Reference : Negative velocity fluctuations and non-equilibrium fluctuation relation for a driven ...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Physics
Negative velocity fluctuations and non-equilibrium fluctuation relation for a driven high critical current vortex state
Bag, Biplab [> >]
Shaw, Gorky mailto [Université de Liège > Département de physique > Physique expérimentale des matériaux nanostructurés >]
Banerjee, S. S. [> >]
Majumdar, Sayantan [> >]
Sood, A. K. [> >]
Grover, A. K. [> >]
Scientific Reports
Nature Publishing Group
Yes (verified by ORBi)
United Kingdom
[en] Under the influence of a constant drive the moving vortex state in 2H-NbS2 superconductor exhibits a negative differential resistance (NDR) transition from a steady flow to an immobile state. This state possesses a high depinning current threshold ( $$\boldsymbolI_\boldsymbolc^\boldsymbolh$$ I c h ) with unconventional depinning characteristics. At currents well above $$\boldsymbolI_\boldsymbolc^\boldsymbolh$$ I c h , the moving vortex state exhibits a multimodal velocity distribution which is characteristic of vortex flow instabilities in the NDR regime. However at lower currents which are just above $$\boldsymbolI_\boldsymbolc^\boldsymbolh$$ I c h , the velocity distribution is non-Gaussian with a tail extending to significant negative velocity values. These unusual negative velocity events correspond to vortices drifting opposite to the driving force direction. We show that this distribution obeys the Gallavotti-Cohen Non-Equilibrium Fluctuation Relation (GC-NEFR). Just above $$\boldsymbolI_\boldsymbolc^\boldsymbolh$$ I c h , we also find a high vortex density fluctuating driven state not obeying the conventional GC-NEFR. The GC-NEFR analysis provides a measure of an effective energy scale (E eff ) associated with the driven vortex state. The E eff corresponds to the average energy dissipated by the fluctuating vortex state above $$\boldsymbolI_\boldsymbolc^\boldsymbolh$$ I c h . We propose the high E eff value corresponds to the onset of high energy dynamic instabilities in this driven vortex state just above $$\boldsymbolI_\boldsymbolc^\boldsymbolh$$ I c h .

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