Ideal Weyl points, which are related by symmetry and thus reside at the same frequency, could promote the deep development and utilization of the Weyl physics. Although the ideal type-I Weyl points have been achieved in photonic crystals, the ideal type-II Weyl points with tilted cone-like band dispersions, are still beyond discovery. Here we realize ideal type-II Weyl points of minimal number in three-dimensional layer-stacked phononic crystals, and demonstrate topological phase transition from Weyl semimetal to valley insulators of two distinct types. The Fermi-arc surface states exist on the interface of the Weyl and valley phases, while the Fermi-circle ones occur on that of the two distinct valley phases. We show the interesting wave partition of Fermi-circle surface states on the interfaces formed by distinct valley phases.
@article{arxiv.1910.04518,
title = {Ideal type-II Weyl phase and topological transition in phononic crystals},
author = {Xueqin Huang and Jiuyang Lu and Feng Li and Weiyin Deng and Zhengyou Liu},
journal= {arXiv preprint arXiv:1910.04518},
year = {2020}
}