Seminar : Competing superconducting states in a Rashba superconductor

Topological superconductors are elusive superconductors that host Majorana fermions, current forerunning candidates for error-resistant qubits. Theoretically it has been predicted that materials which combine superconductivity and spin-orbit coupling should harbour topological superconductivity, although practically, it helps immensely if the material is semiconducting.
Consequently, despite there being several candidate topological superconductor materials, the clearest demonstrations of Majorana excitations to date have been in hybrid systems wherein spin-orbit coupled semiconductors are rendered superconducting via proximity effects.
In this talk Dr Narayan will discuss his recent results on the material GeTe which simultaneously shows all three ingredients: it is semiconducting in the normal state, it has a giant Rashba spin-orbit coupling, and it is inherently superconducting. In particular, he will show that GeTe displays a remarkable non-equilibrium magneto-response at low temperatures which reveals a transient superconducting state that is distinct from the equilibrium superconducting state. The non-equilibrium superconducting state is extremely long-lived, relaxing on the timescale of minutes, and has a higher critical temperature and field than the equilibrium state. He will discuss the origin of the non-equilibrium behaviour and show that the slow relaxation is a consequence of the Rashba dispersion, and provide experimental evidence of similar effects in other normal Rashba systems. Dr Narayan will conclude with some preliminary results towards investigating the precise nature of the superconducting phases.

[1] V. Narayan et al. https://onlinelibrary.wiley.com/doi/full/10.1002/pssr.201510430
[2] V. Narayan et al. https://arxiv.org/abs/1902.04675 (PRB, accepted)
[3] P. C. Verpoort and V. Narayan, https://arxiv.org/abs/1902.04678 (PRB, under review)