Hybrid higher-order skin-topological effect in hyperbolic lattices

We investigate the non-Hermitian Haldane model on hyperbolic {8, 3} and {12, 3} lattices and showcase its intriguing topological properties in the simultaneous presence of non-Hermitian effect and hyperbolic geometry. From bulk descriptions of the system, we calculate the real-space non-Hermitian Chern numbers by generalizing the method from its Hermitian counterpart and present a corresponding phase diagram of the model. For boundaries, we find that skin-topological modes appear in the range of the bulk energy gap under certain boundary conditions, which can be explained by an effective one-dimensional zigzag chain model mapped from a hyperbolic lattice boundary. Remarkably, these skin-topological modes are localized at specific corners of the boundary, constituting a hybrid higher-order skin-topological effect on hyperbolic lattices.