Hinge Modes of Surface Arcs in a Synthetic Weyl Phononic Crystal

Phys Rev Lett. 2024 Sep 20;133(12):126602. doi: 10.1103/PhysRevLett.133.126602.

Abstract

Chiral bulk Landau levels and surface arcs, as the two distinctive features unique to Weyl semimetals, have each attracted enormous interest. Recent works have revealed that surface-arc modes can support one-sided chiral hinge modes, a hallmark of the three-dimensional quantum Hall effect, as a combined result of chiral Landau levels of bulk states and magnetic response of surface arcs. Here, we exploit a two-dimensional phononic crystal to construct an ideal Weyl semimetal under a pseudomagnetic field, in which a structural parameter is combined to construct a synthetic three-dimensional space. By directly measuring the acoustic pressure fields, we have not only visualized the one-sided chiral hinge modes, but also observed the quantized Landau level modes. The results pave the way to explore the high-dimensional quantum Hall physics in low-dimensional phononic platforms.