We study theoretically transverse photoconductivity induced by circularly polarized radiation, i.e. the photovoltaic Hall effect, and linearly polarized radiation causing intraband optical transitions in two-dimensional electron gas (2DEG). We develop a microscopic theory of these effects based on analytical solution of the Boltzmann equation for arbitrary electron spectrum and scattering mechanism. We calculate the transverse photoconductivity of 2DEG with parabolic and linear dispersion for short-range and Coulomb scatterers at different temperatures. We show that the transverse electric current is significantly enhanced at frequencies comparable to the inverse energy relaxation time, whereas at higher frequencies the excitation spectrum and the direction of current depend on the scattering mechanism. We also analyse the effect of thermalization processes caused by electron-electron collisions on the photoconductivity.
Response of electronic systems in intense lights (AC electric fields) to DC source-drain fields is formulated with the Floquet method. We have then applied the formalism to graphene, for which we show that a non-linear effect of a circularly polarized light can open a gap in the Dirac cone, which leads to a photo-induced dc Hall current. This is numerically confirmed for a graphene ribbon attached to electrodes with the Keldysh Green's function.
We theoretically study the circularly polarized light-induced Floquet state in line-node semimetals with time-reversal symmetry and inversion symmetry. It is found that the Floquet state can show the photovoltaic anomalous Hall effect when an applied circularly polarized light gaps out the line node in the bulk and leave Weyl point nodes. The Hall conductivity is sensitive to the location of Fermi level: When the Fermi level locates at the node, the Hall conductivity depends on the radius of line node and is nearly independent of the intensity of light. Away from the line node, the Hall conduc…
Photovoltaic Hall effect -- the Hall effect induced by intense, circularly-polarized light in the absence of static magnetic fields -- has been proposed in Phys. Rev. B 79, 081406R (2009) for graphene where a massless Dirac dispersion is realized. The photovoltaic Berry curvature (a nonequilibrium extension of the standard Berry curvature) is the key quantity to understand this effect, which appears in the Kubo formula extended to Hall transport in the presence of strong AC field backgrounds. Here we elaborate the properties of the photovoltaic curvature such as the frequency and field strengt…
We propose an all optical way to measure the recently proposed "photovoltaic Hall effect", i.e., a DC Hall effect induced by a circularly polarized light in the absence of static magnetic fields. For this, we have calculated the Faraday rotation angle induced by the photovoltaic Hall effect with the Kubo formula extended for photovoltaic optical response in the presence of strong AC electric fields treated with the Floquet formalism. We also point out the possibility of observing the effect in three-dimensional graphite, and more generally in multi-band systems such as materials described by t…
Successful incorporation of the spin degree of freedom in semiconductor technology requires the development of a new paradigm allowing for a scalable, non-destructive electrical detection of the spin-polarization of injected charge carriers as they propagate along the semiconducting channel. In this paper we report the observation of a spin-injection Hall effect (SIHE) which exploits the quantum-relativistic nature of spin-charge transport and which meets all these key requirements on the spin detection. The two-dimensional electron-hole gas photo-voltaic cell we designed to observe the SIHE a…
Using very-high mobility GaAs/AlGaAs 2D electron Hall bar samples, we have experimentally studied the photoresistance/photovoltaic oscillations induced by microwave irradiation in the regime where both 1/B and B-periodic oscillations can be observed. In the frequency range between 27 and 130 GHz we found that these two types of oscillations are decoupled from each other, consistent with the respective models that 1/B oscillations occur in bulk while the B-oscillations occur along the edges of the Hall bars. In contrast to the original report of this phenomenon (Ref. 1) the periodicity of the B…
A two dimensional electron system without spatial inversion symmetry develops a sample specific dc voltage when exposed to a microwave radiation at low temperature. We investigate this photovoltaic (PV) effect, in the case where spatial symmetry is broken by an evanescent high-frequency potential. We measure the induced PV voltage in a ${\rm GaAs/Ga_{1-x}Al_{x}As}$ Hall bar at magnetic fields in the Tesla range. We find that in this regime the induced PV voltage is anti-symmetric with magnetic field, and exhibits regular Shubnikov-de Haas like oscillations. Our experimental results can be unde…
The implementation of a wide range of novel concepts for next-generation high-efficiency solar cells is based on nanostructures with configuration-tunable optoelectronic properties. On the other hand, effective nano-optical light-trapping concepts enable the use of ultra-thin absorber architectures. In both cases, the local density of electronic and optical states deviates strongly from that in a homogeneous bulk material. At the same time, non-local and coherent phenomena like tunneling or ballistic transport become increasingly relevant. As a consequence, the semi-classical, diffusive bulk p…
Harnessing hidden quantum metric response in a 2D magnet via nonlocal photovoltaic effect
State Key Laboratory of Semiconductor Physics and Chip Technologies, Institute of Semiconductors, Chinese Academy of Sciences（中国科学院半导体研究所半导体物理与芯片技术国家重点实验室）；School of Electronics and Information Engineering, Tiangong University（天津工业大学电子信息工程学院）；College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences（中国科学院大学材料科学与光电技术学院）；Institute of Physical Science and Information Technology, Anhui University（安徽大学物理科学与技术学院）；Anhui Provincial Key Laboratory of Magnetic Functional Materials and Devices, Anhui University（安徽大学安徽省磁性功能材料与器件重点实验室）；Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences（中国科学院合肥物质科学研究院固体物理研究所材料物理重点实验室）；National Laboratory of Solid-State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University（南京大学物理学院固态微结构国家重点实验室先进微结构协同创新中心）；School of Physics, Zhejiang University（浙江大学物理学院）
The bulk photovoltaic effect (BPVE) -- generation of electric currents by light in noncentrosymmetric materials in the absence of electric fields and gradients -- has been intensively investigated in the end of the last century. The outcomes including all main aspects of this phenomenon were summarized in review and books. A new upsurge of interest to the BPVE occurred recently and resulted in a flux of misleading theoretical and experimental publications centered around the so-called shift current. Numerous top-rated recent publications ignore the basic principles of charge-transport phenomen…
We argue that the static non-linear Hall conductivity can always be represented as a vector in two-dimensions and as a pseudo-tensor in three-dimensions independent of its microscopic origin. In a single band model with a constant relaxation rate this vector or tensor is proportional to the Berry curvature dipole \cite{Sodemann_2015}. Here, we develop a quantum Boltzmann formalism to second order in electric fields. We find that in addition to the Berry Curvature Dipole term, there exist additional disorder mediated corrections to the non-linear Hall tensor that have the same scaling in impuri…
Van der Waals heterojunctions between two-dimensional (2D) layered materials and nanomaterials of different dimensions present unique opportunities for gate-tunable optoelectronic devices. Mixed dimensional p-n heterojunction diodes, such as p-type pentacene (0D) and n-type monolayer MoS2 (2D), are especially interesting for photovoltaic applications where the absorption cross-section and charge transfer processes can be tailored by rational selection from the vast library of organic molecules and 2D materials. Here, we study the kinetics of excited carriers in pentacene-MoS2 p-n type-II heter…
We propose a modified Boltzmann nonlinear electric-transport framework which differs from the nonlinear generalization of the linear Boltzmann formalism by a contribution that has no counterpart in linear response. This contribution follows from the interband-coherence effect of dc electric-fields during scattering and is related to the interband Berry connection. As an application, we demonstrate it in the second-order nonlinear Hall effect of the tilted massive Dirac model. The intuitive Boltzmann constructions are confirmed by a quantum kinetic theory, which shows that arbitrary $n$th-order…
Dynamic dipolar toroidal response is demonstrated by an optical plasmonic metamaterial composed of double disks. This response with a hotspot of localized E-field concentration is a well-behaved toroidal cavity mode that exhibits a large Purcell factor due to its deep-subwavelength mode volume. All-optical Hall effect (photovoltaic) due to this optical toroidal moment is demonstrated numerically, in mimicking the magnetoelectric effect in multiferroic systems. The result shows a promising avenue to explore various optical phenomena associated with this intriguing dynamic toroidal moment.
The kinetics of the extrinsic spin Hall conductivity induced by the skew scattering is performed from the fully microscopic kinetic spin Bloch equation approach in $(001)$ GaAs symmetric quantum well. In the steady state, the extrinsic spin Hall current/conductivity vanishes for the linear-$\mathbf k$ dependent spin-orbit coupling and is very small for the cubic-$\mathbf k$ dependent spin-orbit coupling. The spin precession induced by the Dresselhaus/Rashba spin-orbit coupling plays a very important role in the vanishment of the extrinsic spin Hall conductivity in the steady state. An in-plane…
We present a two-band kinetic equation method to investigate the anomalous Hall effect in a Rashba two-dimensional electron system subjected to a homogeneous magnetization. The electron-impurity scattering is taken into account in the self-consistent Born approximation. It is demonstrated that the impurity-density-free anomalous Hall conductivity arises from an intrinsic and a disorder-mediated mechanisms, associated respectively with the electron states under and near the Fermi surface. The intrinsic mechanism relates to a dc-field-induced transition process, or in other words, a linear stati…
Based on quantum field theory, we formulate the Wigner function and quantum kinetic theory for polarized photons in curved spacetimes which admit a covariantly constant timelike vector. From this framework, the photonic chiral/zilch vortical effects are reproduced in a rigidly rotating coordinate. In a spatially inhomogeneous coordinate, we derive the spin Hall effect for the photon helicity current and energy current in equilibrium. Our derivation reveals that such photonic Hall effect are related to the photonic vortical effect via the Lorentz invariance and their transport coefficients matc…
Electrons moving in a Bloch band are known to acquire an anomalous Hall velocity proportional to the Berry curvature of the band which is responsible for the intrinsic linear Hall effect in materials with broken time-reversal symmetry. Here, we demonstrate that there is also an anomalous correction to the electron acceleration which is proportional to the Berry curvature dipole and is responsible for the Nonlinear Hall effect recently discovered in materials with broken inversion symmetry. This allows us to uncover a deeper meaning of the Berry curvature dipole as a nonlinear version of the Dr…
We present a theory of the photovoltaic valley-dependent Hall effect in a two-dimensional Dirac semiconductor subject to an intense near-resonant electromagnetic field. Our theory captures and elucidates the influence of both the field-induced resonant interband transitions and the nonequilibrium carrier kinetics on the resulting valley Hall transport in terms of photon-dressed quasiparticles. The non-perturbative renormalization effect of the pump field manifests itself in the dynamics of the photon-dressed quasiparticles, with a quasienergy spectrum characterized by {dynamical gaps $δ_η$ ($η…
We present a systematic microscopic derivation of the semiclassical Boltzmann equation for band structures with the finite Berry curvature based on Keldysh technique of nonequilibrium systems. In the analysis, an ac electrical driving field is kept up to quadratic order, and both cases of small and large frequencies corresponding to intra- and interband transitions are considered. In particular, this formulation is suitable for the study of nonlinear Hall effect and photogalvanic phenomena. The role of impurity scattering is carefully addressed. Specifically, in addition to previously studied …
The coupled kinetic equation for density and spin Wigner functions are derived including spin-orbit coupling, electric and magnetic field as well as selfconsistent Hartree meanfields suited for SU(2) transport. The interactions are assumed to be with scalar and magnetic impurities as well as scalar and spin-flip potentials among the particles. The spin-orbit interaction is used in a form suitable to solid state physics with Rashba or Dresselhaus coupling, graphene, extrinsic spin-orbit coupling as well as effective nuclear matter coupling. The deficiencies of the two-fluid model are worked out…
We propose a mechanism of spin Hall effect in two-dimensional electron gas with spatially random Rashba spin-orbit interaction. The calculations based on the Kubo formalism and kinetic equation show that in contrast to the constant spin-orbit coupling, spin Hall conductivity in the random spin-orbit field is not totally suppressed by the potential impurity scattering. Even if the regular contribution is removed by the vertex corrections, the terms we consider, remain. Therefore, the intrinsic spin-Hall effect exists being, however, non-universal.
We discuss a quasi-particle formulation of effective edge theories for the fractional quantum Hall effect. Fundamental quasi-particles for the Laughlin state with filling fraction ν=1/3 are edge electrons of charge -e and edge quasi-holes of charge +e/3. These quasi-particles satisfy exclusion statistics in the sense of Haldane. We exploit algebraic properties of edge electrons to derive a kinetic equation for charge transport between a ν=1/3 fractional quantum Hall edge and a normal metal.
We show that an electric field applied to a strained topological Dirac semimetal, such as Na3Bi and Cd3As2, induces a spin Hall current that is quadratic in the electric field. By regarding the strain as an effective "axial magnetic field" for the Dirac electrons, we investigate the electron and spin transport semiclassically in terms of the chiral kinetic theory. The nonlinear spin Hall effect arises as the cross effect between the regular Hall effect driven by the axial magnetic field and the anomalous Hall effect coming from the momentum-space topology. It provides an efficient way to gener…
We consider the conductivity tensor for composite fermions in a close to half-filled Landau band in the temperature regime where the scattering off the potential and the trapped gauge field of random impurities dominates. The Boltzmann equation approach is employed to calculate the quasiclassical transport properties at finite effective magnetic field, wavevector and frequency. We present an exact solution of the kinetic equation for all parameter regimes. Our results allow a consistent description of recently observed surface acoustic wave resonances and other findings.
The flow of momentum and energy in a fluid is typically associated with dissipative transport coefficients: viscosity and thermal conductivity. Fluids that break certain symmetries such as mirror symmetry and time-reversal invariance can display non-dissipative transport coefficients called odd (or Hall) viscosities and thermal conductivities. The goal of this paper is to elucidate the microscopic origin of these dissipationless transport coefficients using kinetic theory. We show that odd viscosity and odd thermal conductivity arise when the linearized collision operator is not Hermitian. Thi…
In absence of time-reversal symmetry, viscous electron flow hosts a number of interesting phenomena, of which we focus here on the Hall viscosity. Taking a step beyond the hydrodynamic definition of the Hall viscosity, we derive a generalized relation between Hall viscosity and transverse electric field using a kinetic equation approach. We explore two different geometries where the Hall viscosity is accessible to measurement. For hydrodynamic flow of electrons in a narrow channel, we find that the viscosity may be measured by a local probe of the transverse electric field near the center of t…
The manuscript contains Comment to "Quantum Spin Hall Effect and Topological Phase Transitio in HGTe Quantum Wells" by B. Andrei Bernevig, Taylor L. Hughes and Shou-Cheng Zhang Science 314, 1757 (2006). The text proves that the quantum state, identified by these authors as the surface state located inside HgTe well is incorrect physically. The kinetic energy of the state is negative. The state cannot be identified as proper eigenfunction (vector) in the Hilbert space. Therefore the state could be used as a primer in the topological state theory, developed in the following publications.
There are a variety of nonlinear optical effects including higher harmonic generations, photovoltaic effects, and nonlinear Kerr rotations. They are realized by the strong light irradiation to materials that results in nonlinear polarizations in the electric field. These are of great importance in studying the physics of excited states of the system as well as for applications to optical devices and solar cells. Nonlinear properties of materials are usually described by the nonlinear susceptibilities $χ$'s, which have complex expressions including many matrix elements and energy denominators. …
Using the Keldysh technique, we derive a set of quasiclassical equations for Bloch electrons in noncentrosymmetric crystals upon excitation with quasimonochromatic radiation in the presence of external electrical and magnetic fields. These equations are the analog to the semiconductor-Bloch-equations for the dynamics of electrons including the photogalvanic effect (PGE) in particular the shift mechanism. The shift PGE was recently identified as showing promise for the development of new photovoltaic materials. In addition, our theory may be useful to investigate the interplay between breaking …
Using a mean field theory on the von Neumann lattice, we study compressible anisotropic states around $ν=l+1/2$ in the quantum Hall system. The Hartree-Fock energy of the UCDW are calculated self-consistently. In these states the unidirectional charge density wave (UCDW) seems to be the most plausible state. We show that the UCDW is regarded as a collection of the one-dimensional lattice fermion systems which extend to the uniform direction. The kinetic energy of this one-dimensional system is induced from the Coulomb interaction term and the self-consistent Fermi surface is obtained.
A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precessional effects displays a complex spatial dependence that can be exploit…
A proposal to detect the purported canted antiferromagnet order for the $ν=0$ quantum Hall state of graphene based on a two-terminal spin transport setup is theoretically discussed. In the presence of a magnetic field normal to the graphene plane, a dynamic and inhomogeneous texture of the Néel vector lying within the plane should mediate (nearly dissipationless) superfluid transport of spin angular momentum polarized along the $z$ axis, which could serve as a strong support for the canted antiferromagnet scenario. Spin injection and detection can be achieved by coupling two spin-polarized edg…
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 ambigu…
Giant resonant nonlinear THz valley Hall effect in 2D Dirac semiconductors
Guangdong Technion – Israel Institute of Technology（广东以色列理工学院）；Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Science（俄罗斯科学院西伯利亚分院热诺夫半导体物理研究所）；Novosibirsk State Technical University（新西伯利亚国立技术大学）；Technion – Israel Institute of Technology（以色列理工学院）
We study the chiral electric separation effect (CESE) in Weyl semimetals (WSM). Within the model based on the kinetic equation we show that there is a non-zero chirality current in external electric and magnetic fields. We distinguish longitudinal, in-plane transverse, Hall, and anomalous Hall components of the CESE. It is shown that the first two components are quadratic in electric field and linear in magnetic field, while the Hall component is quadratic in both the electric and magnetic fields. All three are due to the chiral anomaly. In WSMs the chirality current can be associated with the…
In a thin strip of a two-dimensional semiconductor electronic system, spin-orbit coupling may be induced near both edges of the strip due to the substantial spatial variation of the confining potential in the boundary regions. In this paper we show that, in the presence of boundary-confinement induced spin-orbit coupling, a longitudinal charge current circulating through a 2D semiconductor strip may cause \textit{strong} non-equilibrium spin accumulation near both edges of the strip. The spins will be polarized along the normal of the 2DEG plane but in opposite directions at both edges of the …
A circularly polarized a.c. pump field illuminated near resonance on two-dimensional transition metal dichalcogenides (TMDs) produces an anomalous Hall effect in response to a d.c. bias field. In this work, we develop a theory for this photo-induced anomalous Hall effect in undoped TMDs irradiated by a strong coherent laser field. The strong field renormalizes the equilibrium bands and opens up a dynamical energy gap where single-photon resonance occurs. The resulting photon dressed states, or Floquet states, are treated within the rotating wave approximation. A quantum kinetic equation approa…
We propose a nonequilibrium Green's function approach to study the spin-Hall effect in a two-dimensional electron system with both the Rashba and Dresselhaus spin-orbit couplings. By taking into account the long-range electron-impurity scattering, the derived kinetic equations are solved numerically. It is found the vanishing of the total zero-temperature dissipationless spin-Hall effect, contributing from the intrinsic and disorder-mediated processes. This result has been examined in the wide ranges of spin-orbit coupling constants and electron density.
A nonequilibrium Green's functions approach to spin-Hall effect is developed in a diffusive two-dimensional electron system with Rashba spin-orbit interaction. In the presence of long-range impurities, the coupled quantum kinetic equations are solved analytically in the self-consistent Born approximation. It is shown that the intrinsic spin-Hall effect stems from the dc-field-induced perturbation of the density of states. In addition, there is an additional disorder-mediated process, which involves the transition of nonequilibrium electrons between two spin-orbit-coupled bands. It results in a…
We consider spin-polarized electrons in a single Landau level on a cylinder as the circumference of the cylinder goes to infinity. This gives a model of interacting electrons on a circle where the momenta of the particles are restricted and there is no kinetic energy. Quantum Hall states are exact ground states for appropriate short range interactions, and there is a gap to excitations. These states develop adiabatically from this one-dimensional quantum Hall circle to the bulk quantum Hall states and further on into the Tao-Thouless states as the circumference goes to zero. For low filling fr…
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 effect, and the basic aspects of the fractional quantum Hall effect are described in chapter 4. In chapter…
We develop a systematic theory of microwave-induced oscillations in the magnetoresistivity of a two-dimensional electron gas, focusing on the regime of strongly overlapping Landau levels. At linear order in microwave power, two novel mechanisms of the oscillations (``quadrupole'' and ``photovoltaic'') are identified, in addition to those studied before (``displacement'' and ``inelastic''). The quadrupole and photovoltaic mechanisms are shown to be the only ones that give rise to oscillations in the nondiagonal part of the photoconductivity tensor. In the diagonal part, the inelastic contributi…
Recent measurements of the 2D Hall resistance show that the Hall coefficient is independent of the applied in-plane magnetic field, i.e., the spin-polarization of the system. We calculate the weak-field Hall coefficient and the magnetoresistance of a spin polarized 2D system using the semi-classical transport approach based on the screening theory. We solve the coupled kinetic equations of the two carrier system including electron-electron interaction. We find that the in-plane magnetic field dependence of the Hall coefficient is suppressed by the weakening of screening and the electron-electr…
Considering finite-temperature screened electron-impurity scattering, we present a kinetic equation approach to investigate transport properties of two-dimensional massive fermions in silicene. We find that the longitudinal conductivity is always nonvanishing when chemical potential lies within the energy gap. This residual conductivity arises from interband correlation and strongly depends on strength of electron-impurity scattering. We also clarify that the electron-impurity interaction makes substantial contributions to the spin- and valley-Hall conductivities, which, however, are almost in…
The quintessential two-dimensional lattice model that describes the competition between the kinetic energy of electrons and their short-range repulsive interactions is the repulsive Hubbard model. We study a time-reversal symmetric variant of the repulsive Hubbard model defined on a planar lattice: Whereas the interaction is unchanged, any fully occupied band supports a quantized spin Hall effect. We show that at 1/2 filling of this band, the ground state develops spontaneously and simultaneously Ising ferromagnetic long-range order and a quantized charge Hall effect when the interaction is su…
We study the Hall conductivity of a two-dimensional electron gas under an inhomogeneous magnetic field $B(x)$. First, we prove using the quantum kinetic theory that an odd magnetic field can lead to a purely nonlinear Hall response. Second, considering a real-space magnetic dipole consisting of a sign-changing magnetic field and based on numerical semiclassical dynamics, we unveil a parametric resonance involving the cyclotron ratio and a characteristic width of $B(x)$, which can greatly enhance the Hall response. Different from previous mechanisms that rely on the bulk Berry curvature dipole,…
We propose a quasi-particle formulation of effective edge theories for the fractional quantum Hall effect. For the edge of a Laughlin state with filling fraction ν=1/m, our fundamental quasi-particles are edge electrons of charge -e and edge quasi-holes of charge +e/m. These quasi-particles satisfy exclusion statistics in the sense of Haldane. We exploit algebraic properties of edge electrons to derive a kinetic equation for charge transport between a ν=1/m fractional quantum Hall edge and a normal metal. We also analyze alternative `Boltzmann' equations that are directly based on the exclusio…
We consider a two-dimensional electron system subjected to a short-ranged nonmagnetic disorder potential, Coulomb interactions, and Rashba spin-orbit coupling. The path-integral approach incorporated within the Keldysh formalism is used to derive the kinetic equation for the semiclassical Green's function and applied to compute the spin current within the linear response theory. We discuss the frequency dependence of the spin Hall conductivity and further elucidate the role of electron interactions at finite temperatures for both the ballistic and diffusive regimes of transport. We argue that …
In this paper, the chiral Hall effect of strained Weyl semimetals without any external magnetic field is proposed. Electron-phonon coupling emerges in the low-energy fermionic sector through a pseudogauge potential. We show that, by using chiral kinetic theory, the chiral Hall effect appears as a response to a real time-varying electric field in the presence of structural distortion and it causes spatial chirality and charges separation in a Weyl system. We also show that the coupling of the electrons to acoustic phonons as a gapless excitation leads to emerging an optical absorption peak at $…
We review the theoretical basis and understanding of electronic interactions in graphene Landau levels, in the limit of strong correlations. This limit occurs when inter-Landau-level excitations may be omitted because they belong to a high-energy sector, whereas the low-energy excitations only involve the same level, such that the kinetic energy (of the Landau level) is an unimportant constant. Two prominent effects emerge in this limit of strong electronic correlations: generalised quantum Hall ferromagnetic states that profit from the approximate four-fold spin-valley degeneracy of graphene'…
For a long period of time, we have been seeking how Berry curvature influnces the transport properties in materials breaking time-reversal symmetry. In time-reversal symmetric material, there will be no thermoelectric current induced by Berry curvature in linear regime. However, the nonlinear Hall current can be shown in non-magnetic and non-centrosymmetric materials, where Berry curvature dipole plays an important role. Most studies are developed from semi-classical Boltzmann equation. Here we show the quantum kinetic theory for nonlinear Nernst effect and introduce a new type of Berry curvat…
