Ata Yamaguchi | Searcharxiv

arXiv2024

Topological phase transition in nonchiral Rice-Mele model with bond disorder

The Rice-Mele model consists of a one-dimensional lattice with two sublattice sites in each unit cell subjected to a staggered sublattice potential. The onsite potential constitutes a mass term that breaks chiral symmetry. In this paper, we show that a topological phase transition is induced in this model by disordering intracell and intercell hopping energies unequally, by means of a symmetry-independent global invariant. For small enough mass, the phase transition is accompanied by anomalous localization, which is accounted for in terms of geometric means of random variables. The specific disorder strength at which anomalous localization occurs is independent of mass. In contrast, the critical disorder strength at which the phase transition takes place decreases as mass increases, and eventually becomes invariable for large enough mass. For large enough mass, we show that the phase transition is characterized by arithmetic means instead of geometric means.

cond-mat.mes-hall↗

arXiv2023

Real-space formulation of topology for disordered Rice-Mele chains without chiral symmetry

In this paper, we derive a real-space topological invariant that involves all energy states in the system. This global invariant, denoted by $Q$, is always quantized to be 0 or 1, independent of symmetries. In terms of $Q$, we numerically investigate topological properties of the nonchiral Rice-Mele model including random onsite potentials to show that nontrivial bulk topology is sustained for weak enough disorder. In this regime, a finite spectral gap persists, and then $Q$ is definitely identified. We also consider sublattice polarization of disorder potentials. In this case, the energy spectrum retains a gap regardless of disorder strength so that $Q$ is unaffected by disorder. This implies that bulk topology remains intact as long as the spectral gap opens.

cond-mat.mes-hall↗