Force-free state in a superconducting single crystal and angle-dependent vortex helical instability

TL;DR

This study investigates vortex dynamics and dissipation mechanisms in a superconducting 2H-NbSe2 single crystal, revealing the role of vortex helical instability in the force-free state and its angular dependence.

Contribution

It demonstrates the applicability of the elliptic critical state model to vortex dissipation and shows the influence of vortex helical instability beyond the ideal force-free configuration.

Findings

Voltage dissipation follows an exponential dependence in the force-free state.

Vortex helical instability affects dissipation up to 40 degrees off the current direction.

The elliptic critical state model describes the vortex behavior in this regime.

Abstract

Superconducting 2H-NbSe2 single crystals show intrinsic low pinning values. Therefore, they are ideal materials with which to explore fundamental properties of vortices. (V, I) characteristics are the experimental data we have used to investigate the dissipation mechanisms in a rectangular shape 2H-NbSe2 single crystal. Particularly, we have studied dissipation behavior with magnetic fields applied in the plane of the crystal and parallel to the injected currents, i.e. in the force-free state where the vortex helical instability governs the vortex dynamics. In this regime, the data follow the elliptic critical state model and the voltage dissipation shows an exponential dependence.Moreover, this exponential dependence can be observed for in-plane applied magnetic fields up to 40 degrees off the current direction, which implies that the vortex helical instability plays a role in dissipation even out of the force-free configuration.