Stimulation of superconductivity by microwave radiation in wide tin films (Review Article)

Abstract

The review is devoted to an experimental study of simulation of superconductivity by microwave radiation in superconducting films. An influence of the power, frequency of microwave radiation, as well as temperature and width of superconducting films on behavior of experimental dependencies of stimulated the critical current and the current at which a vortex structure of the resistive state vanishes and the phase-slip first line appears is analyzed. The experimental studies of films with different width reveal that the effect of superconductivity stimulation by microwave field is common and occurs in both the case of uniform (narrow films) and non-uniform (wide films) distribution of superconducting current over the film width. It is shown that stimulation of superconductivity in a wide film increases not only the critical current and the critical temperature, but also the maximum current at which there is a vortex state in the film. The effect of superconductivity stimulation by microwave radiation in wide films can be described by the Eliashberg theory, which was used to explain the same phenomenon in narrow channels. For the first time it was found experimentally that when the film width increases, the range of radiation power, at which the effect of superconductivity stimulation is observed, shrinks abruptly, and hence the probability of its detection decreases.

Moving flux quanta cool superconductors by a microwave breath

“…It is important to stress that the known effects of of superconductivity by a microwave stimulus in the absence of an external magnetic field include an enhancement of the Ginzburg-Landau depairing current (in narrow channels) implying a transition to a resistive state due to the formation of phase-slip centers [31] or the Aslamazov-Lempitskii maximum current (in wide films) at which the vortex structure induced by the self-field evolves into the first phase-slip line [70]. By contrast, in the presence of an external magnetic field when Abrikosov vortices move under the action of the transport current, there is an additional phenomenon leading to an abrupt quenching of the superconductor to the normally conducting state earlier than the Ginzburg-Landau or Aslamazov-Lempitskii critical current is reached.…”

“…This counterintuitive effect was explained as a consequence of an irradiation-induced redistribution of quasiparticles away from the superconducting gap edge * oleksandr.dobrovolskiy@univie.ac.at [26]. While microwave-stimulated superconductivity was since then observed in various systems [31][32][33], no theory of this effect in the presence of vortices is available so far. At the same time, investigations of stimulated superconductivity in the vortex state could have important implications both inside and outside the condensed matter physics community, as mapping solutions of astrophysics problems to scalar condensates allows for modeling the physics of black holes and gravity upon holographic superconductors [34].…”

Abrikosov fluxonics in washboard nanolandscapes

“…An interesting related phenomenon is the effect of microwave-stimulated superconductivity observed in both, flat [113] and nanopatterned [103] films. In addition, dynamic pinning landscapes, which can be provided by, e. g. a pulsed laser excitation of the superconductor surface, were predicted [114] to support synchronization effects but not experimentally realized so far.…”

Alternating current-driven microwave loss modulation in a fluxonic metamaterial

“…A further tendency in vortex matter research consists in a special interest to studying the vortex dynamics in the regime of GHz frequencies. Namely, from the viewpoint of basic research a few fundamental questions relate to the elucidation of the flux transport mechanisms at microwaves 3 and the phenomenon of microwave-stimulated superconductivity 5,21 . From the viewpoint of the development of applications, new functionalities have been reported due to vortex lattice matching effects 15,22 and the ability to reduce the depinning frequency [23][24][25][26] by a superimposed dc bias 15 .…”

“…Example of synthesizing (a) three different insertion loss levels by a serial connection of samples S and A for an ac current I = 50 mA and a frequency 3.02 GHz.In summary, we have introduced afluxonic metamaterial on the basis of superconducting Nb microstrips with symmetric and asymmetric nanogrooves and investigated the time dependences of the excess losses ∆S 21 (t) due to Abrikosov vortices in the presence of a quasistatic ac current for the fundamental geometrical matching of the vortex lattice with the periodic pinning nanolandscape (H = 7.2 mT). The ac-driven modulation of ∆S21 (t) accompanied by a sine-to-triangular and a sine-to-rectangular pulse shape conversion has been reported and the possibility of synthesizing pre-defined quantized loss levels for serial connection of samples S and A has been exemplified. These findings are relevant for the development of more sophisticated, multilevel excess-loss-based fluxonic devices.…”