Experimental observation of super-Klein tunneling in phononic crystals
Yifan Zhu, Aurélien Merkel, Liyun Cao, Yi Zeng, Sheng Wan, Tong Guo, Zihao Su, Siyuan Gao, Haohan Zeng, Hui Zhang, Badreddine Assouar
Abstract
We numerically and experimentally report the acoustic analogue of the super-Klein tunneling in a heterojunction of phononic crystals formed with Willis scatterers that exhibit pseudospin-1 Dirac cones. By comparing with the pseudospin-1/2 Dirac cones, pseudospin-1 ones require in the band structure an additional flatband across the Dirac points. The conventional Klein tunneling, which is predicted in pseudospin-1/2 systems like graphene, consists of perfect transmission only under normal incidence through a potential barrier of any width. However, the super-Klein tunneling that we evidence here is defined for pseudospin-1 systems as a perfect transmission for all incidence angles at one single frequency within the energy barrier. This direct observation may have important implications in the exploration of the rich physics of pseudospin-1 quasiparticles.