RAS Institute for Physics of Microstructures

Nizhni Novgorod, Russia

RAS Institute for Physics of Microstructures

Nizhni Novgorod, Russia

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Vodolazov D.Y.,RAS Institute for Physics of Microstructures
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

The structure and energy of saddle point (SP) states in a two-dimensional (2D) superconducting film of finite width w with transport current I are found in the framework of the Ginzburg-Landau model. We show that very near the depairing current I dep, a SP state with a vortex does not exist; it transforms to a 2D nucleus state, which is a finite region with partially suppressed order parameter. It is also shown that for slightly lower currents the contribution of the vortex core energy is important for a SP state with a vortex and it cannot be neglected for I 0.6I dep. It is demonstrated that in a film with local current concentration near a bend, the energy of the SP state may be much smaller than that in the straight film, and this favors the effect of fluctuations in such samples. © 2012 American Physical Society.


Vodolazov D.Yu.,RAS Institute for Physics of Microstructures
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We find the relation between the energy of the absorbed photon and the threshold current at which the resistive state appears in the current-carrying superconducting film with probability about unity. In our calculations we use the modified hot-spot model, which assumes a different strength of suppression of the superconducting order parameter in the finite area of the film around the place where the photon is absorbed. To find the threshold current we solve the Ginzburg-Landau equation for the superconducting order parameter, which automatically includes the current continuity equation and it allows us to consider the back effect of current redistribution near the hot spot on the stability of the superconducting state. We find quantitative agreement with recent experiments, where we use the single fitting parameter which describes what part of the energy of the photon goes for the local destruction of the superconductivity in the film. © 2014 American Physical Society.


Zotova A.N.,RAS Institute for Physics of Microstructures | Vodolazov D.Y.,RAS Institute for Physics of Microstructures
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We study the dynamics of the order parameter in a superconducting film with transport current after absorption of a single photon. The system from the time-dependent Ginszburg-Landau equation, Poisson's equation for an electrical potential, and the heat-diffusion equation were solved numerically. For each photon energy in the absence of fluctuations there exists a corresponding threshold current below which the superconducting state is stable and no voltage appears between the ends of the film. At larger currents, the superconducting state collapses starting from the appearance of a vortex-antivortex pair in the center of the region with suppressed superconducting order parameter, which has been created by the absorbed photon. Lorentz force causes motion of these vortices that heats the film locally and gives rise to a normal domain. When biased with the fixed current, the film latches in the normal state. In the regime when the current via superconductor may change, which is more relevant for experiments, the normal domain exists only for a short time, resulting in the voltage pulse with the duration controlled by the kinetic inductance of the superconducting film. © 2012 American Physical Society.


Vodolazov D.Y.,RAS Institute for Physics of Microstructures
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

In the framework of the Ginzburg-Landau model, it is shown that narrow superconducting films with width w3-8ξ(T) [ξ(T) is a temperature-dependent coherence length] exhibit unusual transport properties. In the absence of bulk pinning, its critical current Ic nonmonotonically depends on perpendicular magnetic field H and has one minima (dip) and one maxima (peak) at some magnetic fields. At currents IIc(H), the finite magnetoresistance R(H) of such a sample due to thermoactivated vortex hopping via edge barriers also shows both local maxima (peak) and minima (dip) nearly at the same magnetic fields. In narrower films, such an effect is absent due to absence of the vortices and in wider films the effect is weaker due to increased vortex-vortex interaction. The finite length of the film produces additional periodic variation in both Ic(H) and R(H) because of discrete changes in the number of the vortices, which is superimposed on the above-mentioned nonmonotonic dependence. The obtained results are directly related to many experiments on narrow superconducting films/bridges where such nonmonotonic dependencies Ic(H) and R(H) were observed. © 2013 American Physical Society.


Silaev M.A.,RAS Institute for Physics of Microstructures
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We show that a periodic lattice of Abrikosov vortices in the type-II superconductor can support fermionic states with zero energy. Zero modes appear at the intersection of electronic Bloch bands with the Fermi level. In a chiral px+ipy wave superconductor the spectrum contains Majorana states at the center of an effective Brillouin zone. The Bloch bands formed by the overlapping vortex core states can transmit energy flow across the lattice. The hallmark of zero modes in electronic heat conductivity is discussed. © 2013 American Physical Society.


Krishtopenko S.S.,RAS Institute for Physics of Microstructures
Journal of Physics Condensed Matter | Year: 2013

We report a theoretical study of the energies of cyclotron resonance (CR) and electron spin resonance (ESR) for fractional quantum Hall states (FQHS) in n-type narrow-gap quantum well (QW) heterostructures. Using the generalized single-mode approximation (GSMA) based on the 8-band k ṡp Hamiltonian, we calculate the many-body corrections to the CR and ESR energies for FQHS, providing theoretical evidence of the Kohn and Larmor theorem violation in narrow-gap QWs. We predict the correlation-induced reduction of CR energies and the correlation-induced enhancement of ESR energies as compared with the values obtained within the Hartree-Fock approximation. We demonstrate a nonlinear dependence of the CR and ESR energies on a Landau level filling factor. © 2013 IOP Publishing Ltd.


Silaev M.A.,RAS Institute for Physics of Microstructures
Physical Review Letters | Year: 2012

We show that the vortex dynamics in Fermi superfluids at ultralow temperatures is governed by the local heating of the vortex cores creating the heat flux carried by nonequilibrium quasiparticles emitted by moving vortices. This mechanism provides a universal zero temperature limit of dissipation in Fermi superfluids. For the typical experimental conditions realized by the turbulent motion of He3-B, the temperature of the vortex cores is estimated to be of the order 0.2T c. The dispersion of Kelvin waves is derived, and the heat flow generated by Kelvin cascade is shown to have a value close to that experimentally observed. © 2012 American Physical Society.


Dorofeyev I.A.,RAS Institute for Physics of Microstructures | Vinogradov E.A.,Russian Academy of Sciences
Physics Reports | Year: 2011

Various theoretical methods to calculate the spectral and correlation properties of fluctuating electromagnetic fields generated by solids are reviewed, all of which essentially reduce to solving the Maxwell equations for a specified geometry and boundary conditions and then using the fluctuation-dissipation theorem. The spectral and correlation properties of thermally stimulated fields of a system in equilibrium and out of equilibrium with surrounding bodies are described. A special attention is put to the difference between the spectral and correlation properties of the propagating and evanescent waves of the thermally stimulated fields of solids. The dispersion interaction between solid bodies in different thermodynamic states, the resonance dispersion interaction in a three-body system, the fluctuating fields as a means of body-to-body energy transfer, and the shift, broadening, and deexcitation of energy levels in a particle near a solid surface are discussed using the theory of thermally stimulated electromagnetic fields. Thermally stimulated emission of infrared radiation of semiconductor crystals and films (heated up to 150 °C) on metal substrates are measured in frequency range of vibrational polaritons both for propagating waves and for evanescent waves transformed into propagating waves due to ATR prism over the samples. The experimental results on thermally stimulated electromagnetic fields from solids are in qualitative and quantitative agreement with model calculations and theoretical expectations. © 2011 Elsevier B.V.


Silaev M.A.,RAS Institute for Physics of Microstructures
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

In the framework of London theory we study the unconventional magnetic state in two-component superconductors with a finite density of fractional flux vortices stabilized near the surface. We show that the process of vortex entry into the two-component superconductor consists of several steps, while the external magnetic field increases from zero. At the first stage only vortices in one of the order parameter components penetrate and sit at the equilibrium position near the surface. When the magnetic field is increased further, vortices in the second-order parameter component eventually enter the superconductor. Such a complex partial vortex penetration leads to the modification of a Bean-Livingston barrier and a magnetization curve as compared to conventional single-component superconductors. We discuss the possibility of experimental identification of protonic superconductivity in the projected superconducting state of liquid metallic hydrogen and hydrogen-rich alloys with the help of the partial vortex penetration effect. © 2011 American Physical Society.


Silaev M.A.,RAS Institute for Physics of Microstructures
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

The topological superfluid 3He-B supports massless Dirac spectrum of surface bound states which can be described in terms of the self-conjugated Majorana field operators. We discuss here the possible signature of surface bound states in nuclear magnetic resonance absorption spectrum in a 3He-B film. It is shown that transitions between different branches of the surface states spectrum lead to the nonzero absorption signal in longitudinal NMR scheme when the frequency is larger than the Larmour one. © 2011 American Physical Society.

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