Escaping AB caging via Floquet engineering: photo-induced long-range interference in an all-band-flat model

TL;DR

This paper demonstrates how high-frequency periodic driving can transform flat-band lattices into tunable systems with long-range interference, enabling control over quantum states and entanglement in engineered lattice models.

Contribution

It introduces a method to engineer quasi-flat bands and control interference in flat-band lattices via Floquet driving, revealing new ways to manipulate quantum correlations.

Findings

Periodic driving creates tunable quasi-flat bands.

Drive-induced tunneling enables escape from Aharonov-Bohm caging.

The system can generate and manipulate quantum entanglement.

Abstract

Flat-band lattices hosting compact localized states are highly sensitive to external modulation, and the tailored design of a perturbation to imprint specific features becomes relevant. Here we show that periodic driving in the high-frequency regime transforms the all-flat-band diamond chain into one featuring two tunable quasi-flat bands and a residual flat band pinned at $E=0$. The interplay between lattice geometry and the symmetries of the driven system gives rise to drive-induced tunneling processes that redefine the interference conditions and open a controllable route to escaping Aharonov-Bohm caging. Under driving, the diamond chain effectively acquires the geometry of a dimerized lattice, exhibiting charge oscillations between opposite boundaries. This feature can be exploited to generate two-particle entanglement that is directly accessible experimentally. The resulting drive-engineered quasi-flat bands thus provide a versatile platform for manipulating quantum correlations, revealing a direct link between spectral fine structure and dynamical entanglement.