arXiv subjects

D. A. Pesin

Publications and source records attributed to D. A. Pesin.

At least 19 recordsLinked to original sources

arXiv2025

Revealing electron-lattice decoupling by Peltier thermometry and nanoscale thermal imaging in graphene

Electrical currents in low-dimensional quantum materials can drive electrons far from equilibrium, creating stark imbalance between electron and lattice temperatures. Yet, no existing methods enable simultaneous nanoscale mapping of both temperatures at cryogenic conditions. Here, we introduce a scanning probe technique that images the local lattice temperature and extracts electron temperature at gate-defined p-n junctions in graphene. By applying an alternating electrical current and analyzing first- and second-harmonic responses, we disentangle Joule heating from the Peltier effect-the latter encoding the local electron temperature. This enables the first spatially resolved cryogenic imaging of both phenomena in graphene. Even under modest current bias, the electron temperature increases by nearly three orders of magnitude more than the lattice temperature, revealing strong electron-phonon decoupling and indicating a previously unrecognized electron cooling pathway. Our minimally invasive method is broadly applicable to van der Waals heterostructures and opens new avenues for probing energy dissipation and non-equilibrium transport in correlated and hydrodynamic electron systems.

cond-mat.mes-hall↗

arXiv2025

Magnetochiral anisotropy on a quantum spin Hall edge

We develop a theory of nonlinear low-magnetic-field magnetotransport on a helical edge of a quantum spin Hall insulator due to the edge state coupling to bulk midgap states. We focus on the part of the nonlinear I-V characteristic that is odd in the applied magnetic field, and quadratic in the applied bias voltage. This part of the I-V characteristic corresponds to the resistance of the sample being dependent on the relative orientation of the current and an external magnetic field, hence represents a type of edge magnetochiral anisotropy. We identify two mechanisms of the magnetochiral anisotropy. One is related to the Hubbard interaction on the midgap state, which leads to the dependence of the scattering characteristics on the current flowing on the edge, which results in bias-voltage-dependent resistance, or equivalently conductance, hence a nonlinear I-V. The other is related to the modification of the edge dispersion by a magnetic field, and requires nonlinearity in the edge dispersion. We compare the developed theory to the experiments on monolayer $\mathrm{WTe}_{2}$, and find good agreement with the developed theory.

cond-mat.mes-hall↗

arXiv2023

Collective spin oscillations in a magnetized graphene sheet

We investigate collective spin excitations of graphene electrons with short-ranged interactions and subject to the external Zeeman magnetic field. We find that in addition to the familiar Silin spin wave, a collective spin-flip excitation that reduces to the uniform precession when the wave's momentum approaches zero, the magnetized graphene supports another collective mode visible in the transverse spin susceptibility: a collective spin-current mode. Unlike the Silin wave, this mode is not dictated by the spin-rotational symmetry but rather owns its existence to the pseudo-spin structure of the graphene lattice. We find the new collective excitation to become sharply defined in a finite interval of wave's momenta, the range of which is determined by the interaction and the magnetization.

cond-mat.mes-hall↗

arXiv2023

Magnetic vortex control with current-induced axial magnetization in centrosymmetric Weyl materials

We consider magnetic Weyl metals as a platform to achieve current control of magnetization textures with transport currents, utilizing their underlying band geometry. We show that the transport current in a Weyl semimetal produces an axial magnetization due to orbital magnetic moments of the Weyl electrons. The associated axial magnetization can generate a torque acting on the localized magnetic moments. For the case of a magnetic vortex in a nanodisk of Weyl materials, this current-induced torque can be used to reverse its circulation and polarity. We discuss the axial magnetization torques in Weyl metals on general symmetry grounds, and compare their strength to current-induced torques in more conventional materials.

cond-mat.mes-hall↗

arXiv2023

Geometric phase for nonlinear oscillators from perturbative renormalization group

We formulate a renormalization group approach to a general nonlinear oscillator problem. The approach is based on the exact group law obeyed by solutions of the corresponding ordinary differential equation. We consider both the autonomous models with time-independent parameters, as well as nonautonomous models with slowly varying parameters. We show that the renormalization group equations for the nonautonomous case can be used to determine the geometric phase acquired by the oscillator during the change of its parameters. We illustrate the obtained results by applying them to the Van der Pol, and Van der Pol-Duffing models.

math-ph↗

arXiv2023

Magnetotransport on quantum spin Hall edge coupled to bulk midgap states

We consider magnetotransport on a helical edge of a quantum spin Hall insulator, in the presence of bulk midgap states ``side-coupled" to the edge. In the presence of a magnetic field, the midgap levels are spin-split, and hybridization of these levels with the itinerant edge states leads to backscattering, and the ensuing increase in the resistance. We show that there is a singular cusp-like contribution to the positive magnetoresistance stemming from resonant midgap states weakly coupled to the edge. The singular behavior persists for both coherent and incoherent edge transport regimes. We use the developed theory to fit the experimental data for the magnetoresistance for monolayer WTe$_2$ at liquid helium temperatures. The results of the fitting suggest that the cusp-like behavior of the resistance in weak magnetic fields observed in experiments on monolayer WTe$_2$ with long edge channels might indeed be explained by hybridization of the helical edge states with spin-split bulk midgap states. In particular, the dependence of the magnetoresistance on the direction of the external magnetic field is well described by the incoherent edge transport theory, at the same time being quite distinct from the one expected for a magnetic-field-induced edge gap.

cond-mat.mes-hall↗

arXiv2022

Low-energy effective theory and anomalous Hall effect in monolayer $\mathrm{WTe}_2$

We develop a symmetry-based low-energy theory for monolayer $\mathrm{WTe}_2$ in its 1T$^{\prime}$ phase, which includes eight bands (four orbitals, two spins). This model reduces to the conventional four-band spin-degenerate Dirac model near the Dirac points of the material. We show that measurements of the spin susceptibility, and of the magnitude and time dependence of the anomalous Hall conductivity induced by injected or equilibrium spin polarization can be used to determine the magnitude and form of the spin-orbit coupling Hamiltonian, as well as the dimensionless tilt of the Dirac bands.

cond-mat.mes-hall↗

arXiv2021

Nonreciprocal optics and magnetotransport in Weyl metals as signatures of band topology

We consider effects of spatial dispersion in noncentrosymmetric time-reversal invariant Weyl metals in the presence of a static magnetic field. In particular, we study currents that are linear in both the spatial derivatives of an applied electric field, and the static magnetic field, which are responsible for the phenomenon of gyrotropic birefringence. We show that the chiral anomaly and the chiral magnetic effect make the leading contribution to this class of phenomena in metals. We apply the obtained results to the problem of electromagnetic wave transmission through a thin slab of a Weyl semimetal, and show that the transmission coefficient contains a component that is odd in the applied static magnetic field. As such, it can be easily distinguished from conventional Ohmic magnetotransport effects, which are quadratic in the applied magnetic field. The relative magnitude of the effect can reach a few percent in Weyl materials subject to magnetic fields of 0.1Tesla, while the effect is several orders of magnitude smaller in metals without Berry monopoles. We conclude that the nonreciprocal optical and magnetotransport effects can be a robust probe of band topology in metals.

cond-mat.mes-hall↗

arXiv2021

Anomaly-induced sound absorption in Weyl semimetals

We develop a semiclassical theory of sound absorption in Weyl semimetals in magnetic fields. We focus on the contribution to the absorption that stems from the existence of Berry monopoles in the band structure of such materials, or, equivalently, due to the chiral anomaly and chiral magnetic effect. Sound absorption is shown to come primarily from the motion of Weyl nodes in energy space, associated with the propagation of a sound wave. We argue that acoustic magneto-chiral dichroism, which occurs when absorption of sound is different for opposite propagation directions, and for opposite directions of the magnetic field, can be a definitive probe of band topology. The part of the monopole-related sound magnetoabsorption that is even in the magnetic field is negative in time-reversal Weyl materials. The difference in the sign of the effect as compared to the positive anomaly-related transport magnetoconductance stems from the existence of valley electrochemical imbalances without magnetic field in the sound propagation problem. In centrosymmetric Weyl semimetals with few Weyl nodes, the magneto-absorption is negative at low frequencies, but can change sign with increasing frequency.

cond-mat.mes-hall↗

arXiv2020

Chiral magnetic effect of hot electrons

We propose a way to observe the chiral magnetic effect in non-centrosymmetric Weyl semimetals under the action of strong electric field, via the non-linear part of their I-V characteristic that is odd in the external magnetic field, or odd-in-magnetic field voltages in electrically open circuits. This effect relies on valley-selective heating in such materials, which in general leads to nonequilibrium valley population imbalances. In the presence of an external magnetic field, such a valley-imbalanced Weyl semimetal will in general develop an electric current along the direction of the magnetic field -- the chiral magnetic effect. We also discuss a specific experimental setup to observe the chiral magnetic effect of hot electrons.

cond-mat.mes-hall↗

arXiv2019

Magnetodrag in hydrodynamic regime: effects of magnetoplasmon resonance and Hall viscosity

In this work we study magnetotransport properties in electronic double layers of strongly correlated electron liquids. For sufficiently clean high-mobility samples, the high-temperature regime of transport in these systems can be described in pure hydrodynamic terms. We concentrate on the magnetic field dependence of longitudinal drag effect mediated by the interlayer Coulomb scattering and identify several mechanisms of transresistance which is caused by viscous flows, magnetoplasmon resonance, and dissipative thermal fluxes. In particular, we elucidate how Hall viscosity enters magnetodrag and modifies its temperature dependence in the magnetic field.

cond-mat.mes-hall↗

arXiv2019

Superfluid-insulator transition and the BEC-BCS crossover in the Rashba moat band

We study the superconducting transition in a two-dimensional electron gas with strong Rashba spin-orbit coupling. We assume low electron density, such that only the majority spin band participates in the transition. We show that the superconducting transition follows either the Bose-Einstein condensation (BEC), or the Bardeen-Cooper-Schrieffer (BCS) scenarios, depending on the position of the chemical potential with respect to the bottom of the majority band, and the strength of the Coulomb repulsion between electrons. Hence, the BEC-BCS crossover in this system can be driven either by the change in the chemical potential, or the distance to a gate.

cond-mat.supr-con↗

arXiv2018

Gyrotropic Hall effect in Berry-curved materials

We study the ac Hall response induced by passage of dc transport current in two- and three-dimensional metals with gyrotropic point groups -- the gyrotropic Hall effect -- and consider the phenomenon of current-induced optical activity in noncentrosymmetric metals as a physical application of our theory. While the effect is expected to be present in single crystals of any noncentrosymmetric metal, we expect it to be strongest in enantiomorphic Weyl semimetals. Using the semiclassical kinetic equation approach we present several mechanisms underlying the gyrotropic Hall effect. Amongst them, the intrinsic mechanism is determined by the Berry curvature dipole, while extrinsic impurity-induced processes are related to skew scattering and side jump phenomena. In general, the intrinsic and extrinsic contributions can be of similar magnitude. We discuss the gyrotropic Hall effect for all frequencies of practical interest, from the DC transport limit, to optical frequencies. We show that for frequencies that are small compared to relevant band splittings, the trace of the gyrotropic Hall tensor in three-dimensional materials is proportional to a topological, quantized Berry charge, and therefore is robust in gyrotropic Weyl systems. This implies that polycrystals of strongly gyrotropic Weyl semimetals will demonstrate strong current-induced optical activity, whereas the response vanishes for polycrystalline ordinary metals. Therefore, the current-induced optical activity can be considered a valuable tool in identifying the topological nature of a material.

cond-mat.mes-hall↗

arXiv2018

Two-particle collisional coordinate shifts and hydrodynamic anomalous Hall effect in systems without Lorentz invariance

We show that electrons undergoing a two-particle collision in a crystal experience a coordinate shift that depends on their single-particle Bloch wave functions, and derive a gauge-invariant expression for such shift, valid for arbitrary band structures, and arbitrary two-particle interaction potentials. As an application of the theory, we consider two-particle coordinate shifts for Weyl fermions in space of three spatial dimensions. We demonstrate that such shifts in general contribute to the anomalous Hall conductivity of a clean electron liquid.

cond-mat.mes-hall↗

arXiv2017

Pancharatnam-Berry phase and kinetic magnetoelectric effect in a three-dimensional helical crystal (Te)

We study the kinetic magnetoelectric effect (current-induced magnetization including both the orbital and spin contributions) in three-dimensional conductors, specializing to the case of p-doped trigonal tellurium. We include both intrinsic and extrinsic contributions to the effect, which stem from the band structure of the crystal, and from disorder scattering, respectively. Specifically, we determine the dependence of the kinetic magnetoelectric response on the hole doping in tellurium, and show that the intrinsic and extrinsic effects dominate for low and high levels of doping, respectively. The results of this work imply that three-dimensional helical metals are promising for spintronics applications, in particular, they can provide robust control over current-induced magnetic torques.

cond-mat.mes-hall↗

arXiv2017

Anomalous Hall Effect in type-I Weyl metals

We study the ac anomalous Hall conductivity $σ_{xy}(ω)$ of a Weyl semimetal with broken time-reversal symmetry. Even in the absence of free carriers these materials exhibit a "universal" anomalous Hall response determined solely by the locations of the Weyl nodes. We show that the free carriers, which are generically present in an undoped Weyl semimetal, give an additional contribution to the ac Hall conductivity. We elucidate the physical mechanism of the effect and develop a microscopic theory of the free carrier contribution to $σ_{xy}(ω)$. The latter can be expressed in terms of a small number of parameters (the electron velocity matrix, the Fermi energy $μ$, and the "tilt" of the Weyl cone). The resulting $σ_{xy}(ω)$ has resonant features at $ω\sim 2 μ$ which may be used to separate the free carrier response from the filled-band response using, for example, Kerr effect measurements. This may serve as diagnostic tool to characterize the doping of individual valleys.

cond-mat.mes-hall↗

arXiv2017

Photogalvanic effect in Weyl semimetals

We theoretically study the impact of impurities on the photogalvanic effect (PGE) in Weyl semimetals with weakly tilted Weyl cones. Our calculations are based on a two-nodes model with an inversion symmetry breaking offset and we employ a kinetic equation approach in which both optical transitions as well as particle-hole excitations near the Fermi energy can be taken into account. We focus on the parameter regime with a single photoactive node and control the calculation in small impurity concentration. Internode scattering is treated generically and therefore our results allow to continuously interpolate between the cases of short range and long range impurities. We find that the time evolution of the circular PGE may be nonmonotonic for intermediate internode scattering. Furthermore, we show that the tilt vector introduces three additional linearly independent components to the steady state photocurrent. Amongst them, the photocurrent in direction of the tilt takes a particular role inasmuch it requires elastic internode scattering or inelastic intranode scattering to be relaxed. It may therefore be dominant. The tilt also generates skew scattering which leads to a current component perpendicular to both the incident light and the tilt. We extensively discuss our findings and comment on the possible experimental implications.

cond-mat.mes-hall↗

arXiv2017

Kinetic orbital moments and nonlocal transport in disordered metals with nontrivial geometry

We study the effects of spatial dispersion in disordered noncentrosymmetric metals. These include the kinetic magnetoelectric effect, natural optical activity of metals, as well as the so-called dynamic chiral magnetic effect as a particular case of the latter. These effects are determined by the linear in the wave vector of an electromagnetic perturbation contribution to the conductivity tensor of a material, and stem from the magnetic moments of quasiparticles near the Fermi surface. We identify new disorder-induced contributions to these magnetic moments that come from the skew scattering and side jump processes, familiar from the theory of anomalous Hall effect. We show that at low frequencies the spatial dispersion of the conductivity tensor comes mainly either from the skew scattering or intrinsic contribution, and there is always a region of frequencies in which the intrinsic mechanism dominates. Our results imply that in clean three-dimensional metals, current-induced magnetization is in general determined by impurity skew scattering, rather than intrinsic contributions. Intrinsic effects are expected to dominate in cubic enantiomorphic crystals with point groups $T$ and $O$, and in polycrystalline samples, regardless of their mobility.

cond-mat.mes-hall↗