Symmetry Protected Topological Corner Modes in a Periodically Driven Interacting Spin Lattice*

Periodic driving has a longstanding reputation for generating exotic phases of matter with no static counterparts. In this work we explore the interplay between periodic driving, interaction effects, and Z₂ symmetry that leads to the emergence of Floquet symmetry protected second-order topological phases in a simple but insightful two-dimensional spin-1/2 lattice. Through a combination of analytical and numerical treatments, we verify the formation of corner-localized 0 and π modes, i.e., Z₂ symmetry broken operators that respectively commute and anticommute with the one-period time evolution operator, as well as establish the topological nature of these modes by demonstrating their presence over a wide range of parameter values and explicitly deriving their associated topological invariants under special conditions. Finally, we also propose a means to detect the signature of these topological modes on superconducting circuit platforms and discuss the effect of imperfections such as perturbations and disorder.