Anomalous Floquet Chiral Topological Superconductivity in a Topological Insulator Sandwich Structure

Abstract

We show that Floquet chiral topological superconductivity arises naturally in Josephson junctions made of magnetic topological insulator-superconductor sandwich structures. The Josephson phase modulation associated with an applied bias voltage across the junction drives the system into the anomalous Floquet chiral topological superconductor hosting chiral Majorana edge modes in the quasienergy spectrum, with the bulk Floquet bands carrying zero Chern numbers. The bias voltage acts as a tuning parameter enabling novel dynamical topological quantum phase transitions driving the system into a myriad of exotic Majorana-carrying Floquet topological superconducting phases. Our theory establishes a new paradigm for realizing Floquet chiral topological superconductivity in solid-state systems, which should be experimentally directly accessible.

Dynamical symmetry indicators for Floquet crystals

“…As the symmetryrepresentation theories for static crystals inspired the proposal of fragile topology 23,24 , another interesting direction is to generalize the concept of fragile topology to Floquet crystals 107 . Besides, generalizing our theoret-ical frame work to Floquet crystals with time-reversal, particle-hole, or chiral symmetries is another interesting direction, since it would help identify exotic physical phenomena like anomalous boundary Majorana modes protected by particle-hole symmetries 47,[108][109][110][111] . As our framework focuses on operators, it is interesting to ask whether it is possible to formalize an equivalent statebased formalism 64 .…”

Dynamical fragile topology in Floquet crystals

“…We now discuss the physical implication of the defined dynamical fragile topology. One way [50,58,107,108] to generate a well-defined Floquet system is applying a temporal drive to certain modes in a static system, while leaving the other modes (effectively) static. For example, Ref.…”