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.

中文翻译：

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声子晶体中超克莱因隧穿的实验观察

我们通过数值和实验报告了声子晶体异质结中超克莱因隧道的声学模拟，该声子晶体由威利斯散射体形成，表现出赝自旋 1 狄拉克锥。通过与 pseudospin-1/2 Dirac 锥相比，pseudospin-1 需要在能带结构中跨 Dirac 点增加一个平带。在像石墨烯这样的赝自旋 1/2 系统中预测到的传统克莱因隧道效应仅在法向入射下通过任何宽度的势垒实现完美传输。然而，我们在这里证明的超级克莱因隧道效应是为赝自旋 1 系统定义的，它是能垒内一个单一频率下所有入射角的完美传输。