Regensburg 2025 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 53: Topology: Other Topics
TT 53.12: Talk
Friday, March 21, 2025, 12:30–12:45, H32
Network Model for Magnetic Higher-Order Topological Phases — Hui Liu1,2, Ali G. Moghaddam3,4,5, •Daniel Varjas1,2,6,7, and Ion Cosma Fulga1 — 1IFW Dresden, Dresden, Germany — 2Stockholm University, Stockholm, Sweden — 3Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran — 4Research Center for Basic Sciences and Modern Technologies (RBST), Zanjan, Iran — 5Tampere University, Tampere, Finland — 6Max Planck Institute for the Physics of Complex Systems, Dresden, Germany — 7Budapest University of Technology and Economics, Budapest, Hungary
We propose a network-model realization of magnetic higher-order topological phases (HOTPs) in the presence of the combined space-time symmetry C4T – the product of a fourfold rotation and time-reversal symmetry. We show that the system possesses two types of HOTPs. The first type, analogous to Floquet topology, generates a total of 8 corner modes at 0 or π eigenphase, while the second type, hidden behind a weak topological phase, yields a unique phase with 8 corner modes at ±π/2 eigenphase (after gapping out the counterpropagating edge states), arising from the product of particle-hole and phase-rotation symmetry. By using a bulk Z4 topological index (Q), we found both HOTPs have Q=2, whereas Q=0 for the trivial and the conventional weak topological phase. Together with a Z2 topological index associated with the reflection matrix, we are able to fully distinguish all phases. Our work suggests that such phases may find their experimental realization in coupled-ring-resonator networks.
Keywords: Topology; Floquet; Transport; Magnetic symmetry; d.varjas@ifw-dresden.de