Measuring topological invariants of even-dimensional line-gapped non-Hermitian systems through quench dynamics

TL;DR

This paper introduces a general quench-dynamics-based method to measure topological invariants in even-dimensional non-Hermitian systems with real line gaps, using auxiliary Hermitian matrices and band-inversion surfaces.

Contribution

It extends dynamical topological characterization to even-dimensional non-Hermitian systems by leveraging auxiliary Hermitian matrices and band-inversion surfaces, including higher-order BISs.

Findings

Successfully characterizes NH Chern insulators.

Extends framework to higher even dimensions.

Generalizes to imaginary line-gapped phases.

Abstract

The accurate determination of non-Hermitian (NH) topological invariants plays a central role in the study of NH topological phases. In this work, we propose a general framework for directly measuring NH topological invariants in even-dimensional systems with real line gaps through quench dynamics. Our approach hinges on constructing an auxiliary Hermitian matrix topologically equivalent to the original NH Hamiltonian, enabling topological characterization via reduced-dimensional momentum subspaces called band-inversion surfaces (BISs). A key insight lies in the emergence of chiral symmetry in the NH Hamiltonian specifically on BISs -- a critical property that allows extension of the dynamical characterization scheme previously developed for odd-dimensional NH systems with chiral or sublattice symmetry [Lin et al., Phys. Rev. Res. 7, L012060 (2025)]. We show that NH topological invariants can be extracted from the winding patterns of a dynamical field constructed from post-quench spin textures on BISs. We demonstrate our approach through a detailed analysis of NH Chern insulators and then extend the framework to higher even-dimensional systems by introducing second-order BISs for characterization. The framework is also generalized to imaginary line-gapped topological phases. This work establishes an experimentally accessible protocol for detecting NH topological invariants in quantum platforms.