arXiv subjects

V. N. Neverov

Publications and source records attributed to V. N. Neverov.

At least 19 recordsLinked to original sources

arXiv2026

Current - voltage characteristics in magnetic field for layered superconductor with intrinsic pinning of Josephson vortices

The results of measurements of the transverse voltage in the Hall configuration, Uy, under conditions of motion of the charge and vortex subsystems in orhtogonal magnetic and electric fields on epitaxial films of the layered high-temperature superconductor Nd2-xCexCuO4 are presented. the motion of Josephson vortices across CuO2 layers (along the c-axis) is analyzed considering the effects of intrinsic pinning. An exponential dependence of critical depinning current jc(B) for Josephson vortices is established in contrast to the power law dependences for Abrikosov vortices. With increasing external magnetic field after the depinning by a magnetic field at B=Bc, the onset of the vortex creep regime, which evolves into the flux-flow regime at crossover field B=Bf, is observed.

cond-mat.supr-con↗

arXiv2026

Self-resonance effects for intrinsic Josephson junctions in Nd(2-x)CexCuO4 films

To detect Josephson self-resonances, we used an original method, namely, studying the voltage Uy at the Hall contacts in the Nd2-xCexCuO4/SrTiO3 film, where the CuO2 planes are aligned along the longest side of the sample, perpendicular to the substrate. It is argued that the observed Uy(j) oscillations are a set of Fiske steps in a layered superconductor system, indicating the manifestation of the ac-Josephson effect in a multilayer superconductor Nd2-xCexCuO4 with a significant number of intrinsic Josephson junctions.

cond-mat.supr-con↗

arXiv2025

Josephson vortex system in a flux-flow regime in electron doped high-Tc superconductor Nd(2-x)CexCuO4

For an epitaxial film of an electron-doped superconductor Nd(2-x)CexCuO4 (x=0.145), in a mixed state, a well-defined step structure is observed on the dependence of the c-axis flux-flow resistance on the magnetic field parralel to CuO2 layers. It is shown that in the region of a free flow of Josephson vortices, the structure is periodic with a period of deltaB~Phi0/(lambdaablambdac). It is essential that the magnetic penetration depths in the ab-plane (lambdaab) and along the c-axis (lambdac) determine the sizes of the Josephson vortices in the Lawrence-Doniach model for an anisotropic layered superconductor.

cond-mat.supr-con↗

arXiv2024

Intrinsic Josephson junction characteristics of Nd2-xCexCuO4/SrTiO3 epitaxial films

The current-voltage (I-V) properties along the c axis on Nd2-xCexCuO4 /SrTiO3 epitaxial films with x = 0.145, 0.15 were investigated. For all the samples it has been established that the I-V characteristics exhibit several resistive branches, which correspond to the resistive states of individual Josephson junctions. The results confirm the idea of a tunneling mechanism between the CuO2 layers (superconductor - insulator - superconductor junction) for the investigated Nd2-xCexCuO4 compound. The I-V dependence of this compound with x = 0.15 points out on the nonmonotonic nature of the d-wave or anisotropic s-wave symmetry order parameter associated with the coexistence of superconductivity and antiferromagnetic fluctuations.

cond-mat.supr-con↗

arXiv2023

Magnetotransport in Weyl semimetal WTe2 single crystal

A WTe2 single crystal was grown by the chemical vapor transport method, and its electrical resistivity and galvanomagnetic properties were investigated. Single-band and two-band models were used to estimate the concentration and mobility of charge carriers in WTe2 at temperatures from 4.2 to 150 K.

cond-mat.mtrl-sci↗

arXiv2020

Determination of the magnetocaloric effect from thermophysical parameters and their relationships near magnetic phase transition in doped manganites

We present the results of a comparative analysis of the magnetocaloric effect (MCE) in Pr0.7Sr0.2Ca0.1MnO3, through direct and indirect measurements, using experimentally measured magnetization, specific heat, magnetostriction, resistivity, thermal diffusivity and thermal conductivity parameters. We have demonstrated that the change in each parameter in response to a magnetic field near the ferromagnetic-paramagnetic phase transition temperature of the material correlates with the change in magnetic entropy. These findings allow us to interrelate these parameters and provide an alternative, effective approach for accessing the usefulness of magnetocaloric materials.

cond-mat.mtrl-sci↗

arXiv2019

Nontrivial topology of bulk HgSe from the study of cyclotron effective mass, electron mobility and phase shift of Shubnikov-de Haas oscillations

In this paper, the authors report the results of an experimental study of effective mass, electron mobility and phase shift of Shubnikov de Haas oscillations of transverse magnetoresistance in an extended electron concentration region from 8.8*10^15 cm^-3 to 4.3*10^18 cm^-3 in single crystals of mercury selenide. The revealed features confirm the existence of a Weyl semimetal phase in HgSe at low electron density, which has been indicated by previous magnetotransport studies. However, the most significant result is the discovery of an abrupt change of Berry phase of Pi at electron concentration 2*10^18 cm^-3, which we explain in terms of a manifestation of topological Lifshitz transition in HgSe that occurs by tuning Fermi energy via doping.

cond-mat.mtrl-sci↗

arXiv2018

Unconventional Reentrant Quantum Hall Effect in a HgTe/CdHgTe Double Quantum Well

We report on observation of an unconventional structure of the quantum Hall effect (QHE) in a $ p$-type HgTe/Cd$_x$Hg$_{1-x}$Te double quantum well (DQW) consisting of two HgTe layers of critical width. The observed QHE is a reentrant function of magnetic field between two $i=2$ states (plateaus at $ρ_{xy}=h/ie^2$) separated by an intermediate $i=1$ state, which looks like some anomalous peak on the extra-long $i=2$ plateau when weakly expressed. The anomalous peak apparently separates two different regimes: a traditional QHE at relatively weak fields for a small density of mobile holes $p_s$ and a high-field QH structure with a $2-1$ plateau--plateau transition corresponding to much larger $p_s$. We show that only a part of holes, residing in an additional light hole subband in the DQW, participate in QHE at weak fields while the rest of holes is excluded into the reservoir formed in the lateral maximum of the valence subband. All the holes come into play at high fields due to a peculiar behavior of the zero-mode levels.

cond-mat.mes-hall↗

arXiv2018

Effect of exchange electron-electron interaction on conductivity of InGaAs single and double quantum wells in ballistic regime

We report an experimental study of quantum conductivity corrections for two-dimensional electron gas in a GaAs/InGaAs/GaAs single and double quantum wells in a wide temperature range (1.8-100) K. We perform a comparison of our experimental data for the longitudinal conductivity at zero magnetic field to the theory of interaction-induced corrections to th transport coefficients. In the temperature range from 10 K up to (45-60) K, wich covers the ballistic interaction regimes for our samples, a rather good agreement between the theory and our experimental results has been found.

cond-mat.mes-hall↗

arXiv2017

Large-scale impurity potential in the quantum Hall effect for the HgTe quantum well with inverted band structure

We report on the longitudinal and Hall resistivities of a HgTe quantum well with inverted energy spectrum (dQW = 20.3 nm) measured in the quantum Hall (QH) regime at magnetic fields up to 9 T and temperatures 2-50 K. The temperature dependence of the QH plateau-plateau transition (PPT) widths and of variable range hopping (VRH) conduction on the Hall plateaus are analyzed. The data are presented in a genuine scale form both for PPT regions and for VRH regime. Estimations for the degree of the carrier localization length divergence reveal a decisive role of the long-range random potential (the potential of remote ionized impurities) in the localization - delocalization processes in the QH regime for the system under study.

cond-mat.mes-hall↗

arXiv2017

Novel magnetoresistance features in HgSe single crystal with low electron concentration

For the first time, magnetoresistive properties of the single crystal of HgSe with a low electron concentration were studied in wide range of temperature and magnetic field. Some fundamental parameters of spectrum and scattering of electrons were experimentally determined. Two important features of magnetic transport were found - strong transverse magnetoresistance (MR) and negative longitudinal MR, which can indicate the existence of the topological phase of the Weyl semimetal (WSM) in HgSe. Taking this hypothesis into account we suggest a modified band diagram of the mercury selenide at low electron energies. The obtained results are essential for the deeper understanding of both physics of gapless semiconductors and WSMs - promising materials for various applications in electronics, spintronics, computer and laser technologies.

cond-mat.mtrl-sci↗

arXiv2014

Doping effect on the evolution of the pairing symmetry in n-type superconductor near antiferromagnetic phase boundary

We present the investigation results of the in-plane \{rho}(T) resistivity tensor at the temperature range 0.4-40 K in magnetic fields up to 90kOe (H||c, J||ab) for electron-doped Nd{2-x}Ce{x}CuO{4+δ} with different degree of disorder near antiferromagnetic - superconducting phase boundary. We have experimentally found that for optimally doped compound both the upper critical field slope and the critical temperature decrease with increasing of the disorder parameter (d-wave pairing) while in the case of the underdoped system the critical temperature remains constant and (dHc2/dT)|Tc increases with increasing of the disorder (s-wave pairing). These features suggest a possible implementation of the complex mixture state as the (s+id)-pairing.

cond-mat.supr-con↗

arXiv2012

Upper critical field in electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_{4+δ}$: two-gap model

We present resistivity measurements of the upper critical field (H$_{c2}$) phase diagram as a function of temperature (T) for Nd$_{1.85}$Ce$_{0.15}$CuO$_{4+δ}$/SrTiO$_3$ single crystal films with different degree of disorder ($δ$) in magnetic fields up to 90 kOe at temperatures down to 0.4 K. The data are well described by a two-band/two-gap model for a superconductor in the dirty limit.

cond-mat.supr-con↗

arXiv2011

Doping effect on the anomalous behavior of the Hall effect in electron-doped superconductor Nd$_{2-x}$Ce$_x$CuO$_{4+δ}$

Transport properties of Nd$_{2-x}$Ce$_x$CuO$_{4+δ}$ single crystal films are investigated in magnetic fields $B$ up to 9T at $T$=(0.4-4.2)K. An analysis of normal state (at $B>B_{c2}$) Hall coefficient $R_H$$^n$ dependence on Ce doping takes us to a conclusion about the existence both of electron-like and hole-like contributions to transport in nominally electron-doped system. In accordance with $R_H$$^n$(x) analysis an anomalous sign reversal of Hall effect in mixed state at $B<B_{c2}$ may be ascribed to a flux-flow regime for two types of carriers with opposite charges.

cond-mat.supr-con↗

arXiv2010

Anomalous behavior of the Hall effect in electron-doped superconductor $Nd_{2-x}$Ce_{x}Cu$O_{4+δ} with nonstoichiometric disorder

Magnetoresistivity and Hall effect measured in magnetic fields up to B=9T (B||c, J||ab) in electron-doped $Nd_{2-x}$Ce_{x}Cu$O_{4+δ} single crystal films with x = 0.14; 0.15; 0.18 and different oxygen content (δ) were studied in a temperature range of 0.4-4.2 K. The resistivity and Hall coefficient behaviors in the mixed state are discussed in the framework of flux-flow model with the inclusion of the back-flow of vortices owing to the pinning forces.

cond-mat.supr-con↗

arXiv2005

Transport properties of 2D-electron gas in a n-InGaAs/GaAs DQW in a vicinity of low magnetic-field-induced Hall insulator--quantum Hall liquid transition

The resistivity (R) of low mobility dilute 2D-electron gas in a n-InGaAs/GaAs double quantum well (DQW) exhibits the monotonic 'insulating-like' temperature dependence (dR/dT < 0) at T = 1.8 -- 70K in zero magnetic field. This temperature interval corresponds to a ballistic regime (kTtau/hbar > 0.1 -- 3.5) for our samples, and the electron density is on a 'insulating' side of the so-called B = 0 2D metal--insulator transition. We show that the observed localization and Landau quantization is due to the Sigma_xy(T)anomalous T-dependence.

cond-mat.mes-hall↗

arXiv2004

Effect of Zeeman splitting on magnetoresistivity of 2D hole gas in a Ge_{1-x}Si_x/Ge/Ge_{1-x}Si_x quantum well

For a two-dimensional (2D) hole system (confined within Ge layers of a multilayered p-Ge/Ge_{1-x}Si_x heterostructure) described by Luttinger Hamiltonian with the g-factor highly anisotropic for orientations of magnetic field perpendicular and parallel to the 2D plane (g_perp >> g_par), reported is an observation of low-temperature transition from metallic (dR/dT > 0) to insulator (dR/dT < 0) behavior of resistivity R(T) induced by a perpendicular magnetic field B. The revealed positive magnetoresistance scales as a function of B/T. We attribute this finding to a suppression of the triplet channel of electron-electron (hole-hole) interaction due to Zeeman splitting in the hole spectrum.

cond-mat.mes-hall↗

arXiv2003

Parallel magnetic field induced magnetoresistance peculiarities of the double quantum well filled with electrons or holes

In In_xGa_{1-x}As/n-GaAs double quantum wells (DQWs) containing an electron gas, the magnetoresistance (MR) peculiarities under parallel magnetic fields caused by the passing of the tunnel gap edges through the Fermi level are revealed. Peculiarities positioned in high fields (~30 T) can only be explained if the spin-splitting of the In_xGa_{1-x}As conduction band is considered, that was neglected in the GaAs/AlGaAs heterostructures, for which solely the effects of this nature have been observed so far. In Ge/p-Ge_{1-x}Si_x DQWs containing a hole gas, local MR peculiarities under parallel fields are discovered as well. But the tunnel gap in these DQWs is too narrow to be responsible for these observations. We suppose, they are due to a complicated shape of the hole confinement subbands.

cond-mat.mes-hall↗