Acoustic type-II Weyl nodes from stacking dimerized chains

TL;DR

This paper introduces an acoustic analog of type-II Weyl semimetals by stacking dimerized chains of acoustic resonators, revealing unique surface state transport properties and offering a new way to realize topological phases acoustically.

Contribution

It constructs the first acoustic type-II Weyl Hamiltonian using stacked dimerized chains, demonstrating distinct physical features and a method to create topological phases acoustically.

Findings

Distinct finite density of states in the acoustic type-II Weyl system

Unique transport properties of Fermi-arc-like surface states

Surface state velocities determined by tilting direction, not chirality

Abstract

Lorentz-violating type-II Weyl fermions, which were missed in Weyl's prediction of nowadays classified type-I Weyl fermions in quantum field theory, have recently been proposed in condensed matter systems. The semimetals hosting type-II Weyl fermions offer a rare platform for realizing many exotic physical phenomena that are different from type-I Weyl systems. Here we construct the acoustic version of type-II Weyl Hamiltonian by stacking one-dimensional dimerized chains of acoustic resonators. This acoustic type-II Weyl system exhibits distinct features in finite density of states and unique transport properties of Fermi-arc-like surface states. In a certain momentum space direction, the velocity of these surface states are determined by the tilting direction of the type-II Weyl nodes, rather than the chirality dictated by the Chern number. Our study also provides an approach of constructing acoustic topological phases at different dimensions with the same building blocks.