Tuning three-dimensional higher-order topological insulators by surface state hybridization

Abstract

We analytically and numerically study hybridization in films of three-dimensional chiral second-order topological insulators. Reducing the film thickness increases the gaps of two gapped Chern-insulator surfaces, while hybridization of chiral edge states can gap the hinge states and destroy the second-order phase. Gapless surfaces also generally become gapped through surface-state hybridization in finite-sized systems.