Real-Space Vortex Glass Imaging and the Vortex Phase Diagram of SnMo6S8

Abstract

Using scanning tunneling microscopy at 400 mK, we have obtained maps of around 100 vortices in SnMo6S8 from 2–9 T. The orientational and positional disorder at 5 and 9 T show that these are the first large-scale images of a vortex glass. At higher temperature a magnetization peak effect is observed, whose upper boundary coincides with a lambda anomaly in the specific heat. Our data favor a kinetic glass description of the vortex melting transition, indicating that vortex topological disorder persists at fields and temperatures far below the peak effect in low-Tc superconductors.