Boundary-Robust Transmission Asymmetry as a Topological Signature in Open Floquet Lattices

TL;DR

This paper reveals a boundary-robust topological signature in open Floquet lattices, where the integrated transmission asymmetry reflects the bulk Floquet winding number, independent of boundary effects.

Contribution

It introduces a deep-bulk branch-population principle explaining the topological transmission asymmetry in open Floquet systems, with potential experimental detection methods.

Findings

The integrated transmission asymmetry saturates to a plateau set by the bulk Floquet winding number.

The transmission imbalance is robust against boundary reshaping of the transmission profile.

Proposed detection via cold-atom transmission spectroscopy and electrical readouts in electronic transport.

Abstract

We identify a boundary-robust topological signature of open Floquet lattices: although nonadiabatic boundaries strongly reshape the transmission lineshape, the integrated left--right transmission asymmetry saturates to a plateau set by the bulk Floquet winding number. Its origin is a deep-bulk branch-population principle: in the long-sample limit, each propagating Floquet--Bloch branch is generically populated with unit weight, since true Floquet bound states are nongeneric. The robust observable is therefore the cumulative transmission imbalance rather than the boundary-sensitive transmission profile. We propose direct detection by cold-atom transmission spectroscopy. For electronic transport, the same asymmetry admits contact-model-dependent electrical readouts: a coherent Floquet--Landauer--B\"uttiker interpretation predicts a near-\(2ef\) response in weak SAW devices, whereas a blocking-factor post-processing yields a qualitatively different signal.