Valley-dependent electron retroreflection and anomalous Klein tunneling in an 8- Pmmn borophene-based n−p−n junction

Abstract

We investigate the transport properties in an 8-$Pmmn$ borophene-based $n\text{\ensuremath{-}}p\text{\ensuremath{-}}n$ junction. The valley-dependent electron retroreflection is generated by changing the direction of junction, which breaks up the conventional wisdom that only the electron specular reflection occurs at an interface. Furthermore, the valley-dependent anomalous Klein tunneling, i.e., the perfect transmission at a nonzero incident angle of electron regardless of the width and height of potential barrier, is found. Interestingly, this anomalous Klein tunneling depends on the direction of junction and the tilted velocity. These two findings arise from the same fact that the anisotropic band structure, induced by tilted and anisotropic velocities, leads to the release of locking relation between the transverse wave vector and velocity component along the interface. Our work gives insight into the understanding of the electron retroreflection and the Klein tunneling.