heterostructures*

Topological insulator, whose boundary states are described by the massless Dirac equation, is of great interest to realize unusual states of quantum matter. We report the observation of perfect Andreev reflection as a manifestation of Klein tunneling (perfect transmission of massless Dirac particles through any potential barrier) at the interface between a normal metal and a SmB₆/YB₆ heterostructure. We have previously demonstrated proximity-induced superconductivity in the surface state of SmB₆. Conductance spectra of point contact junctions between a PtIr tip and the surface of the superconducting SmB₆ show perfect conductance doubling within the induced superconducting gap (Δ). The absence of electron reflection under such finite Z is attributed to the interplay of the Dirac material in Andreev reflection process i.e., Klein tunneling. The observation can be described by a modified BTK theory with Dirac Hamiltonian, Dirac-BTK theory.