Avoided Band Crossing in Locally Periodic Elastic Rods

TL;DR

This paper experimentally demonstrates avoided band crossings in locally periodic elastic rods, showing how they can tune wave propagation and metal-insulator transitions, with results matching theoretical transfer matrix calculations.

Contribution

It provides the first experimental observation of avoided band crossings in a classical elastic system using torsional waves in locally periodic rods.

Findings

Experimental observation of avoided band crossing in elastic rods

Agreement between transfer matrix calculations and measurements

Identification of a border-induced bulk level transition

Abstract

Avoided band crossings have been studied theoretically and it has been shown that they can provide a tunning of the metal-insulator transition. Here we present an experimental example of an avoided band crossing for a classical undulatory system: torsional waves in locally periodic rods. To excite and detect the torsional waves, an electromagnetic-acoustic transducer for low-frequencies that we have recently developed, is used. Calculations performed using the transfer matrix method agree with the experimental measurements. In the observed avoided band crossing one level, which is a border-induced bulk level, moves from one band to the next.