. These phenomena are most naturally attributed to charging effects. We argu...

  4. Compensation on Hall effect sensor of PWM switching control

    International Nuclear Information System (INIS)

    In this paper, it mainly investigates the relationship between switching frequency and measured currents of Hall effect sensor. How to effectively measure the current waveforms to improve the PWM switching control performance is the main subject of concern. A compensation circuit is designed to enlarge the operational range of Hall effect sensor, and the measurement error can be reduced without additional temperature sensor

  5. Avalanche breakdown of the quantum hall effects

    CERN Document Server

    Komiyama, S

    1999-01-01

    Heat stability of two-dimensional electron gas (2DEG) systems in the integer quantum hall effect (IQHE) regime is discussed, and a heat instability is suggested to be the intrinsic mechanism behind the breakdown of the IQHE. Phenomenological argument is provided to suggest that the 2DEG system in the IQHE state becomes thermally unstable when the Hall electric field E sub y reaches a threshold value E sub b. Above E sub b , excited nonequilibrium electrons (holes), which are initially present in the conductor as the temperature fluctuation, are accelerated by E sub y and the 2DEG thereby undergoes a transition to a warm dissipative state. The critical field, E sub b , of this abrupt transition is theoretically estimated and shown to be in fare agreement with experimentally reported values. Consideration of the dynamics of electrons suggests that the transition is a process of avalanche electron-hole pair multiplication, in which a small number of non-equilibrium carriers, gains kinetic energy within a Landau ...

  6. Topological insulator in junction with ferromagnets: quantum Hall effects

    OpenAIRE

    Chudnovskiy, A. L.; Kagalovsky, V.

    2014-01-01

    The ferromagnet-topological insulator-ferromagnet (FM-TI-FM) junction exhibits thermal and electrical quantum Hall effects. The generated Hall voltage and transverse temperature gradient can be controlled by the directions of magnetizations in the FM leads, which inspires the use of FM-TI-FM junctions as electrical and as heat switches in spintronic devices. Thermal and electrical Hall coefficients are calculated as functions of the magnetization directions in ferromagnets and the spin-relaxa...

  7. Supersymmetric Quantum Hall Effect on Fuzzy Supersphere

    OpenAIRE

    Hasebe, Kazuki

    2004-01-01

    Supersymmetric quantum Hall liquids are constructed on a supersphere in a supermonopole background. We derive a supersymmetric generalization of the Laughlin wavefunction, which is a ground state of a hard-core $OSp(1|2)$ invariant Hamiltonian. We also present excited topological objects, which are fractionally charged deficits made by super Hall currents. Several relations between quantum Hall systems and their supersymmetric extensions are discussed.

  8. Anomalous Interlayer Transport of Quantum Hall Bilayers in the Strongly Josephson-Coupled Regime

    Science.gov (United States)

    Zhang, Ding; Dietsche, Werner; von Klitzing, Klaus

    2016-05-01

    We investigate Josephson coupling in a closely spaced quantum Hall bilayer. Reduction of the interlayer barrier from the widely used values of 10-12 nm to the present one of 8 nm leads to qualitatively different interlayer transport properties. The breakdown of interlayer coherence can be spatially confined in regions that are smaller than the device size. Such a spatial inhomogeneity depends crucially on the Josephson-coupling strength and can be removed by adding an in-plane magnetic field of about 0.5 T. At higher in-plane fields, the interlayer tunneling I -V curve develops unexpected overshoot features. These results challenge current theoretical understanding and suggest that our bilayer system has entered a previously unexplored regime.

  9. Hall effect in a moving liquid

    International Nuclear Information System (INIS)

    A simple experiment, suitable for performing in an undergraduate physics laboratory, illustrates electromagnetic induction through the water entering into a cylindrical rubber tube by detecting the voltage developed across the tube in the direction transverse both to the flow velocity and to the magnetic field. The apparatus is a very simple example of an electromagnetic flowmeter, a device which is commonly used both in industrial and physiological techniques. The phenomenology observed is similar to that of the Hall effect in the absence of an electric current in the direction of motion of the carriers. The experimental results show a dependence on the intensity of the magnetic field and on the carrier velocity, in good agreement with the theory. Discussion of the system, based on classical electromagnetism, indicates that the effect depends only on the flow rate, and is independent both of the velocity profile and of the electrical conductivity of the medium.

  10. Planar Hall Effect Sensors for Biodetection

    DEFF Research Database (Denmark)

    Rizzi, Giovanni

    -of-care devices can effectively reduce the time for the analysis and the costs that are related to a delay in the diagnosis. Many technologies are available for biosensing devices. In this work, we study and employ magnetic biosensing on magnetoresistive sensors. For magnetic biodetection magnetic beads are used...... as labels and planar Hall effect bridge (PHEB) magnetic field sensor as readout for the beads. The choice of magnetic beads as label is motivated by the lack of virtually any magnetic background from biological samples. Moreover, magnetic beads can be manipulated via an external magnetic field...... and be employed for sample preparation in a lab-on-a-chip device. The PHEB sensors are formed by four magnetoresistive arms in a Wheatstone bridge geometry. In this thesis two different sensor geometries are used. In the first geometry (PHEB), the magnetic bead signals from the sensor arms are additive...

  11. Gauge Physics of Spin Hall Effect

    Science.gov (United States)

    Tan, Seng Ghee; Jalil, Mansoor B. A.; Ho, Cong Son; Siu, Zhuobin; Murakami, Shuichi

    2015-12-01

    Spin Hall effect (SHE) has been discussed in the context of Kubo formulation, geometric physics, spin orbit force, and numerous semi-classical treatments. It can be confusing if the different pictures have partial or overlapping claims of contribution to the SHE. In this article, we present a gauge-theoretic, time-momentum elucidation, which provides a general SHE equation of motion, that unifies under one theoretical framework, all contributions of SHE conductivity due to the kinetic, the spin orbit force (Yang-Mills), and the geometric (Murakami-Fujita) effects. Our work puts right an ambiguity surrounding previously partial treatments involving the Kubo, semiclassical, Berry curvatures, or the spin orbit force. Our full treatment shows the Rashba 2DEG SHE conductivity to be instead of -, and Rashba heavy hole instead of -. This renewed treatment suggests a need to re-derive and re-calculate previously studied SHE conductivity.

  12. Photonic spin Hall effect for precision metrology

    CERN Document Server

    Zhou, Xinxing; Liu, Yachao; Luo, Hailu; Wen, Shuangchun

    2014-01-01

    The photonic spin Hall effect (SHE) is generally believed to be a result of an effective spin-orbit coupling, which describes the mutual influence of the spin (polarization) and the trajectory of the light beam. The photonic SHE holds great potential for precision metrology owing to the fact that the spin-dependent splitting in photonic SHE are sensitive to the physical parameter variations of different systems. Remarkably, using the weak measurements, this tiny spin-dependent shifts can be detected with the desirable accuracy so that the corresponding physical parameters can be determined. Here, we will review some of our works on using photonic SHE for precision metrology, such as measuring the thickness of nanometal film, identifying the graphene layers, detecting the strength of axion coupling in topological insulators, and determining the magneto-optical constant of magnetic film.

  13. Hall-Effect Thruster Utilizing Bismuth as Propellant

    Science.gov (United States)

    Szabo, James; Gasdaska, Charles; Hruby, Vlad; Robin, Mike

    2008-01-01

    A laboratory-model Hall-effect spacecraft thruster was developed that utilizes bismuth as the propellant. Xenon was used in most prior Hall-effect thrusters. Bismuth is an attractive alternative because it has a larger atomic mass, a larger electron-impact-ionization cross-section, and is cheaper and more plentiful.

  14. Skyrmions in the Quantum Hall effect and noncommutative solitons

    OpenAIRE

    Pasquier, V.

    2000-01-01

    It has been recently shown that solitons are fundamental classical solutions of non-commutative field theories. We reconsider this issue from the standpoint of the Hall effect and identify some solutions with known solutions in the integer Hall effect with no Zeeman coupling.

  15. Bulk Versus Edge in the Quantum Hall Effect

    OpenAIRE

    Kao, Y. -C.; Lee, D. -H.

    1996-01-01

    The manifestation of the bulk quantum Hall effect on edge is the chiral anomaly. The chiral anomaly {\\it is} the underlying principle of the ``edge approach'' of quantum Hall effect. In that approach, $\\sxy$ should not be taken as the conductance derived from the space-local current-current correlation function of the pure one-dimensional edge problem.

  16. QUANTUM HALL EFFECT OF HARD-CORE BOSONS

    OpenAIRE

    Jain, J. K.; Rao, Sumathi

    1995-01-01

    Motivated by a mean-field approach, which has been employed for anyon superfluidity and the fractional quantum Hall effect, the quantum Hall effect (QHE) of hard-core bosons is investigated. It is shown that QHE is possible {\\em only} in the thermodynamic limit. The filling factors where QHE may be expected are obtained with the help of two adiabatic schemes.

  17. Useful Pedagogical Applications of the Classical Hall Effect

    Science.gov (United States)

    Houari, Ahmed

    2007-01-01

    One of the most known phenomena in physics is the Hall effect. This is mainly due to its simplicity and to the wide range of its theoretical and practical applications. To complete the pedagogical utility of the Hall effect in physics teaching, I will apply it here to determine the Faraday constant as a fundamental physical number and the number…

  18. Mesoscopic spin Hall effect in semiconductor nanostructures

    Science.gov (United States)

    Zarbo, Liviu

    The spin Hall effect (SHE) is a name given to a collection of diverse phenomena which share two principal features: (i) longitudinal electric current flowing through a paramagnetic semiconductor or metallic sample leads to transverse spin current and spin accumulation of opposite sign at opposing lateral edges; (ii) SHE does not require externally applied magnetic field or magnetic ordering in the equilibrium state of the sample, instead it relies on the presence of spin-orbit (SO) couplings within the sample. This thesis elaborates on a new type of phenomenon within the SHE family, predicted in our recent studies [Phys. Rev. B 72, 075361 (2005); Phys. Rev. Lett. 95, 046601 (2005); Phys. Rev. B 72, 075335 (2005); Phys. Rev. B 73 , 075303 (2006); and Europhys. Lett. 77, 47004 (2007)], where pure spin current flows through the transverse electrodes attached to a clean finitesize two-dimensional electron gas (2DEG) due to unpolarized charge current injected through its longitudinal leads. If transverse leads are removed, the effect manifests as nonequilibrium spin Hall accumulation at the lateral edges of 2DEG wires. The SO coupling driving this SHE effect is of the Rashba type, which arises due to structural inversion asymmetry of semiconductor heterostructure hosting the 2DEG. We term the effect "mesoscopic" because the spin Hall currents and accumulations reach optimal value in samples of the size of the spin precession length---the distance over which the spin of an electron precesses by an angle pi. In strongly SO-coupled structures this scale is of the order of ˜100 nm, and, therefore, mesoscopic in the sense of being much larger than the characteristic microscopic scales (such as the Fermi wavelength, screening length, or the mean free path in disordered systems), but still much smaller than the macroscopic ones. Although the first theoretical proposal for SHE, driven by asymmetry in SO-dependent scattering of spin-up and spin-down electrons off impurities

  19. Magnetic circuit for hall effect plasma accelerator

    Science.gov (United States)

    Manzella, David H. (Inventor); Jacobson, David T. (Inventor); Jankovsky, Robert S. (Inventor); Hofer, Richard (Inventor); Peterson, Peter (Inventor)

    2009-01-01

    A Hall effect plasma accelerator includes inner and outer electromagnets, circumferentially surrounding the inner electromagnet along a thruster centerline axis and separated therefrom, inner and outer magnetic conductors, in physical connection with their respective inner and outer electromagnets, with the inner magnetic conductor having a mostly circular shape and the outer magnetic conductor having a mostly annular shape, a discharge chamber, located between the inner and outer magnetic conductors, a magnetically conducting back plate, in magnetic contact with the inner and outer magnetic conductors, and a combined anode electrode/gaseous propellant distributor, located at a bottom portion of the discharge chamber. The inner and outer electromagnets, the inner and outer magnetic conductors and the magnetically conducting back plate form a magnetic circuit that produces a magnetic field that is largely axial and radially symmetric with respect to the thruster centerline.

  20. Scaling of the anomalous Hall effect in the insulating regime

    Czech Academy of Sciences Publication Activity Database

    Liu, X.-J.; Liu, X.; Sinova, Jairo

    2011-01-01

    Roč. 84, č. 16 (2011), 165304/1-165304/11. ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : disordred-systems * impurity conduction * percolation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011 http://link.aps.org/doi/10.1103/PhysRevB.84.165304

  1. Formulation of the Relativistic Quantum Hall Effect and "Parity Anomaly"

    CERN Document Server

    Yonaga, Kouki; Shibata, Naokazu

    2016-01-01

    We present a relativistic formulation of the quantum Hall effect on a Riemann sphere. An explicit form of the pseudopotential is derived for the relativistic quantum Hall effect with/without mass term.We clarify particular features of the relativistic quantum Hall states with use of the exact diagonalization study of the pseudopotential Hamiltonian. Physical effects of the mass term to relativistic quantum Hall states are investigated in detail.The mass term acts as an interporating parameter between the relativistic and non-relativistic quantum Hall effects. It is pointed out that the mass term inequivalently affects to many-body physics of the positive and negative Landau levels and brings instability of the Laughlin state of the positive first relativistic Landau level as a consequence of the "parity anomaly".

  2. Fast micro Hall effect measurements on small pads

    DEFF Research Database (Denmark)

    Østerberg, Frederik Westergaard; Petersen, Dirch Hjorth; Nielsen, Peter F.;

    2011-01-01

    square onto the infinite half-plane, where well-established solutions are known. Hall effect measurements are performed to show, experimentally, that it is possible to measure Hall mobility in less than one minute on squares as small as 7070 lm2 with a deviation of 66.5% on a 1r level from accurate...

  3. Quantum Theory of Conducting Matter Superconductivity and Quantum Hall Effect

    CERN Document Server

    Fujita, Shigeji; Godoy, Salvador

    2009-01-01

    Explains major superconducting properties including zero resistance, Meissner effect, sharp phase change, flux quantization, excitation energy gap, and Josephson effects using quantum statistical mechanical calculations. This book covers the 2D superconductivity and the quantum Hall effects

  4. Topological insulator in junction with ferromagnets: Quantum Hall effects

    Energy Technology Data Exchange (ETDEWEB)

    Chudnovskiy, A.L. [Institut für Theoretische Physik, Universität Hamburg, Jungiusstr 9, D-20355 Hamburg (Germany); Kagalovsky, V., E-mail: victork@sce.ac.il [Shamoon College of Engineering, Basel/Bialik Sts, Beer-Sheva 84100 (Israel)

    2015-06-01

    The ferromagnet–topological insulator–ferromagnet (FM–TI–FM) junction exhibits thermal and electrical quantum Hall effects. The generated Hall voltage and transverse temperature gradient can be controlled by the directions of magnetizations in the FM leads, which inspires the use of FM–TI–FM junctions as electrical and as heat switches in spintronic devices. Thermal and electrical Hall coefficients are calculated as functions of the magnetization directions in ferromagnets and the spin-relaxation time in TI. Both the Hall voltage and the transverse temperature gradient decrease but are not completely suppressed even at very short spin-relaxation times. The Hall coefficients turn out to be independent of the spin-relaxation time for symmetric configuration of FM leads. - Highlights: • We consider topological insulator (TI) in junction with two ferromagnets (FM). • FM–TI–FM junction exhibits both electrical and thermal quantum Hall effect (QHE). • The Hall resistances can be tuned by magnetization direction in ferromagnets. • The Hall coefficients are independent of magnetic disorder for a symmetric junction.

  5. Dissipationless spin-Hall current contribution in the extrinsic spin-Hall effect

    Institute of Scientific and Technical Information of China (English)

    Yan Yu-Zhen; Li Hui-Wu; Hu Liang-Bin

    2009-01-01

    This paper shows that a substantial amount of dissipationless spin-Hall current contribution may exist in the extrinsic spin-Hall effect, which originates from the spin-orbit coupling induced by the applied external electric field itself that drives the extrinsic spin-Hall effect in a nonmagnetic semiconductor (or metal). By assuming that the impurity density is in a moderate range such that the total scattering potential due to all randomly distributed impurities is a smooth function of the space coordinate, it is shown that this dissipationless contribution shall be of the same orders of magnitude as the usual extrinsic contribution from spin-orbit dependent impurity scatterings (or may even be larger than the latter one). The theoretical results obtained are in good agreement with recent relevant experimental results.

  6. Generic Superweak Chaos Induced by Hall Effect

    OpenAIRE

    Ben-Harush, Moti; Dana, Itzhack

    2016-01-01

    We introduce and study the "kicked Hall system" (KHS), i.e., charged particles periodically kicked in the presence of uniform magnetic ($\\mathbf{B}$) and electric ($\\mathbf{E}$) fields that are perpendicular to each other and to the kicking direction. We show that for resonant values of $B$ and $E$ and in the weak-chaos regime of sufficiently small nonintegrability parameter $\\kappa$ (the kicking strength), there exists a \\emph{generic} family of periodic kicking potentials for which the Hall...

  7. Piezo Voltage Controlled Planar Hall Effect Devices

    OpenAIRE

    Bao Zhang; Kang-Kang Meng; Mei-Yin Yang; Edmonds, K. W.; Hao Zhang; Kai-Ming Cai; Yu Sheng; Nan Zhang; Yang Ji; Jian-Hua Zhao; Hou-Zhi Zheng; Kai-You Wang

    2016-01-01

    The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the pie...

  8. Unconventional quantum Hall effect in Floquet topological insulators.

    Science.gov (United States)

    Tahir, M; Vasilopoulos, P; Schwingenschlögl, U

    2016-09-28

    We study an unconventional quantum Hall effect for the surface states of ultrathin Floquet topological insulators in a perpendicular magnetic field. The resulting band structure is modified by photon dressing and the topological property is governed by the low-energy dynamics of a single surface. An exchange of symmetric and antisymmetric surface states occurs by reversing the light's polarization. We find a novel quantum Hall state in which the zeroth Landau level undergoes a phase transition from a trivial insulator state, with Hall conductivity [Formula: see text] at zero Fermi energy, to a Hall insulator state with [Formula: see text]. These findings open new possibilities for experimentally realizing nontrivial quantum states and unusual quantum Hall plateaus at [Formula: see text]. PMID:27460419

  9. Topological insulator in junction with ferromagnets: Quantum Hall effects

    Science.gov (United States)

    Chudnovskiy, A. L.; Kagalovsky, V.

    2015-06-01

    The ferromagnet-topological insulator-ferromagnet (FM-TI-FM) junction exhibits thermal and electrical quantum Hall effects. The generated Hall voltage and transverse temperature gradient can be controlled by the directions of magnetizations in the FM leads, which inspires the use of FM-TI-FM junctions as electrical and as heat switches in spintronic devices. Thermal and electrical Hall coefficients are calculated as functions of the magnetization directions in ferromagnets and the spin-relaxation time in TI. Both the Hall voltage and the transverse temperature gradient decrease but are not completely suppressed even at very short spin-relaxation times. The Hall coefficients turn out to be independent of the spin-relaxation time for symmetric configuration of FM leads.

  10. Observation of the inverse spin Hall effect in silicon

    OpenAIRE

    Ando, Kazuya; Saitoh, Eiji

    2011-01-01

    The spin–orbit interaction in a solid couples the spin of an electron to its momentum. This coupling gives rise to mutual conversion between spin and charge currents: the direct and inverse spin Hall effects. The spin Hall effects have been observed in metals and semiconductors. However, the spin/charge conversion has not been realized in one of the most fundamental semiconductors, silicon, where accessing the spin Hall effects has been believed to be difficult because of its very weak spin–o...

  11. Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect

    International Nuclear Information System (INIS)

    We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (Js) in the FePt|Y3Fe5O12 (YIG) structure, and Js was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt

  12. Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect

    Energy Technology Data Exchange (ETDEWEB)

    Seki, Takeshi, E-mail: go-sai@imr.tohoku.ac.jp; Takanashi, Koki [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Uchida, Ken-ichi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency, Saitama 332-0012 (Japan); Kikkawa, Takashi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Qiu, Zhiyong [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577 (Japan); Saitoh, Eiji [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577 (Japan); Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195 (Japan)

    2015-08-31

    We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (J{sub s}) in the FePt|Y{sub 3}Fe{sub 5}O{sub 12} (YIG) structure, and J{sub s} was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt.

  13. The current-voltage characteristics of Corbino disk in the quantum Hall effect regime

    International Nuclear Information System (INIS)

    Discussed are the details of the current-voltage curve (IVC) of 2D Corbino disk with uniform density of mobile carriers within the quantum Hall effect plateau. It is demonstrated that diffusion, among other reasons, can be responsible for variety of observed IVCs. Anomalous role of diffusion in formation of Corbino disk IVC is determined not only by the problem dimensionality but also by the ''quality'' of density of states of the magnetized 2D conducting system. The diffusion hypothesis is advanced to specific results allowing to explain the difference between IVCs presented in Figs. 1 and 2.

  14. Hall effect across the quantum phase transition of CeCu6-xAux

    International Nuclear Information System (INIS)

    While CeCu6 is a Pauli-paramagnetic heavy-fermion (HF) system, Au doping introduces long-range incommensurate antiferromagnetism for x>xc∼0.1. At the critical concentration xc, the system experiences a quantum phase transition (QPT). Here, both unusual magnetic fluctuations, studied by inelastic neutron scattering, and non-Fermi-liquid behavior, i.e. to anomalous low-temperature thermodynamic and transport properties have been observed. We report on Hall effect measurements that probe the electronic structure of heavy fermions across the critical concentration xc of the QPT

  15. Anomalous Wien Effects in Supercooled Ionic Liquids

    Science.gov (United States)

    Patro, L. N.; Burghaus, O.; Roling, B.

    2016-05-01

    We have measured conductivity spectra of several supercooled monocationic and dicationic ionic liquids in the nonlinear regime by applying ac electric fields with large amplitudes up to about 180 kV /cm . Thereby, higher harmonic ac currents up to the 7th order were detected. Our results point to the existence of anomalous Wien effects in supercooled ionic liquids. Most ionic liquids studied here exhibit a conductivity-viscosity relation, which is close to the predictions of the Nernst-Einstein and Stokes-Einstein equations, as observed for classical strong electrolytes like KCl. These "strong" ionic liquids show a much stronger nonlinearity of the conductivity than classical strong electrolytes. On the other hand, the conductivity-viscosity relation of the ionic liquid [P6 ,6 ,6 ,14][Cl ] points to ion association effects. This "weak" ionic liquid shows a strength of the nonlinear effect, which is comparable to classical weak electrolytes. However, the nonlinearity increases quadratically with the field. We suggest that a theory for explaining these anomalies will have to go beyond the level of Coulomb lattice gas models.

  16. Anomalous Wien Effects in Supercooled Ionic Liquids.

    Science.gov (United States)

    Patro, L N; Burghaus, O; Roling, B

    2016-05-01

    We have measured conductivity spectra of several supercooled monocationic and dicationic ionic liquids in the nonlinear regime by applying ac electric fields with large amplitudes up to about 180  kV/cm. Thereby, higher harmonic ac currents up to the 7th order were detected. Our results point to the existence of anomalous Wien effects in supercooled ionic liquids. Most ionic liquids studied here exhibit a conductivity-viscosity relation, which is close to the predictions of the Nernst-Einstein and Stokes-Einstein equations, as observed for classical strong electrolytes like KCl. These "strong" ionic liquids show a much stronger nonlinearity of the conductivity than classical strong electrolytes. On the other hand, the conductivity-viscosity relation of the ionic liquid [P_{6,6,6,14}][Cl] points to ion association effects. This "weak" ionic liquid shows a strength of the nonlinear effect, which is comparable to classical weak electrolytes. However, the nonlinearity increases quadratically with the field. We suggest that a theory for explaining these anomalies will have to go beyond the level of Coulomb lattice gas models. PMID:27203333

  17. Overlooked Contribution to the Hall Effect in Ferromagnetic Metals

    OpenAIRE

    Hirsch, J. E.

    1999-01-01

    It is pointed out that in ferromagnetic metals a contribution to the Hall voltage arises when a non-zero spin current exists, which is generally the case in the presence of a charge current. This contribution is independent of any scattering effects and exists down to zero temperature. The sign of the resulting Hall coefficient may be either equal or opposite to the one of the ordinary Hall coefficient depending on the band filling. This effect seems to have been left out in previous analyses...

  18. Hall Effect and Magneto Optical MFL Sensing

    Science.gov (United States)

    Jallouli, Wissem

    The need for a reliable sensing tool has stimulated countless researchers to develop techniques trying to extract maximum information. In the field of nondestructive testing (NDT), various sensors have been established to fulfill that function. Examples include the ultrasonic, eddy current, and magnetic flux leakage (MFL) based techniques. Because they are extremely reliable, MFL based techniques represent one of the best inspection technologies. These technologies have numerous applications in diverse domains, including petroleum pipeline and tank inspections, airplane inspections, and production quality control. In this work, we will present two technologies based on MFL technique. The first is the Hall Effect sensor. This device has been extensively developed during the last century, especially after the use of integrated circuit technology. Its reliable results even under extreme conditions made it an extremely useful tool. The second technology is Magneto Optical Imaging. This technique rose very recently, and scientists hold high expectations about its performance once proper techniques are developed. The study of these two sensing devices gives a better understanding of the MFL technique by allowing us to investigate the potential of each technology, experience each in studied conditions to derive its characteristics, and discuss its performance.

  19. SUSY Quantum Hall Effect on Non-Anti-Commutative Geometry

    Directory of Open Access Journals (Sweden)

    Kazuki Hasebe

    2008-02-01

    Full Text Available We review the recent developments of the SUSY quantum Hall effect [hep-th/0409230, hep-th/0411137, hep-th/0503162, hep-th/0606007, arXiv:0705.4527]. We introduce a SUSY formulation of the quantum Hall effect on supermanifolds. On each of supersphere and superplane, we investigate SUSY Landau problem and explicitly construct SUSY extensions of Laughlin wavefunction and topological excitations. The non-anti-commutative geometry naturally emerges in the lowest Landau level and brings particular physics to the SUSY quantum Hall effect. It is shown that SUSY provides a unified picture of the original Laughlin and Moore-Read states. Based on the charge-flux duality, we also develop a Chern-Simons effective field theory for the SUSY quantum Hall effect.

  20. A non-invasive Hall current distribution measurement system for Hall Effect thrusters

    Science.gov (United States)

    Mullins, Carl Raymond

    A direct, accurate method to measure thrust produced by a Hall Effect thruster on orbit does not currently exist. The ability to calculate produced thrust will enable timely and precise maneuvering of spacecraft---a capability particularly important to satellite formation flying. The means to determine thrust directly is achievable by remotely measuring the magnetic field of the thruster and solving the inverse magnetostatic problem for the Hall current density distribution. For this thesis, the magnetic field was measured by employing an array of eight tunneling magnetoresistive (TMR) sensors capable of milligauss sensitivity when placed in a high background field. The array was positioned outside the channel of a 1.5 kW Colorado State University Hall thruster equipped with a center-mounted electride cathode. In this location, the static magnetic field is approximately 30 Gauss, which is within the linear operating range of the TMR sensors. Furthermore, the induced field at this distance is greater than tens of milligauss, which is within the sensitivity range of the TMR sensors. Due to the nature of the inverse problem, the induced-field measurements do not provide the Hall current density by a simple inversion; however, a Tikhonov regularization of the induced field along with a non-negativity constraint and a zero boundary condition provides current density distributions. Our system measures the sensor outputs at 2 MHz allowing the determination of the Hall current density distribution as a function of time. These data are shown in contour plots in sequential frames. The measured ratios between the average Hall current and the discharge current ranged from 0.1 to 10 over a range of operating conditions from 1.3 kW to 2.2 kW. The temporal inverse solution at 2.0 kW exhibited a breathing mode of 37 kHz, which was in agreement with temporal measurements of the discharge current.

  1. Anomalous Nernst Effect with Magnetocrystalline Anisotropy (110)

    Science.gov (United States)

    Chesman, Carlos; Costa Neto, Jose; Department of Physics-UFRN Team

    2014-03-01

    When a ferromagnetic material is submitted to a temperature gradient and the magnetic field generates voltage on the edges of the samples, this is called the Anomalous Nernst Effect (ANE). The Heusler alloys that currently exhibit this effect are the most promising for spintronics and spin caloritronics. In this study we perform a theoretical investigation of voltage curves associated to the ANE, when the material displays magnetocrystalline anisotropy for experimental results in two configurations, ANE versus applied magnetic field and planar angle variations of ANE. We analyzed three types of magnetocrystalline anisotropy: cubic anisotropy (100) with C4 symmetry, uniaxial anisotropy with C2 symmetry and cubic anisotropy (110). The aim was to prove that cubic anisotropy (110) is equivalent to anisotropy (100) combined with uniaxial anisotropy. Theoretical fitting of experimental ANE data demonstrates this total equivalence and that a new interpretation with the use of cubic anisotropy (110) may be due to the atomic arrangement of the so-called full-Heusler. Comparative analyses of Co2FeAl and Co2MnGe alloys will be presented. CNPq, CAPES, FAPERN.

  2. Synchronization of spin-transfer torque oscillators by spin pumping, inverse spin Hall, and spin Hall effects

    International Nuclear Information System (INIS)

    We have proposed a method to synchronize multiple spin-transfer torque oscillators based on spin pumping, inverse spin Hall, and spin Hall effects. The proposed oscillator system consists of a series of nano-magnets in junction with a normal metal with high spin-orbit coupling, and an accumulative feedback loop. We conduct simulations to demonstrate the effect of modulated charge currents in the normal metal due to spin pumping from each nano-magnet. We show that the interplay between the spin Hall effect and inverse spin Hall effect results in synchronization of the nano-magnets

  3. Nobel Prize in physics 1985: Quantum Hall effect

    International Nuclear Information System (INIS)

    The conditions (like very strong magnetic fields, ultralow temperatures, and occurrence of a two-dimensional electron gas in microelectronic structures) for the measurement of the quantum Hall effect are explained. Two possible measuring methods are described. Measuring results for p-Si-MOSFET, GaAs/AlGaAs heterojuntions and grain boundaries in InSb crystals are reported. Differences between normal (integer) and fractional quantum Hall effect are discussed. One of the important consequences is that by means of the quantum Hall effect the value h/e2 can be determined with very high accuracy. In 1985 Klaus von Klitzing was awarded the Nobel Prize for his work on the quantum Hall effect

  4. The quantum spin Hall effect and topological insulators

    OpenAIRE

    Qi, Xiao-Liang; Zhang, Shou-Cheng

    2010-01-01

    Comment: 7 pages, 5 figures, an introduction of the quantum spin Hall effect and topological insulators. For a video introduction of topological insulators, see http://www.youtube.com/watch?v=Qg8Yu-Ju3Vw

  5. Enigmatic 12/5 fractional quantum Hall effect

    Science.gov (United States)

    Pakrouski, Kiryl; Troyer, Matthias; Wu, Yang-Le; Das Sarma, Sankar; Peterson, Michael R.

    2016-08-01

    We numerically study the fractional quantum Hall effect at filling factors ν =12 /5 and 13/5 (the particle-hole conjugate of 12/5) in high-quality two-dimensional GaAs heterostructures via exact diagonalization including finite well width and Landau-level mixing. We find that Landau-level mixing suppresses the ν =13 /5 fractional quantum Hall effect relative to ν =12 /5 . By contrast, we find both ν =2 /5 and (its particle-hole conjugate) ν =3 /5 fractional quantum Hall effects in the lowest Landau level to be robust under Landau-level mixing and finite well-width corrections. Our results provide a possible explanation for the experimental absence of the 13/5 fractional quantum Hall state as caused by Landau-level mixing effects.

  6. The Hall effect in ballistic junctions

    Science.gov (United States)

    Ford, C. J. B.; Washburn, S.; Büttiker, M.; Knoedler, C. M.; Hong, J. M.

    1990-04-01

    In narrow high-mobility conductors the predominant source of scattering is reflection of carriers off the confining potential. We demonstrate that by changing the geometry of the intersection of the Hall probes with the conductor, the Hall resistance can be quenched, negative or enhanced. More complex junction geometries can lead to one of these phenomena for one field polarity and to another for the other field polarity. At liquid helium temperatures these results can be explained by following trajectories. In the milli-Kelvin range fluctuations are superimposed. At high fields strong resonant depressions of the Hall resistance are found which may be associated with bound states in the region of the cross.

  7. The stability of protostellar disks with Hall effect and buoyancy

    OpenAIRE

    Urpin, V.; Rüdiger, G.

    2003-01-01

    The stability properties of inviscid protostellar disks are examined taking into account the Hall effect and buoyancy. Depending on the parameters, different types of instabilities can exist in different regions of disks. In a very low ionized region, the instability associated with baroclinic effects of buoyancy is likely most efficient. The Hall-driven shear instability can lead to destabilization of regions with a higher ionization. The magnetorotational instability modified by buoyancy ca...

  8. Nulling Hall-Effect Current-Measuring Circuit

    Science.gov (United States)

    Sullender, Craig C.; Vazquez, Juan M.; Berru, Robert I.

    1993-01-01

    Circuit measures electrical current via combination of Hall-effect-sensing and magnetic-field-nulling techniques. Known current generated by feedback circuit adjusted until it causes cancellation or near cancellation of magnetic field produced in toroidal ferrite core by current measured. Remaining magnetic field measured by Hall-effect sensor. Circuit puts out analog signal and digital signal proportional to current measured. Accuracy of measurement does not depend on linearity of sensing components.

  9. The Quantum Hall Effect: Novel Excitations and Broken Symmetries

    OpenAIRE

    Girvin, Steven M.

    1999-01-01

    These pedagogical lecture notes present a general introduction to most aspects of the integer and fractional quantum Hall effects. This is followed by an extensive discussion of quantum Hall ferromagnetism, both for spins in single-layer systems and `pseudospins' in double-layer systems. The effective field theories describing various broken symmetry states and `skyrmion' and `meron' spin textures are derived and discussed in some detail. Pedagogical presentations on Berry phases and lowest L...

  10. Inter-Edge interaction in the Quantum Hall Effect

    OpenAIRE

    Oreg, Yuval; Finkel'stein, Alexander M.

    1995-01-01

    We consider effects of the interaction between electrons drifting along the opposite sides of a narrow sample under the conditions of the quantum Hall effect. A spatial variation of this interaction leads to backward scattering of collective excitations propagating along the edges. Experiments on propagation of the edge modes in samples with constrictions may give information about the strength of the inter-edge electron interaction in the quantum Hall regime.

  11. Hall-Petch effect: Another manifestation of size effect

    Science.gov (United States)

    Li, Yuan; Dunstan, David; Bushby, Andy

    In the 1950s, Hall and Petch first established a quantitative relationship, expressed by the famous Hall-Petch equation: σd =σ0 +kHP/√{ d} There is a very large body of experimental data in the literature reinforcing this dependence in a very wide range of metals. Recently, we presented some of the classic data sets which have been considered to confirm the Hall-Petch equation and showed they are equally well consistent with the equation ɛel (d) =ɛ0 +kln/(d) d Eq. 2 is based on critical thickness theory. Fitting to Eq.1 with the exponent 0.5 replaced by the free fitting parameter x, the confidence interval for the exponent is 0.5 Hall-Petch dependence of the strength on grain size, if it obeys Eq.2, is another manifestation of the size effect.

  12. Hall effect studies in YBCO films

    International Nuclear Information System (INIS)

    The longitudinal, ρxx(T), transverse, ρxy(T), and Hall, ρH(T) resistivities have been measured for YBa2Cu3Ox (YBCO) films, showing positive resistivity buckling and those with usual linear ρxx(T) dependence. In the former case unexpected peak on ρxy(T) and unusual ρH(T) dependence with double sign change just above transition temperature Tc have been revealed. The data are analyzed using recent theory for the sign of the Hall conductivity in strongly correlated systems

  13. Is the quantum Hall effect influenced by the gravitational field?

    Science.gov (United States)

    Hehl, Friedrich W; Obukhov, Yuri N; Rosenow, Bernd

    2004-08-27

    Most of the experiments on the quantum Hall effect (QHE) were made at approximately the same height above sea level. A future international comparison will determine whether the gravitational field g(x) influences the QHE. In the realm of (1+2)-dimensional phenomenological macroscopic electrodynamics, the Ohm-Hall law is metric independent ("topological"). This suggests that it does not couple to g(x). We corroborate this result by a microscopic calculation of the Hall conductance in the presence of a post-Newtonian gravitational field. PMID:15447125

  14. Hall effect in CNT doped YBCO high temperature superconductor

    Directory of Open Access Journals (Sweden)

    S Dadras

    2010-09-01

    Full Text Available In order to study Hall effect in pure and CNT doped YBCO polycrystalline samples, we have measured longitudinal and transverse voltages at the different magnetic field (0-9T in the vortex state. We found a sign reversal for pure sample near 3T and double sign reversal of the Hall coefficient for CNT doped sample near 3 and 5T. It can be deduced that CNT doping caused strong flux pinning and Hall double sign reversal in this compound.

  15. Azimuthal Spoke Propagation in Hall Effect Thrusters

    Science.gov (United States)

    Sekerak, Michael J.; Longmier, Benjamin W.; Gallimore, Alec D.; Brown, Daniel L.; Hofer, Richard R.; Polk, James E.

    2013-01-01

    Spokes are azimuthally propagating perturbations in the plasma discharge of Hall Effect Thrusters (HETs) that travel in the E x B direction and have been observed in many different systems. The propagation of azimuthal spokes are investigated in a 6 kW HET known as the H6 using ultra-fast imaging and azimuthally spaced probes. A spoke surface is a 2-D plot of azimuthal light intensity evolution over time calculated from 87,500 frames/s videos. The spoke velocity has been determined using three methods with similar results: manual fitting of diagonal lines on the spoke surface, linear cross-correlation between azimuthal locations and an approximated dispersion relation. The spoke velocity for three discharge voltages (300, 400 and 450 V) and three anode mass flow rates (14.7, 19.5 and 25.2 mg/s) yielded spoke velocities between 1500 and 2200 m/s across a range of normalized magnetic field settings. The spoke velocity was inversely dependent on magnetic field strength for low B-field settings and asymptoted at B-field higher values. The velocities and frequencies are compared to standard drifts and plasma waves such as E x B drift, electrostatic ion cyclotron, magnetosonic and various drift waves. The empirically approximated dispersion relation yielded a characteristic velocity that matched the ion acoustic speed for 5 eV electrons that exist in the near-anode and near-field plume regions of the discharge channel based on internal measurements. Thruster performance has been linked to operating mode where thrust-to-power is maximized when azimuthal spokes are present so investigating the underlying mechanism of spokes will benefit thruster operation.

  16. Mode Transitions in Hall Effect Thrusters

    Science.gov (United States)

    Sekerak, Michael J.; Longmier, Benjamin W.; Gallimore, Alec D.; Brown, Daniel L.; Hofer, Richard R.; Polk, James E.

    2013-01-01

    Mode transitions have been commonly observed in Hall Effect Thruster (HET) operation where a small change in a thruster operating parameter such as discharge voltage, magnetic field or mass flow rate causes the thruster discharge current mean value and oscillation amplitude to increase significantly. Mode transitions in a 6-kW-class HET called the H6 are induced by varying the magnetic field intensity while holding all other operating parameters constant and measurements are acquired with ion saturation probes and ultra-fast imaging. Global and local oscillation modes are identified. In the global mode, the entire discharge channel oscillates in unison and azimuthal perturbations (spokes) are either absent or negligible. Downstream azimuthally spaced probes show no signal delay between each other and are very well correlated to the discharge current signal. In the local mode, signals from the azimuthally spaced probes exhibit a clear delay indicating the passage of "spokes" and are not well correlated to the discharge current. These spokes are localized oscillations propagating in the ExB direction that are typically 10-20% of the mean value. In contrast, the oscillations in the global mode can be 100% of the mean value. The transition between global and local modes occurs at higher relative magnetic field strengths for higher mass flow rates or higher discharge voltages. The thrust is constant through mode transition but the thrust-to-power decreased by 25% due to increasing discharge current. The plume shows significant differences between modes with the global mode significantly brighter in the channel and the near-field plasma plume as well as exhibiting a luminous spike on thruster centerline. Mode transitions provide valuable insight to thruster operation and suggest improved methods for thruster performance characterization.

  17. A heuristic quantum theory of the integer quantum Hall effect

    OpenAIRE

    Kramer, Tobias

    2005-01-01

    Contrary to common belief, the current emitted by a contact embedded in a two-dimensional electron gas (2DEG) is quantized in the presence of electric and magnetic fields. This observation suggests a simple, clearly defined model for the quantum current through a Hall device that does not invoke disorder or interactions as the cause of the integer quantum Hall effect (QHE), but is based on a proper quantization of the classical electron drift motion. The theory yields a quantitative descripti...

  18. Hall effect in the extremely large magnetoresistance semimetal WTe$_2$

    OpenAIRE

    Luo, Yongkang; Li, H.; Dai, Y. M.; Miao, H; Shi, Y. G.; H. Ding; Taylor, A. J.; Yarotski, D. A.; Prasankumar, R. P.; Thompson, J. D.

    2015-01-01

    We systematically measured the Hall effect in the extremely large magnetoresistance semimetal WTe$_2$. By carefully fitting the Hall resistivity to a two-band model, the temperature dependencies of the carrier density and mobility for both electron- and hole-type carriers were determined. We observed a sudden increase of the hole density below $\\sim$160~K, which is likely associated with the temperature-induced Lifshitz transition reported by a previous photoemission study. In addition, a mor...

  19. First-principles evaluation of intrinsic, side-jump, and skew-scattering parts of anomalous Hall conductivities in disordered alloys

    OpenAIRE

    Hyodo, K; Kota, Y; Sakuma, A.

    2016-01-01

    We develop a first-principles procedure for the individual evaluation of the intrinsic, side-jump, and skew-scattering contributions to the anomalous Hall conductivity ${\\sigma}_{xy}$. This method is based on the different microscopic conductive processes of each origin of ${\\sigma}_{xy}$ in the Kubo-Streda formula. We also present an approach for implementing this scheme in the tight-binding linear muffin-tin orbital (TB-LMTO) method with the coherent potential approximation (CPA). The valid...

  20. Magnetohydrodynamic simulations of Gamble I POS with Hall effect

    International Nuclear Information System (INIS)

    Two dimensional single fluid magnetohydrodynamic simulations have been conducted to investigate the effects of the Hall electric field on magnetic field transport in plasma opening switches of the type used on Gamble I. The Hall terms were included in the magnetic field transport equation in the two dimensional simulation code MACH2 through the use of a generalized Ohm's law. Calculations show the Hall terms augment the field transport previously observed to occur through ion fluid motion and diffusion. For modest values of microturbulent collision frequency, board current channels were observed . Results also show the magnetic field transport to be affected by the cathode boundary conditions with the Hall terms included. In all cases center of mass motion was slight

  1. Frequency doubling and memory effects in the Spin Hall Effect

    OpenAIRE

    Pershin, Yu. V.; Di Ventra, M.

    2008-01-01

    We predict that when an alternating voltage is applied to a semiconducting system with inhomogeneous electron density in the direction perpendicular to main current flow, the spin Hall effect results in a transverse voltage containing a double-frequency component. We also demonstrate that there is a phase shift between applied and transverse voltage oscillations, related to the general memristive behavior of semiconductor spintronic systems. A different method to achieve frequency doubling ba...

  2. Spin Seebeck Effect vs. Anomalous Nernst Effect in Ta/CoFeB /Ta Structures

    Science.gov (United States)

    Yang, Bowen; Xu, Yadong; Schneider, Mike; Shi, Jing; Univ of California-Riverside Team; Everspin Technologies Inc. Team

    2014-03-01

    We have studied the spin Seebeck effect (SSE) and anomalous Nernst effect (ANE) in a vertical trilayer structure under a vertical temperature gradient. The structure consists of a 3nm CoFeB layer sandwiched by β-phase tantalum (Ta) layers. The samples are deposited by magnetron sputtering. The existence of Ta β-phase is verified by the resistivity and its negative temperature coefficient of resistance(TCR). Under a fixed vertical temperature gradient, the measured transverse thermoelectric voltage is linearly proportional to the total sample resistance when the Ta thickness exceeds 2 nm, which can be explained by a shunting resistor model. When the Ta thickness is below 2 nm, the voltage deviates from the linear resistance dependence and merges to the ANE voltage of the CoFeB single layer, due to a weakened inverse spin Hall effect (ISHE) in Ta thinner than the spin diffusion length. In the linear regime, the slope contains both a varying SSE and a fixed ANE responses, thus the SSE contribution could be quantitatively separated out from the ANE of CoFeB. Our results indicate a large SSE from the β-phase Ta due to its large Spin Hall Angle. This work was supported by CNN/DMEA and DOE.

  3. The quantum Hall's effect:A quantum electrodynamic phenomenon

    Institute of Scientific and Technical Information of China (English)

    A.I. Arbab

    2012-01-01

    We have applied Maxwell's equations to study the physics of quantum Hall's effect.The electromagnetic properties of this system are obtained.The Hall's voltage,VH =2πh2ns/e rn,where ns is the electron number density,for a 2-dimensional system,and h =2πh is the Planck's constant,is found to coincide with the voltage drop across the quantum capacitor.Consideration of the cyclotronic motion of electrons is found to give rise to Hall's resistance.Ohmic resistances in the horizontal and vertical directions have been found to exist before equilibrium state is reached.At a fundamental level,the Hall's effect is found to be equivalent to a resonant LCR circuit with LH =2π m/e2ns and CH =me2/2πh2ns satisfying the resonance condition with resonant frequency equal to the inverse of the scattering (relaxation) time,Ts.The Hall's resistance is found to be RH =√LH/CH.The Hall's resistance may be connected with the impedance that the electron wave experiences when it propagates in the 2-dimeasional gas.

  4. A classical picture of anomalous effects in a Tokamak

    Science.gov (United States)

    Hirano, K.

    1984-01-01

    Atomic collisions between plasma ions and a very small amount of neutral particles remaining in a hot plasma plays a very important role for plasma transports and may be an origin of anomalous effects observed in a Tokamak such as the diffusion coefficient independent of the field strength, a rapid plasma density increase during gas puffing and current penetration with anomalously high speed in the start-up phase. The Ohm's law derived by Cowling is used for the analysis.

  5. Crossover between spin swapping and Hall effect in disordered systems

    KAUST Repository

    Saidaoui, Hamed Ben Mohamed

    2015-07-16

    We theoretically study the crossover between spin Hall effect and spin swapping, a recently predicted phenomenon that consists of the interchange between the current flow and its spin polarization directions [M. B. Lifshits and M. I. Dyakonov, Phys. Rev. Lett. 103, 186601 (2009)]. Using a tight-binding model with spin-orbit coupled disorder, spin Hall effect, spin relaxation, and spin swapping are treated on equal footing. We demonstrate that spin swapping and spin Hall effect present very different dependencies as a function of the spin-orbit coupling and disorder strengths and confirm that the former exceeds the latter in the parameter range considered. Three setups are proposed for the experimental observation of the spin swapping effect.

  6. Spin Hall magnetoresistance induced by a nonequilibrium proximity effect.

    Science.gov (United States)

    Nakayama, H; Althammer, M; Chen, Y-T; Uchida, K; Kajiwara, Y; Kikuchi, D; Ohtani, T; Geprägs, S; Opel, M; Takahashi, S; Gross, R; Bauer, G E W; Goennenwein, S T B; Saitoh, E

    2013-05-17

    We report anisotropic magnetoresistance in Pt|Y(3)Fe(5)O(12) bilayers. In spite of Y(3)Fe(5)O(12) being a very good electrical insulator, the resistance of the Pt layer reflects its magnetization direction. The effect persists even when a Cu layer is inserted between Pt and Y(3)Fe(5)O(12), excluding the contribution of induced equilibrium magnetization at the interface. Instead, we show that the effect originates from concerted actions of the direct and inverse spin Hall effects and therefore call it "spin Hall magnetoresistance." PMID:25167435

  7. Composed planar Hall effect sensors with dual-mode operation

    Directory of Open Access Journals (Sweden)

    Vladislav Mor

    2016-02-01

    Full Text Available We present a composed planar Hall effect sensor with two modes of operation: (a an ON mode where the composed sensor responds to magnetic field excitations similarly to the response of a regular planar Hall effect sensor, and (b an OFF mode where the response is negligible. The composed planar Hall effect sensor switches from the OFF mode to the ON mode when it is exposed to a magnetic field which exceeds a certain threshold determined by the sensor design. The features of this sensor make it useful as a switch triggered by magnetic field and as a sensing device with memory, as its mode of operation indicates exposure to a magnetic field larger than a certain threshold without the need to be activated during the exposure itself.

  8. Micro-four-point Probe Hall effect Measurement method

    DEFF Research Database (Denmark)

    Petersen, Dirch Hjorth; Hansen, Ole; Lin, Rong;

    2008-01-01

    barriers and with a magnetic field applied normal to the plane of the sheet. Based on this potential, analytical expressions for the measured four-point resistance in presence of a magnetic field are derived for several simple sample geometries. We show how the sheet resistance and Hall effect...... contributions may be separated using dual configuration measurements. The method differs from conventional van der Pauw measurements since the probe pins are placed in the interior of the sample region, not just on the perimeter. We experimentally verify the method by micro-four-point probe measurements on......We report a new microscale Hall effect measurement method for characterization of semiconductor thin films without need for conventional Hall effect geometries and metal contact pads. We derive the electrostatic potential resulting from current flow in a conductive filamentary sheet with insulating...

  9. Diaphragm Effect of Steel Space Roof Systems in Hall Structures

    Directory of Open Access Journals (Sweden)

    Mehmet FENKLİ

    2015-09-01

    Full Text Available Hall structures have been used widely for different purposes. They have are reinforced concrete frames and shear wall with steel space roof systems. Earthquake response of hall structures is different from building type structures. One of the most critical nodes is diaphragm effect of steel space roof on earthquake response of hall structures. Diaphragm effect is depending on lateral stiffness capacity of steel space roof system. Lateral stiffness of steel space roof system is related to modulation geometry, support conditions, selected sections and system geometry. In current paper, three representative models which are commonly used in Turkey were taken in to account for investigation. Results of numerical tests were present comparatively

  10. Thermal Hall Effect of Spin Excitations in a Kagome Magnet.

    Science.gov (United States)

    Hirschberger, Max; Chisnell, Robin; Lee, Young S; Ong, N P

    2015-09-01

    At low temperatures, the thermal conductivity of spin excitations in a magnetic insulator can exceed that of phonons. However, because they are charge neutral, the spin waves are not expected to display a thermal Hall effect. However, in the kagome lattice, theory predicts that the Berry curvature leads to a thermal Hall conductivity κ(xy). Here we report observation of a large κ(xy) in the kagome magnet Cu(1-3, bdc) which orders magnetically at 1.8 K. The observed κ(xy) undergoes a remarkable sign reversal with changes in temperature or magnetic field, associated with sign alternation of the Chern flux between magnon bands. The close correlation between κ(xy) and κ(xx) firmly precludes a phonon origin for the thermal Hall effect. PMID:26382691

  11. Microwave Hall effect measurements on biological and organic semiconductors

    International Nuclear Information System (INIS)

    Microwave Hall effect measurements have been performed by improved 10 GHz bimodal cavity resonators with hybrid end walls used to avoid the background signal that obscures the measurements on low mobility materials. Hall mobility results on copper phthalocyanines CuPc and other organic semiconductors, in the range of 8 cm2/V s to 60 cm2/V s, provide evidence of acoustic phonon scattering as the dominant conduction mechanism. Presently, the microwave Hall effect seems to represent the only means available for quantitative measurements on biological substances like DNA and proteins, which yield mobility values lower than 10 cm2/V s, and are therefore consistent with conduction mechanism involving hopping of charge carriers between localized energy sites

  12. The quantum Hall effect in quantum dot systems

    International Nuclear Information System (INIS)

    It is proposed to use quantum dots in order to increase the temperatures suitable for observation of the integer quantum Hall effect. A simple estimation using Fock-Darwin spectrum of a quantum dot shows that good part of carriers localized in quantum dots generate the intervals of plateaus robust against elevated temperatures. Numerical calculations employing local trigonometric basis and highly efficient kernel polynomial method adopted for computing the Hall conductivity reveal that quantum dots may enhance peak temperature for the effect by an order of magnitude, possibly above 77 K. Requirements to potentials, quality and arrangement of the quantum dots essential for practical realization of such enhancement are indicated. Comparison of our theoretical results with the quantum Hall measurements in InAs quantum dot systems from two experimental groups is also given

  13. The quantum Hall effect as an electrical resistance standard

    International Nuclear Information System (INIS)

    The quantum Hall effect (QHE) provides an invariant reference for resistance linked to natural constants. It is used worldwide to maintain and compare the unit of resistance. The reproducibility reached today is almost two orders of magnitude better than the uncertainty of the determination of the ohm in the international system of units SI. In this article, mainly the aspects of the QHE relevant for its metrological application are reviewed. After a short introduction of the theoretical models describing the integer QHE, the properties of the devices used in metrology and the measurement techniques are described. A detailed summary is given on the measurements carried out to demonstrate the universality of the quantized Hall resistance and to assess all the effects leading to deviations of the Hall resistance from the quantized value. In addition, the present and future role of the QHE in the SI and the field of natural constants is discussed. (author)

  14. Hall viscosity and momentum transport in lattice and continuum models of the integer quantum Hall effect in strong magnetic fields

    Science.gov (United States)

    Tuegel, Thomas I.; Hughes, Taylor L.

    2015-10-01

    The Hall viscosity describes a nondissipative response to strain in systems with broken time-reversal symmetry. We develop a method for computing the Hall viscosity of lattice systems in strong magnetic fields based on momentum transport, which we compare to the method of momentum polarization used by Tu et al. [Phys. Rev. B 88, 195412 (2013), 10.1103/PhysRevB.88.195412] and Zaletel et al. [Phys. Rev. Lett. 110, 236801 (2013), 10.1103/PhysRevLett.110.236801] for noninteracting systems. We compare the Hall viscosity of square-lattice tight-binding models in magnetic field to the continuum integer quantum Hall effect (IQHE) showing agreement when the magnetic length is much larger than the lattice constant, but deviation as the magnetic field strength increases. We also relate the Hall viscosity of relativistic electrons in magnetic field (the Dirac IQHE) to the conventional IQHE. The Hall viscosity of the lattice Dirac model in magnetic field agrees with the continuum Dirac Hall viscosity when the magnetic length is much larger than the lattice constant. We also show that the Hall viscosity of the lattice model deviates further from the continuum model if the C4 symmetry of the square lattice is broken to C2, but the deviation is again minimized as the magnetic length increases.

  15. Anomalous radiation effects on oxide material surface

    International Nuclear Information System (INIS)

    Various different kind of radiation influence on surface properties, in particular, adsorptive, was revealed and at some cases the general observation regularity of the radiation adsorption is upset. So, the hydrogen photo-adsorption is not observed on silicon dioxide and on some other oxides. At the same time hydrogen adsorption takes place at the same oxides irradiation by more power nuclear particles, such as gamma-rays, protons of high energies, alpha-particles, neutrons, high-velocity electrons, and also at a X-ray irradiation. At the same time oxygen adsorption takes place on the majority of the studied oxides. So it is possible to conclude that at the irradiated adsorbents the formation of electronic centers is general regularity. The radiation adsorption of oxygen is well studied on many systems and its regularities are established on numerous experiments. On an example of such oxide systems, as silicon dioxide, oxides of rare-earth elements, beryllium oxide, aluminum oxide, the zeolites we have studied a general regularity of the oxygen and hydrogen radiation adsorption, i.e. their electron-hole properties at irradiation by protons with energy 30 MeV, alpha-particles and ions of helium-3 with energy 40 and 50 MeV, gamma-rays and ultra-violet-radiation, and also neutrons from the nuclear reactor. Parallel with adsorptive properties of oxides their paramagnetic properties and thermal desorption characteristics in a wide range of temperatures were studied. The received data have allowed to find the dependence of paramagnetic centers from adsorptive centers. It was established that the adsorptive centers do not always coincide with paramagnetic ones and vise versa. It was established that the anomalous effects in a radiation adsorption at irradiation of the oxide rare-earth elements on of scandium, lanthanum, erbium and dysprosium oxides are observed. It was found out that radiation adsorption of hydrogen is absent on oxides of a lanthanum, erbium and

  16. Planar Hall effect sensor with magnetostatic compensation layer

    DEFF Research Database (Denmark)

    Dalslet, Bjarke Thomas; Donolato, Marco; Hansen, Mikkel Fougt

    2012-01-01

    Demagnetization effects in cross-shaped planar Hall effect sensors cause inhomogeneous film magnetization and a hysteretic sensor response. Furthermore, when using sensors for detection of magnetic beads, the magnetostatic field from the sensor edges attracts and holds magnetic beads near the...

  17. Depletion effect of oxide semiconductor analyzed by Hall effects.

    Science.gov (United States)

    Oh, Teresa

    2014-12-01

    This letter discusses the tunneling behavior of amorphous indium-gallium-zinc-oxide (a-IGZO) analyzed through the observation of its Hall effects. The properties of the a-IGZO changed from those of a majority carrier to those of a minority carrier after the annealing process as a result of the electron-hole recombination due to the thermal activation energy and the formation of a depletion layer with a high-potential Schottky barrier. Therefore, the diffusion current of these minority charge carriers caused ambipolar transfer characteristics, a tunneling behavior, in the metal-oxide semiconductor (MOS) transistor. PMID:25971008

  18. Band Collapse and the Quantum Hall Effect in Graphene

    Energy Technology Data Exchange (ETDEWEB)

    Bernevig, B.Andrei; Hughes, Taylor L.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.; Chen, Han-Dong; /Illinois U., Urbana; Wu, Congjun; /Santa Barbara, KITP

    2010-03-16

    The recent Quantum Hall experiments in graphene have confirmed the theoretically well-understood picture of the quantum Hall (QH) conductance in fermion systems with continuum Dirac spectrum. In this paper we take into account the lattice, and perform an exact diagonalization of the Landau problem on the hexagonal lattice. At very large magnetic fields the Dirac argument fails completely and the Hall conductance, given by the number of edge states present in the gaps of the spectrum, is dominated by lattice effects. As the field is lowered, the experimentally observed situation is recovered through a phenomenon which we call band collapse. As a corollary, for low magnetic field, graphene will exhibit two qualitatively different QHE's: at low filling, the QHE will be dominated by the 'relativistic' Dirac spectrum and the Hall conductance will be odd-integer; above a certain filling, the QHE will be dominated by a non-relativistic spectrum, and the Hall conductance will span all integers, even and odd.

  19. High-Resolution ac Measurements of the Hall Effect in Organic Field-Effect Transistors

    Science.gov (United States)

    Chen, Y.; Yi, H. T.; Podzorov, V.

    2016-03-01

    We describe a high resolving power technique for Hall-effect measurements, efficient in determining Hall mobility and carrier density in organic field-effect transistors and other low-mobility systems. We utilize a small low-frequency ac magnetic field (BrmsHall voltage, with the necessary corrections for Faraday induction. This method significantly enhances the signal-to-noise ratio and eliminates the necessity of using high magnetic fields in Hall-effect studies. With the help of this method, we are able to obtain the Hall mobility and carrier density in organic transistors with a mobility as low as μ ˜0.3 cm2 V-1 s-1 by using a compact desktop apparatus and low magnetic fields. We find a good agreement between Hall-effect and electric-field-effect measurements, indicating that, contrary to the common belief, certain organic semiconductors with mobilities below 1 cm2 V-1 s-1 can still exhibit a fully developed, band-semiconductor-like Hall effect, with the Hall mobility and carrier density matching those obtained in longitudinal transistor measurements. This suggests that, even when μ Hall-effect studies in a wide range of low-mobility materials and devices, where it is typically very difficult to resolve the Hall effect even in very high dc magnetic fields.

  20. A Simulation Study of Hall Effect on Double Tearing Modes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chenglong; MA Zhiwei; DONG Jiaqi

    2008-01-01

    A Hall magnetohydrodynamics (MHD) simulation is carried out to study the dy-namic process of double tearing mode. The results indicated that the growth rates in the earlier nonlinear and transition phases agree with the previous results. With further development of reconnection, the current sheet thickness is much smaller than the ion inertia length, which leads to a strong influence of the Hall effects. As a result, the reconnection in the late nonlinear phase exhibits an explosive nature with a time scale nearly independent of resistivity. A localized and severely intensified current density is observed and the maximum kinetic energy is over one order of magnitude higher in Hall MHD than that in resistive MHD.

  1. The Quantum Hall Effect in Supersymmetric Chern-Simons Theories

    CERN Document Server

    Tong, David

    2015-01-01

    In d=2+1 dimensions, there exist gauge theories which are supersymmetric but non-relativistic. We solve the simplest U(1) gauge theory in this class and show that the low-energy physics is that of the fractional quantum Hall effect, with ground states given by the Laughlin wavefunctions. We do this by quantising the vortices and relating them to the quantum Hall matrix model. We further construct coherent state representations of the excitations of vortices. These are quasi-holes. By an explicit computation of the Berry phase, without resorting to a plasma analogy, we show that these excitations have fractional charge and spin.

  2. Inverse spin Hall effect in Pt/(Ga,Mn)As

    Energy Technology Data Exchange (ETDEWEB)

    Nakayama, H. [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Chen, L. [WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Chang, H. W. [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Department of Physics and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Ohno, H.; Matsukura, F., E-mail: f-matsu@wpi-aimr.tohoku.ac.jp [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2015-06-01

    We investigate dc voltages under ferromagnetic resonance in a Pt/(Ga,Mn)As bilayer structure. A part of the observed dc voltage is shown to originate from the inverse spin Hall effect. The sign of the inverse spin Hall voltage is the same as that in Py/Pt bilayer structure, even though the stacking order of ferromagnetic and nonmagnetic layers is opposite to each other. The spin mixing conductance at the Pt/(Ga,Mn)As interface is determined to be of the order of 10{sup 19 }m{sup −2}, which is about ten times greater than that of (Ga,Mn)As/p-GaAs.

  3. Inverse spin Hall effect in Pt/(Ga,Mn)As

    International Nuclear Information System (INIS)

    We investigate dc voltages under ferromagnetic resonance in a Pt/(Ga,Mn)As bilayer structure. A part of the observed dc voltage is shown to originate from the inverse spin Hall effect. The sign of the inverse spin Hall voltage is the same as that in Py/Pt bilayer structure, even though the stacking order of ferromagnetic and nonmagnetic layers is opposite to each other. The spin mixing conductance at the Pt/(Ga,Mn)As interface is determined to be of the order of 1019 m−2, which is about ten times greater than that of (Ga,Mn)As/p-GaAs

  4. Hall effect of La2/3(Ca,Pb)1/3MnO3 single crystals

    International Nuclear Information System (INIS)

    The Hall resistivity ρxy of a La2/3(Ca,Pb)1/3MnO3 single crystal has been measured as a function of temperature and field. The overall behavior is similar to that observed previously in thin-film samples. At 5 K, ρxy is positive and linear in field, indicating that the anomalous contribution is negligible. However, the slope is small and, if a free carrier, single band model were used, the carrier density would be 2.4 holes per unit cell, even larger than the 0.85 - 1.9 holes per cell that have been reported using thin-film data and far larger than the 0.33 holes per cell expected from the doping level. As the temperature is increased, a strong, negative contribution to ρxy appears, due to the anomalous contribution to the Hall effect. Making use of a detailed measurement of the magnetization M(B,T), we separate the ordinary (∝B) and anomalous (∝M) contributions. The anomalous contribution is negative and proportional to the zero-field resistivity ρxx below TC, indicating that magnetic skew scattering is the dominant mechanism in the metallic ferromagnetic regime. Far above TC, ρxy shows a negative slope, and is to be associated with the hopping of small polarons. Above TC, the Hall mobility is field independent despite the changes in ρxx and nonlinear ρxy. copyright 1999 American Institute of Physics

  5. Valley Hall Effect in Two-Dimensional Hexagonal Lattices

    Science.gov (United States)

    Yamamoto, Michihisa; Shimazaki, Yuya; Borzenets, Ivan V.; Tarucha, Seigo

    2015-12-01

    Valley is a quantum number defined for energetically degenerate but nonequivalent structures in energy bands of a crystalline material. Recent discoveries of two-dimensional (2D) layered materials have shed light on the potential use of this degree of freedom for information carriers because the valley can now be potentially manipulated in integrated 2D architectures. The valleys separated by a long distance in a momentum space are robust against external disturbance and the flow of the valley, the valley current, is nondissipative because it carries no net electronic current. Among the various 2D valley materials, graphene has by far the highest crystal quality, leading to an extremely long valley relaxation length in the bulk. In this review, we first describe the theoretical background of the valley Hall effect, which converts an electric field into a valley current. We then describe the first observation of the valley Hall effect in monolayer MoS2. Finally, we describe experiments on the generation and detection of the pure valley current in monolayer and bilayer graphene, achieved recently using the valley Hall effect and inverse valley Hall effect. While we show unambiguous evidence of a pure valley current flowing in graphene, we emphasize that the field of "valleytronics" is still in its infancy and that further theoretical and experimental investigations are necessary.

  6. Planar Hall effect sensor for magnetic micro- and nanobead detection

    DEFF Research Database (Denmark)

    Ejsing, Louise Wellendorph; Hansen, Mikkel Fougt; Menon, Aric Kumaran;

    2004-01-01

    Magnetic bead sensors based on the planar Hall effect in thin films of exchange-biased permalloy have been fabricated and characterized. Typical sensitivities are 3 muV/Oe mA. The sensor response to an applied magnetic field has been measured without and with coatings of commercially available 2 ...

  7. Field theory of anyons and the fractional quantum Hall effect

    Energy Technology Data Exchange (ETDEWEB)

    Viefers, S.F

    1997-11-01

    The thesis is devoted to a theoretical study of anyons, i.e. particles with fractional statistics moving in two space dimensions, and the quantum Hall effect. The latter constitutes the only known experimental realization of anyons in that the quasiparticle excitations in the fractional quantum Hall system are believed to obey fractional statistics. First, the properties of ideal quantum gases in two dimensions and in particular the equation of state of the free anyons gas are discussed. Then, a field theory formulation of anyons in a strong magnetic field is presented and later extended to a system with several species of anyons. The relation of this model to fractional exclusion statistics, i.e. intermediate statistics introduced by a generalization of the Pauli principle, and to the low-energy excitations at the edge of the quantum Hall system is discussed. Finally, the Chern-Simons-Landau-Ginzburg theory of the fractional quantum Hall effect is studied, mainly focusing on edge effects; both the ground state and the low-energy edge excitations are examined in the simple one-component model and in an extended model which includes spin effects.

  8. Quantum Hall Effect: proposed multi-electron tunneling experiment

    International Nuclear Information System (INIS)

    Here we propose a tunneling experiment for the fractional and Integral Quantum Hall Effect. It may demonstrate multi-electron tunneling and may provide information about the nature of the macroscopic quantum states of 2D electronic liquid or solid. (author)

  9. Field theory of anyons and the fractional quantum Hall effect

    International Nuclear Information System (INIS)

    The thesis is devoted to a theoretical study of anyons, i.e. particles with fractional statistics moving in two space dimensions, and the quantum Hall effect. The latter constitutes the only known experimental realization of anyons in that the quasiparticle excitations in the fractional quantum Hall system are believed to obey fractional statistics. First, the properties of ideal quantum gases in two dimensions and in particular the equation of state of the free anyons gas are discussed. Then, a field theory formulation of anyons in a strong magnetic field is presented and later extended to a system with several species of anyons. The relation of this model to fractional exclusion statistics, i.e. intermediate statistics introduced by a generalization of the Pauli principle, and to the low-energy excitations at the edge of the quantum Hall system is discussed. Finally, the Chern-Simons-Landau-Ginzburg theory of the fractional quantum Hall effect is studied, mainly focusing on edge effects; both the ground state and the low-energy edge excitations are examined in the simple one-component model and in an extended model which includes spin effects

  10. Hall Effect Thruster for High Power Solar Electric Propulsion Technology Demonstration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek proposes to develop a flight version of a high power Hall Effect thruster. While numerous high power Hall Effect thrusters have been demonstrated in the...

  11. Spatial sensitivity mapping of Hall crosses using patterned magnetic nanostructures

    NARCIS (Netherlands)

    Alexandrou, M.; Nutter, P.W.; Delalande, M.Y.; Vries, de J.; Hill, E.W.; Schedin, F.; Abelmann, L.; Thomson, T.

    2010-01-01

    Obtaining an accurate profile of the spatial sensitivity of Hall cross structures is crucial if such devices are to be used to analyze the switching behavior of magnetic nanostructures and determine the switching field distribution of bit patterned media. Here, we have used the anomalous Hall effect

  12. Galvanomagnetic Effects ¨Sensors based on Hall Effect¨

    OpenAIRE

    Panagiotis D. Dimitropoulos; Vlassis N. Petousis

    2009-01-01

    The Hall effect is the generation of a transverse electromotive force in a sample carrying an electric current and exposed to perpendicular magnetic field. Depending on the sample geometry, this electromotive force may cause the appearance of a transverse voltage across the sample, or a current deflection in the sample. The generation of this transverse voltage, called Hall voltage, is the generally known way for the of the appearance of the Hall effect.The resistance of this sample increasin...

  13. Universality Lost: Relation between quantizations of the Hall conductance and the edge exponents in fractional quantum Hall effect

    OpenAIRE

    Hutasoit, Jimmy A.

    2014-01-01

    We note an implication of chiral Luttinger liquid based edge state description of the fractional quantum Hall effect. By considering several examples that involve backward moving neutral modes, arising from either composite fermions with reverse flux attached or edge reconstruction, we show that non-universality of the edge exponent implies non-universality of the Hall conductance, as measured in the two-terminal conductance.

  14. Quantum Hall effect in polycrystalline CVD graphene: grain boundaries impact

    Science.gov (United States)

    Ribeiro-Palau, Rebeca; Lafont, Fabien; Schopfer, Felicien; Poirier, Wilfrid; Bouchiat, Vincent; Han, Zhen; Cresti, Alessandro; Cummings, Aron; Roche, Stephan

    2014-03-01

    It was demonstrated by Janssen et al. (New J. Phys. 2011) that graphene could surpass GaAs for quantum Hall resistance standards with an accuracy better than 10-10. Graphene should render possible the realization of a standard operating at T > 4 K and B graphene with outstanding electronic transport properties is required. We present measurements performed in large area Hall bars made of polycrystalline CVD graphene on Si/SiO2, with a carrier mobility of 0.6 T-1. Even at 20.2 T and 300 mK, the Hall resistance plateaus are insufficiently quantized at ν = +/- 2 and +/- 6 . This is due to a high dissipation manifested by a longitudinal resistance which does not drop to zero. We pointed out unusual power-law temperature dependencies of Rxx and an exponential magnetic field dependence. We do not observe the common thermally activated or VRH behaviors. This can be attributed to the grain boundaries in the sample that short-circuit the edge states, as supported by our numerical simulations. This reveals new and peculiar aspects of the quantum Hall effect in polycrystalline systems. Another unexpected feature is the observation of the ν = 0 and 1 states in such low mobility systems.

  15. Low-field Hall effect near the percolation threshold

    Science.gov (United States)

    Marianer, S.; Bergman, D. J.

    1989-06-01

    We use a random-resistor-network model to study the critical behavior of the low-field Hall constant in a three-dimensional (3D) metal-insulator composite near the percolation threshold. The transfer-matrix method, which was originally introduced for calculating conductivity, is generalized to be applicable to the calculation of the Hall constant and the magnetoresistance as well. We then use this generalized method to perform a renormalization-group calculation for a cubic random resistor network and two simulations of random resistor networks at the percolation threshold: one of cubes and the other of long (3D) strips. Fitting an expression RH~(p-pc)-g to the effective Hall constant RH of the network, we find a divergent Hall constant both from the renormalization-group calculation (g=0.625) and from the simulation of cubes (g=0.25), while the long-strips simulation yields one that is concentration independent, i.e., g=0.

  16. Low-field Hall effect near the percolation threshold

    Energy Technology Data Exchange (ETDEWEB)

    Marianer, S.; Bergman, D. J.

    1989-06-01

    We use a random-resistor-network model to study the critical behavior of the low-field Hall constant in a three-dimensional (3D) metal-insulator composite near the percolation threshold. The transfer-matrix method, which was originally introduced for calculating conductivity, is generalized to be applicable to the calculation of the Hall constant and the magnetoresistance as well. We then use this generalized method to perform a renormalization-group calculation for a cubic random resistor network and two simulations of random resistor networks at the percolation threshold: one of cubes and the other of long (3D) strips. Fitting an expression /ital R//sub /ital H///proportional to/(p/minus/p/sub c/)/sup /minus/g/ to the effective Hall constant /ital R//sub /ital H// of the network, we find a divergent Hall constant both from the renormalization-group calculation (/ital g/=0.625) and from the simulation of cubes (/ital g/=0.25), while the long-strips simulation yields one that is concentration independent, i.e., /ital g/=0.

  17. Investigation of carrier scattering mechanisms in TlInS2 single crystals by Hall effect measurements

    International Nuclear Information System (INIS)

    TlInS2 single crystals are studied through the conductivity and Hall effect measurements in the temperature regions of 100-400 and 170-400 K, respectively. An anomalous behavior of Hall voltage, which changes sign below 315 K, is interpreted through the existence of deep donor impurity levels that behave as acceptor levels when are empty. The hole and electron mobility are limited by the hole- and electron-phonon short range interactions scattering above and below 315 K, respectively. An energy level of 35 meV and a set of donor energy levels located at 360, 280, 220 and 170/152 meV are determined from the temperature dependencies of the carrier concentration and conductivity. A hole, electron, hole-electron pair effective masses of 0.24 mo, 0.14 mo and 0.09 mo and hole- and electron-phonon coupling constants of 0.50 and 0.64, respectively, are obtained from the Hall effect measurements. The theoretical fit of the Hall coefficient reveals a hole to electron mobility ratio of 0.8. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Current-voltage characteristics of Corbino disks under quantum Hall effect conditions

    Science.gov (United States)

    Shikin, V.

    2016-01-01

    This is a discussion of the details of the current-voltage characteristics of a 2D Corbino disk with a uniform density of mobile carriers in the quantum Hall effect plateau. It is shown that diffusion may be one of the reasons for the variety of observed current-voltage characteristics. The anomalous role of diffusion in the formation of the current-voltage characteristics of Corbino disks is determined by the dimensionality of the problem, as well as by the "quality" of the density of states of the magnetized 2D conducting system. The diffusion hypothesis is applied to some specific results and provides an explanation of the difference between the current-voltage characteristics shown in Figs. 1 and 2.

  19. Examining the Connection between Gauge Invariance and the Integral Quantum Hall Effect

    OpenAIRE

    Brueckner, Reinhold

    2000-01-01

    We show the inconsistency of the argument linking the integral quantum Hall effect to gauge invariance. The inconsistency mainly consists of equating gauge and real vector potential transformations for a particular system geometry. Correct handling gives no Hall quantization.

  20. Homogenization of the three-dimensional Hall effect and change of sign of the Hall coefficient

    OpenAIRE

    Briane, Marc; Milton, Graeme W.

    2009-01-01

    17 pages, 4 figures International audience The notion of a Hall matrix, associated with a possibly anisotropic conducting material in the presence of a small magnetic field, is introduced. Then, for any material having a microstructure we prove a general homogenization result satisfied by the Hall matrix in the framework of the H-convergence of Murat-Tartar. Extending a result of Bergman, it is shown that the Hall matrix can be computed from the corrector associated with the homogenizat...

  1. Crossover of the Hall-voltage distribution in AC quantum Hall effect

    OpenAIRE

    Akera, H.

    2011-01-01

    The distribution of the Hall voltage induced by low-frequency AC current is studied theoretically in the incoherent linear transport of quantum Hall systems. It is shown that the Hall-voltage distribution makes a crossover from the uniform distribution to a concentrated-near-edges distribution as the frequency is increased or the diagonal conductivity is decreased. This crossover is also reflected in the frequency dependence of AC magnetoresistance.

  2. Crossover of the Hall-voltage distribution in AC quantum Hall effect

    OpenAIRE

    Akera, Hiroshi

    2009-01-01

    The distribution of the Hall voltage induced by low-frequency AC current is studied theoretically in the incoherent linear transport of quantum Hall systems. It is shown that the Hall-voltage distribution makes a crossover from the uniform distribution to a concentrated-near-edges distribution as the frequency is increased or the diagonal conductivity is decreased. This crossover is also reflected in the frequency dependence of AC magnetoresistance.

  3. Nanoelectronics: the Hall Effect and Measurement of Electrochemical Potentials by «Bottom-Up» Approach

    OpenAIRE

    Yu.A. Kruglyak; P.A. Kondratenko; Yu.М. Lopatkin

    2015-01-01

    Classical and quantum Hall effects, measurement of electrochemical potentials, the Landauer formulas and Buttiker formula, measurement of Hall potential, an account of magnetic field in the NEGF method, quantum Hall effect, Landau method, and edge states in graphene are discussed in the frame of the «bottom-up» approach of modern nanoelectronics.

  4. Nanoelectronics: the Hall Effect and Measurement of Electrochemical Potentials by «Bottom-Up» Approach

    Directory of Open Access Journals (Sweden)

    Yu.A. Kruglyak

    2015-06-01

    Full Text Available Classical and quantum Hall effects, measurement of electrochemical potentials, the Landauer formulas and Buttiker formula, measurement of Hall potential, an account of magnetic field in the NEGF method, quantum Hall effect, Landau method, and edge states in graphene are discussed in the frame of the «bottom-up» approach of modern nanoelectronics.

  5. Galvanomagnetic Effects ¨Sensors based on Hall Effect¨

    Directory of Open Access Journals (Sweden)

    Panagiotis D. Dimitropoulos

    2009-01-01

    Full Text Available The Hall effect is the generation of a transverse electromotive force in a sample carrying an electric current and exposed to perpendicular magnetic field. Depending on the sample geometry, this electromotive force may cause the appearance of a transverse voltage across the sample, or a current deflection in the sample. The generation of this transverse voltage, called Hall voltage, is the generally known way for the of the appearance of the Hall effect.The resistance of this sample increasing under influence of the magnetic field, this called magnetoresistance effect. Both the Hall effect and the magnetoresistance effect belong to the more general class of phenomena called galvanomagnetic effects. Galvamomagnetic effects are the manifestations of charge transport phenomena in condensed matter in the presence of a magnetic field.The sensor applications of Hall effect became important only with the development of semiconductor technology. For one thing, the Hall effect is only strong enough for this propose in some semiconductors. Therefore, the first Hall effect magnetic sensor became commercially available in the mid 1950s, a few year after the discovery of high-mobility compound semiconductors. Our goal in this paper is to understand the physically background of the Hall and the magnetoresistance effects. We are going to discuss the effect of parameters in those phenomena and how we can make better our technology to improve better efficiency.

  6. Quantum Hall Effect under Rotation and Mass of the Laughlin Quasiparticles

    OpenAIRE

    Zhao, Bo; Chen, Zeng-Bing

    2003-01-01

    We consider the quantum Hall effect induced by magnetic field and rotation, which can drive the Hall samples into the quantum Hall regime and induce fractional excitations. Both the mass and the charge of the Laughlin quasiparticles are predicted to be fractionally quantized. The observable effects induced by rotation are discussed. Based on the usual Hall samples under rotation, we propose an experimental setup for detecting the macroscopic quantization phenomena and the fractional mass of t...

  7. Hall effect in electrolyte flow measurements: introduction to blood flow measurements.

    Science.gov (United States)

    Szwast, Maciej; Piatkiewicz, Wojciech

    2012-06-01

    The Hall effect has been applied to electrolyte flow measurement. It has been proven that Hall voltage does not depend on electrolyte concentration; however, there is a linear relationship between Hall voltage and flow velocity. Obtained results for electrolyte allow us to suppose that Hall effect can be used to determine blood flow. Research on blood will be conducted as the next step. PMID:22145845

  8. Observation of the geometric spin Hall effect of light

    CERN Document Server

    Korger, Jan; Chille, Vanessa; Banzer, Peter; Wittmann, Christoffer; Lindlein, Norbert; Marquardt, Christoph; Leuchs, Gerd

    2013-01-01

    The spin Hall effect of light (SHEL) is the photonic analogue of spin Hall effects occurring for charge carriers in solid-state systems. A prime example of this intriguing phenomenon occurs when a light beam refracts at an air-glass interface. It amounts to a polarization-dependent displacement perpendicular to the plane of incidence. At optical wavelengths, this shift is about a few tens of nanometres. Recently, it was predicted that a light beam projected onto an oblique plane can undergo a significantly larger displacement. This effect, named geometric SHEL, is a consequence of spin-orbit coupling and is largely independent from the physical implementation of the projection. Here, we experimentally demonstrate this novel phenomenon by observing an optical beam transmitted across an oblique polarizer. The spatial intensity distribution of the transmitted beam depends on the incident state of polarization and its centroid undergoes a positional displacement exceeding one wavelength. This novel type of spin-o...

  9. Predicted Quantum Topological Hall Effect and Noncoplanar Antiferromagnetism in K0.5 RhO2

    Science.gov (United States)

    Zhou, Jian; Liang, Qi-Feng; Weng, Hongming; Chen, Y. B.; Yao, Shu-Hua; Chen, Yan-Feng; Dong, Jinming; Guo, Guang-Yu

    2016-06-01

    The quantum anomalous Hall (QAH) phase is a two-dimensional bulk ferromagnetic insulator with a nonzero Chern number in the presence of spin-orbit coupling (SOC) but in the absence of applied magnetic fields. Associated metallic chiral edge states host dissipationless current transport in electronic devices. This intriguing QAH phase has recently been observed in magnetic impurity-doped topological insulators, albeit, at extremely low temperatures. Based on first-principles density functional calculations, here we predict that layered rhodium oxide K0.5RhO2 in the noncoplanar chiral antiferromagnetic state is an unconventional three-dimensional QAH insulator with a large band gap and a Néel temperature of a few tens of Kelvins. Furthermore, this unconventional QAH phase is revealed to be the exotic quantum topological Hall effect caused by nonzero scalar spin chirality due to the topological spin structure in the system and without the need of net magnetization and SOC.

  10. Hall effect across the quantum phase transition of CeCu{sub 6-x}Au{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Bartolf, H. [Physikalisches Institut, Universitaet Karlsruhe, Wolfgang-Gaede-St. 1, D-76128 Karlsruhe (Germany); Pfleiderer, C. [Physikalisches Institut, Universitaet Karlsruhe, Wolfgang-Gaede-St. 1, D-76128 Karlsruhe (Germany); Forschungszentrum Karlsruhe, Institut fuer Festkoerperphysik, D-76021 Karlsruhe (Germany); Stockert, O. [Max-Planck-Institut fuer chemische Physik fester Stoffe, D-01187 Dresden (Germany); Vojta, M. [Institut fuer Theorie der Kondensierten Materie, Universitaet Karlsruhe, D-76128 Karlsruhe (Germany); Loehneysen, H. von [Physikalisches Institut, Universitaet Karlsruhe, Wolfgang-Gaede-St. 1, D-76128 Karlsruhe (Germany) and Forschungszentrum Karlsruhe, Institut fuer Festkoerperphysik, D-76021 Karlsruhe (Germany)]. E-mail: h.vl@phys.uni-karlsruhe.de

    2005-04-30

    While CeCu{sub 6} is a Pauli-paramagnetic heavy-fermion (HF) system, Au doping introduces long-range incommensurate antiferromagnetism for x>x{sub c}{approx}0.1. At the critical concentration x{sub c}, the system experiences a quantum phase transition (QPT). Here, both unusual magnetic fluctuations, studied by inelastic neutron scattering, and non-Fermi-liquid behavior, i.e. to anomalous low-temperature thermodynamic and transport properties have been observed. We report on Hall effect measurements that probe the electronic structure of heavy fermions across the critical concentration x{sub c} of the QPT.

  11. Polarization transport of transverse acoustic waves: Berry phase and spin Hall effect of phonons

    Science.gov (United States)

    Bliokh, K. Yu.; Freilikher, V. D.

    2006-11-01

    We carry out a detailed analysis of the short-wave (semiclassical) approximation for the linear equations of the elasticity in a smoothly inhomogeneous isotropic medium. It is shown that the polarization properties of the transverse waves are completely analogous to those of electromagnetic waves and can be considered as spin properties of optical phonons. In particular, the Hamiltonian of the transverse waves contains an additional term of the phonon spin-orbit interaction arising from the Berry gauge potential in the momentum space. This potential is diagonal in the basis of the circularly polarized waves and corresponds to the field of two “magnetic monopoles” of opposite signs for phonons of opposite helicities. This leads to the appearance of the Berry phase in the equation for the polarization evolution and an additional “anomalous velocity” term in the ray equations. The anomalous velocity has the form of the “Lorentz force” caused by the Berry gauge field in momentum space and gives rise to the transverse transport of waves of opposite helicities in opposite directions. This is a manifestation of the spin Hall effect of optical phonons. The effect directly relates to the conservation of total angular momentum of phonons and also influences reflection from a sharp boundary (acoustic analog of the transverse Ferdorov-Imbert shift).

  12. Hall effect in quantum critical charge-cluster glass.

    Science.gov (United States)

    Wu, Jie; Bollinger, Anthony T; Sun, Yujie; Božović, Ivan

    2016-04-19

    Upon doping, cuprates undergo a quantum phase transition from an insulator to a d-wave superconductor. The nature of this transition and of the insulating state is vividly debated. Here, we study the Hall effect in La2-xSrxCuO4(LSCO) samples doped near the quantum critical point atx∼ 0.06. Dramatic fluctuations in the Hall resistance appear belowTCG∼ 1.5 K and increase as the sample is cooled down further, signaling quantum critical behavior. We explore the doping dependence of this effect in detail, by studying a combinatorial LSCO library in which the Sr content is varied in extremely fine steps,Δx∼ 0.00008. We observe that quantum charge fluctuations wash out when superconductivity emerges but can be restored when the latter is suppressed by applying a magnetic field, showing that the two instabilities compete for the ground state. PMID:27044081

  13. Design and construction of a Hall Effect Measurement system

    Science.gov (United States)

    Gully, Ethan; Little, Travis; Requena, Sebastian; Sauncy, Toni

    2010-10-01

    We have constructed a Hall Effect sample holder that facilitates quick sample change and insures that the sample is uniformly located for each measurement. The 4 point off-the-shelf sample card was integrated into an existing floor magnet with custom designed and constructed mounts. The sample holder is well suited for these measurements, allowing for adjustments in all three of the coordinate axes directions so that even small samples can be accurately positioned for measurement between the poles of the magnet. The sample holder is interfaced and controlled with LABView software. The measurements are made using a suite of Keithley instruments. The design and construction will be discussed and preliminary calibration of the Hall Effect system will be presented.

  14. Hall Effects on MHD Flow Through a Porous Straight Channel

    Directory of Open Access Journals (Sweden)

    N. Bhaskara Reddy

    1982-10-01

    Full Text Available The effect of Hall currents on the flow of a viscous incompressible slightly conducting fluid through a porous straight channel under a uniform transverse magnetic field is considered. The pressure gradient is taken as constant quantity and the case of steady flow is obtained by taking the time since the start of the motion to be infinite. Skin friction, temperature distribution and coefficients of heat transfer at both the plates have been evaluated. The effects of Hall parameter, magnetic parameter and Reynolds number on the above physical quantities have been investigated. Velocity distribution when the pressure gradient (i varies linearly with time, and (ii decreases exponentially with time has also been evaluated.

  15. Quasiparticle Aggregation in the Fractional Quantum Hall Effect

    Science.gov (United States)

    Laughlin, R. B.

    1984-10-10

    Quasiparticles in the Fractional Quantum Hall Effect behave qualitatively like electrons confined to the lowest landau level, and can do everything electrons can do, including condense into second generation Fractional Quantum Hall ground states. I review in this paper the reasoning leading to variational wavefunctions for ground state and quasiparticles in the 1/3 effect. I then show how two-quasiparticle eigenstates are uniquely determined from symmetry, and how this leads in a natural way to variational wavefunctions for composite states which have the correct densities (2/5, 2/7, ...). I show in the process that the boson, anyon and fermion representations for the quasiparticles used by Haldane, Halperin, and me are all equivalent. I demonstrate a simple way to derive Halperin`s multiple-valued quasiparticle wavefunction from the correct single-valued electron wavefunction. (auth)

  16. Hall effect in quantum critical charge-cluster glass

    Science.gov (United States)

    Wu, Jie; Bollinger, Anthony T.; Sun, Yujie

    2016-04-01

    Upon doping, cuprates undergo a quantum phase transition from an insulator to a d-wave superconductor. The nature of this transition and of the insulating state is vividly debated. Here, we study the Hall effect in La2-xSrxCuO4 (LSCO) samples doped near the quantum critical point at x ˜ 0.06. Dramatic fluctuations in the Hall resistance appear below TCG ˜ 1.5 K and increase as the sample is cooled down further, signaling quantum critical behavior. We explore the doping dependence of this effect in detail, by studying a combinatorial LSCO library in which the Sr content is varied in extremely fine steps, Δx ˜ 0.00008. We observe that quantum charge fluctuations wash out when superconductivity emerges but can be restored when the latter is suppressed by applying a magnetic field, showing that the two instabilities compete for the ground state.

  17. Theory of spin-Hall effect in HgTe

    International Nuclear Information System (INIS)

    We study theoretically a ballistic transport in HgTe H-shaped nanostructures using Landauer-Buettiker formalism. We model inverted HgTe nanostructures using realistic parameters describing properly the spin-orbit splittings and effective mass in these structures. The idea of the transport measurements is as follows. When an electric current flows in one of the legs of the H-bar structure, a transverse spin current due to the intrinsic spin-Hall effect is induced in the connecting part. Subsequently, this spin current produces, due to the inverse spin-Hall effect, a voltage difference in the opposite leg of the H-bar structure which can be measured by a voltmeter. We predict that the spin-Hall effect in H-shaped HgTe/HgCdTe inverted band structure quantum wells can be significant (on the order of a few % of the excitation voltage (microvolts)) if the size of the structure is below a ballistic length.

  18. Dynamics of the (spin-) Hall effect in topological insulators and graphene

    OpenAIRE

    Dóra, Balázs; Moessner, Roderich

    2010-01-01

    A single two-dimensional Dirac cone with a mass gap produces a quantized (spin-) Hall step in the absence of magnetic field. What happens in strong electric fields? This question is investigated by analyzing time evolution and dynamics of the (spin-) Hall effect. After switching on a longitudinal electric field, a stationary Hall current is reached through damped oscillations. The Hall conductivity remains quantized as long as the electric field (E) is too weak to induce Landau-Zener transiti...

  19. Effects of Segmented Electrode in Hall Current Plasma Thrusters

    International Nuclear Information System (INIS)

    Segmented electrodes with a low secondary electron emission are shown to alter significantly plasma flow in the ceramic channel of the Hall thruster. The location of the axial acceleration region relative to the magnetic field can be moved. The radial potential distribution can also be altered near the channel walls. A hydrodynamic model shows that these effects are consistent with a lower secondary electron emission of the segmented electrode as compared to ceramic channel walls

  20. Another Nulling Hall-Effect Current-Measuring Circuit

    Science.gov (United States)

    Thibodeau, Phillip E.; Sullender, Craig C.

    1993-01-01

    Lightweight, low-power circuit provides noncontact measurement of alternating or direct current of many ampheres in main conductor. Advantages of circuit over other nulling Hall-effect current-measuring circuits is stability and accuracy increased by putting both analog-to-digital and digital-to-analog converters in nulling feedback loop. Converters and rest of circuit designed for operation at sampling rate of 100 kHz, but rate changed to alter time or frequency response of circuit.

  1. Hall Effect Influence on a Highly Conducting Fluid

    International Nuclear Information System (INIS)

    The properties of an incompressible perfect fluid exhibiting Hall effect is investigated in the limit of infinite electrical conductivity and mobility. The magnetic field strength and the fluid velocity are found to obey the equations B = μρ/σ x curlV and V -μ/(σμ0) x curlB (MKS units) where ρ, σ and μ denote mass density, conductivity and charge carrier mobility. Some physical interpretations and applications are given

  2. Interaction and multiband effects in the intrinsic spin-Hall effect of an interacting multiorbital metal

    Science.gov (United States)

    Arakawa, Naoya

    The spin-Hall effect is a spin-current version of the usual-Hall effect, and its potential for application may be great. For the efficient application utilizing the spin-Hall effect, an understanding of interaction effects may be helpful because the interaction effects sometimes become remarkable in transport phenomena (e.g., fractional-quantum-Hall effect). However, a lot of theoretical studies neglected the interaction effects, and the interaction effects in the spin-Hall effect had been little understood. To improve this situation, I developed a general formalism for the intrinsic spin-Hall effect including the interaction effects and multiband effects by using the linear-response theory with approximations appropriate for an interacting multiorbital metal (see arXiv:1510.03988). In this talk, I explain how the electron-electron interaction modifies the spin-Hall conductivity and show several new and remarkable interactions effects, new mechanisms of the damping dependence and a crossover of the damping dependence in a clean system and a temperature-dependent correction due to the spin-Coulomb drag. I also show guidelines useful for general formulations of other transport phenomena including the interaction effects and multiband effects.

  3. Admittance measurements in the quantum Hall effect regime

    Energy Technology Data Exchange (ETDEWEB)

    Hernández, C., E-mail: carlos.hernandezr@unimilitar.edu.co [Departamento de Física, Universidad Militar Nueva Granada, Carrera 11 # 101-80, Bogotá D.C. (Colombia); Laboratorio de Magnetismo, Departamento de Física, Universidad de los Andes, A.A. 4976, Bogotá D.C. (Colombia); Consejo, C.; Chaubet, C. [Laboratoire Charles Coulomb L2C, Université Montpellier II, Pl. E. Bataillon, 34095 Montpellier Cedex 5 (France)

    2014-11-15

    In this work we present an admittance study of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime. We have studied several Hall bars in different contacts configurations in the frequency range 100 Hz–1 MHz. Our interpretation is based on the Landauer–Büttiker theory and takes into account both the capacitance and the topology of the coaxial cables which are connected to the sample holder. We show that we always observe losses through the capacitive impedance of the coaxial cables, except in the two contacts configuration in which the cable capacitance does not influence the admittance measurement of the sample. In this case, we measure the electrochemical capacitance of the 2DEG and show its dependence with the filling factor ν.

  4. Fractionally charged skyrmions in fractional quantum Hall effect

    Science.gov (United States)

    Balram, Ajit C.; Wurstbauer, U.; Wójs, A.; Pinczuk, A.; Jain, J. K.

    2015-11-01

    The fractional quantum Hall effect has inspired searches for exotic emergent topological particles, such as fractionally charged excitations, composite fermions, abelian and nonabelian anyons and Majorana fermions. Fractionally charged skyrmions, which support both topological charge and topological vortex-like spin structure, have also been predicted to occur in the vicinity of 1/3 filling of the lowest Landau level. The fractional skyrmions, however, are anticipated to be exceedingly fragile, suppressed by very small Zeeman energies. Here we show that, slightly away from 1/3 filling, the smallest manifestations of the fractional skyrmion exist in the excitation spectrum for a broad range of Zeeman energies, and appear in resonant inelastic light scattering experiments as well-defined resonances slightly below the long wavelength spin wave mode. The spectroscopy of these exotic bound states serves as a sensitive tool for investigating the residual interaction between composite fermions, responsible for delicate new fractional quantum Hall states in this filling factor region.

  5. Spin Hall effect-driven spin torque in magnetic textures

    KAUST Repository

    Manchon, Aurelien

    2011-07-13

    Current-induced spin torque and magnetization dynamics in the presence of spin Hall effect in magnetic textures is studied theoretically. The local deviation of the charge current gives rise to a current-induced spin torque of the form (1 - ΒM) × [(u 0 + αH u 0 M) ∇] M, where u0 is the direction of the injected current, H is the Hall angle and is the non-adiabaticity parameter due to spin relaxation. Since αH and ×can have a comparable order of magnitude, we show that this torque can significantly modify the current-induced dynamics of both transverse and vortex walls. © 2011 American Institute of Physics.

  6. Effects of Enhanced Eathode Electron Emission on Hall Thruster Operation

    Energy Technology Data Exchange (ETDEWEB)

    Y. Raitses, A. Smirnov and N. J. Fisch

    2009-04-24

    Interesting discharge phenomena are observed that have to do with the interaction between the magnetized Hall thruster plasma and the neutralizing cathode. The steadystate parameters of a highly ionized thruster discharge are strongly influenced by the electron supply from the cathode. The enhancement of the cathode electron emission above its self-sustained level affects the discharge current and leads to a dramatic reduction of the plasma divergence and a suppression of large amplitude, low frequency discharge current oscillations usually related to an ionization instability. These effects correlate strongly with the reduction of the voltage drop in the region with the fringing magnetic field between the thruster channel and the cathode. The measured changes of the plasma properties suggest that the electron emission affects the electron cross-field transport in the thruster discharge. These trends are generalized for Hall thrusters of various configurations.

  7. Hall effect analysis in irradiated silicon samples with different resistivities

    Energy Technology Data Exchange (ETDEWEB)

    Borchi, E.; Bruzzi, M.; Pirollo, S. [I.N.F.N., Firenze (Italy)]|[Dipt. di Energetica di Firenze (Italy); Dezillie, B.; Li, Z. [Brookhaven National Lab., Upton, NY (United States); Lazanu, S. [National Inst. of Material Physics, Bucharest-Magurele (Romania)

    1999-08-01

    The changes induced by neutron irradiation in n- and p-type silicon samples with starting resistivities from 10 {Omega}-cm up to 30 K{Omega}-cm, grown using different techniques, as Float-Zone (FZ), Czochralski (CZ) and epitaxial, have been analyzed by Van der Pauw and Hall effect measurements. Increasing the fluence, each set of samples evolved toward a quasi-intrinsic p-type material. This behavior has been explained in the frame of a two-level model, that considers the introduction during irradiation of mainly two defects. A deep acceptor and a deep donor, probably related to the divacancy and to the C{sub i}O{sub i} complex, are placed in the upper and lower half of the forbidden gap, respectively. This simple model explains quantitatively the data on resistivity and Hall coefficient of each set of samples up to the fluence of {approx} 10{sup 14} n/cm{sup 2}.

  8. Interaction driven quantum Hall effect in artificially stacked graphene bilayers

    Science.gov (United States)

    Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood; Nam, Jungtae; Kim, Keun Soo; Eom, Jonghwa

    2016-04-01

    The honeycomb lattice structure of graphene gives rise to its exceptional electronic properties of linear dispersion relation and its chiral nature of charge carriers. The exceptional electronic properties of graphene stem from linear dispersion relation and chiral nature of charge carries, originating from its honeycomb lattice structure. Here, we address the quantum Hall effect in artificially stacked graphene bilayers and single layer graphene grown by chemical vapor deposition. The quantum Hall plateaus started to appear more than 3 T and became clearer at higher magnetic fields up to 9 T. Shubnikov-de Hass oscillations were manifestly observed in graphene bilayers texture. These unusual plateaus may have been due to the layers interaction in artificially stacked graphene bilayers. Our study initiates the understanding of interactions between artificially stacked graphene layers.

  9. Hall effect in the extremely large magnetoresistance semimetal WTe2

    Science.gov (United States)

    Luo, Yongkang; Li, H.; Dai, Y. M.; Miao, H.; Shi, Y. G.; Ding, H.; Taylor, A. J.; Yarotski, D. A.; Prasankumar, R. P.; Thompson, J. D.

    2015-11-01

    We systematically measured the Hall effect in the extremely large magnetoresistance semimetal WTe2. By carefully fitting the Hall resistivity to a two-band model, the temperature dependencies of the carrier density and mobility for both electron- and hole-type carriers were determined. We observed a sudden increase in the hole density below ˜160 K, which is likely associated with the temperature-induced Lifshitz transition reported by a previous photoemission study. In addition, a more pronounced reduction in electron density occurs below 50 K, giving rise to comparable electron and hole densities at low temperature. Our observations indicate a possible electronic structure change below 50 K, which might be the direct driving force of the electron-hole "compensation" and the extremely large magnetoresistance as well. Numerical simulations imply that this material is unlikely to be a perfectly compensated system.

  10. Hall effect in the extremely large magnetoresistance semimetal WTe2

    International Nuclear Information System (INIS)

    We systematically measured the Hall effect in the extremely large magnetoresistance semimetal WTe2. By carefully fitting the Hall resistivity to a two-band model, the temperature dependencies of the carrier density and mobility for both electron- and hole-type carriers were determined. We observed a sudden increase in the hole density below ∼160 K, which is likely associated with the temperature-induced Lifshitz transition reported by a previous photoemission study. In addition, a more pronounced reduction in electron density occurs below 50 K, giving rise to comparable electron and hole densities at low temperature. Our observations indicate a possible electronic structure change below 50 K, which might be the direct driving force of the electron-hole “compensation” and the extremely large magnetoresistance as well. Numerical simulations imply that this material is unlikely to be a perfectly compensated system

  11. Interaction driven quantum Hall effect in artificially stacked graphene bilayers

    Science.gov (United States)

    Iqbal, Muhammad Zahir; Iqbal, Muhammad Waqas; Siddique, Salma; Khan, Muhammad Farooq; Ramay, Shahid Mahmood; Nam, Jungtae; Kim, Keun Soo; Eom, Jonghwa

    2016-01-01

    The honeycomb lattice structure of graphene gives rise to its exceptional electronic properties of linear dispersion relation and its chiral nature of charge carriers. The exceptional electronic properties of graphene stem from linear dispersion relation and chiral nature of charge carries, originating from its honeycomb lattice structure. Here, we address the quantum Hall effect in artificially stacked graphene bilayers and single layer graphene grown by chemical vapor deposition. The quantum Hall plateaus started to appear more than 3 T and became clearer at higher magnetic fields up to 9 T. Shubnikov-de Hass oscillations were manifestly observed in graphene bilayers texture. These unusual plateaus may have been due to the layers interaction in artificially stacked graphene bilayers. Our study initiates the understanding of interactions between artificially stacked graphene layers. PMID:27098387

  12. Generalized Surface Polaritons and their quantum spin Hall effect

    CERN Document Server

    Xu, Yadong; Chen, Huanyang

    2016-01-01

    Surface polaritons, e.g., surface plasmon polaritons, are invaluable tools in nanophotonics. However, considerable plasmon loss narrows the application regime of plasmonic devices. Here we reveal some general conditions for lossless surface polaritons to emerge at the interface of a gain and a loss media. The gain medium does not only compensate the energy loss, but also modifies surface wave oscillation mechanisms. A new type of surface polaritons induced by the sign switch of the imaginary part of the permittivity across the interface is discovered. The surface polaritons exhibit spin Hall effect due to spin-momentum locking and unique Berry phase. The spin Hall coefficient changes the sign across the parity-time symmetric limit and becomes quantized for perfect metal-dielectric interface and for dielectric-dielectric interface with very large permittivity contrast, carrying opposite topological numbers. Our study opens a new direction for manipulating light with surface polaritons in non-Hermitian optical ...

  13. Effects of wall electrodes on Hall effect thruster plasma

    International Nuclear Information System (INIS)

    This paper investigates the physical mechanisms that cause beneficial and detrimental performance effect observed to date in Hall effect thrusters with wall electrodes. It is determined that the wall electrode sheath can reduce ion losses to the wall if positioned near the anode (outside the dense region of the plasma) such that an ion-repelling sheath is able to form. The ability of the wall electrode to form an ion-repelling sheath is inversely proportional to the current drawn—if the wall electrode becomes the dominant sink for the thruster discharge current, increases in wall electrode bias result in increased local plasma potential rather than an ion-repelling sheath. A single-fluid electron flow model gives results that mimic the observed potential structures and the current-sharing fractions between the anode and wall electrodes, showing that potential gradients in the presheath and bulk plasma come at the expense of current draw to the wall electrodes. Secondary electron emission from the wall electrodes (or lack thereof) is inferred to have a larger effect if the electrodes are positioned near the exit plane than if positioned near the anode, due to the difference in energy deposition from the plasma

  14. Anomalous Doppler effects in bulk phononic crystal

    International Nuclear Information System (INIS)

    Doppler effects in simple cubic phononic crystal are studied theoretically and numerically. In addition to observing Doppler shifts from a moving source's frequencies inside the gap, we find that Doppler shifts can be multi-order, anisotropic, and the dominant order of shift depends on the band index that the source's frequency is in.

  15. Hall effect in a strong magnetic field: Direct comparisons of compressible magnetohydrodynamics and the reduced Hall magnetohydrodynamic equations

    International Nuclear Information System (INIS)

    In this work we numerically test a model of Hall magnetohydrodynamics in the presence of a strong mean magnetic field: the reduced Hall magnetohydrodynamic model (RHMHD) derived by [Gomez et al., Phys. Plasmas 15, 102303 (2008)] with the addition of weak compressible effects. The main advantage of this model lies in the reduction of computational cost. Nevertheless, up until now the degree of agreement with the original Hall MHD system and the range of validity in a regime of turbulence were not established. In this work direct numerical simulations of three-dimensional Hall MHD turbulence in the presence of a strong mean magnetic field are compared with simulations of the weak compressible RHMHD model. The results show that the degree of agreement is very high (when the different assumptions of RHMHD, such as spectral anisotropy, are satisfied). Nevertheless, when the initial conditions are isotropic but the mean magnetic field is maintained strong, the results differ at the beginning but asymptotically reach a good agreement at relatively short times. We also found evidence that the compressibility still plays a role in the dynamics of these systems, and the weak compressible RHMHD model is able to capture these effects. In conclusion the weak compressible RHMHD model is a valid approximation of the Hall MHD turbulence in the relevant physical context.

  16. Hall effect of K-doped superconducting thin films

    International Nuclear Information System (INIS)

    We have studied Hall effect for potassium (K)-doped BaFe2As2superconducting thin films by analyzing the relation between the longitudinal resistivity (ρxy) and the Hall resistivity (ρxy). The thin films used in this study were fabricated on AlO3 (000l) substrates by using an ex-situ pulsed laser deposition (PLD) technique under a high-vacuum condition of ∼10-6 Torr. The samples showed the high superconducting transition temperatures (TC) of ∼40 K. The ρxx and ρxythe for K-doped BaFeAs2 thin films were measured by using a physical property measurement system (PPMS) with a temperature sweep (T-sweep) mode at an applied current density of 100 A/cm2 and at magnetic fields from 0 up to 9 T. We report the T-sweep results of the ρxx and the ρxy to investigate Hall scaling behavior on the basis of the relation of ρxy = A(ρxy)β. The ρxx values are 3.0 ± 0.2 in the c-axis-oriented K-doped BaFeAs2 thin films, whereas the thin films with various oriented-directions like a polycrystal showed slightly lower β than that of c-axis-oriented thin films. Interestingly, the β value is decreased with increasing magnetic fields.

  17. Application of the quantum Hall effect to resistance metrology

    Science.gov (United States)

    Poirier, Wilfrid; Schopfer, Félicien; Guignard, Jérémie; Thévenot, Olivier; Gournay, Pierre

    2011-05-01

    The quantum Hall effect (QHE) discovery has revolutionized metrology by providing with a representation of the unit of resistance, R, that can be reproduced within a relative uncertainty of one part in 10 9 and is theoretically only linked to Planck's constant h and the electron charge e. This breakthrough also results from the development of resistance comparison bridges using cryogenic current comparator (CCC). The QHE experimental know-how now allows the realization of perfectly quantized Quantum Hall Array Resistance Standards (QHARS) by combining a large number of single Hall bars. In the context of an evolution of the Système International (SI) of units by fixing some fundamental constants of physics, the determination of the von Klitzing constant R through the use of the so-called Thompson-Lampard calculable capacitor and the realization of refined universality tests of the QHE are of prime importance. Finally, the fascinating graphene material might be a new turning point in resistance metrology.

  18. Thermopower, Hall effect and magnetoresistivity of Ru 1- xSb xSr 2Sm 1.5Ce 0.5Cu 2O 10- d

    Science.gov (United States)

    Ilonca, G.; Patapis, S.; Beiusan, F.; Lung, C.; Toma, V.; Balint, P.; Bodea, M.; Jurcut, T.

    2007-09-01

    Magnetoresistivity, thermopower and Hall effect on the samples of Ru1-xSbxSr2Sm1.5Ce0.5Cu2O10-d were investigated in the temperature range 4-300 K with a magnetic field up to 9 T. Superconducting transition temperature decreases with increases content of Sb, due to a distortion of RuO6 octahedral, which is responsible of the increase in hole localization, reflected by Hall concentration, too. The inhomogeneous granular structure is put in evidence by the intragranular, Tco, and intergranular Tcg, transition temperatures. Hall effect and thermopower anomalous decreases below Tmagnetic can be explained within a simple two-band model by a transition from localized to more itinerant behavior in the RuO2 layer at Tmagnetic.

  19. Effects of Anomalous Propagation Conditions on Weather Radar Observations

    OpenAIRE

    Bech, Joan; Magaldi, Adolfo; Codina, Bernat; Lorente, Jeroni

    2012-01-01

    In this chapter our objective is to provide an overview of the effects of anomalous propagation conditions on weather radar observations, based mostly on studies performed by the authors during the last decade, summarizing results from recent publications, presentations, or unpublished material. We believe this chapter may be useful as an introductory text for graduate students, or researchers and practitioners dealing with this topic. Throughout the text a spherical symmetric atmosphere is a...

  20. Quark confinement and the fractional quantum Hall effect

    Institute of Scientific and Technical Information of China (English)

    WANG Hai-Jun; GENG Wen-Tong

    2008-01-01

    Working in the physics of Wilson factor and Aharonov-Bohm effect,we find in the fluxtubequark system the topology of a baryon consisting of three heavy flavor quarks resembles that of the fractional quantum Hall effect(FQHE)in condensed matter.This similarity yields the result that the constituent quarks of baryon have the"filling factor"1/3.thus the previous conjecture that quark confinement is a correlation effect is confirmed.Moreover,by deriving a Hamiltonian of the system analogous to that of FQHE,we predict an energy gap for the ground state of a heavy three-quark system.

  1. Spin Hall Magnetoresistance Induced by a Nonequilibrium Proximity Effect

    OpenAIRE

    Nakayama, H.; Althammer, M.; Chen, Y. T.; Uchida, K.; Kajiwara, Y.; Kikuchi, D.; Ohtani, T.; Geprägs, S.; Opel, M.; Takahashi, S.; Gross, R.; Bauer, G. E. W.; Goennenwein, S. T. B.; Saitoh, E.

    2013-01-01

    We report anisotropic magnetoresistance in Pt|Y3Fe5O12 bilayers. In spite of Y3Fe5O12 being a very good electrical insulator, the resistance of the Pt layer reflects its magnetization direction. The effect persists even when a Cu layer is inserted between Pt and Y3Fe5O12, excluding the contribution of induced equilibrium magnetization at the interface. Instead, we show that the effect originates from concerted actions of the direct and inverse spin Hall effects and therefore call it “spin Hal...

  2. Spatial gradient of dynamic nuclear spin polarization induced by breakdown of quantum Hall effect

    OpenAIRE

    Kawamura, Minoru; Kono, Kimitoshi; Hashimoto, Yoshiaki; Katsumoto, Shingo; Machida, Tomoki

    2010-01-01

    We studied spatial distribution of dynamic nuclear polarization (DNP) in a Hall-bar device in a breakdown regime of the quantum Hall effect (QHE). We detected nuclear magnetic resonance (NMR) signals from the polarized nuclear spins by measuring the Hall voltage $V_{xy}$ using three pairs of voltage probes attached to the conducting channel of the Hall bar. We find that the amplitude of the NMR signal depends on the position of the Hall voltage probes and that the largest NMR signal is obtain...

  3. Complex scattering dynamics and the integer quantum Hall effect

    International Nuclear Information System (INIS)

    The effect of a magnetic field on potential scattering is investigated microscopically. A magnetic field renders the scattering of a classical charged particle far more complex than previously suspected. Consequences include possible 1/f noise and an explanation of the observed breakdown of the quantum Hall effect at large currents. A particular scatterer is described by a discontinuous one dimensional Hamiltonian map, a class of maps that has not previously been studied. A renormalization group analysis indicates that singular behavior arises from the interplay of electron orbits that are periodic and orbits that are quasiperiodic

  4. Quantum Hall Effect and Chaotic Motion in Phase Space

    OpenAIRE

    Ghaboussi, F.

    1996-01-01

    We discuss the relation between the Quantum Hall behaviour of charged carriers and their chaotic motion in phase space. It is shown that the quantum Hall diagram is comparable with the stepped diagram in phase space of a chaotic motion.

  5. High temperature hall effect measurement system design, measurement and analysis

    Science.gov (United States)

    Berkun, Isil

    A reliable knowledge of the transport properties of semiconductor materials is essential for the development and understanding of a number of electronic devices. In this thesis, the work on developing a Hall Effect measurement system with software based data acqui- sition and control for a temperature range of 300K-700K will be described. A system was developed for high temperature measurements of materials including single crystal diamond, poly-crystalline diamond, and thermoelectric compounds. An added capability for monitor- ing the current versus voltage behavior of the contacts was used for studying the influence of ohmic and non-ohmic contacts on Hall Effect measurements. The system has been primar- ily used for testing the transport properties of boron-doped single crystal diamond (SCD) deposited in a microwave plasma-assisted chemical vapor deposition (MPCVD) reactor [1]. Diamond has several outstanding properties that are of high interest for its development as an electronic material. These include a relatively wide band gap of 5.5 (eV), high thermal conductivity, high mobility, high saturation velocity, and a high breakdown voltage. For a temperature range of 300K-700K, IV curves, Hall mobilities and carrier concentrations are shown. Temperature dependent Hall effect measurements have shown carrier concentrations from below 1017cm --3 to approximately 1021 cm--3 with mobilities ranging from 763( cm2/V s) to 0.15(cm 2/V s) respectively. Simulation results have shown the effects of single and mixed carrier models, activation energies, effective mass and doping concentrations. These studies have been helpful in the development of single crystal diamond for diode applications. Reference materials of Ge and GaAs were used to test the Hall Effect system. The system was also used to characterize polycrystalline diamond deposited on glass for electrochemical applications, and Mg2(Si,Sn) compounds which are promising candidates of low-cost, light weight and non

  6. Orbitronics: the Intrinsic Orbital Hall Effect in p-Doped Silicon

    Energy Technology Data Exchange (ETDEWEB)

    Bernevig, B.Andrei; Hughes, Taylor L.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-01-15

    The spin Hall effect depends crucially on the intrinsic spin-orbit coupling of the energy band. Because of the smaller spin-orbit coupling in silicon, the spin Hall effect is expected to be much reduced. We show that the electric field in p-doped silicon can induce a dissipationless orbital current in a fashion reminiscent of the spin Hall effect. The vertex correction due to impurity scattering vanishes and the effect is therefore robust against disorder. The orbital Hall effect can lead to the accumulation of local orbital momentum at the edge of the sample, and can be detected by the Kerr effect.

  7. Fractional Quantum Hall Effect in the Second Landau Level

    OpenAIRE

    Choi, H. C.; Kang, W; Sarma, S. Das; Pfeiffer, L. N.; West, K. W.

    2007-01-01

    We present activation gap measurements of the fractional quantum Hall effect (FQHE) in the second Landau level. Signatures for 14 (5) distinct incompressible FQHE states are seen in a high (low) mobility sample with the enigmatic 5/2 even denominator FQHE having a large activation gap of $\\sim$600 ($\\sim$300mK) in the high (low) mobility sample. Our measured large relative gaps for 5/2, 7/3, and 8/3 FQHE indicate emergence of exotic FQHE correlations in the second Ladau level, possibly quite ...

  8. Theory of quantum Hall effect and high Landau levels

    OpenAIRE

    Shrivastava, Keshav N.

    2001-01-01

    The angular momentum model which couples the spin and charge is discussed as a possible theory of the quantum Hall effect. The high Landau level filling fractions 5/2, 7/3 and 8/3 are understood by this model. It is found that 7/3 and 8/3 are the particle-hole conjugates and 5/2 arises due to a limiting level at 1/2 with Landau level number n=5 which makes the fraction as 5/2.

  9. Quantum percolation and plateau transitions in the quantum Hall effect

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.; Wang, Z.; Kivelson, S. (IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States) Center for Materials Science and Theoretical Division T-11, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States) Department of Physics, University of California at Los Angeles, Los Angeles, California 90024-1547 (United States))

    1993-06-28

    We introduce a simple model of quantum percolation and analyze it numerically using transfer matrix methods. A central point of this paper is that 3 both integer and fractional plateau transitions in the quantum Hall effect are due to quantum percolation. Within this model, we obtained the localization length exponent [nu]=2.4[plus minus]0.2, the dynamical exponent [ital z]=1, and the scaling functions for the conductivity tensor for both the integer and the fractional transitions. We show that our results agree extremely well with the experimental results for the integer plateau transition obtained by McEuen [ital et] [ital al].

  10. Quantum percolation and plateau transitions in the quantum Hall effect

    International Nuclear Information System (INIS)

    We introduce a simple model of quantum percolation and analyze it numerically using transfer matrix methods. A central point of this paper is that 3 both integer and fractional plateau transitions in the quantum Hall effect are due to quantum percolation. Within this model, we obtained the localization length exponent ν=2.4±0.2, the dynamical exponent z=1, and the scaling functions for the conductivity tensor for both the integer and the fractional transitions. We show that our results agree extremely well with the experimental results for the integer plateau transition obtained by McEuen et al

  11. Redundant speed control for brushless Hall effect motor

    Science.gov (United States)

    Nola, F. J. (Inventor)

    1973-01-01

    A speed control system for a brushless Hall effect device equipped direct current (D.C.) motor is described. Separate windings of the motor are powered by separate speed responsive power sources. A change in speed, upward or downward, because of the failure of a component of one of the power sources results in a corrective signal being generated in the other power source to supply an appropriate power level and polarity to one winding to cause the motor to be corrected in speed.

  12. Automated High-Temperature Hall-Effect Apparatus

    Science.gov (United States)

    Parker, James B.; Zoltan, Leslie D.

    1992-01-01

    Automated apparatus takes Hall-effect measurements of specimens of thermoelectric materials at temperatures from ambient to 1,200 K using computer control to obtain better resolution of data and more data points about three times as fast as before. Four-probe electrical-resistance measurements taken in 12 electrical and 2 magnetic orientations to characterize specimens at each temperature. Computer acquires data, and controls apparatus via three feedback loops: one for temperature, one for magnetic field, and one for electrical-potential data.

  13. Spin-injection Hall effect in a planar photovoltaic cell

    Czech Academy of Sciences Publication Activity Database

    Wunderlich, J.; Irvine, A.C.; Sinova, J.; Park, B.G.; Zarbo, L.P.; Xu, X.L.; Kaestner, B.; Novák, Vít; Jungwirth, Tomáš

    2009-01-01

    Roč. 5, č. 9 (2009), s. 675-681. ISSN 1745-2473 R&D Projects: GA MŠk LC510; GA AV ČR KAN400100652; GA ČR GEFON/06/E002; GA ČR GEFON/06/E001 Grant ostatní: AS CR(CZ) Premium Academiae; SemiSpinNet(XE) FP7- #215368 Institutional research plan: CEZ:AV0Z10100521 Keywords : extraordinary Hall effects * spintronics * photvoltaics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 15.491, year: 2009

  14. Hall effect in Fe$_3$O$_4$ epitaxial thin films

    OpenAIRE

    Reisinger, D.; Majewski, P.; Opel, M.; Alff, L.; Gross, R.

    2004-01-01

    Magnetite epitaxial thin films have been prepared by pulsed laser deposition at 340 C on MgO and Si substrates. One key result is that the thin film properties are almost identical to the properties of bulk material. For 40 - 50 nm thick films, the saturation magnetization and conductivity are respectively 453 emu/cm^3 and 225 1/(Ohm cm) at room temperature. The Verwey transition is at 117 K. The Hall effect indicates an electron concentration corresponding to 0.22 electrons per formula unit ...

  15. Spin Hall effect of a light beam in anisotropic metamaterials

    International Nuclear Information System (INIS)

    We theoretically investigate a switchable spin Hall effect of light (SHEL) in reflection for three specific dispersion relations at an air-anisotropic metamaterial interface. The displacements of horizontal and vertical polarization components vary with the incident angle at different dispersion relations. The transverse displacements can be obtained with the relevant metamaterial whose refractive index can be arbitrarily tailed. The results of the SHEL in the metamaterial provide a new way for manipulating the transverse displacements of a specific polarization component. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  16. $W_{\\infty}$ algebra in the integer quantum Hall effects

    OpenAIRE

    Azuma, Hiroo

    1994-01-01

    We investigate the $W_{\\infty}$ algebra in the integer quantum Hall effects. Defining the simplest vacuum, the Dirac sea, we evaluate the central extension for this algebra. A new algebra which contains the central extension is called the $W_{1+\\infty}$ algebra. We show that this $W_{1+\\infty}$ algebra is an origin of the Kac-Moody algebra which determines the behavior of edge states of the system. We discuss the relation between the $W_{1+\\infty}$ algebra and the incompressibility of the int...

  17. Proposal for the quantum spin-valley Hall effect in monolayer graphene

    OpenAIRE

    Islam, SK Firoz; Benjamin, Colin

    2016-01-01

    Quantum spin Hall effect was first predicted in graphene. However, the weak spin orbit interaction in graphene meant that the search for quantum spin Hall effect in graphene never fructified. In this work we show how to generate the quantum spin-valley Hall effect in graphene via quantum pumping by adiabatically modulating a magnetic impurity and an electrostatic potential in a monolayer of strained graphene. We see that not only exclusive spin polarized currents can be pumped in the two vall...

  18. Disorder effect of resonant spin Hall effect in a tilted magnetic field

    OpenAIRE

    Shen, SQ; Zhang, FC; Jiang, ZF

    2009-01-01

    We study the disorder effect of resonant spin Hall effect in a two-dimensional electron system with Rashba coupling in the presence of a tilted magnetic field. The competition between the Rashba coupling and the Zeeman coupling leads to the energy crossing of the Landau levels, which gives rise to the resonant spin Hall effect. Utilizing the Streda's formula within the self-consistent Born approximation, we find that the impurity scattering broadens the energy levels and the resonant spin Hal...

  19. Photo-induced Hall Effect in graphene - effect of boundary types

    Energy Technology Data Exchange (ETDEWEB)

    Oka, Takashi; Aoki, Hideo, E-mail: oka@cms.phys.s.u-tokyo.ac.j [Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan)

    2009-02-01

    We theoretically predict, with the Keldysh Green's function combined with the Floquet method, that the AC electric field of a circularly polarized light should induce a Hall effect, in the absence of uniform magnetic fields, in graphene with a pair of Dirac dispersions. Although the Hall coefficient is not quantized, the dynamical gap generated by the AC field and the associated Hall effect bear a topological origin which can be traced back to the Dirac cones. We also study the dependence on boundary conditions. The required AC field strength is estimated to be realistic.

  20. Comparative Study on the Performance of Five Different Hall Effect Devices

    OpenAIRE

    Paun, Maria-Alexandra; Sallese, Jean-Michel; Kayal, Maher

    2013-01-01

    Five different Hall Effect sensors were modeled and their performance evaluated using a three dimensional simulator. The physical structure of the implemented sensors reproduces a certain technological fabrication process. Hall voltage, absolute, current-related, voltage-related and power-related sensitivities were obtained for each sensor. The effect of artificial offset was also investigated for cross-like structures. The simulation procedure guides the designer in choosing the Hall cell op...

  1. Comparison of Performance of Magneto Hydrodynamics Generator in Presence of Hall Effect

    Directory of Open Access Journals (Sweden)

    Ahmadali Khatibzadeh

    2012-08-01

    Full Text Available Studying of high-temperature plasmas exposed to strong electromagnetic field is Magneto Hydrodynamics. Also, it is used to obtain an electrical power. This paper proposes a simple model of MHD generator. Moreover, efficiency of different configuration of this generator is obtained by this model. Also, this paper compares different configurations of Faraday generator with the Hall generator based on their isotropic efficiency. Moreover, this model considers the effect of Hall Effect (Ion slip on the efficiency. This analysis proof that Hall Effect decrease the efficiency in Faraday generator but increase the efficiency in the Hall generator.

  2. Anyons and the quantum Hall effect-A pedagogical review

    International Nuclear Information System (INIS)

    The dichotomy between fermions and bosons is at the root of many physical phenomena, from metallic conduction of electricity to super-fluidity, and from the periodic table to coherent propagation of light. The dichotomy originates from the symmetry of the quantum mechanical wave function to the interchange of two identical particles. In systems that are confined to two spatial dimensions particles that are neither fermions nor bosons, coined 'anyons', may exist. The fractional quantum Hall effect offers an experimental system where this possibility is realized. In this paper we present the concept of anyons, we explain why the observation of the fractional quantum Hall effect almost forces the notion of anyons upon us, and we review several possible ways for a direct observation of the physics of anyons. Furthermore, we devote a large part of the paper to non-abelian anyons, motivating their existence from the point of view of trial wave functions, giving a simple exposition of their relation to conformal field theories, and reviewing several proposals for their direct observation

  3. Urbanization effects on natural radiation in anomalous areas

    International Nuclear Information System (INIS)

    The urbanization effects and their possible causes on the environmental gamma radiation levels, in an anomalous area, were studied. The field work was accomplished in Guarapari, located in the seacoast of the Brazilian state of Espirito Santo, which is rich in monazite sands, with thorium and uranium contents. The results show clearly that there was a reduction in the levels of external exposition in the streets and squares of Guarapari. It was ascertained that the reduction was due to the materials used in the urbanization. (L.C.J.A.)

  4. Non-local effects of edge excitations in the quantum Hall regime

    OpenAIRE

    Deviatov, E. V.; Lorke, A; Biasiol, G.; Sorba, L.

    2010-01-01

    We use a novel sample geometry to study non-local effects of edge excitations in the integer quantum Hall effect regime. We find that the condition of local equilibrium at the quantum Hall edge is affected by the diffusion of dynamically polarized nuclei. Our analysis indicates, that the nuclear diffusion is effectively one-dimensional in the present experiment.

  5. Emergence of integer quantum Hall effect from chaos

    CERN Document Server

    Tian, Chushun; Wang, Jiao

    2015-01-01

    We present an analytic microscopic theory showing that in a large class of spin-$\\frac{1}{2}$ quasiperiodic quantum kicked rotors, a dynamical analog of the integer quantum Hall effect (IQHE) emerges from an intrinsic chaotic structure. Specifically, the inverse of the Planck's quantum ($h_e$) and the rotor's energy growth rate mimic the `filling fraction' and the `longitudinal conductivity' in conventional IQHE, respectively, and a hidden quantum number is found to mimic the `quantized Hall conductivity'. We show that for an infinite discrete set of critical values of $h_e$, the long-time energy growth rate is universal and of order of unity (`metallic' phase), but otherwise vanishes (`insulating' phase). Moreover, the rotor insulating phases are topological, each of which is characterized by a hidden quantum number. This number exhibits universal behavior for small $h_e$, i.e., it jumps by unity whenever $h_e$ decreases, passing through each critical value. This intriguing phenomenon is not triggered by the...

  6. Hall effect measurements on proton-irradiated ROSE samples

    International Nuclear Information System (INIS)

    Bulk samples obtained from two wafers of a silicon monocrystal material produced by Float-Zone refinement have been analyzed using the four-point probe method. One of the wafers comes from an oxygenated ingot; two sets of pure and oxygenated samples have been irradiated with 24 GeV/c protons in the fluence range from 1013 p/cm2 to 2x1014 p/cm2. Van der Pauw resistivity and Hall coefficient have been measured before and after irradiation as a function of the temperature. A thermal treatment (30 minutes at 100C) has been performed to accelerate the reverse annealing effect in the irradiated silicon. The irradiated samples show the same exponential dependence of the resistivity and of the Hall coefficient on the temperature from 370K to 100K, corresponding to the presence of radiation-induced deep energy levels around 0.6-0.7eV in the silicon gap. The free carrier concentrations (n, p) have been evaluated in the investigated fluence range. The inversion of the conductivity type from n to p occurred respectively at 7x1013 p/cm2 and at 4x1013 p/cm2 before and after the annealing treatment, for both the two sets. Only slight differences have been detected between the pure and oxygenated samples

  7. Quantum Hall effect in graphene: A functional determinant approach

    CERN Document Server

    Beneventano, C G

    2007-01-01

    We start the paper with a brief presentation of the main characteristics of graphene, and of the Dirac theory of massless fermions in 2+1 dimensions obtained as the associated low-momentum effective theory, in the absence of external fields. We then summarize the main steps needed to obtain the Hall conductivity in the effective theory at finite temperature and density, with emphasis on its dependence on the phase of the Dirac determinant selected during the evaluation of the effective action. Finally, we discuss the behavior, under gauge transformations, of the contribution due to the lowest Landau level, and interpret gauge transformations as rotations of the corresponding spinors around the magnetic field.

  8. Electrical polarization of nuclear spins in a breakdown regime of quantum Hall effect

    OpenAIRE

    Kawamura, M.; Takahashi, H; Sugihara, K; Masubuchi, S.; Hamaya, K.; Machida, T.

    2006-01-01

    We have developed a method for electrical polarization of nuclear spins in quantum Hall systems. In a breakdown regime of odd-integer quantum Hall effect (QHE), excitation of electrons to the upper Landau subband with opposite spin polarity dynamically polarizes nuclear spins through the hyperfine interaction. The polarized nuclear spins in turn accelerate the QHE breakdown, leading to hysteretic voltage-current characteristics of the quantum Hall conductor.

  9. Thermal Hall Effect of Spins in a Paramagnet

    OpenAIRE

    Lee, Hyunyong; Han, Jung Hoon; Lee, Patrick A.

    2014-01-01

    Theory of Hall transport of spins in a correlated paramagnetic phase is developed. By identifying the thermal Hall current operator in the spin language, which turns out to equal the spin chirality in the pure Heisenberg model, various response functions can be derived straightforwardly. Subsequent reduction to the Schwinger boson representation of spins allows a convenient calculation of thermal and spin Hall coefficients in the paramagnetic regime using self-consistent mean-field theory. Co...

  10. Hall effect: the role of nonequilibrium charge carriers

    Directory of Open Access Journals (Sweden)

    S. Molina Valdovinos

    2011-01-01

    Full Text Available Presentamos un nuevo modelo del efecto Hall en el caso de semiconductores bipolares. Se toma en cuenta portadores fuera de equilibrio, procesos de generación y recombinación asistidos por trampas (modelo de Shockley-Read. Se obtienen expresiones para los potenciales electroquímicos de electrones y huecos, campo de Hall y constante de Hall RH. Estudiamos la dependencia de estás expresiones de la distribución de portadores a lo largo de la dirección del campo Hall, en el caso de semiconductores intrínsecos y extrínsecos.

  11. Hall effect: the role of nonequilibrium charge carriers

    OpenAIRE

    S. Molina Valdovinos; Gurevich, Yu. G.

    2011-01-01

    Presentamos un nuevo modelo del efecto Hall en el caso de semiconductores bipolares. Se toma en cuenta portadores fuera de equilibrio, procesos de generación y recombinación asistidos por trampas (modelo de Shockley-Read). Se obtienen expresiones para los potenciales electroquímicos de electrones y huecos, campo de Hall y constante de Hall RH. Estudiamos la dependencia de estás expresiones de la distribución de portadores a lo largo de la dirección del campo Hall, en el caso de semiconductore...

  12. Thermoelectric effects in quantum Hall systems beyond linear response

    International Nuclear Information System (INIS)

    We consider a quantum Hall system with an antidot acting as a energy dependent scatterer. In the purely charge case, we find deviations from the Wiedemann-Franz law that take place in the nonlinear regime of transport. We also discuss Peltier effects beyond linear response and describe both effects using magnetic-field asymmetric transport coefficients. For the spin case such as that arising along the helical edge states of a two-dimensional topological insulator, we investigate the generation of spin currents as a result of applied voltage and temperature differences in samples attached to ferromagnetic leads. We find that in the parallel configuration the spin current can be tuned with the leads' polarization even in the linear regime of transport. In contrast, for antiparallel magnetizations the spin currents has a strict nonlinear dependence on the the applied fields

  13. Controlling the optical spin Hall effect with light

    CERN Document Server

    Lafont, O; Lewandowski, P; Kwong, N H; Chan, K P; Babilon, M; Leung, P T; Galopin, E; Lemaitre, A; Tignon, J; Schumacher, S; Baudin, E; Binder, R

    2016-01-01

    The optical spin Hall effect (OSHE) is a transport phenomenon of exciton polaritons in semiconductor microcavities, caused by the polaritonic spin-orbit interaction, that leads to the formation of spin textures. In the semiconductor cavity, the physical basis of the spin orbit coupling is an effective magnetic field caused by the splitting of transverse-electric and transverse-magnetic (TE-TM) modes. The spin textures can be observed in the near field (local spin distribution of polaritons), and as light polarization patterns in the more readily observable far field. For future applications in spinoptronic devices, a simple and robust control mechanism, which establishes a one-to-one correspondence between stationary incident light intensity and far-field polarization pattern, is needed. We present such a control scheme, which is made possible by a specific double-microcavity design.

  14. A Model for the Quantization of the Hall Resistance in the Quantum Hall Effect

    OpenAIRE

    Paul Bracken

    2010-01-01

    Some aspects of anyon physics are reviewed with the intention of establishing a model for the quantization of the Hall conductance. A single particle Schrödinger model is introduced and coupled with a constraint equation formulated from the anyon picture. The Schrödinger equation-constraint system can be converted to a single nonlinear differential equation and solutions for the model can be produced.

  15. Scaling in the Integer Quantum Hall Effect: interactions and low magnetic fields

    OpenAIRE

    Huckestein, Bodo; Backhaus, Michael

    2000-01-01

    Recent developments in the scaling theory of the integer quantum Hall effect are discussed. In particular, the influence of electron-electron interactions on the critical behavior are studied. It is further argued that recent experiments on the disappearance of the quantum Hall effect at low magnetic fields support rather than disprove the scaling theory, when interpreted properly.

  16. Temporal Oscillation of Conductances in Quantum Hall Effect of Bloch Electrons

    OpenAIRE

    Machida, Manabu; Hatano, Naomichi; Goryo, Jun

    2006-01-01

    We study a nonadiabatic effect on the conductances in the quantum Hall effect of two-dimensional electrons with a periodic potential. We found that the Hall and longitudinal conductances oscillate in time with a very large frequencies due to quantum fluctuation.

  17. Statistics transmutations in two-dimensional systems and the fractional quantum Hall effect

    OpenAIRE

    Sitko, P.

    1994-01-01

    Statistics transmutations to composite fermions in fractional-quantum-Hall-effect systems are considered in the Hartree-Fock approximation and in the RPA. The Hartree-Fock ground-state energy shows that the transmutations are not energetically preferable. Within the RPA it is found that the system exhibits a fractional quantum Hall effect.

  18. Local Hall effect in a hybrid InSb cross junction

    International Nuclear Information System (INIS)

    We present the local Hall effect in a hybrid Hall device incorporating a micron-scaled InSb semiconductor cross junction and a single microstructured ferromagnetic element. A clear hysteresis loop was found to appear in the output signal for the cross junction with a ferromagnetic element due to the strong perpen- dicular component of the magnetic fringe field emanating from the edge of the ferromagnet. We demon- strate that the local fringe field from the ferromagnetic element inducing a Hall voltage improves the Hall sensitivity (4.5 Ω/Oe). (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. A Circuit Model for CMOS Hall Cells Performance Evaluation including Temperature Effects

    Directory of Open Access Journals (Sweden)

    Maria-Alexandra Paun

    2013-01-01

    Full Text Available In order to provide the information on their Hall voltage, sensitivity, and drift with temperature, a new simpler lumped circuit model for the evaluation of various Hall cells has been developed. In this sense, the finite element model proposed by the authors in this paper contains both geometrical parameters (dimensions of the cells and physical parameters such as the mobility, conductivity, Hall factor, carrier concentration, and the temperature influence on them. Therefore, a scalable finite element model in Cadence, for behavior simulation in circuit environment of CMOS Hall effect devices, with different shapes and technologies assessing their performance, has been elaborated.

  20. Correlations and anomalous transport effects related to stochastic instability

    International Nuclear Information System (INIS)

    In this paper, we analyse turbulent transport in the framework of the correlation approach to obtain the effective diffusion coefficient and characteristic increment in the scaling form. Such factors as anisotropy, seed diffusion mechanisms and reconstruction of flow topology significantly have an impact on the effective diffusivity. We consider the different aspects of stochastic instability such as the decorrelation mechanism to estimate characteristic correlation times and correlation scales in the framework of the scaling approach. The topics to be discussed include the Rechester-Rosenbluth correlation scalings, percolation transport in time dependent flows, anisotropic MHD spectra and a multi-scale approach to the analysis of anomalous transport. To treat long-range correlation effects, the percolation renormalization is analysed in time-dependent regimes. In the framework of the multiscale approach, a scaling for an increment of the stochastic instability in two-dimensional random flow is suggested

  1. Correlations and anomalous transport effects related to stochastic instability

    Energy Technology Data Exchange (ETDEWEB)

    Bakunin, O G [Department of Physics and Astronomy, University of Kansas, Malott Hall, 1251 Wescoe Hall Drive, Lawrence, KS 66044 (United States); Nuclear Fusion Institute, RRC ' Kurchatov Institute' , pl. Kurchatova 1, Moscow, 123182 (Russian Federation); FOM Instituut voor Plasmafysica ' Rijnhuizen' , Associate Euroatom-FOM, 3430 BE Nieuwegein (Netherlands)

    2005-11-15

    In this paper, we analyse turbulent transport in the framework of the correlation approach to obtain the effective diffusion coefficient and characteristic increment in the scaling form. Such factors as anisotropy, seed diffusion mechanisms and reconstruction of flow topology significantly have an impact on the effective diffusivity. We consider the different aspects of stochastic instability such as the decorrelation mechanism to estimate characteristic correlation times and correlation scales in the framework of the scaling approach. The topics to be discussed include the Rechester-Rosenbluth correlation scalings, percolation transport in time dependent flows, anisotropic MHD spectra and a multi-scale approach to the analysis of anomalous transport. To treat long-range correlation effects, the percolation renormalization is analysed in time-dependent regimes. In the framework of the multiscale approach, a scaling for an increment of the stochastic instability in two-dimensional random flow is suggested.

  2. Hořava-Lifshitz gravity and effective theory of the fractional quantum Hall effect

    Science.gov (United States)

    Wu, Chaolun; Wu, Shao-Feng

    2015-01-01

    We show that Hořava-Lifshitz gravity theory can be employed as a covariant framework to build an effective field theory for the fractional quantum Hall effect that respects all the spacetime symmetries such as non-relativistic diffeomorphism invariance and anisotropic Weyl invariance as well as the gauge symmetry. The key to this formalism is a set of correspondence relations that maps all the field degrees of freedom in the Hořava-Lifshitz gravity theory to external background (source) fields among others in the effective action of the quantum Hall effect, according to their symmetry transformation properties. We originally derive the map as a holographic dictionary, but its form is independent of the existence of holographic duality. This paves the way for the application of Hořava-Lifshitz holography on fractional quantum Hall effect. Using the simplest holographic Chern-Simons model, we compute the low energy effective action at leading orders and show that it captures universal electromagnetic and geometric properties of quantum Hall states, including the Wen-Zee shift, Hall viscosity, angular momentum density and their relations. We identify the shift function in Hořava-Lifshitz gravity theory as minus of guiding center velocity and conjugate to guiding center momentum. This enables us to distinguish guiding center angular momentum density from the internal one, which is the sum of Landau orbit spin and intrinsic (topological) spin of the composite particles. Our effective action shows that Hall viscosity is minus half of the internal angular momentum density and proportional to Wen-Zee shift, and Hall bulk viscosity is half of the guiding center angular momentum density.

  3. Low-frequency noise in planar Hall effect bridge sensors

    DEFF Research Database (Denmark)

    Persson, Anders; Bejhedb, R.S.; Bejhed, R.S.;

    2011-01-01

    The low-frequency characteristics of planar Hall effect bridge sensors are investigated as function of the sensor bias current and the applied magnetic field. The noise spectra reveal a Johnson-like spectrum at high frequencies, and a 1/f-like excess noise spectrum at lower frequencies, with a knee...... frequency of around 400Hz. The 1/f-like excess noise can be described by the phenomenological Hooge equation with a Hooge parameter of γH=0.016. The detectivity is shown to depend on the total length, width and thickness of the bridge branches. The detectivity is improved by the square root of the length...... increase. Moreover, the detectivity is shown to depend on the amplitude of the applied magnetic field, revealing a magnetic origin to part of the 1/f noise....

  4. Quantum Hall effects recent theoretical and experimental developments

    CERN Document Server

    Ezawa, Zyun Francis

    2013-01-01

    Enthusiasm for research on the quantum Hall effect (QHE) is unbounded. The QHE is one of the most fascinating and beautiful phenomena in all branches of physics. Tremendous theoretical and experimental developments are still being made in this sphere. Composite bosons, composite fermions and anyons were among distinguishing ideas in the original edition. In the 2nd edition, fantastic phenomena associated with the interlayer phase coherence in the bilayer system were extensively described. The microscopic theory of the QHE was formulated based on the noncommutative geometry. Furthermore, the unconventional QHE in graphene was reviewed, where the electron dynamics can be treated as relativistic Dirac fermions and even the supersymmetric quantum mechanics plays a key role. In this 3rd edition, all chapters are carefully reexamined and updated. A highlight is the new chapter on topological insulators. Indeed, the concept of topological insulator stems from the QHE. Other new topics are recent prominent experime...

  5. Hall current effects in mean-field dynamo theory

    CERN Document Server

    Lingam, Manasvi

    2016-01-01

    The role of the Hall term on large scale dynamo action is investigated by means of the First Order Smoothing Approximation. It is shown that the standard $\\alpha$ coefficient is altered, and is zero when a specific double Beltrami state is attained, in contrast to the Alfv\\'enic state for MHD dynamos. The $\\beta$ coefficient is no longer positive definite, and thereby enables dynamo action even if $\\alpha$-quenching were to operate. The similarities and differences with the (magnetic) shear-current effect are pointed out, and a mechanism that may be potentially responsible for $\\beta < 0$ is advanced. The results are compared against previous studies, and their astrophysical relevance is also highlighted.

  6. Spin Hall effect of light in photon tunneling

    CERN Document Server

    Luo, Hailu; Shu, Weixing; Fan, Dianyuan

    2010-01-01

    We reveal a novel spin Hall effect (SHE) of light in photon tunneling. A polarization-dependent transverse shift for a classic wavepacket tunneling through a prism-air-prism barrier is demonstrated. We resolve the breakdown of angular momentum conservation on two-dimensional photon tunneling by considering SHE of light. For a certain circularly polarized component, whether the transverse shift is positive or negative depends on the magnitude of the refractive index gradient associated with the two prisms. We find that the SHE in the conventional beam refraction can be evidently enhanced via photon tunneling. The polarization-dependent transverse shifts governed by the total angular momentum conservation law, while the polarization-dependent angular shifts governed by the total linear momentum law. These findings open the possibility for developing new nano-photonic devices and can be extrapolated to other physical systems.

  7. Current-induced domain wall motion attributed to spin Hall effect and Dzyaloshinsky–Moriya interaction in Pt/GdFeCo (100 nm) magnetic wire

    Science.gov (United States)

    Kurokawa, Yuichiro; Kawamoto, Masaya; Awano, Hiroyuki

    2016-07-01

    We investigated the current-induced domain wall motion (CIDWM) in Pt/GdFeCo bilayer wires where the thicknesses of the GdFeCo layer are 110 and 150 nm. We found that the direction of CIDWM in the Pt/GdFeCo wires is the same as the current flow direction. The velocity of the domain wall depends on the in-plane magnetic field. These results indicate that the CIDWM along the current direction in the Pt/GdFeCo wires is probably attributed to the spin Hall effect and Dzyaloshinsky–Moriya interaction. Generally, these effects do not appear in thick magnetic wires because they effectively occur at the interfaces of a heavy metal and magnetic layers. Therefore, these results are interesting phenomena because they probably suggest that the spin Hall effect and Dzyaloshinsky–Moriya interaction in the Pt/GdFeCo wire have an anomalously long-range influence.

  8. Hall Effect Thruster Plume Contamination and Erosion Study

    Science.gov (United States)

    Jaworske, Donald A.

    2000-01-01

    The objective of the Hall effect thruster plume contamination and erosion study was to evaluate the impact of a xenon ion plume on various samples placed in the vicinity of a Hall effect thruster for a continuous 100 hour exposure. NASA Glenn Research Center was responsible for the pre- and post-test evaluation of three sample types placed around the thruster: solar cell cover glass, RTV silicone, and Kapton(R). Mass and profilometer), were used to identify the degree of deposition and/or erosion on the solar cell cover glass, RTV silicone, and Kapton@ samples. Transmittance, reflectance, solar absorptance, and room temperature emittance were used to identify the degree of performance degradation of the solar cell cover glass samples alone. Auger spectroscopy was used to identify the chemical constituents found on the surface of the exposed solar cell cover glass samples. Chemical analysis indicated some boron nitride contamination on the samples, from boron nitride insulators used in the body of the thruster. However, erosion outweighted contamination. All samples exhibited some degree of erosion. with the most erosion occurring near the centerline of the plume and the least occurring at the +/- 90 deg positions. For the solar cell cover glass samples, erosion progressed through the antireflective coating and into the microsheet glass itself. Erosion occurred in the solar cell cover glass, RTV silicone and Kapton(R) at different rates. All optical properties changed with the degree of erosion, with solar absorptance and room temperature emittance increasing with erosion. The transmittance of some samples decreased while the reflectance of some samples increased and others decreased. All results are consistent with an energetic plume of xenon ions serving as a source for erosion.

  9. Anomalous Skin Effect for Anisotropic Electron Velocity Distribution Function

    Energy Technology Data Exchange (ETDEWEB)

    Igor Kaganovich; Edward Startsev; Gennady Shvets

    2004-02-19

    The anomalous skin effect in a plasma with a highly anisotropic electron velocity distribution function (EVDF) is very different from skin effect in a plasma with the isotropic EVDF. An analytical solution was derived for the electric field penetrated into plasma with the EVDF described as a Maxwellian with two temperatures Tx >> Tz, where x is the direction along the plasma boundary and z is the direction perpendicular to the plasma boundary. The skin layer was found to consist of two distinctive regions of width of order nTx/w and nTz/w, where nTx,z/w = (Tx,z/m)1/2 is the thermal electron velocity and w is the incident wave frequency.

  10. Anomalous transport effects in magnetically-confined plasma columns

    International Nuclear Information System (INIS)

    The evolution of density structure in a magnetized plasma column is analyzed accounting for anomalous diffusion due to the lower hybrid drift instability. The plasma column is found to be divided into regions of classical, anomalous, and intermediate diffusivity. The bulk behavior, described in terms of radial confinement time, depends most sensitively upon the particle line density (ion/cm). For broad plasmas (large line density), the transport is characteristic of classical diffusion, and for slender plasmas (small line density) the transport is characteristic of anomalous diffusion. For intermediate line densities, the transport undertakes a rapid transition from classical to anomalous. Correlations between the theoretical results and past experiments are described

  11. Horava-Lifshitz Gravity and Effective Theory of the Fractional Quantum Hall Effect

    CERN Document Server

    Wu, Chaolun

    2014-01-01

    We show that Horava-Lifshitz gravity theory can be employed as a covariant framework to build an effective field theory for the fractional quantum Hall effect that respects all the spacetime symmetries such as non-relativistic diffeomorphism invariance and anisotropic Weyl invariance as well as the gauge symmetry. The key to this formalism is a set of correspondence relations that maps all the field degrees of freedom in the Horava-Lifshitz gravity theory to external background (source) fields among others in the effective action of the quantum Hall effect, according to their symmetry transformation properties. We originally derive the map as a holographic dictionary, but its form is independent of the existence of holographic duality. This paves the way for the application of Horava-Lifshitz holography on fractional quantum Hall effect. Using the simplest holographic Chern-Simons model, we compute the low energy effective action at leading orders and show that it captures universal electromagnetic and geomet...

  12. THE SIGN REVERSAL AND SCALING RELATIONS OF HALL ANOMALY IN THE MIXED STATE TYPE-II SUPERCONDUCTORS

    Institute of Scientific and Technical Information of China (English)

    WEI YEU CHEN; MING JU CHOU; HUANG ZHONG BING

    2000-01-01

    We present a new model for the anomalous Hall effect in the mixed state of type-II superconductors. In this model we consider the thermally activated motion of the many body correlating vortex lattice system. The sign change of the Hall resistivity is the result of the competition between the motion of effective antivortices and the motion of the pinned vortex lattice together with the interstitial vortices. Within this model many essential experimental results for the complicated Hall effect can be explained.

  13. Excitation wavelength dependence of the anomalous circular photogalvanic effect in undoped InGaAs/AlGaAs quantum wells

    International Nuclear Information System (INIS)

    The excitation wavelength dependence of the anomalous circular photogalvanic effect (ACPGE) current arising from the reciprocal spin Hall effect (RSHE) in undoped InGaAs/AlGaAs quantum wells is measured under normal incidence of circularly polarized light at room temperature. We found that the spot location with the maximum ACPGE current is wavelength independent. And the normalized ACPGE current decreases at smaller wavelengths, which can be attributed to the sharp decrease of the spin relaxation time (τs) and the hot electron relaxation time (τ1) at smaller wavelengths. The study of the excitation wavelength dependence of ACPGE current is a good supplement to the in-depth investigation of RSHE

  14. Domain-wall depinning dominated by the Spin Hall effect

    Science.gov (United States)

    Swagten, Henk

    2013-03-01

    Current induced domain wall motion (CIDWM) in perpendicular materials is believed to be very efficient. We will show that the Spin Hall effect (SHE) provides a radically new mechanism for CIDWM in these systems. Using focused-ion-beam irradiation we are able to stabilize and pin two DWs in a Pt/Co/Pt nanowire. By depinning the DWs under the application of a perpendicular field as well as an injected charge current and in-plane magnetic field, we are able to disentangle the contributions to DW motion originating from (1) conventional spin transfer torques that act on magnetization gradients and (2) from the hitherto unexplored SHE torques. The fact the perpendicular depinning field H as a function of charge current J for the two DWs has equal slope dH/dJ, as well as a sign change of the slope when we change the polarity of the DWs, directly proves the dominance of the SHE contribution. To further proof that the SHE is governing the depinning process, we have tuned the internal spin structure of the DW from Bloch to Néel, by varying the in-plane field parallel to the current, and find that the influence of current on the depinning is highest when the DW has the Néel structure. This behavior is verified by macrospin simulations, which can quantitatively explain our data. As a final compelling evidence, we have varied the thickness of the bottom and top Pt, showing that we are able to tune the spin Hall currents originating from the nonmagnetic Pt layers. The work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM), which is part of the Netherlands Organisation for Scientific Research (NWO).

  15. Hot-electron noise suppression in n-Si via the Hall effect

    OpenAIRE

    Ciccarello, F.; Zammito, S.; Zarcone, M.

    2009-01-01

    We investigate how hot-electron fluctuations in n-type Si are affected by the presence of an intense (static) magnetic field in a Hall geometry. By using the Monte Carlo method, we find that the known Hall-effect-induced redistribution of electrons among valleys can suppress electron fluctuations with a simultaneous enhancement of the drift velocity.

  16. Hall-effect device with both voltage leads on one side of the conductor

    NARCIS (Netherlands)

    Fluitman, J.H.J.

    1980-01-01

    A Hall effect device has been designed and tested with both voltage contacts on one side of the Hall element. The proposed layout lends itself to placing the device on the edge of a substratum (possible application as position detector and recording read head). The response of the device to inhomoge

  17. Hall-effect device with both voltage leads on one side of the conductor

    OpenAIRE

    Fluitman, J.H.J.

    1980-01-01

    A Hall effect device has been designed and tested with both voltage contacts on one side of the Hall element. The proposed layout lends itself to placing the device on the edge of a substratum (possible application as position detector and recording read head). The response of the device to inhomogeneous magnetic fields has been calculated and the results are in agreement with experiment.

  18. Anomalous supercurrent switching in graphene under proximity effect

    Science.gov (United States)

    Levchenko, Alex; Coskun, U. C.; Brenner, M.; Hymel, T.; Vakaryuk, V.; Bezryadin, A.

    2012-02-01

    We report a study of hysteretic current-voltage characteristics in superconductor-graphene-superconductor (SGS) junctions. The stochastic nature of the phase slips is characterized by measuring the distribution of the switching currents. We find that in SGS junctions the dispersion of the switching current scales with temperature as σIT^αG with αG 1/3. This observation is in sharp contrast with the known Josephson junction behavior where σIT^αJ with αJ=2/3. We propose an explanation using a modified version of Kurkijarvi's theory for the flux stability in rf-SQUID and attribute this anomalous effect to the temperature dependence of the critical current which persists down to low temperatures.

  19. Effective Field Theory of Fractional Quantized Hall Nematics

    Energy Technology Data Exchange (ETDEWEB)

    Mulligan, Michael; /MIT, LNS; Nayak, Chetan; /Station Q, UCSB; Kachru, Shamit; /Stanford U., Phys. Dept. /SLAC

    2012-06-06

    We present a Landau-Ginzburg theory for a fractional quantized Hall nematic state and the transition to it from an isotropic fractional quantum Hall state. This justifies Lifshitz-Chern-Simons theory - which is shown to be its dual - on a more microscopic basis and enables us to compute a ground state wave function in the symmetry-broken phase. In such a state of matter, the Hall resistance remains quantized while the longitudinal DC resistivity due to thermally-excited quasiparticles is anisotropic. We interpret recent experiments at Landau level filling factor {nu} = 7/3 in terms of our theory.

  20. Effects of Hall Current in the Driven Reconnection with Various Scales

    Institute of Scientific and Technical Information of China (English)

    YANG Hong-Ang; JIN Shu-Ping

    2004-01-01

    In the driven reconnection process with various scales, the effect of Hall current is studied numerically using a Hall magnetohydrodynamics (MHD) code derived from a multi-step implicit scheme. In the cases with Lc/di ≤ 1.0 (Lcis the half-thickness of initial current layer, di is the ion inertial length), the features of Hall MHD reconnection are shown as follows: a quasi-steady single X-line reconnection is obtained, the By component with a quadrupolar structure is generated and the maximum reconnection rate is larger than 0.11. In the cases with Lc/di > 1.0, the effect of Hall current on the reconnection dynamics weakens and Hall MHD reconnection is gradually transformed into resistive MHD reconnection as Lc/di increases.

  1. Quantum spin/valley Hall effect and topological insulator phase transitions in silicene

    KAUST Repository

    Tahir, M.

    2013-04-26

    We present a theoretical realization of quantum spin and quantum valley Hall effects in silicene. We show that combination of an electric field and intrinsic spin-orbit interaction leads to quantum phase transitions at the charge neutrality point. This phase transition from a two dimensional topological insulator to a trivial insulating state is accompanied by a quenching of the quantum spin Hall effect and the onset of a quantum valley Hall effect, providing a tool to experimentally tune the topological state of silicene. In contrast to graphene and other conventional topological insulators, the proposed effects in silicene are accessible to experiments.

  2. Hall effect of La2/3(Ca,Pb)1/3MnO3 single crystals near the critical temperature

    International Nuclear Information System (INIS)

    The Hall resistivity ρxy of a La2/3(Ca,Pb)1/3MnO3 single crystal has been measured as a function of temperature and field. The overall behavior is similar to that observed previously in thin films. At 5 K, ρxy is positive and linear in field, indicating that the anomalous contribution RS is negligible. However, the effective carrier density in a free electron model is neff=2.4 holes/Mn, even larger than the 0.85 - 1.9 holes/Mn reported for thin films and far larger than the 0.33 holes/Mn expected from the doping level. As temperature increases, a strong, negative contribution to ρxy appears, that we ascribe to RS. Using detailed magnetization data, we separate the ordinary (∝B) and anomalous (∝M) contributions. Below Tc, |RS|∝ρxx, indicating that magnetic skew scattering is the dominant mechanism in the metallic ferromagnetic regime. At and above the resistivity-peak temperature, we find that ρxy/ρxxM is a constant, independent of temperature and field. This implies that the anomalous Hall coefficient is proportional to the magnetoresistance. A different explanation based on the two-fluid model is also presented. copyright 1999 The American Physical Society

  3. Quantum Hall effect observations in commercial MOSFETs and effects of thermoelectric power

    International Nuclear Information System (INIS)

    Quantum Hall effect measurements on commercial low-mobility n-channel MOSFETs have been performed. The channel resistance vs. electron concentration has the expected oscillating behaviour and gives the quantized values for the Hall resistance, at least in the region of higher mobility. One class of the tested samples gave a surprising behaviour, both in QHE and in field effect mobility measurements: this is thought to be due to uncontrolled differences in the diffusion zones at the interface between the channel and the contacts. In particular, it is attributed the deformation of the QHE curves to the onset of a thermoelectromotive force which is present in the electron gas even if the sample is isothermal. A clear evidence for thermoelectric effects is given by measurements made on a high-quality Hall geometry MOSFET

  4. Gauge potential formulations of the spin Hall effect in graphene

    International Nuclear Information System (INIS)

    Two different gauge potential methods are engaged to calculate explicitly the spin Hall conductivity in graphene. The graphene Hamiltonian with spin-orbit interaction is expressed in terms of kinematic momenta by introducing a gauge potential. A formulation of the spin Hall conductivity is established by requiring that the time evolution of this kinematic momentum vector vanishes. We then calculated the conductivity employing the Berry gauge fields. We show that both of the gauge fields can be deduced from the pure gauge field arising from the Foldy-Wouthuysen transformations. -- Highlights: → The graphene Hamiltonian is expressed by introducing a gauge potential. → The spin Hall conductivity is formulated by Heisenberg equations of motion. → The spin Hall conductivity is calculated in terms of Berry phases.

  5. Partition noise and statistics in the fractional quantum Hall effect

    OpenAIRE

    Safi, I.; Devillard, P.; Martin, T

    2000-01-01

    A microscopic theory of current partition in fractional quantum Hall liquids, described by chiral Luttinger liquids, is developed to compute the noise correlations, using the Keldysh technique. In this Hanbury-Brown and Twiss geometry, at Laughlin filling factor \

  6. Quantum Spin Hall Effect in Inverted Type II Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chaoxing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Hughes, Taylor L.; Qi, Xiao-Liang; /Stanford U., Phys. Dept.; Wang, Kang; /UCLA; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    The quantum spin Hall (QSH) state is a topologically non-trivial state of quantum matter which preserves time-reversal symmetry; it has an energy gap in the bulk, but topologically robust gapless states at the edge. Recently, this novel effect has been predicted and observed in HgTe quantum wells. In this work we predict a similar effect arising in Type-II semiconductor quantum wells made from InAs/GaSb/AlSb. Because of a rare band alignment the quantum well band structure exhibits an 'inverted' phase similar to CdTe/HgTe quantum wells, which is a QSH state when the Fermi level lies inside the gap. Due to the asymmetric structure of this quantum well, the effects of inversion symmetry breaking and inter-layer charge transfer are essential. By standard self-consistent calculations, we show that the QSH state persists when these corrections are included, and a quantum phase transition between the normal insulator and the QSH phase can be electrically tuned by the gate voltage.

  7. Prediction of giant intrinsic spin-Hall effect in strained p-GaAs quantum wells

    International Nuclear Information System (INIS)

    We perform spin resolved non-equilibrium Green's function calculations in nanostructured, strained two-dimensional GaAs electron and hole gases. Inelastic scattering is taken into account. We show theoretically that the intrinsic inverse spin-Hall effect provides a simple, sensitive, and purely electrical scheme to measure the spin polarization in nanostructures. We predict large spin polarizations and spin-Hall voltages for several concrete device geometries. We propose tensile strained p-GaAs as being optimally suited for detecting the inverse spin Hall effect and show that the effect is absent in n-GaAs.

  8. Intrinsic Spin Hall Effect Induced by Quantum Phase Transition in HgCdTe Quantum Wells

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Wen; Chang, Kai; /Beijing, Inst. Semiconductors; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-19

    Spin Hall effect can be induced both by the extrinsic impurity scattering and by the intrinsic spin-orbit coupling in the electronic structure. The HgTe/CdTe quantum well has a quantum phase transition where the electronic structure changes from normal to inverted. We show that the intrinsic spin Hall effect of the conduction band vanishes on the normal side, while it is finite on the inverted side. This difference gives a direct mechanism to experimentally distinguish the intrinsic spin Hall effect from the extrinsic one.

  9. Origin of anomalous inverse notch effect in bulk metallic glasses

    Science.gov (United States)

    Pan, J.; Zhou, H. F.; Wang, Z. T.; Li, Y.; Gao, H. J.

    2015-11-01

    Understanding notch-related failure is crucial for the design of reliable engineering structures. However, substantial controversies exist in the literature on the notch effect in bulk metallic glasses (BMGs), and the underlying physical mechanism responsible for the apparent confusion is still poorly understood. Here we investigate the physical origin of an inverse notch effect in a Zr-based metallic glass, where the tensile strength of the material is dramatically enhanced, rather than decreased (as expected from the stress concentration point of view), by introduction of a notch. Our experiments and molecular dynamics simulations show that the seemingly anomalous inverse notch effect is in fact caused by a transition in failure mechanism from shear banding at the notch tip to cavitation and void coalescence. Based on our theoretical analysis, the transition occurs as the stress triaxiality in the notched sample exceeds a material-dependent threshold value. Our results fill the gap in the current understanding of BMG strength and failure mechanism by resolving the conflicts on notch effects and may inspire re-interpretation of previous reports on BMG fracture toughness where pre-existing notches were routinely adopted.

  10. Effect of anomalous resistivity on the dynamics of plasma switching

    International Nuclear Information System (INIS)

    Some of the conditions for electron MHD are recollected, and it is shown how this leads to anomalous resistivity which may play an important role in the dynamics of POS. It has been shown that not only the order of value of the resistance of the plasma-filled diode but rather basic scalings have to be changed in the regime of essential anomalous resistivity. (author). 11 refs

  11. Separately contacted edge states at high imbalance in the integer and fractional quantum Hall effect regime

    OpenAIRE

    Deviatov, E. V.; Lorke, A

    2008-01-01

    This review presents experimental results on the inter-edge-state transport in the quantum Hall effect, mostly obtained in the regime of high imbalance. The application of a special geometry makes it possible to perform I-V spectroscopy between individual edge channels in both the integer and the fractional regime. This makes it possible to study in detail a number of physical effects such as the creation of topological defects in the integer quantum Hall effect and neutral collective modes e...

  12. On the gauge invariant and topological nature of the localization determining the Quantum Hall Effect plateaus

    International Nuclear Information System (INIS)

    It is shown how the electromagnetic response of 2DEG under Quantum Hall Effect regime, characterized by the Chern-Simons topological action, transforms the sample impurities and defects in charge-reservoirs that stabilize the Hall conductivity plateaus. The results determine the basic dynamical origin of the singular properties of localization under the occurrence of the Quantum Hall Effect obtained in the pioneering works of Laughlin and of Joynt and Prange, by means of a gauge invariance argument and a purely electronic analysis, respectively. The common intuitive picture of electrons moving along the equipotential lines gets an analytical realization through the Chern-Simons current and charge densities. (author)

  13. Investigation of electrical characteristics of different ceramic samples using Hall effect measurement

    Directory of Open Access Journals (Sweden)

    Radomir Džakula

    2008-06-01

    Full Text Available Hall effect is a very popular technique and is widely used to quantify important electrical parameters such as carrier concentration, resistivity, mobility and Hall coeffi cient of different types of samples. In this paper, electrical characteristics of three ceramic samples will be analyzed using a Hall effect measurement system (Ecopia, HMS-3000, which is based on the van der Pauw method. Measured results for mobility and electrical resistivity at three temperatures (25°C, 50°C and 80°C will be presented. Current-voltage and current-resistance dependence between terminals of four point contact of different samples will be also demonstrated.

  14. Comparative Study on the Performance of Five Different Hall Effect Devices

    Directory of Open Access Journals (Sweden)

    Maher Kayal

    2013-02-01

    Full Text Available Five different Hall Effect sensors were modeled and their performance evaluated using a three dimensional simulator. The physical structure of the implemented sensors reproduces a certain technological fabrication process. Hall voltage, absolute, current-related, voltage-related and power-related sensitivities were obtained for each sensor. The effect of artificial offset was also investigated for cross-like structures. The simulation procedure guides the designer in choosing the Hall cell optimum shape, dimensions and device polarization conditions that would allow the highest performance.

  15. Quantum Hall states stabilized in semi-magnetic bilayers of topological insulators

    Science.gov (United States)

    Yoshimi, R.; Yasuda, K.; Tsukazaki, A.; Takahashi, K. S.; Nagaosa, N.; Kawasaki, M.; Tokura, Y.

    2015-10-01

    By breaking the time-reversal symmetry in three-dimensional topological insulators with the introduction of spontaneous magnetization or application of magnetic field, the surface states become gapped, leading to quantum anomalous Hall effect or quantum Hall effect, when the chemical potential locates inside the gap. Further breaking of inversion symmetry is possible by employing magnetic topological insulator heterostructures that host non-degenerate top and bottom surface states. Here we demonstrate the tailored-material approach for the realization of robust quantum Hall states in the bilayer system, in which the cooperative or cancelling combination of the anomalous and ordinary Hall responses from the respective magnetic and non-magnetic layers is exemplified. The appearance of quantum Hall states at filling factor 0 and +1 can be understood by the relationship of energy band diagrams for the two independent surface states. The designable heterostructures of magnetic topological insulator may explore a new arena for intriguing topological transport and functionality.

  16. Does the Hall Effect Solve the Flux Pileup Saturation Problem?

    Science.gov (United States)

    Dorelli, John C.

    2010-01-01

    It is well known that magnetic flux pileup can significantly speed up the rate of magnetic reconnection in high Lundquist number resistive MHD,allowing reconnection to proceed at a rate which is insensitive to the plasma resistivity over a wide range of Lundquist number. Hence, pileup is a possible solution to the Sweet-Parker time scale problem. Unfortunately, pileup tends to saturate above a critical value of the Lundquist number, S_c, where the value ofS_c depends on initial and boundary conditions, with Sweet-Parker scaling returning above S_c. It has been argued (see Dorelli and Bim [2003] and Dorelli [2003]) that the Hall effect can allow flux pileup to saturate (when the scale of the current sheet approaches ion inertial scale, di) before the reconnection rate begins to stall. However, the resulting saturated reconnection rate, while insensitive to the plasma resistivity, was found to depend strongly on the di. In this presentation, we revisit the problem of magnetic island coalescence (which is a well known example of flux pileup reconnection), addressing the dependence of the maximum coalescence rate on the ratio of di in the "large island" limit in which the following inequality is always satisfied: l_eta di lambda, where I_eta is the resistive diffusion length and lambda is the island wavelength.

  17. 4.5-kW Hall Effect Thruster Evaluated

    Science.gov (United States)

    Mason, Lee S.

    2000-01-01

    As part of an Interagency Agreement with the Air Force Research Lab (AFRL), a space simulation test of a Russian SPT 140 Hall Effect Thruster was completed in September 1999 at Vacuum Facility 6 at the NASA Glenn Research Center at Lewis Field. The thruster was subjected to a three-part test sequence that included thrust and performance characterization, electromagnetic interference, and plume contamination. SPT 140 is a 4.5-kW thruster developed under a joint agreement between AFRL, Atlantic Research Corp, and Space Systems/Loral, and was manufactured by the Fakal Experimental Design Bureau of Russia. All objectives were satisfied, and the thruster performed exceptionally well during the 120-hr test program, which comprised 33 engine firings. The Glenn testing provided a critical contribution to the thruster development effort, and the large volume and high pumping speed of this vacuum facility was key to the test s success. The low background pressure (1 10 6 torr) provided a more accurate representation of space vacuum than is possible in most vacuum chambers. The facility had been upgraded recently with new cryogenic pumps and sputter shielding to support the active electric propulsion program at Glenn. The Glenn test team was responsible for all test support equipment, including the thrust stand, power supplies, data acquisition, electromagnetic interference measurement equipment, and the contamination measurement system.

  18. Quantum Hall effect of self-organized graphene monolayers on the C-face of 6H-SiC

    International Nuclear Information System (INIS)

    We review some of the electric properties of self-organized graphene monolayers on the carbon face of SiC. From sparse surface defects acting as nucleation centres, isolated graphene layers grow in the shape of triangles or ribbons on the step bunched SiC surface. Using e-beam lithography, standard Hall bars have been made. At low magnetic fields, conductance fluctuations, weak localization, electron–electron interactions are usually observed. At higher magnetic fields, the anomalous quantum Hall (QHE) effect typical of monolayer graphene is also observed. In this regime, the breakdown of the QHE appears at moderate currents, which we attribute to the persistence of impurities in the vicinity of the graphene layer. Moderate heating (150 °C) is not sufficient to overcome this issue, and moreover, the carrier concentration cannot be controlled. In order to control the carrier concentration, bottom-gated samples are also presented. In these devices, the carrier concentration can be modulated, but the breakdown current remains very small. (paper)

  19. Preliminary Results of Performance Measurements on a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

    Science.gov (United States)

    Polzin, K. A.; Raitses, Y.; Merino, E.; Fisch, N. J.

    2008-01-01

    The performance of a low-power cylindrical Hall thruster, which more readily lends itself to miniaturization and low-power operation than a conventional (annular) Hall thruster, was measured using a planar plasma probe and a thrust stand. The field in the cylindrical thruster was produced using permanent magnets, promising a power reduction over previous cylindrical thruster iterations that employed electromagnets to generate the required magnetic field topology. Two sets of ring-shaped permanent magnets are used, and two different field configurations can be produced by reorienting the poles of one magnet relative to the other. A plasma probe measuring ion flux in the plume is used to estimate the current utilization for the two magnetic configurations. The measurements indicate that electron transport is impeded much more effectively in one configuration, implying a higher thrust efficiency. Preliminary thruster performance measurements on this configuration were obtained over a power range of 100-250 W. The thrust levels over this power range were 3.5-6.5 mN, with anode efficiencies and specific impulses spanning 14-19% and 875- 1425 s, respectively. The magnetic field in the thruster was lower for the thrust measurements than the plasma probe measurements due to heating and weakening of the permanent magnets, reducing the maximum field strength from 2 kG to roughly 750-800 G. The discharge current levels observed during thrust stand testing were anomalously high compared to those levels measured in previous experiments with this thruster.

  20. Effect of NiO inserted layer on spin-Hall magnetoresistance in Pt/NiO/YIG heterostructures

    Science.gov (United States)

    Shang, T.; Zhan, Q. F.; Yang, H. L.; Zuo, Z. H.; Xie, Y. L.; Liu, L. P.; Zhang, S. L.; Zhang, Y.; Li, H. H.; Wang, B. M.; Wu, Y. H.; Zhang, S.; Li, Run-Wei

    2016-07-01

    We investigate spin-current transport with an antiferromagnetic insulator NiO thin layer by means of the spin-Hall magnetoresistance (SMR) over a wide range of temperature in Pt/NiO/Y3Fe5O12 (Pt/NiO/YIG) heterostructures. The SMR signal is comparable to that without the NiO layer as long as the temperature is near or above the blocking temperature of the NiO, indicating that the magnetic fluctuation of the insulating NiO is essential for transmitting the spin current from the Pt to YIG layer. On the other hand, the SMR signal becomes negligibly small at low temperature, and both conventional anisotropic magnetoresistance and the anomalous Hall resistance are extremely small at any temperature, implying that the insertion of the NiO has completely suppressed the Pt magnetization induced by the YIG magnetic proximity effect (MPE). The dual roles of the thin NiO layer are, to suppress the magnetic interaction or MPE between Pt and YIG, and to maintain efficient spin current transmission at high temperature.