Ion-Gated 2D Crystalline Superconductors

Yu Saito
July 9th, 2019 YU SAITO California NanoSystems Institute
University of California

Recent advances have developed methods to produce ideal two-dimensional (2D) electron systems such as molecular-epitaxy-grown films, mechanically exfoliated flakes and gate-induced 2D gas/liquid, which are highly-crystalline 2D systems with minimal disorder. In particular, ionic-liquid gating, one of such techniques, which uses ionic liquid as a gate dielectric, is capable of realizing high density and relatively clean 2D systems on the surface of sigle crystals. In the talk, we introduce the recent developments of highly-crystalline 2D superconductors and a series of unprecedented physical properties discovered in gated-induced superconductivity. First of all, we highlight the quantum phases, i.e., quantum metallic state and the quantum Griffiths phase [3] in out-of-plane magnetic fields, both of which comes from the enhanced quantum fluctuation and random disorder. These quantum states are unique to highly crystalline and weak pinning systems. In addition, we focus on the nonreciprocal superconducting transport, which is later expected to be universal phenomena in noncentrosymmetric superconductors. This nonreciprocal transport can be regarded as the intrinsic Cooper pairs and/or vortex ratchet effect originating from crystal noncentrosymmetric structures, which has never observed in conventional amorphous thin films, and have a potential to become an ideal tool to probe the nonequilibrium vortex states. These series of unprecedented phenomena suggest that ion-gated highly-crystalline 2D superconductors evidently offer great opportunities to unveil the intrinsic and exotic nature of superconductors.

Seminar, July 9, 2019, 12:00. ICFO’s Blue Lecture Room

Hosted by Prof. Dmitri Efetov