Non-Hermitian Mosaic Maryland model

TL;DR

This paper introduces the non-Hermitian mosaic Maryland model, revealing how structural modulation influences localization, mobility edges, and topological phases in complex quasiperiodic systems, with analytical and numerical validation.

Contribution

It presents an exactly solvable non-Hermitian model with mosaic modulation, deriving explicit formulas for Lyapunov exponents and mobility edges, and uncovering robust extended bands and topological features.

Findings

Existence of kappa-1 robust extended bands for modulation period kappa >= 2.

Derivation of exact Lyapunov exponents and explicit mobility edge formulas.

Confirmation of analytical predictions through numerical inverse participation ratio and fractal dimension calculations.

Abstract

We introduce the non-Hermitian mosaic Maryland model, where a discrete modulation period and a non-Hermitian phase are incorporated into the potential, rendering the originally exactly solvable system generally non-integrable. This model provides a unique platform to investigate how structural modulation governs localization in complex quasiperiodic potentials. Using Avila's global theory, we analytically derive the exact Lyapunov exponent and obtain explicit formulas for the complex mobility edges. Remarkably, for modulation periods kappa >= 2, the system intrinsically hosts kappa-1 robust extended bands that persist independently of the potential strength and non-Hermiticity. We further characterize the topological nature of these phases via the spectral winding number. Unlike the standard Maryland model, the mosaic modulation induces mobility edges, and the resulting phase transitions are continuous, reflecting the non-integrable nature of the system. Numerical calculations of the inverse participation ratio and fractal dimension confirm the analytical predictions for the asymptotic form of the mobility edges in the large non-Hermiticity limit. This work establishes structural design as a powerful degree of freedom for engineering wave transport and enhancing the robustness of extended states in non-Hermitian systems.