Self-duality of One-dimensional Quasicrystals with Spin-Orbit Interaction

TL;DR

This paper investigates how spin-orbit coupling influences the metal-insulator transition and multifractal properties of eigenstates in one-dimensional quasicrystals modeled by the Aubry-André-Harper Hamiltonian.

Contribution

It extends the analysis of the AAH model by including Rashba spin-orbit coupling, revealing its effects on the self-dual point and phase diagram, with detailed multifractal and localization analysis.

Findings

Self-dual point is significantly affected by spin-orbit coupling.

Eigenstates at the critical point are multifractal and non-ergodic.

Phase diagram mapped in potential and spin-orbit coupling parameters.

Abstract

Non-interacting spinless electrons in one-dimensional quasicrystals, described by the Aubry-Andr\'{e}-Harper (AAH) Hamiltonian with nearest neighbour hopping, undergoes metal to insulator transition (MIT) at a critical strength of the quasi-periodic potential. This transition is related to the self-duality of the AAH Hamiltonian. Interestingly, at the critical point, which is also known as the self-dual point, all the single particle wave functions are multifractal or non-ergodic in nature, while they are ergodic and delocalized (localized) below (above) the critical point. In this work, we have studied the one dimensional quasi-periodic AAH Hamiltonian in the presence of spin-orbit (SO) coupling of Rashba type, which introduces an additional spin conserving complex hopping and a spin-flip hopping. We have found that, although the self-dual nature of AAH Hamiltonian remains unaltered, the self-dual point gets affected significantly. Moreover, the effect of the complex and spin-flip hoppings are identical in nature. We have extended the idea of Kohn's localization tensor calculations for quasi-particles and detected the critical point very accurately. These calculations are followed by detailed multifractal analysis along with the computation of inverse participation ratio and von Neumann entropy, which clearly demonstrate that the quasi-particle eigenstates are indeed multifractal and non-ergodic at the critical point. Finally, we mapped out the phase diagram in the parameter space of quasi-periodic potential and SO coupling strength.