arXiv subjects

V. V. Kabanov

Publications and source records attributed to V. V. Kabanov.

At least 19 recordsLinked to original sources

arXiv2026

Critical photoinduced reflectivity relaxation dynamics in single-layer Bi-based cuprates near the pseudogap end point

A comprehensive study of photoinduced transient reflectivity dynamics in heavily overdoped single-layer cuprate (Bi,Pb)$_{2}$Sr$_{2}$CuO$_{6+δ}$ (Pb-Bi-2201) across the end points of the pseudogap and superconducting phases was conducted using optical ultrafast time-resolved pump-probe spectroscopy. In the Pb-Bi-2201 near the proposed pseudogap end-point doping, the transient reflectivity dynamics above $T_{\rm c}$ resemble the pseudogap response observed in the optimally doped La-Bi-2201. With decreasing temperature, however, the relaxation time exhibits a power-law divergence, $τ\sim10\hbar/k_{\mathrm{B}}T$, consistent with quantum critical behavior near the proposed pseudogap end-point doping. A similar power-law increase in relaxation time is also observed at a slightly more overdoped composition, though it is less pronounced.

cond-mat.supr-con↗

arXiv2024

Anomalous hardening of spin waves in cobalt/molecular-semiconductor heterostructures reveals strongly anisotropic spinterface magnetism

The interface between a ferromagnetic metal and an organic molecular semiconductor, commonly referred to as a spinterface, is an important component for advancing spintronic technologies. Hybridization of the ferromagnetic-metal surface d orbitals with the molecular-semiconductor p orbitals induces profound modifications not only in the interfacial molecular layer, but also in the surface ferromagnetic-metal atomic layer. These effects are particularly pronounced at low temperatures, manifesting as substantial modifications in the magnetic properties of thin-film magnetic-metal/organic heterostructures. Despite extensive research and interest, the magnetic-ordering and magnetic-properties of the spinterface remain poorly understood. Using ultrafast time-resolved magneto-optical spectroscopy, to investigate the magnetic dynamics in such heterostructures, we unveil the unique spinterface-magnetism and its universality for a broad variety of cobalt/molecular-semiconductor interfaces. In particular, our findings demonstrate the presence of highly anisotropic low-temperature superparamagnetism at the cobalt/molecular-semiconductor spinterface. This anisotropic interfacial superparamagnetism is likely driven by strong chemical modifications in the cobalt interfacial layer caused by the chemisorbed molecular layer. These results highlight the pivotal role of molecular chemisorption in tuning the magnetic properties at spinterfaces, paving the way for future spintronic applications.

cond-mat.mtrl-sci↗

arXiv2024

Impact of the impurity symmetry on orbital momentum relaxation and orbital Hall effect studied by the quantum Boltzmann equation

We develop a quantum Boltzman equation approach that incorporates microscopic impurity models into the theory of orbital transport, revealing, how impurity properties, including their symmetry, influence the relaxation of orbital momentum and the orbital Hall effect. Specifically, we demonstrate that when the impurity potential has axial symmetry, the relaxation is governed by the Dyakonov-Perel mechanism. In contrast, when this symmetry is broken, scattering can result in a rapid Elliot-Yafet relaxation of orbital momentum. The details of impurity potential also affect the intrinsic orbital Hall effect even when the impurity concentration is very small. Impurities that alter the orbital texture can also give rise to a skew-scattering contribution to the orbital Hall effect, although this does not necessarily dominate in materials that are nearly pristine due to the Dyakonov-Perel relaxation.

cond-mat.mes-hall↗

arXiv2023

Interface disorder as a cause for kinetic Rashba-Edelstein effect and interface Spin-Hall effect at the metal-insulator boundary

The spin phenomena observed at a clean metall-insulator interface are typically reduced to Rashba-Edelstein effect, that leads to spin accumulation over a few monolayers. We demonstrate that the presence of interface disorder significantly expands the range of potential phenomena. Specifically, the skew scattering at the metal - insulator boundary gives rise to the "kinetic Rashba-Edelstein effect", where spin accumulation occurs on a much larger length scale comparable to mean free path. Moreover, at higher orders of spin-orbit interaction, skew scattering is accompanied with spin relaxation resulting in the interface spin-Hall effect - a conversion of electrical current to spin current at the metal surface. Unlike the conventional spin-Hall effect, this phenomenon persists even within the Born approximation. These two predicted phenomena can dominate the spin density and spin current in devices of intermediate thickness.

cond-mat.mes-hall↗

arXiv2022

First-order kinetics bottleneck during photoinduced ultrafast insulator-metal transition in 3D orbitally-driven Peierls insulator CuIr$_{2}$S$_{4}$

Ultrafast dynamics across the photoinduced three-dimensional Peierls-like insulator-metal (IM) transition in CuIr$_{2}$S$_{4}$ was investigated by means of the all-optical ultrafast multi-pulse time-resolved spectroscopy. The structural coherence of the low-$T$ broken symmetry state is strongly suppressed on a sub-picosecond timescale above a threshold excitation fluence of $F_{\mathrm{c}}\approx3$ mJ/cm$^{2}$ (at 1.55-eV photon energy) resulting in a structurally inhomogeneous transient state which persists for several-tens of picoseconds before reverting to the original low-$T$ state. The electronic order shows a transient gap filling at a significantly lower fluence threshold of $\sim0.6$~mJ/cm$^{2}$. The data suggest that the photoinduced-transition structural dynamics to the high-$T$ metallic phase is governed by first-order-transition nucleation kinetics that prevents the complete structural transition into the high-$T$ phase even at excitation fluences significantly larger than $F_{\mathrm{c}}$. In contrast, the dynamically-decoupled electronic order is suppressed rather independently due to a photoinduced Mott transition.

cond-mat.str-el↗

arXiv2022

Adiabatic theory of the polaron spectral function

An analytic theory for the spectral function for electrons coupled with phonons is formulated in the adiabatic limit. In the case when the chemical potential is large and negative $μ\to -\infty$ the ground state does not have the adiabatic deformation and the spectral function is defined by the standard perturbation theory. In this limit we present the spectral function calculated up to fourth order in the electron-phonon coupling constant which satisfies the sum rules up to the 5th moment. In the case when the chemical potential is pinned at the polaron binding energy the spectral function is defined by the ground state with a nonzero adiabatic deformation. We calculate the spectral function with the finite polaron density in the adiabatic limit. We also demonstrate how the sum rules for higher moments may be evaluated in the adiabatic limit. Contrary to the case of zero polaron density the spectral function with the finite polaron concentration has some contributions which are characteristic for polarons.

cond-mat.str-el↗

arXiv2021

First-order kinetics bottleneck during photoinduced ultrafast insulator-metal transition in 3D orbitally-driven Peierls insulator CuIr$_{2}$S$_{4}$

The spinel-structure CuIr$_{2}$S$_{4}$ compound displays a rather unusual orbitally-driven three-dimensional Peierls-like insulator-metal transition. The low-T symmetry-broken insulating state is especially interesting due to the existence of a metastable irradiation-induced disordered weakly conducting state. Here we study intense femtosecond optical pulse irradiation effects by means of the all-optical ultrafast multi-pulse time-resolved spectroscopy. We show that the structural coherence of the low-T broken symmetry state is strongly suppressed on a sub-picosecond timescale above a threshold excitation fluence resulting in a structurally inhomogeneous transient state which persists for several-tens of picoseconds before reverting to the low-T disordered weakly conducting state. The electronic order shows a transient gap filling at a significantly lower fluence threshold. The data suggest that the photoinduced-transition dynamics to the high-T metallic phase is governed by first-order-transition nucleation kinetics that prevents the complete ultrafast structural transition even when the absorbed energy significantly exceeds the equilibrium enthalpy difference to the high-T metallic phase. In contrast, the dynamically-decoupled electronic order is transiently suppressed on a sub-picosecond timescale rather independently due to a photoinduced Mott transition.

cond-mat.str-el↗

arXiv2021

Robust hybridization gap in a Kondo Insulator YbB${}_{12}$ probed by femtosecond optical spectroscopy

In heavy fermions the relaxation dynamics of photoexcited carriers has been found to be governed by the low energy indirect gap, E$_{g}$, resulting from hybridization between localized moments and conduction band electrons. Here, carrier relaxation dynamics in a prototype Kondo insulator YbB${}_{12}$ is studied over large range of temperatures and over three orders of magnitude. We utilize the intrinsic non-linearity of dynamics to quantitatively determine microscopic parameters, such as electron-hole recombination rate. The extracted value reveals that hybridization is accompanied by a strong charge transfer from localized 4f-levels. The results imply the presence of a hybridization gap up to temperatures of the order of E$_{g}$/k$_{B}\approx200$ K, which is extremely robust against electronic excitation. Finally, below 20 K the data reveal changes in the low energy electronic structure, attributed to short-range antiferromagnetic correlations between the localized levels.

cond-mat.str-el↗

arXiv2020

Light effect on the interface resistance of Ba$_{0.8}$Sr$_{0.2}$TiO$_3$/LaMnO$_3$ heterosctructure

The effect of green and ultraviolet laser light on Ba$_{0.8}$Sr$_{0.2}$TiO$_3$/LaMnO$_3$ heterostructure electrical resistance was studied. In 80-200 K range illumination induces transient resistance component at ~15% of the steady-state value, the time constant associated with the transient component is ~12 s. The negative photoresistance effect is found under green, infrared and ultraviolet illumination.

cond-mat.mes-hall↗

arXiv2020

Electron-electron and electron-phonon relaxation in metals excited by optical pulse

A short overview of theoretical models for the description of the relaxation processes in metals excited by a short laser pulse is presented. The main effort is given to description of different processes which are taking place after absorption of the laser pulse. Widely used two temperature model is discussed and the conditions of applicability of this model are identified. Various approaches for solving the Boltzmann kinetic equations are discussed. It is identified that in the case of low excitation limit the relaxation is determined by the emission of phonons by photoexcited electrons. The possibility to obtain the value of the electron phonon coupling constant from experiments is discussed.

cond-mat.str-el↗

arXiv2019

Magnetic-field effect in the heterostructure Ba$_{0.8}$Sr$_{0.2}$TiO$_3$/LaMnO$_3$

We have studied transport and magnetotransport properties of the heterostructure consisting of the ferroelectric Ba$_{0.8}$Sr$_{0.2}$TiO$_3$ film deposited on the single crystalline manganite LaMnO$_3$. Two-dimensional electron gas arising at the interface transforms the interface region of the antiferromagnetic manganite to the ferromagnetic state with the reoriented magnetic moments. We obtained that the contribution of these ferromagnetic regions to the resistance of the heterostructure appears to be dependent on the external magnetic field applied perpendicularly to the interface (and parallel to {\it c}-axis of the ferromagnetic state of LaMnO$_3$). We believe that the decrease of the resistance of the studied heterostructure under the influence of the external magnetic field is caused by an appearance of the ferromagnetic order in the interface area. This leads to a relatively small resistance. In turn, the cycling of the applied magnetic field leads to the increase of the regions of the ferromagnetic order and, as a result, to decreasing scattering of the current carriers at the ferromagnetic disordering.

cond-mat.mes-hall↗

arXiv2019

Symmetry Enforced Dirac Points in Antiferromagnetic Semiconductors

It is shown that the symmetry enforced Dirac points exist at some time reversal symmetric momenta in antiferroemgnetic compound GdB$_4$. These Dirac points may be controlled by the external magnetic field or by the deformation of the crystal. Application of the external magnetic field leads to splitting of these points into Weyl points or to opening of a gap depending on the field direction. The application of the symmetry breaking deformation also opens a gap in the spectrum. Suppression of the antiferromagnetic order leads to the formation of the nodal line instead of the Dirac points. This indicates that the symmetry enforced Dirac semimetals may be effectively used in different spintronic devices.

cond-mat.str-el↗

arXiv2018

Phase separation and second-order phase transition in the phenomenological model for Coulomb frustrated 2D system

We have considered the model of the phase transition of the second order for the Coulomb frustrated 2D charged system. The coupling of the order parameter with the charge was considered as the local temperature. We have found that in such system, an appearance of the phase-separated state is possible. By numerical simulation, we have obtained different types ("stripes", "rings", "snakes") of phase-separated states and determined the parameter ranges for these states. Thus the system undergoes a series of phase transitions when the temperature decreases. First, the system moves from the homogeneous state with a zero order parameter to the phase-separated state with two phases in one of which the order parameter is zero and, in the other, it is nonzero ($τ>0$). Then a first-order transition occurs to another phase-separated state, in which both phases have different and nonzero values of the order parameter (for $τ<0$). And only a further decrease of temperature leads to a transition to a homogeneous ordered state.

cond-mat.str-el↗

arXiv2018

Magnetoresistance in organic semiconductors: including pair correlations in the kinetic equations for hopping transport

We derive the kinetic equations for polaron hopping in organics that explicitly take into account the double occupation possibility and pair intersite correlations. The equations include simplified phenomenological spin dynamics and provide a self-consistent framework for the description of the bipolaron mechanism of the organic magnetoresistance. At low applied voltages the equations can be reduced to effective resistor network that generalizes the Miller-Abrahams network and includes the effect of spin relaxation on the system resistivity. Our theory discloses the close relationship between the organic magnetoresistance and the intersite correlations. Moreover, in the absence of correlations, as in ordered system with zero Hubbard energy, the magnetoresistance vanishes.

cond-mat.dis-nn↗

arXiv2018

Toward High Temperature Quasi-two-dimensional Superconductivity

The demonstration of a quasi-two-dimensional electron gas (2DEG) and superconducting properties in LaAlO$_3$/SrTiO$_3$ heterostructures has stimulated intense research activity in recent ten years. The 2DEG has unique properties that are promising for applications in all-oxide electronic devices. The superconductivity in such heterostructures has been observed below 300 mK. For superconductivity applications it is desirable to have more wide temperature of the existence range and the ability to control superconductivity properties by external stimulus. Based on first-principles calculations and theoretical consideration we show that all-oxide heterostructures incorporating ferroelectric constituent, such as BaTiO$_3$/La$_2$CuO$_4$, allow creating 2DEG. We predict a possibility of a high temperature guasi-two-dimensional superconductivity state. This state could be switchable between superconducting and conducting states by ferroelectric polarization reversal. We also discuss that such structures must be more simple for preparation. The proposed concept of ferroelectrically controlled interface superconductivity offers the possibility to design novel electronic devices.

cond-mat.supr-con↗

arXiv2018

On strictly Deza graphs with parameters (n,k,k-1,a)

A nonempty $k$-regular graph $Γ$ on $n$ vertices is called a Deza graph if there exist constants $b$ and $a$ $(b \geq a)$ such that any pair of distinct vertices of $Γ$ has precisely either $b$ or $a$ common neighbours. The quantities $n$, $k$, $b$, and $a$ are called the parameters of $Γ$ and are written as the quadruple $(n,k,b,a)$. If a Deza graph has diameter 2 and is not strongly regular, then it is called a strictly Deza graph. In the paper we investigate strictly Deza graphs with parameters $ (n, k, b, a) $, where its quantities satisfy the conditions $k = b + 1$ and $\frac{k(k - 1) - a(n - 1)}{b - a} > 1$.

math.CO↗

arXiv2017

Dynamics of the superconducting order parameter through ultrafast normal-to-superconducting phase transition in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$ from multi-pulse polarization-resolved transient optical reflectivity

A systematic temperature dependent study of the femtosecond optical superconducting (SC) state destruction and recovery in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$ cuprate superconductor by means of the all-optical polarization-sensitive multi-pulse spectroscopy is presented. At low temperatures and a partial SC state suppression an anisotropic SC-gap recovery-timescale is suggested by the data. The SC state destruction and recovery dynamics are compared to the recent TR-ARPES-inferred SC-gap dynamics and a qualitative agreement is found. Using a phenomenological response function the experimental data are also compared to time dependent Ginzburg-Landau model simulations.

cond-mat.supr-con↗

arXiv2016

Upper critical field in the model with finite range interaction between electrons

We develop a theory of the upper critical field in a BCS superconductor with a nonlocal interaction between electrons. We have shown that the nonlocal interaction is characterized by the parameter $k_Fρ_0$ where $k_F$ is the Fermi momentum and $ρ_0$ is the radius of electron-electron interaction. The presence of the external magnetic field leads to the generation of additional components of the order parameter with different angular momentum. This effect leads to the enhancement of the upper critical field above the orbital limiting field. In addition the upward curvature in the temperature dependence of $H_{c2}(T)$ in the clean limit is predicted. The impurity scattering suppresses the effect in the dirty limit.

cond-mat.supr-con↗