arXiv subjects

V. M. Kovalev

Publications and source records attributed to V. M. Kovalev.

At least 19 recordsLinked to original sources

arXiv2026

Acoustic Plasmon Resonance: Breaking the Anderson Stiffness Paradigm in Quasi-Two-Dimensional Superconducting Films

Recent experiments on superconducting films have revealed an acoustic plasmon mode that depends critically on the superconducting transition, directly challenging the long-standing Anderson-Higgs paradigm regarding the stiffness of the plasma spectrum in superconductors. In this Letter, we provide a microscopic theoretical framework that explains this behavior and establishes the physical conditions under which classical Anderson-Higgs constraints are bypassed. We demonstrate that in films of finite thickness, the transverse redistribution of normal and superfluid charge densities enables a unique coupling mechanism to electromagnetic radiation - a feature fundamentally absent in the conventional Carlson-Goldman scenario. Our theory predicts an acoustic mode whose dispersion, temperature scaling, and dependence on film thickness are in remarkable agreement with recent experimental observations. By delineating the regime of this acoustic response, we reconcile the observed electromagnetic activity of collective excitations with the fundamental principles of superconductivity.

cond-mat.supr-con↗

arXiv2026

Quantum tribology: acceleration-induced Stokes friction and Magnus force in correlated Bose fluids

The Landau criterion, a cornerstone of quantum fluid dynamics, dictates that dissipation is forbidden for uniform motion below a critical velocity. Yet, the fundamental question of how acceleration reshapes the principles of quantum friction has remained open since Landau and Pitaevskii's seminal works. Here, we establish a theoretical framework for the quantum tribology of non-inertial motion, describing a probe particle undergoing composite translation and rotation within a weakly interacting Bose condensate. Using the nonlinear Gross-Pitaevskii equation, we show that centripetal acceleration fundamentally modifies the energy-momentum constraints on elementary excitations. This leads to a finite drag force in the subsonic regime of the probe particle motion, and a characteristic quantum stick-slip behaviour in the deeply supersonic regime -- a direct generalization of the classical Landau-Pitaevskii picture. Beyond this dissipative response, we uncover a fundamentally distinct mechanism: the nonlinearity of the quantum fluid, combined with the broken symmetry of the trajectory, gives rise to a non-dissipative anomalous transverse force. This quantum Magnus-like response, emerging from the second-order density perturbation, performs no work and is rooted in the geometric asymmetry of the dynamically induced flow. Our findings lay the foundation for a universal program in quantum tribology of accelerated motion, establishing a direct and experimentally testable connection among non-inertial dynamics, nonlinear response, and topological symmetry breaking across platforms ranging from ultracold atoms and exciton-polariton condensates to cosmological analog systems.

cond-mat.quant-gas↗

arXiv2026

Conductivity of charge-neutral multicomponent 2D electron-hole system

The interplay between distinct carrier species in systems with broken Galilean invariance can give rise to a rich landscape of interaction-driven transport phenomena. Here, we develop a comprehensive theory for the electrical conductivity of a two-dimensional mixture of massless Dirac and massive fermions, a system realized in HgTe quantum wells tuned to the charge neutrality point. In this regime, all carriers are thermally activated, enabling a self-consistent, temperature-dependent interplay between the two species. Crucially, the charge neutrality condition ensures that the chemical potential is not externally pinned but is determined self-consistently, making the system's transport response an intrinsic probe of inter-species quantum friction. We demonstrate that the conductivity undergoes a distinct crossover as temperature increases: at low temperatures, transport is dominated by massless Dirac carriers, yielding nearly temperature-independent conductivity reminiscent of pristine graphene's charge neutrality point. As the temperature rises, massive holes become thermally excited, and their mutual scattering with Dirac carriers induces a specific nonmonotonic temperature behavior of the conductivity both in clean and disordered structures. In particular, in nearly clean structures with strong screening modeled by a short-range interparticle interaction potential, the system conductivity can exhibit an inverse quadratic temperature dependence. Conversely, in disordered structures with a long-range interparticle interaction, it varies quadratically with temperature. Our findings establish HgTe quantum wells at charge neutrality as a clean, highly tunable platform for isolating and quantitatively studying interaction-driven transport in the absence of Galilean invariance, offering a direct pathway to explore regimes where interparticle collisions dominate over disorder.

cond-mat.mes-hall↗

arXiv2026

Anomalous acoustoelectric signatures of chiral superconductivity

The identification of unconventional pairing in two-dimensional materials is a central challenge in modern condensed matter physics. While chiral p-wave superconductivity offers a promising platform for topological quantum computing, its detection remains elusive due to the inherent limitations of optical probes in the two-dimensional limit. We propose the anomalous acoustoelectric effect as a robust, alternative to optical signature of p-wave paring symmetry. We demonstrate that an acoustic wave induces a transverse dc current resulting in a measurable condensate phase difference on sample boundaries originating from the anisotropic scattering of quasiparticles in the absence of an external magnetic field. Crucially, the quasiparticle-mediated acoustoelectric response dominates near the critical temperature and, unlike the superconducting condensate, is not suppressed by electron-hole asymmetry factor. These results establish the anomalous acoustoelectric effect as a high-sensitivity electrical probe of the chiral order parameter, providing a tool for experimental detecting of unconventional pairing in superconductors.

cond-mat.supr-con↗

arXiv2026

Giant resonant nonlinear THz valley Hall effect in 2D Dirac semiconductors

We predict a giant cyclotron resonance in the nonlinear valley Hall response of inversion-asymmetric two-dimensional semiconductors subjected to crossed terahertz electric and static magnetic fields. By employing a two-band Hamiltonian that incorporates both linear and quadratic in momentum terms, thereby capturing the essential orbital texture and broken inversion symmetry, we develop a kinetic theory that accounts for antisymmetric skew scattering from impurities. Solving the Boltzmann transport equation we uncover resonant photocurrents that exhibit a sharp, polarity-switching cyclotron peak and a nontrivial polarization response dictated by the underlying D3h crystal symmetry. Our results establish a universal mechanism for frequency-selective, phase-sensitive valley current control, directly accessible in monolayer transition metal dichalcogenides. This work provides a pathway for harnessing resonant nonlinear transport in valleytronic and terahertz optoelectronic devices.

cond-mat.mes-hall↗

arXiv2025

Interactions-controlled magnetotransport in two-dimensional massless-massive fermion mixtures

The presence of two types of holes, namely the Dirac holes and the massive holes, in a two-dimensional sample exposed to an external permanent magnetic field leads to the emergence of the temperature and magnetic field-dependent contribution to the resistivity due to their interactions. Taking a HgTe-based two-dimensional semimetal as a testbed, we develop a theoretical model describing the role of interactions between the degenerate massive and massless Dirac particles for the magnetoconductivity and resistivity in the presence of a classical magnetic field. If only the Dirac holes are present in the system, the magnetoconductivity acquires a finite interaction-induced contribution, which would vanish for the parabolic spectrum. It demonstrates $T^4\ln(1/T)$ behavior at low temperatures for short-range interhole interaction potential, and $T^2$-like behavior in the case of long-range interhole interaction potential. However, the magnetoresistivity and the Hall effect are not affected by the Dirac holes interparticle correlations in the lowest order of interparticle interaction. In contrast to this, the presence of two types of holes provides a finite contribution to the magnetoconductivity, magnetoresistivity, and the classical Hall effect resistivity. The temperature behavior of the magnetoconductivity here is $\sim T^2$ in the case of the short-range constant interparticle interaction potential and $T^2\ln(1/T)$ for the bare unscreened Coulomb interaction. A classically strong magnetic field suppresses the interaction-induced corrections to magnetoresistivity of massless-massive hole gas mixture.

cond-mat.mes-hall↗

arXiv2025

Ratchet Hall Effect in Fluctuating Superconductors

We propose a superconducting ratchet-induced Hall effect (RHE), characterized by the emergence of a unidirectional, rectified flux of fluctuating Cooper pairs in a two-dimensional thin film exposed to an external electromagnetic field. The RHE is a second-order response with respect to the electromagnetic field amplitude. It consists of a nonzero photocurrent due to the breaking of the system's inversion symmetry driven by the combined action of the in-plane time-dependent electric field and a spatial modulation of the critical temperature. We explore a means to control the electric current by the polarization of the external field accompanied by a non-linear Hall effect of fluctuating Cooper pairs caused by circularly polarized irradiation. Moreover, the nonlinear conductivity tensor exhibits a higher-power dependence on the reduced temperature compared to that of the conventional Aslamazov-Larkin correction (or other fluctuating second-order nonlinear responses). It results in a dramatic enhancement of the non-linear Hall response of fluctuating Cooper pairs in the vicinity of the superconducting criticality.

cond-mat.supr-con↗

arXiv2025

Vertex corrections to nonlinear photoinduced currents in 2D superconductors

The emergence of a rectified steady-state supercurrent as a response to the photoexcited current of the quasiparticles constitutes the concept of a superconducting photodiode. This phenomenon occurs in a two-dimensional thin superconducting film with a built-in DC supercurrent that is exposed to a circularly polarized external electromagnetic field. The flow of a Cooper-pair condensate, resulting as a second-order photo-response in a direction transverse to the initially built-in supercurrent, represents a superconducting counterpart to the photogalvanic effect. In this paper, we examine the photodiode supercurrent by restoring gauge invariance within the mean-field BCS framework. To achieve this, we derive an impurity-sensitive BCS-interaction-induced correction to the vertex function by performing self-consistent calculations within the Keldysh Green's function technique. The resulting photodiode current can be utilized for spectroscopic analysis of typical relaxation times in superconducting films.

cond-mat.supr-con↗

arXiv2025

Resistivity of non-Galilean invariant two dimensional Dirac system

We revisited the influence of electron-electron scattering on the resistivity of a two-dimensional system with linear spectrum. In conventional systems with parabolic spectrum, where Umklapp scattering is either prohibited or ineffective due to small Fermi surface, particle-particle scattering does not contribute to conductivity because it does not change the total momentum. However, within the framework of Boltzmann kinetic model, we demonstrate that electron-electron scattering in Dirac systems can significantly contribute to conductivity, producing distinct temperature-dependent corrections: a T\textsuperscript{4} behavior at low temperatures and T\textsuperscript{2} dependence at moderate temperatures. While the predicted T\textsuperscript{4} scaling is not observed experimentally -- likely suppressed by dominant weak localization effects -- the T\textsuperscript{2} scaling is clearly confirmed in our measurements. Specifically, temperature-dependent resistivity data from gapless single-valley HgTe quantum well exhibit T\textsuperscript{2} corrections, which align well with theoretical predictions. Thus, we challenge the paradigm that T\textsuperscript{2} term in resistivity is absent in single-band 2D metals.

cond-mat.mes-hall↗

arXiv2024

Proposal for Superconducting Photodiode

We propose a concept of a superconducting photodiode - a device that transforms the energy and `spin' of an external electromagnetic field into the rectified steady-state supercurrent and develop a microscopic theory describing its properties. For this, we consider a two-dimensional thin film cooled down below the temperature of superconducting transition with the injected dc supercurrent and exposed to an external electromagnetic field with a frequency smaller than the superconducting gap. As a result, we predict the emergence of a photoexcited quasiparticle current, and, as a consequence, oppositely oriented stationary flow of Cooper pairs. The strength and direction of this photoinduced supercurrent depend on (i) such material properties as the effective impurity scattering time and the nonequilibrium quasiparticles' energy relaxation time and (ii) such electromagnetic field properties as its frequency and polarization.

cond-mat.supr-con↗

arXiv2024

Electronic states bound by repulsive potentials in graphene irradiated by a circularly polarized electromagnetic field

In the framework of the Floquet theory of periodically driven quantum systems, it is demonstrated that irradiation of graphene by a circularly polarized electromagnetic field induces an attractive area in the core of repulsive potentials. Consequently, the quasi-stationary electron states bound by the repulsive potentials appear. The difference between such field-induced states in graphene and usual systems with the parabolic dispersion of electrons is discussed and possible manifestations of these states in electronic transport and optical spectra of graphene are considered.

cond-mat.mes-hall↗

arXiv2024

Renormalization of the valley Hall conductivity due to interparticle interaction

We develop a theory of Coulomb interaction-mediated contribution to valley Hall effect (VHE) in two-dimensional non-centrosymmetric gapped Dirac materials. We assume that the bare valley Hall current occurs in the system due to the presence of disorder caused by impurities and is determined by the valley-selective anisotropic skew scattering. Applying the Boltzmann transport equation to describe the electron and hole transport in the material, we calculate the renormalized VHE conductivity due to electron-electron and electron-hole scattering processes, considering two regimes: (i) an $n$-doped monolayer hosting a degenerate electron gas, and (ii) an intrinsic semiconductor with the Boltzmann statistics of electron and hole gases. In both regimes, the dominant mechanism of interparticle scattering is due to particles residing in different valleys. Moreover, in case (ii), in addition to direct scattering, electron-hole annihilation starts to play a role with the increase in temperature. It might even become the dominant mechanism of the Coulomb interaction-mediated VHE.

cond-mat.mes-hall↗

arXiv2024

Role of Coulomb interaction in the valley photogalvanic effect

We develop a theory of Coulomb interaction-related contribution to the photogalvanic current of the carriers of charge in two-dimensional non-centrosymmetric Dirac materials possessing a nontrivial structure of valleys and exposed to an external electromagnetic field. The valley photogalvanic effect occurs here due to the trigonal warping of electrons and holes' dispersions in a given valley of the monolayer. We study the low-frequency limit of the external field: The field frequency is smaller than the temperature $T$, and the electron-electron and electron-hole scattering times are much larger than the electron-impurity and hole-impurity scattering times. In this regime, we employ the Boltzmann transport equations and show that electron-hole scattering dominates electron-electron scattering in intrinsic semiconductors. A Coulomb electron-hole interaction-related contribution to the valley photogalvanic current can reduce the value of the bare photogalvanic current as electron and hole currents flow in opposite directions.

cond-mat.mes-hall↗

arXiv2024

Interaction-controlled transport in a two-dimensional massless-massive Dirac system: Transition from degenerate to nondegenerate regimes

The resistivity of two-dimensional (2D) metals generally exhibits insensitivity to electron-electron scattering. However, it's worth noting that Galilean invariance may not hold true in systems characterized by a spectrum containing multiple electronic branches or in scenarios involving electron-hole plasma. In the context of our study, we focus on 2D electrons confined within a triple quantum well (TQW) based on HgTe. This system displays a coexistence of energy bands featuring both linear and parabolic-like spectra at low energy and, therefore, lacks the Galilean invariance. This research employs a combined theoretical and experimental approach to investigate the transport properties of this two-component system across various regimes. By manipulating carrier density and temperature, we tune our system from a fully degenerate regime, where resistance follows a temperature-dependent behavior proportional to $T^2$, to a regime where both types of electrons adhere to Boltzmann statistics. In the non-degenerate regime, electron interactions lead to resistance that is weakly dependent on temperature. Notably, our experimental observations closely align with the theoretical predictions derived in this study. This work establishes the HgTe-based TQW as a promising platform for exploring different interaction dominant scenarios for the massless-massive Dirac system.9 pages, 8 figures

cond-mat.mes-hall↗

arXiv2024

Electron-hole scattering-induced temperature behaviour of HgTe-based semimetal quantum well

The semimetal quantum well (QW) based on HgTe structures exhibiting unusual transport properties at low temperature is examined experimentally. It demonstrates either a linear or quadratic growth of resistance with temperature at different top-gate voltages in the semimetal regime. We develop a theoretical model of HgTe-based semimetal QW resistance temperature dependence based on electron-hole scattering processes at low temperatures. We apply the Boltzmann transport equation approach to study the effect of electron-hole scattering in a semimetal QW. The calculated temperature behavior of 2D semimetal resistivity demonstrates an excellent agreement with experimental findings.

cond-mat.mes-hall↗

arXiv2024

Photoinduced Anomalous Supercurrent Hall Effect

We predict a photoinduced Hall effect in an isotropic conventional two-dimensional superconductor with a built-in supercurrent exposed to a circularly-polarized light. This second-order with respect to the electromagnetic field amplitude effect occurs when the frequency of the field exceeds the double value of the superconducting gap. It reveals itself in the emergence of a Cooper-pair condensate flow in the direction transverse to the initial built-in supercurrent, which arises to compensate for the light-induced electric current of quasiparticles photoexcited across the gap. The initial supercurrent breaks both the time-reversal and inversion symmetries, while the presence of dilute disorder in the sample provides the breaking of the Galilean invariance. We develop a microscopic theory of the supercurrent Hall effect in the case of weak disorder and show, that the Hall supercurrent is directly proportional to the quasiparticle recombination time, which can acquire large values.

cond-mat.supr-con↗

arXiv2024

Interaction dominated transport in 2D conductors: from degenerate to partially-degenerate regime

In this study, we investigate the conductivity of a two-dimensional (2D) system in HgTe quantum well comprising two types of carriers with linear and quadratic spectra, respectively. The interactions between the two-dimensional Dirac holes and the heavy holes lead to the breakdown of Galilean invariance, resulting in interaction-limited resistivity. Our exploration of the transport properties spans from low temperatures, where both subsystems are fully degenerate, to higher temperatures, where the Dirac holes remain degenerate while the heavy holes follow Boltzmann statistics, creating a partially degenerate regime. Through a developed theory, we successfully predict the behavior of resistivity as $ρ\sim T^2$ and $ρ\sim T^{3}$ for the fully degenerate and partially degenerate regimes, respectively, which is in reasonable agreement with experimental observations. Notably, at elevated temperatures, the interaction-limited resistivity surpasses the resistivity caused by impurity scattering by a factor of 5-6. These findings imply that the investigated system serves as a versatile experimental platform for exploring various interaction-limited transport regimes in two component plasma.

cond-mat.mes-hall↗

arXiv2023

Probing Luttinger Liquid Properties in Multichannel Two-Site Charge Kondo Simulator

We study the influence of many-body interactions on the transport properties in a two-site charge Kondo circuit recently implemented in a hybrid metal-semiconductor double-quantum dot device [W. Pouse {\it et al.}, Nat. Phys. {\bf 19}, 492 (2023)]. There emerge two principal types of interactions: (i) an intrinsic one, described by the Luttinger liquid model, and (ii) an induced one, which appears due to the coupling of the system to an Ohmic environment. Case (i) could be achieved if the charge Kondo circuit operates in the fractional quantum Hall regime, while case (ii) can be implemented via a finite number of open ballistic channels coupled to both the quantum dots. We demonstrate that the conductance scaling for the case of strong and weak interdot coupling is fully determined by the effective interaction parameter, which is the combination of the fractional filling factor $ν=1/m$ and the number of transmitting channels. Furthermore, we predict that the fractional filling factor $ν$ defines a universal Kondo scaling in the vicinity of a special triple quantum critical point featured by the emergence of a $\mathbb{Z}_3$ parafermion.

cond-mat.mes-hall↗