Topological Anderson insulator phases in one dimensional quasi-periodic mechanical SSH chains

TL;DR

This paper explores topological phase transitions in a quasi-periodic mechanical SSH model, identifying a topological Anderson insulator phase and analyzing localization, mobility edges, and phase boundaries analytically.

Contribution

It introduces an analytical approach to identify and characterize the topological Anderson insulator phase in a quasi-periodic mechanical SSH chain, including mobility edge computation.

Findings

Identification of a topological Anderson insulator phase within specific modulation ranges

Analytical calculation of phase transition boundaries and mobility edges

Demonstration of localization properties and stability of the TAI phase

Abstract

In this paper, we investigate the transition between topological phases in a Su-Schrieffer-Heeger (SSH) model composed of springs and masses in which the intracellular Aubry-Andr\'e disorder modulates the spring constants. We analytically compute the eigenvectors and eigenvalues of the dynamical matrix for both periodic and fixed boundary conditions, and compare them with the dispersion spectrum of the original tight-binding SSH model. We observe the presence of a topological Anderson insulating (TAI) phase within a specific range of quasi-periodic modulation strength and calculate the phase transition boundary analytically. We examine the localization properties of normal modes using their inverse participation ratio (IPR) of eigenstates of the dynamical matrix, and the corresponding fractal dimension associated with quasiperiodic modulation. We also examine the stability of the TAI phase across a range of modulation strengths and comments on the presence of mobility edge that separate localized modes from non-localized ones. We demonstrate the fact that special analytical techniques are needed to compute an exact expression for mobility edges in such scenarios.