Anomalous Andreev reflection in an 8-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>P</mml:mi><mml:mi>m</mml:mi><mml:mi>m</mml:mi><mml:mi>n</mml:mi></mml:mrow></mml:math> borophene-based superconducting junction
Xingfei Zhou
Abstract
We investigate the Andreev reflection in an 8-$Pmmn$ borophene-based normal metal-superconductor junction by solving the Dirac--Bogoliubov--de Gennes equation. There are three unusual features for Andreev reflection of anisotropic massless Dirac fermion: (1) The Andreev retroreflection generates in the interband conversion. (2) The specular Andreev reflection generates in the intraband conversion. (3) The electron-hole conversion with unit efficiency happens at a nonzero incident angle of electron regardless of the magnitude of doping in normal and superconducting regions. These three unique properties are opposite to the ones in a graphene-based normal metal-superconductor junction due to the anisotropic band structure of 8-$Pmmn$ borophene. Interestingly, we can modulate the Andreev reflection by adjusting the direction of junction. Our work gives an insight into the understanding of Andreev reflection of Dirac fermion.