Mobility edge and intermediate phase in one-dimensional incommensurate lattice potentials

TL;DR

This paper investigates localization and intermediate phases in two one-dimensional quasiperiodic models with single-particle mobility edges, revealing a wide regime where localized and extended states coexist, with implications for experimental studies of localization phenomena.

Contribution

It demonstrates the existence of a broad intermediate phase in two distinct 1D quasiperiodic models with mobility edges, highlighting the nonuniversality of localization exponents.

Findings

Both models exhibit a wide single-particle intermediate phase.

Localized and extended states coexist in the spectrum within this phase.

Localization exponents are nonuniversal and model-dependent.

Abstract

We study theoretically the localization properties of two distinct one-dimensional quasiperiodic lattice models with a single-particle mobility edge (SPME) separating extended and localized states in the energy spectrum. The first one is the familiar Soukoulis-Economou trichromatic potential model with two incommensurate potentials, and the second is a system consisting of two coupled 1D Aubry-Andre chains each containing one incommensurate potential. We show that as a function of the Hamiltonian model parameters, both models have a wide single-particle intermediate phase (SPIP), defined as the regime where localized and extended single-particle states coexist in the spectrum, leading to a behavior intermediate between purely extended or purely localized when the system is dynamically quenched from a generic initial state. Our results thus suggest that both systems could serve as interesting experimental platforms for studying the interplay between localized and extended states, and may provide insight into the role of the coupling of small baths to localized systems. We also calculate the Lyapunov (or localization) exponent for several incommensurate 1D models exhibiting SPME, finding that such localization critical exponents for quasiperiodic potential induced localization are nonuniversal and depend on the microscopic details of the Hamiltonian.