arXiv subjects

Dmitrii L. Maslov

Publications and source records attributed to Dmitrii L. Maslov.

At least 19 recordsLinked to original sources

arXiv2026

Conserving relaxation-time approximation for electron-electron collisions

We develop a conserving relaxation-time approximation (cRTA) based on an explicit energy-resolved projection onto the full space of collision invariants. Our cRTA retains the energy dependence of the nonequilibrium quasiparticle distribution, allowing one to describe transport quantities sensitive to states near, but not exactly on, the Fermi surface (FS). We apply the method to several charge-transport problems in both Galilean-invariant and non-Galilean-invariant Fermi liquids. In particular, the cRTA reproduces the low- and high-temperature limits of the dc conductivity of a non-Galilean-invariant Fermi liquid with disorder, the hydrodynamic and collisionless limits of the finite-wavevector longitudinal conductivity of a clean Galilean-invariant Fermi liquid, and the asymptotic scaling forms of the optical conductivity of a clean non-Galilean-invariant Fermi liquid beyond the semiclassical limit. For several observables, the agreement with exact solutions is quantitative at the percent level. These results demonstrate that the cRTA provides a simple and accurate framework for describing transport beyond the FS projection.

cond-mat.str-el↗

arXiv2026

Conductivity of a Non-Galilean--Invariant Fermi Liquid: Exact Solution of the Kinetic Equation

We obtain an exact expression for the conductivity of a disordered, non-Galilean-invariant Fermi liquid by solving the kinetic equation with both screened Coulomb and $z=3$ Pomeranchuk critical interactions. While consistent with previous asymptotic results, our solution shows that electron-electron interactions enter the conductivity solely via the quasiparticle scattering time, $τ_\mathrm{ee}$. Accordingly, the crossovers between the collisionless and hydrodynamic regimes occur when $1/τ_\mathrm{ee}$ becomes comparable to the larger of the impurity scattering rate and the probe frequency, $Ω$. In addition, the exact solution yields the optical response in the hydrodynamic regime, $Ω\ll 1/τ_\mathrm{ee}$, which is inaccessible within perturbation theory. Near a $z=3$ Pomeranchuk quantum critical point, consistency between the kinetic-equation and Kubo approaches requires proper inclusion of mass renormalization within the Eliashberg approximation, which also ensures that the crossover between the collisionless and hydrodynamic regimes in the optical conductivity occurs at the Planckian scale $Ω\sim T$.

cond-mat.str-el↗

arXiv2026

Energy relaxation due to two-phonon scattering of electrons: Breakdown of the energy diffusion model

Recent THz spectroscopy of the quantum paraelectric SrTiO$_3$ (arXiv:2501.15771) and a high-$T_c$ cuprate (arXiv:2503.15646) has renewed interest in energy relaxation in correlated electron systems. We consider a situation in which single-phonon scattering is forbidden by symmetry or momentum conservation, while two-phonon scattering is allowed. Solving the Boltzmann equation, we show that above the Bloch-Grüneisen temperature the energy relaxation rate from two soft transverse optical phonons exceeds the single-phonon one: while the latter scales as $1/T$, the former is linear in $T$. This dominance of two-phonon scattering invalidates the usual picture of energy diffusion due to frequent scattering by subthermal phonons; instead, energy relaxes via rare scattering events involving thermal phonons. Below the Bloch-Grüneisen temperature, the energy relaxation rate scales as the single-particle rate, namely as $T^3$ for soft phonons. For anisotropic electron bands, an intermediate regime appears between two Bloch-Grüneisen temperatures, in which both allowed single-phonon and two-phonon processes scale as $T^2$.

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arXiv2025

Collective excitations and stability of a non-Fermi liquid state near a quantum-critical point of a metal

We examine the spectral properties of collective excitations with finite angular momentum $l$ for a system of interacting fermions near a Pomeranchuk quantum critical point, both in the Fermi liquid and non-Fermi liquid regimes. Previous studies found that deep in the Fermi liquid regime, the spectral functions for even and odd $l$ behave differently - the latter is suppressed compared to the former because of kinematic constraints on scattering processes. The main focus of our paper is to understand how the spectral functions for even and odd $l$ evolve as the system enters the non-Fermi liquid regime. We obtain the full scaling function for the electron polarization bubble at arbitrary $l$, which interpolates between the Fermi liquid and non-Fermi liquid regimes. We show that collective excitations for all $l$ remain stable and causal throughout the crossover and right at the quantum critical point.

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arXiv2025

Resonant Edelstein and inverse-Edelstein effects, charge-to-spin conversion, and spin pumping from chiral-spin modes

Spin-orbit coupling in systems with broken inversion symmetry gives rise to the Edelstein effect, which is the spin polarization induced by an electric field or current, and the inverse-Edelstein effect (also known as the spin-galvanic effect), which is the electric current induced by an oscillatory magnetic field or spin polarization. At the same time, an interplay between spin-orbit coupling and electron-electron interaction leads to a special type of collective excitations -- chiral-spin modes -- which are oscillations of spin polarization in the absence of a magnetic field. As a result, both Edelstein and inverse-Edelstein effects exhibit resonances at the frequencies of chiral-spin collective modes. Here, we present a detailed study of the effect of electron correlation on the resonances in Edelstein and inverse-Edelstein effects in a single-valley two-dimensional electron gas and in a multi-valley Dirac system with proximity-induced spin-orbit coupling. While the chiral-spin modes involve both in-plane and out-of-plane oscillations of spins, we show that only the in-plane modes are responsible for the above resonances. In the multi-valley system, electron correlation splits the in-plane modes into two. We study the spectral weight distribution between the two modes over a large parameter space of intra- and inter-valley interactions. Finally, we demonstrate that using the chiral-spin modes one can get a resonant enhancement of charge-to-spin conversion and gain a directional control of the injected spins in the spin-pumping process, both of which are relevant to spintronics.

cond-mat.mes-hall↗

arXiv2025

Resistive Anomaly near a Ferromagnetic Phase Transition: A Classical Memory Effect

We investigate resistive anomalies in metals near ferromagnetic phase transitions, focusing on the role of long-range critical fluctuations. Our analysis reveals that diffusive motion of electrons near the critical temperature ($T_c$) enhances a singular behavior of the resistivity near $T_c$ through a classical memory effect, surpassing the prediction by Fisher and Langer \cite{Fisher:1968}. We show that, close enough to $T_c$, the resistivity exhibits a cusp or anticusp, whose profile is controlled by the critical exponent of the order parameter. We also parameterize the non-Drude behavior of the optical conductivity due to a classical memory effect in terms of critical exponents. These findings offer a deeper understanding of resistive anomalies and their connection to critical exponents in metallic systems.

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arXiv2025

Magnetoconductivity due to electron-electron interaction in a non-Galilean-invariant Fermi liquid

The $T^2$-scaling of resistivity with temperature is often viewed as a classic hallmark of a Fermi-liquid (FL) behavior in metals. However, if umklapp scattering is suppressed, this scaling is not universally guaranteed to occur. In this case, the resistivity behavior is influenced by several factors, such as dimensionality (two vs. three), topology (simply- vs. multiply-connected Fermi surfaces), and (in two dimensions) the shape (convex vs. concave) of the Fermi surface (FS). Specifically for an isotropic spectrum, as well as for a two-dimensional (2D) convex FS, the $T^2$ term is absent, and the first non-zero contribution scales as $T^4\ln T$ in 2D and as $T^4$ in 3D. In this paper, we study the $T$-dependence of the resistivity, arising from electron-electron interactions, in the presence of a weak magnetic field. We show that, for an isotropic FS in any dimensions and for a convex 2D FS, the $T^2$ term is also absent in both Hall and diagonal components of the magnetoconductivity, which instead scale as $BT^4\ln T$ and $B^2T^4\ln T$, respectively, in 2D and as $BT^4$ and $B^2T^4$ in 3D. The FL-like scaling, i.e., $BT^2$ and $B^2T^2$ of the Hall and diagonal conductivities is recovered for a concave FS in 2D. Furthermore, we show that, for an isotropic spectrum, magnetoresistance is absent even in the presence of electron-electron interactions. Additionally, we examine the high-temperature limit, when electron-electron scattering prevails over electron-impurity one, and show that all the components of the conductivity tensor saturate in this limit at values that are determined by impurity scattering but, in general, differ from the corresponding values at $T=0$.

cond-mat.str-el↗

arXiv2025

Effects of electron correlation on resonant Edelstein and inverse-Edelstein effects

Spin-orbit coupling in systems with broken inversion symmetry gives rise to the Edelstein effect, which is the induced spin polarization in response to an applied electric field or current, and the inverse Edelstein effect, which is the induced electric current in response to an oscillatory magnetic field or spin polarization. At the same time, an interplay between spin-orbit coupling and electron-electron interaction leads to a special type of collective excitations -- chiral-spin modes -- which are oscillations of spin polarization in the absence of a magnetic field. As a result, both Edelstein and inverse Edelstein effects exhibit resonances at the frequencies of spin-chiral collective modes. Here, we present a detailed study of the effect of electron correlation on the Edelstein and inverse Edelstein effects in a single-valley two-dimensional electron gas and a multi-valley Dirac system with proximity-induced spin-orbit coupling. While the chiral-spin modes involve both in-plane and out-of-plane oscillations of spins, we show that only the in-plane modes are responsible for the above resonances. In the multi-valley system, electron correlation splits the in-plane modes into two. We also study the spectral weight distribution between the two resonances over a large parameter space of intra- and inter-valley interactions.

cond-mat.str-el↗

arXiv2024

Integrals of Products of Bessel Functions: An Insight from the Physics of Bloch Electrons

Integrals of products of Bessel functions exhibit an intriguing feature: under certain conditions on the parameters specifying the integrand, they vanish identically. We provide a physical interpretation of this feature in the context of both single-particle and many-body properties of electrons on a lattice (``Bloch electrons''), namely, in terms of their density of states and umklapp scattering rate. (In an umklapp event, the change in the momentum of two colliding electrons is equal to a reciprocal lattice vector, which gives rise to a finite resistivity due to electron-electron interaction.) In this context, the vanishing of an integral follows simply from the condition that either the density of states vanishes due to the electron energy lying outside the band in which free propagation of electron waves is allowed, or that an umklapp process is kinematically forbidden due to the Fermi surface being smaller than a critical value.

math-ph↗

arXiv2024

Quantum criticality and optical conductivity in a two-valley system

We demonstrate that the optical conductivity of a Fermi liquid (FL) in the absence of umklapp scattering is dramatically affected by the topology of the Fermi surface (FS). Specifically, electron-electron (ee) scattering leads to rapid current relaxation in systems with multiple, or multiply connected, FSs, provided the valleys have different effective masses. This effect results from intervalley drag. We microscopically derive the optical conductivity of a two-valley system, both within the FL regime and near a quantum critical point (QCP) of the Ising-nematic type. In the FL regime, intervalley drag restores the Gurzhi-like scaling of the conductivity, $\mathrm{Re} σ(ω) \sim ω^0$. This dependence contrasts sharply with the previously identified sub-leading contribution to the conductivity of a two-dimensional FL with a single convex FS, where $\mathrm{Re} σ(ω) \sim ω^2 \ln |ω|$. The vanishing of the leading term in the optical conductivity is a signature of geometric constraints on ee scattering channels, which are lifted for a multiply connected FS. A large differential response, $d \mathrm{Re} σ/d μ$ with $μ$ being the chemical potential, is predicted at the Lifshitz transition from a single-valley to a multi-valley FS, which should be observable within the experimentally accessible frequency range. Near a QCP, intervalley drag leads to a $|ω|^{-2/3}$ scaling of $\mathrm{Re} σ(ω)$ in 2D, thus providing a specific current-relaxing process for this long-standing conjecture.

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arXiv2023

Optical conductivity of a metal near an Ising-nematic quantum critical point

We study the optical conductivity of a pristine two-dimensional electron system near an Ising-nematic quantum critical point. We discuss the relation between the frequency scaling of the conductivity and the shape of the Fermi surface, namely, whether it is isotropic, convex, or concave. We confirm the cancellation of the leading order terms in the optical conductivity for the cases of isotropic and convex Fermi surfaces and show that the remaining contribution scales as $|ω|^{2/3}$ at $T=0$. On the contrary, the leading term, $\propto |ω|^{-2/3}$, survives for a concave FS. We also address the frequency dependence of the optical conductivity near the convex-to-concave transition. Explicit calculations are carried out for the Fermi-liquid regime using the modified (but equivalent to the original) version of the Kubo formula, while the quantum-critical regime is accessed by employing the space-time scaling of the $Z=3$ critical theory.

cond-mat.str-el↗

arXiv2023

Optical conductivity and damping of plasmons due to electron-electron interaction

We re-visit the issue of plasmon damping due to electron-electron interaction. The plasmon linewidth can related to the imaginary part of the charge susceptibility or, equivalently, to the real part of the optical conductivity, $\mathrm{Re}σ(q,ω)$. Approaching the problem first via a standard semi-classical Boltzmann equation, we show that $\mathrm{Re}σ(q,ω)$ of two-dimensional (2D) electron gas scales as $q^2T^2/ω^4$ for $ω\ll T$, which agrees with the results of Refs. [1] and [2] but disagrees with that of Ref. [3], according to which $\mathrm{Re}σ(q,ω) \propto q^2T^2/ω^2$. To resolve this disagreement, we re-derive $\mathrm{Re}σ(q,ω)$ using the original method of Ref. {mishchenko:2004} for an arbitrary ratio $ω/T$ and show that, while the last term is, indeed, present, it is subleading to the $q^2T^2/ω^4$ term. We give a physical interpretation of both leading and subleading contributions in terms of the shear and bulk viscosities of an electron liquid, respectively. We also calculate $\mathrm{Re}σ(q,ω)$ for a three-dimensional (3D) electron gas and doped monolayer graphene. We find that, with all other parameters being equal, finite temperature has the strongest effect on the plasmon linewidth in graphene, where it scales as $T^4\ln T$ for $ω\ll T$.

cond-mat.str-el↗

arXiv2023

Intrinsic optical absorption in Dirac metals

A Dirac metal is a doped (gated) Dirac material with the Fermi energy ($E_\text{F}$) lying either in the conduction or valence bands. In the non-interacting picture, optical absorption in gapless Dirac metals occurs only if the frequency of incident photons ($Ω$) exceeds the direct (Pauli) frequency threshold, equal to $2E_\text{F}$. In this work, we study, both analytically and numerically, the role of electron-electron ($ee$) and electron-hole ($eh$) interactions in optical absorption of two-dimensional (2D) and three-dimensional (3D) Dirac metals in the entire interval of frequencies below $2E_\text{F}$. We show that, for $Ω\ll E_\text{F}$, the optical conductivity, $\Reσ(Ω)$, arising from the combination of $ee$ and certain $eh$ scattering processes, scales as $Ω^2\lnΩ$ in 2D and as $Ω^2$ in 3D, respectively, both for short-range (Hubbard) and long-range (screened Coulomb) interactions. Another type of $eh$ processes, similar to Auger-Meitner (AM) processes in atomic physics, starts to contribute for $Ω$ above the direct threshold, equal to $E_\text{F}$. Similar to the case of doped semiconductors with parabolic bands studied in prior literature, the AM contribution to $\Reσ(Ω)$ in Dirac metals is manifested by a threshold singularity, $\Reσ(Ω)\propto (Ω-E_\text{F})^{d+2}$, where $d$ is the spatial dimensionality and $0<Ω-E_\text{F}\ll E_\text{F}$. In contrast to doped semiconductors, however, the AM contribution in Dirac metals is completely overshadowed by the $ee$ and other $eh$ contributions. Numerically, $\Reσ(Ω)$ happens to be small in almost the entire range of $Ω<2E_\text{F}$. This finding may have important consequences for collective modes in Dirac metals lying below $2E_\text{F}$.

cond-mat.str-el↗

arXiv2022

Collective spin modes in Fermi liquids with spin-orbit coupling

A combination of spin-orbit coupling and electron-electron interaction gives rise to a new type of collective spin modes, which correspond to oscillations of magnetization even in the absence of the external magnetic field. We review recent progress in theoretical understanding and experimental observation of such modes, focusing on three examples of real-life systems: a two-dimensional electron gas with Rashba and/or Dresselhaus spin-orbit coupling, graphene with proximity-induced spin-orbit coupling, and the Dirac state on the surface of a three-dimensional topological insulator. This paper is dedicated to the 95th birthday of Professor Emmanuel I. Rashba.

cond-mat.str-el↗

arXiv2021

Zero-field spin resonance in graphene with proximity-induced spin-orbit coupling

We investigate collective spin excitations in graphene with proximity-induced spin-orbit coupling (SOC) of the Rashba and valley-Zeeman types, as it is the case, e.g., for graphene on transition- metal-dichalcogenide substrates. It is shown that, even in the absence of an external magnetic field, such a system supports collective modes, which correspond to coupled oscillations of the uniform and valley-staggered magnetizations. These modes can be detected via both zero-field electron spin resonance (ESR) and zero-field electric-dipole spin resonance (EDSR), with EDSR response coming solely from Rashba SOC. We analyze the effect of electron-electron interaction within the Fermi- liquid kinetic equation and show that the interaction splits both the ESR and EDSR peaks into two. The magnitude of splitting and the relative weights of the resonances can be used to extract the spin-orbit coupling constants and many-body interaction parameters that may not be accessible by other methods.

cond-mat.str-el↗

arXiv2021

Optical conductivity of a Dirac-Fermi liquid

A Dirac-Fermi liquid (DFL)--a doped system with Dirac spectrum--is an important example of a non-Galilean-invariant Fermi liquid (FL). Real-life realizations of a DFL include, e.g., doped graphene, surface states of three-dimensional (3D) topological insulators, and 3D Dirac/Weyl metals. We study the optical conductivity of a DFL arising from intraband electron-electron scattering. It is shown that the effective current relaxation rate behaves as $1/τ_{J}\propto \left(ω^2+4π^2 T^2\right)\left(3ω^2+8π^2 T^2\right)$ for $\max\{ω, T\}\ll μ$, where $μ$ is the chemical potential, with an additional logarithmic factor in two dimensions. In graphene, the quartic form of $1/τ_{J}$ competes with a small FL-like term, $\proptoω^2+4π^2 T^2$, due to trigonal warping of the Fermi surface. We also calculated the dynamical charge susceptibility, $χ_\mathrm{c}({\bf q},ω)$, outside the particle-hole continua and to one-loop order in the dynamically screened Coulomb interaction. For a 2D DFL, the imaginary part of $χ_\mathrm{c}({\bf q},ω)$ scales as $q^2ω\ln|ω|$ and $q^4/ω^3$ for frequencies larger and smaller than the plasmon frequency at given $q$, respectively. The small-$q$ limit of $\mathrm{Im} χ_\mathrm{c}({\bf q},ω)$ reproduces our result for the conductivity via the Einstein relation.

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arXiv2021

Spin-valley Silin modes in graphene with substrate-induced spin-orbit coupling

In the presence of external magnetic field the Fermi-liquid state supports oscillatory spin modes known as Silin modes. We predict the existence of the generalized Silin modes in a multivalley system, monolayer graphene. A gauge- and Berry-gauge- invariant kinetic equation for a multivalley Fermi liquid is developed and applied to the case of graphene with extrinsic spin-orbit coupling (SOC). The interplay of SOC and Berry curvature allows for the excitation of generalized Silin modes in the spin and valley-staggered-spin channels via an AC electric field. The resonant contributions from these modes to the optical conductivity are calculated.

cond-mat.mes-hall↗

arXiv2021

Quasiparticle and Nonquasiparticle Transport in Doped Quantum Paraelectrics

Charge transport in doped quantum paralectrics (QPs) presents a number of puzzles, including a pronounced $T^2$ regime in the resistivity. We analyze charge transport in a QP within a model of electrons coupled to a soft transverse optical (TO) mode via a two-phonon mechanism. For $T$ above the soft-mode frequency but below some characteristic scale ($E_0$), the resistivity scales with the occupation number of phonons squared, i.e., as $T^2$. The $T^2$ scattering rate does not depend on the carrier number density and is not affected by a crossover between degenerate and non-degenerate regimes, in agreement with the experiment. Temperatures higher than $E_0$ correspond to a non-quasiparticle regime, which we analyze by mapping the Dyson equation onto a problem of supersymmetric quantum mechanics. The combination of scattering by two TO phonons and by a longitudinal optical mode explains the data quite well.

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