Papers by Valerii Vinokour
NATO Science Series
Summary. We study how the single-electron transport in clean Andreev wires is affected by a weak ... more Summary. We study how the single-electron transport in clean Andreev wires is affected by a weak disorder introduced by impurity scattering. The transport has two contributions, one is the Andreev diffusion inversely proportional to the mean �
AIP Conference Proceedings
The experimental and theoretical study of electrostatically driven granular material are reported... more The experimental and theoretical study of electrostatically driven granular material are reported. It is shown that the charged granular medium undergoes a hysteretic first order phase transition from the immobile condensed state (granular solid) to a fluidized dilated state (granular gas) with a changing applied electric field. In addition a spontaneous precipitation of dense clusters from the gas phase and subsequent coarsening-coagulation of these clusters is observed. Molecular dynamics simulations shows qualitative agreement with experimental results.
Journal of Physics C: Solid State Physics
The authors present numerical results on the conductivity and participation ratio in a three-dime... more The authors present numerical results on the conductivity and participation ratio in a three-dimensional system with off-diagonal disorder. They show that near the transition point the distribution of these quantities expands, i.e. their critical behaviour cannot be described by a single exponent.
Scientific reports, Jan 16, 2017
We study numerically the voltage-induced breakdown of a Mott insulating phase in a system of char... more We study numerically the voltage-induced breakdown of a Mott insulating phase in a system of charged classical particles with long-range interactions. At half-filling on a square lattice this system exhibits Mott localization in the form of a checkerboard pattern. We find universal scaling behavior of the current at the dynamic Mott insulator-metal transition and calculate scaling exponents corresponding to the transition. Our results are in agreement, up to a difference in universality class, with recent experimental evidence of a dynamic Mott transition in a system of interacting superconducting vortices.
Aps March Meeting Abstracts, Mar 1, 1996
We investigate by the numerical solution of TDGL, the vortex dynamics through the systems of para... more We investigate by the numerical solution of TDGL, the vortex dynamics through the systems of parallel and splayed columnar defects. We study the equilibrium configurations of the resulting glassy states. We compare the motion along- and across the direction of splay with the motion through the system of parallel columnar defects and find the corresponding I-V characteristics.
Aps Meeting Abstracts, 2004
Modern Problems in Condensed Matter Sciences, Dec 31, 1989
We investigate theoretically transport properties of one-and two-dimensional regular Josephson ju... more We investigate theoretically transport properties of one-and two-dimensional regular Josephson junction arrays (JJAs) in an insulating state. We derive the low-temperature current-voltage characteristics (the I-V dependencies) for the current mediated by the Cooper pair transfer across the system. In the case where the screening length λc associated with the capacitance of the islands to the ground is much larger than the island's size d, we find that transport is governed by the macroscopic Coulomb blockade effect with the gap ∆c well exceeding a single island charging energy Ec. In the limit of λc ≫ L, where L is the linear size of the array, the gap establishes the dependence on the array size, namely, ∆c ≃ Ec(L/d) in 1D and ∆c ≃ Ec ln(L/d) in 2D arrays. We find two transport regimes: at moderate temperatures, Ec < kBT < ∆c, the low bias transport is thermally activated with the resistance R ∝ exp(T0/T) where the activation energy kBT0 = ∆c. At ultra-low temperatures, kBT < Ec, a JJA falls into a superinsulating state with R ∝ exp[(∆c/Ec) exp(Ec/T)].
Aps Meeting Abstracts, Mar 1, 2001
Local magnetic relaxation measurements in YBa2Cu3O72x crystals show evidence for plastic vortex c... more Local magnetic relaxation measurements in YBa2Cu3O72x crystals show evidence for plastic vortex creep associated with the motion of dislocations in the vortex lattice. This creep mechanism governs the vortex dynamics in a wide range of temperatures and fields below the melting line and above the field corresponding to the peak in the "fishtail" magnetization. In this range the activation energy
Journal de Physique, 1987
Scientific reports, Jan 14, 2015
We report first principle numerical study of domain wall (DW) depinning in two-dimensional magnet... more We report first principle numerical study of domain wall (DW) depinning in two-dimensional magnetic film, which is modeled by 2D random-field Ising system with the dipole-dipole interaction. We observe nonconventional activation-type motion of DW and reveal the fractal structure of DW near the depinning transition. We determine scaling functions describing critical dynamics near the transition and obtain universal exponents establishing connection between thermal softening of pinning potential and critical dynamics. We observe that tuning the strength of the dipole-dipole interaction switches DW dynamics between two different universality classes, corresponding to two distinct dynamic regimes characterized by non-Arrhenius and conventional Arrhenius-type DW motions.
Physical Review B, 2000
We develop a theory for dislocation-mediated structural transitions in the vortex lattice which a... more We develop a theory for dislocation-mediated structural transitions in the vortex lattice which allows for a unified description of phase transitions between the three phases, the elastic vortex glass, the amorphous vortex glass, and the vortex liquid, in terms of a free energy functional for the dislocation density. The origin of a critical endpoint of the melting line at high magnetic fields, which has been recently observed experimentally, is explained.
Physical Review B, 2001
We investigate the influence of columnar defects in layered superconductors on the thermally acti... more We investigate the influence of columnar defects in layered superconductors on the thermally activated penetration of pancake vortices through the surface barrier. Columnar defects, located near the surface, facilitate penetration of vortices through the surface barrier, by creating "weak spots", through which pancakes can penetrate into the superconductor. Penetration of a pancake mediated by an isolated column, located near the surface, is a two-stage process involving hopping from the surface to the column and the detachment from the column into the bulk; each stage is controlled by its own activation barrier. The resulting effective energy is equal to the maximum of those two barriers. For a given external field there exists an optimum location of the column for which the barriers for the both processes are equal and the reduction of the effective penetration barrier is maximal. At high fields the effective penetration field is approximately two times smaller than in unirradiated samples. We also estimate the suppression of the effective penetration field by column clusters. This mechanism provides further reduction of the penetration field at low temperatures.
Measurements of the current-voltage (I-V) characteristics of TiN thin superconducting films revea... more Measurements of the current-voltage (I-V) characteristics of TiN thin superconducting films reveal strongly nonlinear switching behavior in both parallel and perpendicular magnetic fields near the superconductor-insulator transition. At moderate temperatures, T > 60 mK in perpendicular fields and over the whole temperature range in parallel field, the I-V curves are well described by a simple overheating instability model. At low temperatures in perpendicular magnetic fields we observe pre-switching I \propto V^(alpha) dependences with an exponent alpha rapidly growing with decreasing temperature, which constitutes evidence for the charge-Berezinskii-Kosterlitz-Thouless (BKT) mechanism of the insulator-superinsulator transition. Comment: 4 pages, 4 figures
Recent cantilever magnetometry measurements of annular micron-size samples of Sr2RuO4 [1] have re... more Recent cantilever magnetometry measurements of annular micron-size samples of Sr2RuO4 [1] have revealed evidence for the existence of half-quantum vortices (HQVs) in this material. Here we suggest to look for HQVs at temperatures close to Tc in magnetoresistance of "punctured" (perforated) Sr2RuO4 samples which consist of an array of regularly spaced micron-size holes in an otherwise uniform superconducting matrix. Due to the dissipative nature of resistive measurements signatures of HQVs might be seen even if their thermodynamic stability is not expected. We analyze the dependence of magnetoresistance on the thermodynamic stability of HQVs and point out features which may help to identify them. [4pt] [1] J. Jang, D.G. Ferguson, V. Vakaryuk, R. Budakian, S.B. Chung, P.M. Goldbart, Y. Maeno (2010).
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Papers by Valerii Vinokour