Direct Measurement of Zak Phase and Higher Winding Numbers in an Electroacoustic Cavity System

TL;DR

This paper introduces a novel experimental method to directly measure topological invariants, such as the Zak phase and higher winding numbers, in electroacoustic cavity systems through adiabatic state evolution and phase tracking.

Contribution

It demonstrates a new approach for directly measuring topological invariants in acoustic systems, extending the capability beyond indirect boundary state observations.

Findings

Successfully measured the quantized Zak phase in the SSH model

Extended the measurement to a model with next-nearest-neighbor coupling

Provided experimental evidence for the robustness of topological invariants

Abstract

Topological phases are states of matter defined by global topological invariants that remain invariant under adiabatic parameter variations, provided no topological phase transition occurs. This endows them with intrinsic robustness against local perturbations. Experimentally, these phases are often identified indirectly by observing robust boundary states, protected by the bulk-boundary correspondence. Here, we propose an experimental method for the direct measurement of topological invariants via adiabatic state evolution in electroacoustic coupled resonators, where time-dependent cavity modes effectively emulate the bulk wavefunction of a periodic system. Under varying external driving fields, specially prepared initial states evolve along distinct parameter-space paths. By tracking the relative phase differences among states along these trajectories, we successfully observe the quantized Zak phase in both the conventional Su-Schrieffer-Heeger (SSH) model and its extension incorporating with next-nearest-neighbor coupling. This approach provides compelling experimental evidence for the precise identification of topological invariants and can be extended to more complex topological systems.