Mechanisms for pi phase shifts in Little-Parks experiments on single crystals

by Dr Mark Fischer (Uni Zürich)

Tuesday 12 Mar 2024, 11:00 → 12:00 Europe/Zurich

WHGA/121

The Little-Parks effect, the periodic change in the critical temperature upon threading magnetic flux through a superconducting ring, exhibits a maximum or a minimum at zero flux in the presence of time-reversal symmetry. The latter situation, with the rings referred to as pi rings, is only expected for poly-crystalline rings of an unconventional superconductor. Interestingly, recent measurements of the Little-Parks effect in single-crystal rings of 4Hb-TaS2 show zero and pi rings and have been interpreted as evidence of exotic superconductivity. We discuss two scenarios for this unconventional behavior, namely a two-component order parameter and negative interlayer Josephson coupling in a s-wave superconductor, as well as both scenarios’ reliance on crystal defects.