Vortex creep at very low temperatures in single crystals of the extreme type-II superconductor Rh9In4S4

Abstract

We image vortex creep at very low temperatures using scanning tunneling microscopy in the superconductor Rh9In4S4 (Tc=2.25K). We measure the superconducting gap of Rh9In4S4, finding Δ≈0.33meV, and image a hexagonal vortex lattice up to close to Hc2, observing slow vortex creep at temperatures as low as 150 mK. We estimate thermal and quantum barriers for vortex motion and show that thermal fluctuations likely cause vortex creep, in spite of being at temperatures T/Tc<0.1. We study creeping vortex lattices by making images during long times and show that the vortex lattice remains hexagonal during creep with vortices moving along one of the high-symmetry axes of the vortex lattice. Furthermore, the creep velocity changes with the scanning window suggesting that creep depends on the local arrangements of pinning centers. Vortices fluctuate on small-scale erratic paths, indicating that the vortex lattice makes jumps trying different arrangements during its travel along the main direction for creep. The images provide a visual account of how vortex lattice motion maintains hexagonal order, while showing dynamic properties characteristic of a glass.

Source-reported materials — not catalogue approval

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