Fractonic Higher-Order Topological Phases in Open Quantum Systems

In this work, we study the generalization of decohered average symmetry-protected topological (ASPT) phases to open quantum systems with a combination of subsystem symmetries and global symmetries. In particular, we provide examples of two types of intrinsic average higher-order topological phases with average subsystem symmetries. A classification scheme for these phases based on generalized anomaly cancellation criteria of average symmetry is also discussed.