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Published on: February 1, 2017
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Negative velocity fluctuations and non-equilibrium fluctuation relation for a driven high critical current vortex
Biplab Bag1, Gorky Shaw1,2, S S Banerjee3
1Department of Physics, Indian Institute of Technology, Kanpur, 208016, India.
Scientific Reports
|July 19, 2017
Summary
In 2H-NbS2 superconductors, moving vortices show negative differential resistance and unusual flow dynamics. This study reveals non-Gaussian velocity distributions and Gallavotti-Cohen Non-Equilibrium Fluctuation Relation compliance in driven vortex states.
Area of Science:
- Condensed Matter Physics
- Superconductivity
- Materials Science
Background:
- The behavior of vortices in superconductors under applied currents is crucial for understanding their dynamic properties.
- Negative differential resistance (NDR) in driven vortex states suggests complex flow instabilities.
Purpose of the Study:
- To investigate the vortex flow dynamics in 2H-NbS2 superconductor exhibiting NDR.
- To analyze the velocity distributions and depinning characteristics of vortices.
- To explore the applicability of non-equilibrium fluctuation relations to driven vortex states.
Main Methods:
- Experimental observation of vortex flow in 2H-NbS2 under constant current drive.
- Analysis of vortex velocity distributions, including non-Gaussian and multimodal characteristics.
- Application of the Gallavotti-Cohen Non-Equilibrium Fluctuation Relation (GC-NEFR) to characterize the driven vortex state.
Main Results:
- A transition from steady vortex flow to an immobile state with a high depinning current threshold was observed.
- Vortices exhibited multimodal velocity distributions at high currents and non-Gaussian distributions with negative velocity events at lower currents.
- The driven vortex state was found to obey the GC-NEFR, providing an effective energy scale (E_eff) related to dissipated energy.
Conclusions:
- Unconventional depinning characteristics and vortex flow instabilities, including negative velocity events, are present in the NDR regime of 2H-NbS2.
- The GC-NEFR analysis offers insights into the energy dissipation and dynamic instabilities of driven vortex states.
- High E_eff values suggest the onset of significant dynamic instabilities in the superconductor's vortex state.
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