Vortex phase dynamics in yttrium superhydride YH$_6$ at megabar pressures

TL;DR

This paper investigates vortex phase behavior and dynamics in the high-temperature superconductor YH$_6$ under megabar pressures, revealing high flux barriers and a vortex phase diagram, advancing understanding of superhydride superconductors.

Contribution

It provides the first vortex phase diagram for YH$_6$, analyzes vortex dynamics under high pressure, and compares its properties to other high-temperature superconductors.

Findings

Vortex-glass to vortex-liquid transition observed.

High flux flow barriers U$_0$ estimated at 1.5-7*10$^4$ K.

Vortex phase diagram constructed for YH$_6$.

Abstract

A comprehensive study of the vortex phases and vortex dynamics is presented for a recently discovered high-temperature superconductor YH$_6$ with T$_C$ (onset) of 215 K under pressure of 200 GPa.Thermal activation energy (U$_0$) is derived in the framework of thermally activated flux flow (TAFF) theory. The activation energy yields a power law dependence U$_0$ $\propto$ H$^\alpha$ on magnetic field with a possible crossover at a field around 8-10 Tesla. Furthermore, we have depicted the vortex phase transition from vortex-glass to vortex-liquid state according to the vortex-glass theory. Finally, vortex phase diagram is constructed for the first time for superhydrides. Very high estimated values of flux flow barriers U$_0$(H) = 1.5-7*10$^4$ K together with high crossover fields makes YH$_6$ a rather outstanding superconductor as compared to most cuprates and iron-based systems. The Ginzburg number for YH$_6$ Gi = 3-7*10$^{-3}$ indicates that thermal fluctuations are not so strong and cannot broaden superconducting transitions in weak magnetic fields.