arXiv subjects

E. V. Kirichenko

Publications and source records attributed to E. V. Kirichenko.

12 recordsLinked to original sources

arXiv2021

Carrier-induced ferromagnetism in 2D magnetically-doped semiconductor structures

We show theoretically that the magnetic ions, randomly distributed in a two-dimensional (2D) semiconductor system, can generate a ferromagnetic long-range order via the RKKY interaction. The main physical reason is the discrete (rather than continuous) symmetry of the 2D Ising model of the spin-spin interaction mediated by the spin-orbit coupling of 2D free carriers, which precludes the validity of the Mermin-Wagner theorem. Further, the analysis clearly illustrates the crucial role of the molecular field fluctuations as opposed to the mean field. The developed theoretical model describes the desired magnetization and phase-transition temperature $T_c$ in terms of a single parameter; namely, the chemical potential $μ$. Our results highlight a path way to reach the highest possible $T_c$ in a given material as well as an opportunity to control the magnetic properties externally (e.g., via a gate bias). Numerical estimations show that magnetic impurities such as Mn$^{2+}$ with spins $S=5/2$ can realize ferromagnetism with $T_c$ close to room temperature.

cond-mat.mtrl-sci↗

arXiv2020

Chaotic cyclotron and Hall trajectories due to spin-orbit coupling

We demonstrate that the synergistic effect of a gauge field, Rashba spin-orbit coupling (SOC), and Zeeman splitting can generate chaotic cyclotron and Hall trajectories of particles. The physical origin of the chaotic behavior is that the SOC produces a spin-dependent (so-called anomalous) contribution to the particle velocity and the presence of Zeeman field reduces the number of integrals of motion. By using analytical and numerical arguments, we study the conditions of chaos emergence and report the dynamics both in the regular and chaotic regimes. {We observe the critical dependence of the dynamic patterns (such as the chaotic regime onset) on small variations in the initial conditions and problem parameters, that is the SOC and/or Zeeman constants. The transition to chaotic regime is further verified by the analysis of phase portraits as well as Lyapunov exponents spectrum.} The considered chaotic behavior can occur in solid state systems, weakly-relativistic plasmas, and cold atomic gases with synthetic gauge fields and spin-related couplings.

nlin.CD↗

arXiv2018

Lévy flights confinement in a parabolic potential and fractional quantum oscillator

We study Lévy flights confined in a parabolic potential. This has to do with a fractional generalization of ordinary quantum-mechanical oscillator problem. To solve the spectral problem for the fractional quantum oscillator, we pass to the momentum space, where we apply the variational method. This permits to obtain approximate analytical expressions for eigenvalues and eigenfunctions with very good accuracy. Latter fact has been checked by numerical solution of the problem. We point to the realistic physical systems ranging from multiferroics and oxide heterostructures to quantum chaotic excitons, where obtained results can be used.

cond-mat.dis-nn↗

arXiv2018

Revealing quantum spin liquid in the herbertsmithite $\rm ZnCu_{3}(OH)_6Cl_{2}$

Based on experimental data and our theoretical analysis, we provide a strategy for unambiguous establishing of gapless quantum spin liquid state (QSL) in herbertsmithite and other materials. To clarify the nature of QSL, we recommend measurements of heat transport, low-energy inelastic neutron scattering and optical conductivity under the application of external magnetic field at low temperatures. We also suggest that artificially introduced inhomogeneity into $\rm ZnCu_{3}(OH)_6Cl_2$ can stabilize QSL, and serves as a test elucidating the contribution coming from impurities. We predict the results of these measurements in the case of gapless QSL.

cond-mat.str-el↗

arXiv2018

New state of matter: heavy-fermion systems, quantum spin liquids, quasicrystals, cold gases, and high temperature superconductors

We report on a new state of matter manifested by strongly correlated Fermi systems including various heavy-fermion (HF) metals, two-dimensional quantum liquids such as $\rm ^3He$ films, certain quasicrystals, and systems behaving as quantum spin liquids. Generically, these systems can be viewed as HF systems or HF compounds, in that they exhibit typical behavior of HF metals. At zero temperature, such systems can experience a so-called fermion-condensation quantum phase transition (FCQPT). Combining analytical considerations with arguments based entirely on experimental grounds we argue and demonstrate that the class of HF systems is characterized by universal scaling behavior of their thermodynamic, transport, and relaxation properties. That is, the quantum physics of different HF compounds is found to be universal, emerging irrespective of the individual details of their symmetries, interactions, and microscopic structure. This observed universal behavior reveals the existence of a new state of matter manifest in HF compounds. We propose a simple, realistic model to study the appearance of flat bands in two-dimensional ensembles of ultracold fermionic atoms, interacting with coherent resonant light. It is shown that signatures of these flat bands may be found in peculiarities in their thermodynamic and spectroscopic properties. We also show that the FCQPT, in generating flat bands and altering Fermi surface topology, is an essential progenitor of the exotic behavior of the overdoped high-temperature superconductors represented by $\rm La_{2-x}Sr_xCuO_4$, whose superconductivity differs from that predicted by the classical Bardeen-Cooper-Schrieffer theory. The theoretical results presented are in good agreement with recent experimental observations, closing the colossal gap between these empirical findings and Bardeen-Cooper-Schrieffer-like theories.

cond-mat.str-el↗

arXiv2018

Flat bands and the physics of strongly correlated Fermi systems

Some materials can have the dispersionless parts in their electronic spectra. These parts are usually called flat bands and generate the corps of unusual physical properties of such materials. These flat bands are induced by the condensation of fermionic quasiparticles, being very similar to the Bose condensation. The difference is that fermions to condense, the Fermi surface should change its topology, leading to violation of time-reversal (T) and particle-hole (C) symmetries. Thus, the famous Landau theory of Fermi liquids does not work for the systems with fermion condensate (FC) so that several experimentally observable anomalies have not been explained so far. Here we use FC approach to explain recent observations of the asymmetric tunneling conductivity in heavy-fermion compounds and graphene and its restoration in magnetic fields, as well as the violation of Leggett theorem, recently observed experimentally in overdoped cuprates, and recent observation of the challenging universal scaling connecting linear-$T$-dependent resistivity to the superconducting superfluid density.

cond-mat.str-el↗

arXiv2016

Quasi-one-dimensional quantum spin liquid in the $\rm {Cu(C_4H_4N_2)(NO_3)_2}$ insulator

We analyze measurements of the magnetization, differential susceptibility and specific heat of quasi-one dimensional insulator Cu(C$_4$H$_4$N$_2$)(NO$_3$)$_2$ (CuPzN) subjected to magnetic fields. We show that the thermodynamic properties are defined by quantum spin liquid formed with spinons, with the magnetic field tuning the insulator CuPzN towards quantum critical point related to fermion condensation quantum phase transition (FCQPT) at which the spinon effective mass diverges kinematically. We show that the FCQPT concept permits to reveal and explain the scaling behavior of thermodynamic characteristics. For the first time, we construct the schematic $T-H$ (temperature---magnetic field) phase diagram of CuPzN, that contains Landau-Fermi-liquid, crossover and non-Fermi liquid parts, thus resembling that of heavy-fermion compounds.

cond-mat.str-el↗

arXiv2011

High magnetic fields thermodynamics of heavy fermion metal YbRh2Si2

We perform comprehensive theoretical analysis of high magnetic field behavior of the heavy-fermion (HF) compound YbRh2Si2. At low magnetic fields B, YbRh2Si2 has a quantum critical point related to the suppression of antiferromagnetic ordering at a critical magnetic field. Our calculations of the thermodynamic properties of YbRh2Si2 in wide magnetic field range allow us to straddle a possible metamagnetic transition region and probe the properties of both low-field HF liquid and high-field fully polarized one. Namely, high magnetic fields B\sim B^*\sim 10 T fully polarize corresponding quasiparticle band generating Landau Fermi liquid (LFL) state and suppressing HF (actually NFL) one, while at elevating temperatures both HF state and corresponding NFL properties are restored. Our calculations are in good agreement with experimental facts and show that the fermion condensation quantum phase transition is indeed responsible for the observed NFL behavior and quasiparticles survive both high temperatures and high magnetic fields.

cond-mat.str-el↗

arXiv2010

On the theory of domain switching kinetics in ferroelectric thin films

We investigate theoretically the polarization switching kinetics in ferroelectric thin films. In such substances, the domain walls are pinned by (usually dipole) defects, which are present also in ordered samples as technologically unavoidable impurities. This random interaction with dipole pinning centers results, in particular, in exponentially broad distribution of switching times. Under supposition of low pinning centers concentration, we derive the distribution function of switching times showing that it is not simply Lorentzian (as it was first suggested by Tagantsev et al [\prb, {\bf 66}, 214109 (2002)] ), but is a "square of Lorentzian", which is due to the vector nature of electric field. This improved formalism delivers a better description of available experimental data and elucidates the physical mechanism of domain switching times distribution.

cond-mat.mtrl-sci↗

arXiv2009

Stable topological textures in a classical 2D Heisenberg model

We show that stable localized topological soliton textures (skyrmions) with $π_2$ topological charge $ν\geq 1$ exist in a classical 2D Heisenberg model of a ferromagnet with uniaxial anisotropy. For this model the soliton exist only if the number of bound magnons exceeds some threshold value $N_{\rm cr}$ depending on $ν$ and the effective anisotropy constant $K_{\rm eff}$. We define soliton phase diagram as the dependence of threshold energies and bound magnons number on anisotropy constant. The phase boundary lines are monotonous for both $ν=1$ and $ν>2$, while the solitons with $ν=2$ reveal peculiar nonmonotonous behavior, determining the transition regime from low to high topological charges. In particular, the soliton energy per topological charge (topological energy density) achieves a minimum neither for $ν=1$ nor high charges, but rather for intermediate values $ν=2$ or $ν=3$.

cond-mat.stat-mech↗

arXiv2006

Quasiparticles and quantum phase transition in universal low-temperature properties of heavy-fermion metals

We demonstrate, that the main universal features of the low temperature experimental $H-T$ phase diagram of CeCoIn5 and other heavy-fermion metals can be well explained using Landau paradigm of quasiparticles. The main point of our theory is that above quasiparticles form so-called fermion-condensate state, achieved by a fermion condensation quantum phase transition (FCQPT). When a heavy fermion liquid undergoes FCQPT, the fluctuations accompanying above quantum critical point are strongly suppressed and cannot destroy the quasiparticles. The comparison of our theoretical results with experimental data on CeCoIn5 have shown that the electronic system of above substance provides a unique opportunity to study the relationship between quasiparticles properties and non-Fermi liquid behavior.

cond-mat.str-el↗

arXiv2006

Phase Diagram of Heavy Fermion Metal CeCoIn5

We present a comprehensive analysis of the low temperature experimental H-T phase diagram of CeCoIn5. The main universal features of the diagram can be explained within the Fermi-liquid theory provided that quasiparticles form so called fermion-condensate state. We show that in this case the fluctuations accompanying an ordinary quantum critical point are strongly suppressed and cannot destroy the quasiparticles. Analyzing the phase diagram and giving predictions, we demonstrate that the electronic system of CeCoIn5 provides a unique opportunity to study the relationship between quasiparticles properties and non-Fermi liquid behavior.

cond-mat.str-el↗