Orateur
Description
Inverse melting refers to a phenomenon where a liquid transforms into a solid with increase in temperature before melting again at a higher temperature. Predicted more than a century ago, inverse melting is rarely observed. In this talk, I will describe low temperature scanning tunneling spectroscopy experiments on a 20 nm thick amorphous Re6Zr (a-Re6Zr) thin films from which we observe direct signatures of inverse melting of the vortex lattice created under the application of a magnetic field[1]. By identifying distinct signatures of these transitions from magnetotransport and magnetic shielding measurements and integrating with scanning tunneling spectroscopy imaging, we construct a comprehensive vortex-state phase diagram in the magnetic field-temperature parameter space. Comparing these results with those on a 5 nm and 50 nm thick a-Re6Zr thin film [2,3] we demonstrate that inverse melting is thickness-dependent: a 5 nm film retains an inhomogeneous liquid state, while a 50 nm film maintains a crystalline solid structure except near the upper critical field. These results suggest that the re-entrant transformations of the vortex lattice are caused by a complex interplay of dimensionality and disorder.
[1] Rishabh Duhan, Subhamita Sengupta, John Jesudasan, Somak Basistha, Pratap Raychaudhur, Inverse melting and re-entrant transformations of the vortex lattice in amorphous Re6Zr thin film, Nature Communications 16, 2100 (2025).
[2] R. Duhan et al., Structure and dynamics of a pinned vortex liquid in superconducting a-Re{x}Zr (x ~ 6) thin film, Phys. Rev. B 108, L180503 (2023).
[3] [ArXiv: 2605.23567] P. Das et al., Phase diagram of the vortex state in an amorphous Re6Zr thin film exhibiting inverse melting