arXiv subjects

K. A. Baryshnikov

Publications and source records attributed to K. A. Baryshnikov.

6 recordsLinked to original sources

arXiv2026

Hydrodynamics of two-dimensional electrons due to scattering by disorder

The hydrodynamic regime of electron transport, induced by fast inter-electron collisions, was discovered in high-quality nanostructures in recent ten years. However, signs of hydrodynamic transport, primarily, the giant negative magnetoresistance, were observed even at very low temperatures, when electron-electron scattering is too weak to affect the transport. To address this puzzle, here we develop a theory of mixed, hydrodynamic and non-Markovian, magnetotransport of two-dimensional electrons at zero temperature in samples with weak but still important disorder. Namely, we account for both the memory effects at electron scattering by localized defects in magnetic field and an unconventional viscosity effect due to electron scattering by defects in bulk and by rough sample edges. Solution of the model yields a strong negative magnetoresistance, which exhibits at zero magnetic field a sharp maximum in narrower samples or a blunt maximum in wider samples. This and other our results explain various properties of the giant negative magnetoresistance observed on ultra-high-quality GaAs quantum wells, thereby we apparently reveal the nature of low-temperature magnetotransport in these systems.

cond-mat.mes-hall↗

arXiv2024

Optical Orientation of Mn$^{2+}$ Spins in Bulk (Zn, Mn)Se Induced by Magnetic Field

The optical orientation of Mn$^{2+}$ spins in the first excited state $^4$T$_1$ was experimentally observed in bulk (Zn, Mn)Se ($x_\mathrm{Mn}=0.01$) in the an external magnetic field of up to $6\,$T in Faraday geometry. This occurred during quasi-resonant continuous wave circularly polarized photoexcitation of the intracenter d-d transitions. A non-monotonic dependence of the thermal circular polarization of the intracenter photoluminescence on the magnetic field was observed. A theoretical model is proposed to describe the selection rules for resonant optical d-d transitions of an isolated Mn$^{2+}$ ion in a ZnSe cubic crystal. These rules are based on the analysis of the total angular momentum symmetry for the ground ($^6$A$_1$) and first excited ($^4$T$_1$) states of the Mn$^{2+}$ ion. This discussion neglects the specific mechanism for spin-flip processes in a d-shell of the ion during optical excitation. The analysis is founded on the rotational symmetry of the effective total angular momenta and parity for each state as a whole. Additionally, the Jahn-Teller coupling of the excited state orbital parts with tetragonal ($e$-type) local distortions of the crystal lattice is considered. This coupling results in the segregation of cubic axes and spin projections on these axes due to weak spin-orbit and spin-spin coupling in the excited state. This leads to energy splitting for spin states with their projections of $\pm 1/2$ and $\pm 3/2$ on each axis distinguished by specific Jahn-Teller distortion in the corresponding atomic potential minimum. By introducing two different times of relaxation to reach thermodynamic equilibrium for $\pm 1/2$ and $\pm 3/2$ states in each Jahn-Teller configuration, an angle dependent optical orientation contribution in photoluminescence polarization arises in the presence of a magnetic field.

cond-mat.mes-hall↗

arXiv2024

Nonlinear screening and charge redistribution in periodically doped graphene

The screening problem for the Coulomb potential of a charge located in a two-dimensional (2D) system has an intriguing solution with a power law distance screening factor due to out-of-plane electrical fields. This is crucially different from a three-dimensional case with exponential screening. The long-range action of electric fields results in the effective inflow of electrons from high-doped regions to low-doped regions of a 2D heterostructure. In graphene and other materials with linear energy spectrum for electrons, such inflow in low-doped regions also occurs, but its effectiveness is dependent on doping level. This can be used for fabricating high-mobility conducting channels. We provide the theory for determining electron potential and concentration in a periodically doped graphene sheet along one dimension taking into account all effects of long-range 2D screening. This results in a substantially nonlinear integro-differential problem, which is solved numerically via computationally cheap algorithm. Similar nonlinear problems arise in a wide range of doped 2D heterostructures made of linear spectrum materials.

cond-mat.mes-hall↗

arXiv2023

Exchange interaction for Mn acceptor in GaAs: revealing its strong deformation dependence

In this paper we calculate exchange interaction constant between manganese ion inner electronic $d$-shell and GaAs valence band bounded hole using their microscopic multiparticle wave functions. We reveal its parametric dependence on crystal lattice deformations and find out that it could be about and even more than dozens percent when the strain tensor reaches values of $10^{-3} ÷10^{-2}$. This fact is in accordance with the previous hypothesis of deformation dependence of Mn acceptors in GaAs fine energy structure obtained from Raman spectroscopy, and we show that this dependence has the same magnitude. Also, we resolve here the problem of a substantial high temperature mismatch between well-developed theory and experimental data for the static magnetic susceptibility of Mn ions in GaAs. We show by numerical estimates and calculations that quite a strong parametric dependence of the exchange coupling value on GaAs lattice expansion determines the high temperature (above $50~$K) magnetic susceptibility reduction as well.

cond-mat.mtrl-sci↗

arXiv2022

Spin imaging of Poiseuille flow of viscous electronic fluid

Recent progress in fabricating high-quality conductors with small densities of defects has initiated the studies of the viscous electron fluid and has motivated the search for the evidences of the hydrodynamic regime of electron transport. In this work we come up with the spin imaging technique allowing us to attest to the emergence of electron hydrodynamic flows. Based on numerical calculations we demonstrate that the injected electron spin density is inhomogeneous across the channel when the viscous electron fluid forms the Poiseuille flow. We also argue that the Hanle curves at different positions across the channel acquire relative phase shifts resulting from the variation of the electron drift velocity in inhomogeneous hydrodynamic flows. The studied effects can be employed to evidence and study the viscous electron fluid non-invasively.

cond-mat.mes-hall↗

arXiv2021

Anisotropic magnetoresistance and memory effect in bulk systems with extended defects

Memory effects can have a profound impact on the resistivity of semiconductor systems, resulting in giant negative magnetoresistance and MIRO phenomena. This work opens the discussion of the memory effects in 3D conducting systems featured by the presence of the extended one-dimensional defects, such as screw dislocations or static charge stripes. We demonstrate that accounting for the memory effect, that is the capture of electrons on collisionless spiral trajectories winding around extended defects, leads to the strong negative magnetoresistance in case when the external magnetic field direction becomes parallel to the defects axis. This effect gives rise to a significant magnetoresistance anisotropy already for an isotropic Fermi surface and no spin-orbit effects. The proposed resistivity feature can be used to detect one-dimensional scattering defects in these systems.

cond-mat.mes-hall↗