Making Topologically Trivial Non-Hermitian Systems Nontrivial via Gauge Fields

Abstract

<p>Non-Hermiticity significantly enriches the concepts of symmetry and topology in physics. Particularly,<br>non-Hermiticity gives rise to the ramified symmetries, where the non-Hermitian Hamiltonian H is<br>transformed to H†. For time-reversal (T) and sublattice symmetries, there are six ramified symmetry classes<br>leading to novel topological classifications with various non-Hermitian skin effects. As artificial crystals<br>are the main experimental platforms for non-Hermitian physics, there exists the symmetry barrier for<br>realizing topological physics in the six ramified symmetry classes: while artificial crystals are in spinless<br>classes with T2 ¼ 1, nontrivial classifications dominantly appear in spinful classes with T2 ¼ −1. Here, we<br>present a general mechanism to cross the symmetry barrier. With an internal parity symmetry P, the square<br>of the combination ˜T ¼ PT can be modified by appropriate gauge fluxes. Using the general mechanism,<br>we systematically construct spinless models for all non-Hermitian spinful topological phases in one and<br>two dimensions, which are experimentally realizable. Our Letter suggests that gauge structures may<br>significantly enrich non-Hermitian physics at the fundamental level.<br></p>