Direct measurement of acoustic spectral density and fractional topological charge

TL;DR

This paper presents a novel method for directly measuring the local density-of-states (LDOS) in acoustic systems, enabling the experimental detection of fractional topological charges in an acoustic Su-Schrieffer-Heeger model, with implications for wave-matter interactions.

Contribution

It introduces a state-of-the-art technique for measuring acoustic LDOS and demonstrates its application in identifying fractional topological numbers in a 1D acoustic topological system.

Findings

Successful direct measurement of acoustic LDOS.

Experimental detection of fractional topological charge.

Established relation between LDOS and acoustic emission power.

Abstract

Local density-of-states (LDOS) is a fundamental spectral property that plays a central role in various physical phenomena such as wave-matter interactions. Here, we report on the direct measurement of the LDOS of acoustic systems and derive from which the fractional topological number in an acoustic Su-Schrieffer-Heeger system. The acoustic LDOS is quantified here with a state-of-the-art technique through the measurement of the volume flow rate and the acoustic pressure with a local excitation-probe configuration. Based on this method, we study the acoustic Purcell effect and establish experimentally the important relation between the near-field LDOS and the far-field acoustic emission power. Moreover, we detect the LDOS in the one-dimensional acoustic Su-Schrieffer-Heeger model and observe the fractional topological number of the system. Our work unveils the important role of the LDOS in acoustic phenomena and paves the way toward characterizing and tailoring the LDOS in topological systems.