Description:

Abstract: Superconducting properties arise from the broken U(1) symmetry by the phase of the electron pair condensate. In the traditional superconducting ground state, the phase is spatially uniform and rigid. In this talk I will present how a periodic spatial pattern can spontaneously arise in the phase of the superconducting order parameter, lowering the energy and resulting in a more ordered non-uniform ground state. The new state has broken translation invariance, manifested through unusual superflow field and persistent circulating currents, which also break the time-reversal symmetry. The origin of the phase crystallization lies in non-local properties of the superfluid gradient energy, and we list general conditions needed for realization of phase crystals. In particular, I show how these conditions appear near a pairbreaking surface of a semi-infinite superconductor, and highlight the role of zero-energy surface quasiparticle states.

Speaker: Professor Anton Vorontsov, Montana State University 

Host: Prof. James Sauls