Observation of hexatic vortex fluid in a thin superconducting film

When heated, a regular solid melts abruptly into liquid through a first order phase transition. In the case of a 2-dimensional crystalline solid, the, Berezinskii-Kosterlitz-Thouless (BKT) theory predicts that the solid could also melt via an intermediate state, called the hexatic fluid, which possesses the orientational order of a solid but the flow properties of a fluid.  Recently, we unraveled the hexatic vortex fluid in a thin film of the amorphous superconductor, MoGe. Using real space images acquired using a scanning tunneling microscope, I will describe the properties of this hexatic vortex fluid, and present results that point towards the possibility of this state being a quantum fluid. I will also contrast it with more regular melting observed in a bulk superconductor.

Reference:

Indranil Roy et al, arXiv:1805.05193 (to appear in Phys. Rev. Lett.)