Preparation and observation of anomalous counterpropagating edge states in a periodically driven optical Raman lattice

TL;DR

This paper proposes a theoretical framework for preparing and detecting anomalous counterpropagating edge states in a periodically driven optical Raman lattice, highlighting their dependence on initial conditions and robustness against disorder.

Contribution

It introduces a detailed analysis of how initial state parameters influence edge state populations and demonstrates their robustness, advancing understanding of the AFVH phase in cold atom systems.

Findings

Edge state population depends on initial spin and momentum parameters.

Counterpropagating edge states are robust against long-range disorder.

Theoretical framework supports future experimental exploration of AFVH phase.

Abstract

Motivated by the recent observation of real-space edge modes with ultracold atoms [Braun et al., Nat. Phys. 20, 1306 (2024)], we investigate the preparation and detection of anomalous counterpropagating edge states -- a defining feature of the anomalous Floquet valley-Hall (AFVH) phase -- in a two-dimensional periodically driven optical Raman lattice. Modeling the atomic cloud with a Gaussian wave packet state, we explore, both analytically and numerically, how the population of edge modes depends on the initial-state parameters. In particular, we reveal that, in addition to the internal spin state, the initial momenta parallel and perpendicular to the boundary play essential roles: they independently control the selective population of edge states across distinct momenta and within separate quasienergy gaps. Furthermore, we examine the wave-packet dynamics of counterpropagating edge states and demonstrate that their characteristic motion is robust against long-range disorder. These results establish a theoretical framework for future experimental explorations of the AFVH phase and topological phenomena associated with its unique edge modes.