1. flatbands as an arena for designing superconducting and topological systems

Hideo Aoki

University of Tokyo, Japan

12 October 2021 Tue 5 pm

                                      IBS Center for Theoretical Physics of Complex Systems (PCS), Administrative Office (B349), Theory Wing, 3rd floor

                                      Expo-ro 55, Yuseong-gu, Daejeon, South Korea, 34126 Tel: +82-42-878-8633                     

One novel arena for designing superconductors  and topological systems is the flat-band systems. A basic idea is that flat bands give unique opportunities for realising peculiar pairing on the one hand, and for realising topological states on the other. If we turn to non-equilibrium, we have even more versatile opportunities. This talk theoretically gives an overview of these, embracing superconductivity and topology in and out of equilibrium. I'll start with superconductivity, where I examine flat single- and multi-band models, where they are both shown to have unusual pairing properties, leading us beyond the conventional "nesting" physics[1]. A totally different way to make the system

topological is to illuminate the system with circularly-polarised light.  The resulting "Floquet topological insulator" is indeed a prototype of nonequilibrium-induced quantum states. This avenue is then extended to flat-band systems. I'll finally combine the above, which culminates to "Floquet topological superconductivity"[2]. 

[1] H. Aoki, J. Superconductivity and Novel Magnetism 33, 2341 (2020).