Super Klein tunneling in phononic Lieb lattices
Hao Wu, Hailong He, Ze Dong, Liping Ye, Weiyin Deng, Manzhu Ke, Zhengyou Liu
Abstract
Super Klein tunneling is one of the intriguing phenomena found in spin-1 systems and has aroused many research interests due to its extraordinary transport properties. Compared with the traditional Klein tunneling occurring under normal incidence, super Klein tunneling releases the restriction to omnidirectional total transmission around the center of the energy or frequency barrier. Here, we observe super Klein tunneling in a heterojunction of a phononic Lieb lattice, where a single pseudospin-1 Dirac cone is located at the corner of the square Brillouin zone and consists of two linear crossed bands accompanied by an extra flat band. Airborne sound experiments evidence the near-perfect transmissions around the center of the frequency barrier for a wide range of incident angles. Our macroscopic acoustic system with a pseudospin-1 Dirac cone provides an ideal platform to explore the physics and applications related to super Klein tunneling.