Dynamic localization and transport in complex crystals

TL;DR

This paper investigates how a Bloch particle behaves in complex PT-symmetric crystals under sinusoidal forces, revealing conditions for dynamic localization and effects of PT symmetry breaking on wave dynamics.

Contribution

It provides a theoretical analysis of dynamic localization and wave packet behavior in PT-symmetric complex crystals, highlighting the impact of PT symmetry breaking.

Findings

Time reversal symmetry preserves quasienergy reality in unbroken PT phase.

Exact band collapse leads to dynamic localization in sinusoidal band structures.

PT symmetry breaking causes band merging and non-reciprocal Bragg scattering.

Abstract

The behavior of a Bloch particle in a complex crystal with PT symmetry subjected to a sinusoidal ac force is theoretically investigated. For unbroken PT symmetry and in the single-band approximation, it is shown that time reversal symmetry of the ac force preserves the reality of the quasienergy spectrum. Like in ordinary crystals, exact band collapse, corresponding to dynamic localization, is attained for a sinusoidal band shape. The wave packet dynamics turns out to be deeply modified at the PT symmetry breaking point, where band merging occurs and Bragg scattering in the crystal becomes highly non-reciprocal.