AUTHOR=He Qinghua , Sun Jinhua , Deng Hai-Yao , Wakabayashi Katsunori , Liu Feng 

TITLE=Bound states at disclinations: an additive rule of real and reciprocal space topology

JOURNAL=Frontiers in Physics

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2023.1213158

DOI=10.3389/fphy.2023.1213158

ISSN=2296-424X

ABSTRACT=<p>Focusing on the two-dimensional (2D) Su-Schrieffer-Heeger (SSH) model, we propose an additive rule between the real-space topological invariant <bold>s</bold> of disclinations (related to the Burgers vector <bold>B</bold>) and the reciprocal-space topological invariant <bold>p</bold> of bulk wave functions (the vectored Zak phase). The disclination-induced bound states in the 2D SSH model appear only if (<bold>s</bold> + <bold>p</bold>/2<italic>π</italic>) is nonzero modulo the lattice constant. These disclination-bound states are robust against perturbations respecting <italic>C</italic><sub>4</sub> point group symmetry and other perturbations within an amplitude determined by <bold>p</bold>. Besides the disclination-bound states, the proposed additive rule also suggests that a half-bound state extends over only half of a sample and a hybrid-bound state, which always have a nonvanishing component of <bold>s</bold> + <bold>p</bold>/2<italic>π</italic>.</p>