Mixed-State Topology in One-Dimensional Open Floquet Systems
This work investigates topological properties of a periodically driven, dissipative Su-Schrieffer-Heeger chain in its steady state. By analyzing the Hermitian purity spectrum, researchers found that Floquet topology persists in this mixed state system. They established two invariants, $\phi_0$ EGP and $\Delta\phi_{\pi}$ EGP, which characterize a $Z \times Z$ topology, allowing for the detection of edge states in both the 0 and $\pi$ gaps.