arXiv subjects

A. S. Mel'nikov

Publications and source records attributed to A. S. Mel'nikov.

At least 19 recordsLinked to original sources

arXiv2026

Perspectives on Magnetic/Superconductor Hybrid Systems: Long-range Electromagnetic Phenomena Induced by Proximity Effect and Interfacial Spin-orbit Coupling

In this Perspective we review recent achievements in physics and applications of hybrid superconductor-ferromagnet structures. In particular, we focus on the manifestations of the electromagnetic phenomena in these systems originating from the response of the induced superconducting correlations modified by the exchange field and additional effects coming from the interface Rashba-type spin-orbit coupling. The review includes the long-range electromagnetic proximity effect and related modification of magnetic textures, spontaneous currents, properties of vortex matter and its interaction with magnetic ordering, spin-galvanic, photogalvanic and nonreciprocal transport phenomena in exemplary hybrid systems. We also present our views on the future development of this field including both the theoretical challenges and promising opportunities for fundamental experiments.

cond-mat.supr-con↗

arXiv2026

Impurity-induced Inverse Faraday Effect

We provide a quantum-mechanical description of the photoinduced dc current states and magnetic fields around nonmagnetic point impurities in a two-dimensional (2D) electron gas irradiated by a circularly polarized electromagnetic wave. Based on the solution of the corresponding time-dependent Schrodinger equation within the second-order perturbation theory in the electromagnetic wave amplitude we find that the resulting dc magnetic field component perpendicular to the plane of the 2D system is distributed like in a set of random magnetic fluxes bound to the positions of impurities. As a result, the spatially averaged dc magnetic field does not vanish far from the sample edges and, thus, our scenario of the inverse Faraday effect in disordered systems differs strongly from the standard one based on the relaxation time approximation within the hydrodynamic or kinetic equation approaches which would give only the photoinduced currents flowing along the sample edges. The predicted mechanism for formation of rectified currents flowing around the impurity centers is shown to be generic both for 2D and three-dimensional systems. The internal dc magnetic field can give rise to the photoinduced Hall effect and Faraday rotation for a probing electromagnetic signal.

cond-mat.mes-hall↗

arXiv2026

Effect of charge-imbalance potential relaxation on the high-frequency vortex dynamics and kinetic inductance of superconducting circuits

We show that relaxation of the charge-imbalance potential plays a key role in the retarded dynamics of Abrikosov vortices in a type-II superconducting sample carrying a microwave current. Starting from the time-dependent Ginzburg--Landau equations we derive the vortex equation of motion accounting both the dissipation and retardation effects. The retardation is governed by the dynamics of the charge-imbalance potential and reveals itself at characteristic timescales diverging near the superconducting critical temperature $T_{c}$. These retardation effects in vortex dynamics strongly affect the kinetic inductance of superconducting circuits being, thus, responsible for the magnetic field dependence of characteristics of different superconducting devices in the high frequency range.

cond-mat.supr-con↗

arXiv2025

Photogalvanic and photon drag phenomena in superconductors and hybrid superconducting systems

In this paper we review the recent progress in theoretical understanding of the peculiarities of photogalvanic phenomena, photon drag and inverse Faraday effects in superconductors and hybrid superconducting structures. Our study is based on the time-dependent Ginzburg-Landau (TDGL) theory with a complex relaxation constant which provides the simplest description of the mechanisms of the second-order nonlinear effects in the electrodynamic response and related mechanisms of generation of dc photocurrents, magnetic moment and switching between different current states under the influence of electromagnetic radiation of various polarization.

cond-mat.supr-con↗

arXiv2025

Interplay of ferroelectricity and interlayer superconductivity in van der Waals bilayers

We study the distinctive features of the interplay between the interlayer superconductivity and ferroelectricity in van der Waals heterostructures. Corresponding analysis is carried out within the framework of the quasiclassical Eilenberger equations for a tunnel coupled bilayer with inhomogeneous relative shift of the conduction bands between the layers, which describes the net charge transfer in sliding ferroelectrics. It is shown that the critical temperature of the interlayer superconductivity can be significantly enhanced for superconducting nuclei localized in the vicinity of ferroelectric domain walls. We demonstrate that the increase in the tunneling amplitude leads to the decrease (increase) in the difference between the critical temperatures for localized and homogeneous superconducting states for the spin-singlet (spin-triplet) interlayer superconductivity. We also perform an extensive analysis of the effects of the in-plane magnetic field on the interlayer superconductivity. It is shown that the orbital effect can result in the suppression of the spin-singlet interlayer superconductivity and to the enhancement of the spin-triplet one. We find that possible manifestations of the paramagnetic effect include the suppression of the interlayer superconductivity by rather weak Zeeman fields, the two-fold anisotropy of the critical magnetic field for the spin-triplet states as well as the appearance of the reentrant superconducting phases. It is shown that the joint influence of the orbital and paramagnetic mechanisms on the spin-triplet interlayer superconductivity can even lead to a nonmonotonic behavior of the superconducting critical temperature as a function of the external magnetic field. The obtained results are discussed in the context of recent experimental data on van der Waals structures with coexisting superconductivity and sliding ferroelectricity.

cond-mat.supr-con↗

arXiv2025

Vortex structure and intervortex interaction in superconducting structures with intrinsic diode effect

We demonstrate that the intrinsic superconducting diode effect can affect the structure, interactions and dynamics of Abrikosov vortices in non-centrosymmetric superconductor/ferromagnet hybrid structures. The Ginzburg-Landau (GL) theory accounting for the spin-orbit and exchange-field effects predicts a chiral distortion of the superfluid velocity, non-central interaction forces and resulting torque in a vortex-antivortex pair, and anisotropy of the Bean-Livingston barrier. These closed-form results are fully confirmed by time-dependent GL numerical simulations carried out with a fourth-order least-squares finite-difference solver, which captures equilibrium single vortex configuration in realistic mesoscopic geometries. The analysis shows that the cubic gradient term shifts vortex cores by an amount proportional to the in-plane exchange field and simultaneously generates a lateral torque that can rotate entire vortex ensembles, showing how spin-orbit coupling and the exchange field enable breakdown of the vortex-antivortex symmetry in a finite-size sample. By combining transparent analytics with quantitative numerics, the work provides the hallmarks of vortex physics in superconducting structures with an intrinsic diode effect and supplies concrete guidelines for designing non-reciprocal superconducting circuits, fluxonic logic elements, and kinetic-inductance devices.

cond-mat.supr-con↗

arXiv2025

Magnetic force microscopy versus scanning quantum-vortex microscopy: Probing pinning landscape in granular niobium films

We provide an overview of the methodology and fundamental principles associated with newly developed experimental technique -- scanning quantum-vortex microscopy [Hovhannisyan et al., Commun. Mater., vol. 6, 42 (2025)]. This approach appears promising for experimental studies of vortex pinning phenomena in superconducting films and nanodevices. In particular, we studied the magnetic properties of magnetron-sputtered niobium (Nb) films by low-temperature magnetic force microscopy. As the temperature approaches the superconducting critical temperature, the pinning potential caused by structural defects weakens; consequently, the attractive interaction between the magnetic tip of the cantilever and a single-quantum vortex begins to dominate. In this scenario the magnetic probe is capable of trapping a vortex during the scanning process. Because the dragged vortex continues interacting with structural defects, it serves as an efficient nano-probe to explore pinning potentials and visualize grain boundaries in granular Nb films, achieving resolutions (30 nm) comparable to the superconducting coherence length.

cond-mat.supr-con↗

arXiv2025

Superconducting photocurrents induced by structured electromagnetic radiation

We develop a phenomenological theory describing the interaction of superconducting condensate with a Bessel beam of twisted light characterized by a nonzero angular momentum $m$. Starting from the time-dependent Ginzburg-Landau model with the complex relaxation time we calculate the spatial profiles of dc photoinduced currents and magnetic fields as well as the second harmonic response. The photocurrents and magnetic fileds are shown to be determined both by the helicity of light and its orbital momentum $m$. Analyzing the half-space and thin film geometries we discuss possible experimental tests aimed to probe the superconducting photocurrents and magnetic fields.

cond-mat.supr-con↗

arXiv2025

Proximity Induced Non-collinear Magnetic States in Planar Superconductor/Ferromagnet Hybrids

The proximity induced superconducting (S) correlations in ferromagnetic (F) layers of planar S/F hybrids are shown to be responsible for the appearance of a nonlinear interaction between the magnetic moments of the F layers. This interaction originates from the combined influence of the orbital and exchange phenomena and can result in the spontaneous formation of non-collinear magnetic states in these systems. The proposed nonlinear coupling mechanism and resulting changes of magnetic textures are crucial for the design of the superconducting spintronics devices exploiting the long-range spin triplet proximity effect.

cond-mat.supr-con↗

arXiv2024

Inverse spin galvanic effect in proximitized superconductor/paramagnet systems

We show that the interplay between spin-orbit coupling (SOC) and the paramagnetic response of itinerant electrons in proximitized superconductor/paramagnet systems gives rise to the inverse spin galvanic effect, i.e. generation of magnetic moment under the influence of the charge current. Depending on the sign of the SOC constant and the system temperature, the corresponding contribution to the magnetic response of the superconductor can be either diamagnetic or paramagnetic. We discuss the relevance between the discovered phenomena and the recent experiments on Pt/Nb heterostructures as well as the puzzling sign change of the magnetic response observed in clean Ag coated Nb cylinders.

cond-mat.supr-con↗

arXiv2024

Photogalvanic phenomena in superconductors supporting intrinsic diode effect

In this work we suggest a phenomenological theory of photogalvanic phenomena in superconducting materials and structures revealing the diode effect. Starting from a generalized London model including the quadratic nonlinearity in the relation between the supercurrent and superfluid velocity we show that the electromagnetic wave incident on the superconductor can generate a nontrivial superconducting phase difference between the ends of the sample. Being enclosed in a superconducting loop such phase battery should generate a dc supercurrent circulating in the loop. Increasing the electromagnetic wave intensity one can provoke the switching between the loop states with different vorticities.

cond-mat.supr-con↗

arXiv2024

ac Hall Effect and Photon Drag of Superconducting Condensate

We suggest a theoretical description of the photogalvanic phenomena arising in superconducting condensates in the field of electromagnetic wave. The ac Hall effect and photon drag are shown to originate from the second-order nonlinear response of superconducting carriers caused by the suppression of their concentration due to the combined influence of the electron - hole asymmetry and charge imbalance generated by the incident electromagnetic wave. Starting from the time-dependent Ginzburg-Landau theory with the complex relaxation constant we develop a phenomenological description of these phenomena and investigate the resulting behavior of the dc supercurrent and second harmonic induced by microwave radiation incident on a superconductor surface.

cond-mat.supr-con↗

arXiv2023

Unconventional superconductivity and paramagnetic Meissner response triggered by nonlocal pairing interaction in proximitized heterostructures

Proximity phenomena and induced superconducting correlations in heterostructures are shown to be strongly affected by the nonlocal nature of the electronic attraction. The latter can trigger the formation of Cooper pairs consisting of electrons localized in neighbouring layers even in the absence of direct quasiparticle transfer between the layers. We investigate the manifestations of such nonlocal pairing and resulting unconventional induced superconductivity in an exemplary two-dimensional (2D) electronic system coupled to a conventional superconductor. The interplay between the quasiparticle tunneling and spin-triplet interlayer pairing is shown to generate the odd-frequency superconducting correlations in the 2D material which give rise to the paramagnetic contribution to the Meissner response and affect the energy resolved quasiparticle density of states. Experimental evidence for the above nonlocal interface pairing would provide new perspectives in engineering the unconventional superconducting correlations in heterostructures.

cond-mat.supr-con↗

arXiv2023

Adiabatic phase pumping in S/F/S hybrids with non-coplanar magnetization

We study the distinctive features of the phase pumping effect in Josephson transport through a three-layered ferromagnet F$_1$/F/F$_2$ with non-coplanar magnetization. Using Gor'kov and Bogoliubov-de Gennes formalisms we go beyond the quasiclassical approximation and analyze the dependence of the spontaneous Josephson phase $ψ$ on the exchange field $h$ in the F layer and details of magnetization profile. The pumping of the Josephson phase can be generated by the mutual rotation of magnetizations in F$_1$ and F$_2$ layers resulting in the nontrivial phase gain at the rotation period (Berry phase). The increase in $h$ is shown to cause changes in the topology of the phase evolution: the gain of the Josephson phase at the pumping period switches from $0$ to $2π$. We study the scenario of these switchings originating from the interplay between several competing local minima of the free energy of the junction versus the superconducting phase difference. Our analysis provides the basis for the search of experimental setup realizing the phase pumping phenomenon.

cond-mat.supr-con↗

arXiv2023

Collisionless dynamics of superconducting gap excited by spin-splitting field

We study the coherent dynamic interaction of a time-dependent spin-splitting field with the homogeneous superconducting order parameter $Δ(t)$ mediated by spin-orbit coupling using the time-dependent Bogoliubov-de Gennes theory. In the first part of the work we show that linear response of the superconductor is strongly affected by the Zeeman field and spin-flip processes, giving rise to multiple resonant frequencies of the superconducting Higgs modes. These modes can be excited either by a quench, or by an additional non-stationary component of the spin-splitting field, which couples linearly to the Higgs modes. In the second part, we analyze the nonadiabatic dynamics of quasiparticle states arising from the intersection of spectral branches from different spin subbands, which can be provoked by a linearly growing Zeeman field. We provide insights into the dependence of the order parameter $Δ(t)$ on this field and interference effects caused by tunneling of states at the avoided crossing points. We also show that since the nonadiabatic tunneling is related to spin-flip processes, the quasiparticle gas experiences a dynamic magnetization that contributes to its spin susceptibility.

cond-mat.supr-con↗

arXiv2023

Electronic structure of a Josephson vortex in a SIS junction

The Josephson vortex formed in a superconductor-insulator-superconductor (SIS) junction can affect the quantum mechanics of quasiparticles by creating an effective adiabatic potential determined by the inhomogeneous distribution of the phase difference of the order parameter along the junction. Starting from the quasiclassical version of the Bogoliubov-de Gennes (BdG) theory, we found the quasiparticle spectrum and the local density of states (DOS) both for the isolated Josephson vortex and the vortex chain. The spatially resolved DOS reveals a peculiar two-peak structure for each Josephson vortex, which can be detected experimentally using the scanning tunneling microscopy/spectroscopy techniques.

cond-mat.supr-con↗

arXiv2023

All-optical generation of Abrikosov vortices by the Inverse Faraday Effect

Within the framework of the time-dependent Ginzburg-Landau theory we show that circularly polarized THz or far-infrared radiation induces a dc supercurrent that influences the dynamics of vortex-antivortex pair formation in a mesoscopic superconductor undergoing rapid thermal quenching. The Lorentz force arising from the supercurrents promotes vortex-antivortex separation and allows survival of the vortex polarity defined by the helicity of light. Based on this idea, we propose a two-stage irradiation scheme that provides a powerful method for controlled all-optical generation of Abrikosov vortices.

cond-mat.supr-con↗

arXiv2022

Disorder-induced trapping and anti-trapping of vortices in type-II superconductors

We study the features of the superconductivity nucleation and vortex configurations in superconductors with modulated disorder. Using the Ginzburg-Landau-type theory with spatially varying diffusion coefficient, we uncover and explain the switching between the vortex-defect attraction to the repulsion upon the increase in the external magnetic field. It is shown that for rather weak applied magnetic fields, a superconducting nucleus localized near the region with the suppressed diffusion coefficient possesses a nonzero vorticity whereas the increase in the magnetic field can lead to a transition into the state with zero winding number. We demonstrate the manifestations of this switching phenomenon in superconductors with a large number of defects by performing numerical simulations of the vortex structures in superconductors with periodic spatial profiles of the diffusion coefficient. The obtained results clarify the physics of the vortex arrangement in several classes of the superconducting materials including one-dimensional superlattices and nanopatterned superconductors with regular arrays of the defects characterized by the increased concentration of nonmagnetic impurities.

cond-mat.supr-con↗