arXiv subjects

T. B. Charikova

Publications and source records attributed to T. B. Charikova.

16 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

Electrical properties of PbS films doped with iodine by chemical bath deposition

We present the results of measurements of bulk current-voltage (I-V) characteristics and local surface I-V characteristics by atomic force microscopy (AFM) of iodine-doped PbS films. It is established that bulk I-V curves of both undoped and iodine-doped PbS films demonstrate a linear (ohmic) U(I) dependence. The tipe of local surface I-V characteristics is ohmic at the concentration range of the dopant 0<[NH4I]<=0.10 M and becomes rectifying at [NH4I]>=0.15 M, which is determined by a decrease in the size and a change in the shape of the film grains, as well as a decrease in the surface roughness of the film. An increase in the iodine content in the PbS(I) films leads to nonlinear dependences of the microscopic characteristics and photoelectric parameters of the PbS(I) films. A sharp decrease in the diffusion coefficient, the beginning of an increase in the charge carrier lifetime, a maximum in voltage sensitivity and specific detectability are observed in the PbS(I) film chemically deposited from a reaction mixture containing [NH4I] = 0.15 M. This indicates that the optimalconcentration of iodine in the film is 2.7 at.%.

cond-mat.mtrl-sci↗

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↗

arXiv2024

Pairing type symmetry in cuprate superconductors

We report a brief overview ofa number of results on a type of pairing state symmetry in cuprates HTSC from a current literature. The results of recent high-precision measurements of near-nodal d-type gap functions by a modern laser-based ARPES method or by a c-axis twisted Josephson junction for hole-doped Bi-2212 system are presented. Recent experimental evidence in favor of d-type pairing symmetry, with a special nonmonotonic functional form, for electron-doped cuprate NdCeCuO is discussed. A new essential results on the identification of dx^2-y^2 symmetry of superconducting order parameter for parent high-Tc cuprate structure, electron-doped infinite layer SrLaCuO system, by the phase sensitive tests is described. A complex of the data presented indicates a vital role of d-wave pairing symmetry, in the special dx^2-y^2 form for high-temperature conductivity in cuprate systems.

cond-mat.supr-con↗

arXiv2021

Vortex motion in tilted magnetic fields in highly layered electron-doped superconductor Nd2-xCexCuO4

The carrier transport and the motion of a vortex system in a mixed state of an electron-doped high-temperature superconductors Nd2-xCexCuO4 were investigated. To study the anisotropy of galvanomagnetic effects of highly layered NdCeCuO system we have synthesized Nd2-xCexCuO4/SrTiO3 epitaxial films with non-standart orientations of the c-axis and conductive CuO2 layers relative to the substrate. The variation ofe the angle of inclination of the magnetic field B, relative to the current J, reveals that the behavior of both the in-plane r_xx(B) and the out-plane r_xy(B) resistivities in the mixed state is mainly determined by the perpendicular to J component of B, that indicates the crucial role of the Lorentz force F_L~[JxB] and defines the motion of Josephson vortices across the CuO2 layers.

cond-mat.supr-con↗

arXiv2020

Lateral vortex motion in highly layered electron-doped superconductor Nd2-xCexCuO4

The carrier transport and the motion of a vortex system in the electron-doped high-temperature superconductors Nd2-xCexCuO4 in underdoped and optimally doped (x = 0135, 0.145, 0.15) regions, in the area of the evolution from antiferromagnetic to superconducting order were investigated. To study the anisotropy of the transport properties of highly layered NdCeCuO system we have synthesized Nd2-xCexCuO4/SrTiO3 epitaxial films of three types with different orientations of the c-axis and conductive CuO2 layers relative to the substrate. Such a set of samples allowed us to study the processes of both standard (in the CuO2 layers) and lateral (across the CuO2 layers) carrier transfer in the normal and the mixed states of a superconductor. In a flux-flow regime, in magnetic field B, the dynamics of Abrikosov (B||c-axis) and Josephson (B||ab-plane) vortices are thoroughly investigated and analyzed which is perspective for scientific purposes and for practical applications in measurement technology.

cond-mat.supr-con↗

arXiv2016

The mixed-state Hall conductivity of single-crystal films $Nd_{2-x}Ce_xCuO_{4+δ}$ (x=0.14)

The magnetic-field dependencies of the longitudinal and Hall resistivity of the electron-doped compounds $Nd_{2-x}Ce_xCuO_{4+δ}$ in underdoped region (x=0.14) were investigated. It was established experimentally a strong magnetic field dependence of the Hall conductivity, $σ_{xy}(B)=C-b/B$, in the region of magnetic fields corresponding to a transition from superconducting to resistive state. The observed feature can be explained with the sum of contributions of the quasiparticles and moving Abrikosov vortices into Hall effect in a mixed state of type-II superconductor.

cond-mat.supr-con↗

arXiv2016

Resistivity tensor correlations in the mixed state of electron-doped superconductor Nd$_{2-x}$Ce$_x$CuO$_{4+δ}$

The magnetic-field dependencies of the longitudinal and Hall resistance of the electron-doped compounds Nd$_{2-x}$Ce$_x$CuO$_{4+δ}$ in underdoped region with $x$=0.14 and with varying degrees of disorder ($δ$) were investigated. It was established experimentally that the correlation between the longitudinal electrical resistivity and the Hall resistivity can be analyzed on the basis of scaling relationships: $ρ_{xy}$($B$)$\sim$ $ρ^β_{xx}$($B$). For the totality of the investigated single-crystal films of Nd$_{2-x}$Ce$_x$CuO$_{4+δ}$/SrTiO$_3$ the universal value $β$=1.5 $\pm$0.4 is found. The observed feature in the electron-doped two-dimensional systems can be associated both with a displaying of anisotropic $s$ - wave or $d$-wave pairing symmetry and with a rather strong pinning due to an essential degree of disorder in the samples under study.

cond-mat.supr-con↗

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

The estimation of coherence length for electron-doped superconductor Nd$_{2-x}$Ce$_x$CuO$_{4+δ}$

Results of low-temperature upper critical field measurements for Nd$_{2-x}$Ce$_x$CuO$_{4+δ}$ single crystals with various $x$ and nonstoichiometric disorder ($δ$) are presented. The coherence length of pair correlation $ξ$ and the product $k_F$$ξ$, where $k_F$ is the Fermi wave vector, are estimated. It is shown that for investigated single crystals parameter $k_F$$ξ$ $\cong$ 100 and thus phenomenologically NdCeCuO - system is in a range of Cooper-pair-based (BCS) superconductivity.

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↗

arXiv2002

The interplay of superconductivity and localization in Nd{2-x}Ce{x}CuO{4+δ} single crystal films

The influence of nonstoichiometric disorder on the in-plane resistivity and SC-transition has been investigated for Nd{2-x}Ce{x}CuO{4+δ} single crystal films (x=0.15 and 0.18). It is shown that with increasing of $δ$ the in-plane normal state resistivity increases (the mean free path diminishes) and SC-transition temperature decreases with essential broadening of the transition region. The observed evolution from homogeneous metallic (and superconducting) Nd{2-x}Ce{x}CuO{4+δ} system to inhomogeneous dielectric one is described as Anderson-type disorder-induced transition in a two-dimensional electron system.

cond-mat.supr-con↗