arXiv subjects

I. S. Burmistrov

Publications and source records attributed to I. S. Burmistrov.

At least 19 recordsLinked to original sources

arXiv2026

Dissipation-induced nonlocal phase-coherent transport in a topological superconductor

Nonlocal phase-coherent transport via Majorana bound states, so-called teleportation, requires Coulomb blockade to suppress local Andreev reflection. We show that dissipation can replace the need for Coulomb blockade. We study a Kitaev chain coupled to a Markovian bath and identify a regime where the magnitude of nonlocal conductance contribution reach the local one. In this regime, the lowest-energy subspace is maximally mixed, reminiscent of a directly-grounded nontrivial topological superconductor. Phase coherence is confirmed by Aharonov-Bohm oscillations. Our results establish dissipation as a tool for controlling quantum teleportation in Majorana systems.

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arXiv2026

Emergent spin quantum Hall edge states at the boundary of two-dimensional electron gas proximitized by an $s$-wave superconductor

Hybrid two-dimensional electron gas-superconductor (2DEG-S) structures in a quantized magnetic field offer a promising platform for realizing new topological phases. While recent experiments reveal chiral Andreev edge states, their charge conductance is not integer quantized and is disorder sensitive, raising the question of whether topological protection survives. We argue that it does, but manifests in the spin transport channel. The 2DEG-S system belongs to symmetry class C of the Altland-Zirnbauer classification, which supports an even-integer quantized transverse spin conductivity - the spin quantum Hall effect, so far unobserved experimentally. We demonstrate that 2DEG-S hybrids host topologically protected edge states carrying a spin current with an even-integer quantized spin conductance robust against disorder. Finally, we propose an experimental setup to probe this protection via electrical measurements, establishing a concrete route to detect the class C origin of the chiral Andreev edge states.

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arXiv2026

Manipulation of magnetic skyrmions by non-uniform electric fields

Magnetic skyrmions are topologically protected spin textures in ferromagnetic materials that hold great promise for both classical information storage and processing, as well as for fault-tolerant quantum computing. Realizing practical skyrmion-based devices demands an energy-efficient and precise method for their flexible manipulation. In this paper, we theoretically propose such a tool, leveraging the magnetoelectric effect induced by a localized electric field generated by one or several charged tips. Combining complementary numerical simulations and analytical approaches, we develop a consistent theory describing the stability and dynamics of Néel-type skyrmions under the influence of the electric field from a charged tip. Specifically, we demonstrate that the electric field can create, drive, and annihilate skyrmions of both chiralities, as well as more complex textures such as skyrmioniums and target skyrmions. We identify several distinct dynamical regimes of skyrmion motion near the tip and map them onto a phase diagram. Finally, we discuss the feasibility of a practical device capable of controlled skyrmion manipulation based on this principle.

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arXiv2026

Majorana bound states in chiral ferromagnet-superconductor heterostructures revisited

Majorana zero modes are central to the pursuit of fault-tolerant topological quantum computation. While traditionally sought in one-dimensional hybrid nanowires, a robust alternative platform involves heterostructures combining superconductors with noncollinear magnets. This work focuses on a particularly promising system: a chiral ferromagnet hosting a magnetic skyrmion coupled to a superconducting film containing a superconducting vortex. Such skyrmion-vortex pairs have recently been realized experimentally and are theorized to harbor localized Majorana states, offering a potential pathway for braiding operations. We present a comprehensive theoretical analysis of the low-energy quasiparticle bound states in these heterostructures. Extending previous studies, we develop an analytical framework for the Majorana wavefunctions as well as the wavefunctions and spectrum of other lowlying states within a Bogoliubov-de Gennes approach. Our analytical results explicitly demonstrate the critical role of spin-orbit coupling for the stabilization of Majorana modes and provides approximate analytical expressions for low-lying states localized at the vortex, both with and without an accompanying skyrmion. The derived analytical results show excellent agreement with numerical simulations. We further elucidate the role of realistic effects, including vector potentials and texture perturbations from stray magnetic fields, to assess their impact.

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arXiv2026

The class C quantum network model with random tunneling and its nonlinear sigma model representation

The spin quantum Hall effect is a relative of the integer quantum Hall effect, characterized by integer quantized spin Hall conductance. In this work, we formulate and investigate a quantum network model consisting of $\textsf{N}$ channels per chiral link, preserving the fundamental symmetries of the spin quantum Hall effect. We demonstrate that, in the general case, the triplet sector of the theory remains coupled to the singlet sector. In the large-$\textsf{N}$ limit, we systematically derive the effective long-distance, low-energy field theory, identified as a nonlinear sigma model. Our analysis reveals that while triplet modes are typically massive and do not influence the large-$\textsf{N}$ nonlinear sigma model, specific conditions exist where these modes become `soft', thereby increasing the ultraviolet cutoff length of the effective theory. Furthermore, by calculating the bare longitudinal and spin Hall conductances, we show that the standard saddle-point approximation fails in regimes with significant tunneling asymmetry between even and odd links. Finally, we establish that the introduction of a Zeeman field not only breaks the SU(2) symmetry of the nonlinear sigma model action but also generates a term that explicitly violates inversion symmetry.

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arXiv2026

Controlling Quantum Transport in a Superconducting Device via Dissipative Baths

Within the quantum field-theoretical approach describing the evolution of a quadratic Liouvillian in the basis of Keldysh contour coherent states, we investigate the spectral and transport properties of a dissipative superconducting system coupled to normal Fermi reservoirs. We derive a generalization of the Meir-Wingreen formula and Onsager matrix for a superconducting system subject to an arbitrary number of fermionic baths. Following Kirchhoff's rule, we obtain an expression describing the dissipation induced loss current and formulate modified quantum kinetic equations. For wide-band contacts locally coupled to individual sites, we find that each contact reduces the degeneracy multiplicity of the non-equilibrium steady state by one. These results are numerically verified through several cases of the extended Kitaev model at symmetric points with a single contact. Furthermore, in the linear response regime at low temperatures, we demonstrate that (non-)degenerate non-equilibrium steady states correspond to (non-)quantized conductance peaks. Revisiting a paradigmatic problem of resonant transport in the Majorana mode of the Kitaev model we demonstrate that the dissipation accounts for the zero-bias peak suppression and its asymmetry.

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arXiv2026

Dissipation-Induced Steady States in Topological Superconductors: Mechanisms and Design Principles

The search for conditions supporting degenerate steady states in nonequilibrium topological superconductors is important for advancing dissipative quantum engineering, a field that has attracted significant research attention over the past decade. In this study, we address this problem by investigating topological superconductors hosting unpaired Majorana modes under the influence of environmental dissipative fields. Within the Gorini-Kossakowski-Sudarshan-Lindblad framework and the third quantization formalism, we establish a correspondence between equilibrium Majorana zero modes and non-equilibrium kinetic zero modes. We further derive a simple algebraic relation between the numbers of these excitations expressed in terms of hybridization between the single-particle wavefunctions and linear dissipative fields. Based on these findings, we propose a practical recipes how to stabilize degenerate steady states in topological superconductors through controlled dissipation engineering. To demonstrate their applicability, we implement our general framework in the BDI-class Kitaev chain with long-range hopping and pairing terms -- a system known to host a robust edge-localized Majorana modes.

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arXiv2025

Minimal velocity of the travelling wave solutions in two coupled FKPP equations with the global conservation law

We investigate the system of two coupled one-dimensional Fisher-Kolmogorov-Petrovsky-Piskunov (FKPP) equations which possess the global conservation law. Such system of equations has been recently derived for the quasiparticle densities in the two-band fermionic model with the particle-number conserving dissipative protocol. As standard FKPP equation the studied system of equations has one unstable and one stable homogeneous solution with travelling wave switching between them. We demonstrate that the conservation law enforces the synchronization of travelling waves for both densities and determine their minimal possible velocity. Surprisingly, we find the existence of jumps of the minimal velocity as function of control parameters. We obtain that the minimal velocity of the coupled FKPP equations may significantly exceed the minimal velocity for a single FKPP equation in a wide range of control parameters.

cond-mat.stat-mech↗

arXiv2025

Spatially-resolved dynamics of the amplitude Schmid-Higgs mode in disordered superconductors

We investigate the spatially-resolved dynamics of the collective amplitude Schmid-Higgs (SH) mode in disordered $s$-wave superconductors and fermionic superfluids. By analyzing the analytic structure of the zero-temperature SH susceptibility in the complex frequency plane, we find that when the coherence length greatly exceeds the mean free path: (i) the SH response at fixed wave vectors exhibits late-time oscillations decaying as $1/t^2$ with frequency $2Δ$, where $Δ$ is the superconducting gap; (ii) sub-diffusive oscillations with a dynamical exponent $z{=}4$ emerge at late times and large distances; and (iii) spatial oscillations at fixed frequency decay exponentially, with a period that diverges as the frequency approaches $2Δ$ from above. When the coherence length is comparable to the mean free path, additional exponentially-decaying oscillations at fixed wave vectors appear with frequency above $2Δ$. Furthermore, we show that the SH mode induces an extra peak in the third-harmonic generation current at finite wave-vectors. The frequency of this peak is shifted from the conventional resonance at $Δ$, thereby providing an unambiguous signature of order parameter amplitude dynamics.

cond-mat.supr-con↗

arXiv2025

The Effect of Pearl Vortices on the Shape and Position of Néel-Type Skyrmions in Superconductor-Chiral Ferromagnet Heterostructures

This review presents recent work carried out at the Landau Institute for Theoretical Physics of the Russian Academy of Sciences on the study of the effect of superconducting vortices on the shape and position of Néel-type skyrmions in superconductor--chiral ferromagnet heterostructures. Based on analytical and numerical approaches, a number of effects caused by the inhomogeneous magnetic field of the vortex have been predicted: a significant increase in the skyrmion radius, a change in its chirality in the case of a coaxial configuration of the vortex and skyrmion, and modification of the skyrmion shape in the case of an eccentric configuration. Recent experiments studying these effects are discussed.

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arXiv2025

Instability of the engineered dark state in two-band fermions under number-conserving dissipative dynamics

Correlated quantum many-body states can be created and controlled by the dissipative protocols. Among these, particle number-conserving protocols are particularly appealing due to their ability to stabilize topologically nontrivial phases. Is there any fundamental limitation to their performance? We address this question by examining a general class of models involving a two-band fermion system subjected to dissipation designed to transfer fermions from the upper band to the lower band. By construction, these models have a guaranteed steady state - a dark state - with a completely filled lower band and an empty upper band. In the limit of weak dissipation, we derive equations governing the long-wavelength and long-time dynamics of the fermion densities and analyze them numerically. These equations belong to the Fisher-Kolmogorov-Petrovsky-Piskunov reaction-diffusion universality class. Our analysis reveals that the engineered dark state is generically unstable, giving way to a new steady state with a finite density of particles in the upper band. We also estimate the minimum system sizes required to observe this instability in finite systems. Our results suggest that number-conserving dissipative protocols may not be a reliable universal tool for stabilizing dark states.

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arXiv2024

Bound states and scattering of magnons on a superconducting vortex in ferromagnet-superconductor heterostructures

We study the magnon spectrum in a thin ferromagnetic-superconductor heterostructure in the presence of a single superconducting vortex. We employ the Bogolubov-de Gennes Hamiltonian which describes the magnons in the presence of the stray magnetic field and the non-uniform magnetic texture induced by the vortex. We find that the vortex localizes magnon states approximately in the same way as a charge center produces electron bound states due to screened Coulomb interaction in the two-dimensional electron gas. The number of these localized states is substantially determined by the material parameters of the ferromagnetic film only. We solve the scattering problem for an incident plane spin wave and compute the total and transport cross sections. We demonstrate that the vortex-induced non-uniform magnetic texture in chiral ferromagnetic film produces a skew scattering of magnons. We explore the peculiarities of the quantum scattering problem that correspond to orbiting in the classical limit.

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arXiv2024

The bending rigidity exponent of a two-dimensional crystalline membrane with arbitrary number of flexural phonon modes

We investigate the elastic behavior of two-dimensional crystalline membrane embedded into real space taking into account the presence an arbitrary number of flexural phonon modes $d_c$ (the number of out-of-plane deformation field components). The bending rigidity exponent $η$ is extracted by numerical simulation via Fourier Monte Carlo technique of the system behaviour in the universal regime. This universal quantity governess the correlation function of out-of-plane deformations at long wavelengths and defines the behaviour of renormalized bending rigidity at small momentum $\varkappa~\sim~1/q^η$. The resulting numerical estimates of the exponent for various $d_c$ are compared with the numbers obtained from the approximate analytical techniques.

cond-mat.stat-mech↗

arXiv2024

Deformation of a Néel-type Skyrmion in a Weak Inhomogeneous Magnetic Field: Magnetization Ansatz and Interaction with a Pearl Vortex

In this work, we develop a theory of (meta)stable states of Néel-type skyrmions in weak nonuniform magnetic fields. We claim an Ansatz for modeling the non-symmetric magnetization that can be implied for both analytics and numerical simulations. Our theory accounts for changes in the size of skyrmion parameters and also includes deformations from the centrally symmetric shape. The ansatz streamlines the analytic calculation of the skyrmion free energy, enhancing the efficiency of the minimizing process. Performing the minimization in two stages, one can find all the minima, global and local, of the free energy, discovering the stable and metastable states. We apply the developed methodology to investigate the (meta)stable configurations of skyrmions influenced by the stray field of a Pearl vortex. Our study reveals the dependence of skyrmion spatial parameters on the vortex field effective strength and presents a phase diagram identifying regions where metastable configurations are predicted. Corroborated by micromagnetic simulations, our findings offer a detailed perspective on the interaction between magnetic skyrmions and superconducting vortices.

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arXiv2024

Quantum Fluctuations and Multifractally-Enhanced Superconductivity in Disordered Thin Films

The interplay between electron-electron interactions and weak localization (or anti-localization) phenomena in two-dimensional systems can significantly enhance the superconducting transition temperature. We develop the theory of quantum fluctuations within such multifractally-enhanced superconducting states in thin films. In conditions of weak disorder, we employ the Finkel'stein nonlinear sigma model to derive an effective action for the superconducting order parameter and the quasiclassical Green's function, meticulously accounting for the influence of quantum fluctuations. This effective action, applicable for interactions of any strength, reveals the critical role of well-known collective modes in a dirty superconductor, and its saddle point analysis leads to modified Usadel and gap equations. These equations comprehensively incorporate the renormalizations stemming from the interplay between interactions and disorder, resulting in the non-trivial energy dependence of the gap function. Notably, our analysis establishes a direct relation between the self-consistent gap equation at the superconducting transition temperature and the known renormalization group equations for interaction parameters in the normal state.

cond-mat.supr-con↗

arXiv2023

Attenuation of flexural phonons in free-standing crystalline two-dimensional materials

We develop the theory for dynamics of the out-of-plane deformations in flexible two-dimensional materials. We focus on study of attenuation of flexural phonons in free-standing crystalline membranes. We demonstrate that the dynamical renormalization does not involve the ultraviolet divergent logarithmic contributions contrary to the static ones. This fact allows us to find the scaling form of the attenuation, determine its small and large frequency asymptotes, and to derive the exact expression for the dynamical exponent of flexural phonons in the long wave limit: $\textsf{z}{=}2{-}η/2$. Here $η$ is the universal exponent controlling the static renormalization of the bending rigidity. Also we determine the dynamical exponent for the long-wave in-plane phonons: $\textsf{z}^\prime{=}(2{-}η)/(1{-}η/2)$. We discuss implication of our results to experiments on phonon spectra in graphene and dynamics of graphene-based nanomechanical resonators.

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arXiv2023

Narrowing of the flexural phonon spectral line in stressed crystalline two-dimensional materials

We develop the microscopic theory for the attenuation of out-of-plane phonons in stressed flexible two-dimensional crystalline materials. We demonstrate that the presence of nonzero tension strongly reduces the relative magnitude of the attenuation and, consequently, results in parametrical narrowing of the phononspectral line. We predict the specific power-law dependence of the spectral-line width on temperature and tension. We speculate that suppression of the phonon attenuation by nonzero tension might be responsible for high quality factors of mechanical nanoresonators based on flexural two-dimensional materials.

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arXiv2023

Topological phases induced by charge fluctuations in Majorana wires

One of the problems concerning topological phases in solid-state systems which still remains urgent is an issue of many-body effects. In this study we address it within perturbative theory framework by considering topological phase transitions related to charge correlations in the extended Kitaev chain model that belongs to the BDI symmetry class. Obtained corrections to a zero-frequency quasiparticle Green's function allow to separate the mean-field and fluctuation contributions to a total winding number. As a result, the phase transitions caused solely by the latter are unveiled. We thoroughly analyze the mechanism of such transitions in terms of fluctuation-induced nodal points and spectrum renormalization. Additionally, features of other quasiparticle properties such as effective mass and damping are discussed in the context of topological phase transitions.

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