Enhancement of crossed Andreev reflection in normal-superconductor-normal junction of thin topological insulator

The subgapped transport phenomena through a normal-superconductor-normal (NSN) junction made up of ultra thin topological insulator with proximity induced superconductivity has been explored here. The dimensional crossover from three dimensional (3D) topological insulator (TI) to thin two-dimensional (2D) TI introduces a new degree of freedom, the so-called hybridization or coupling between the two surface states. The role of hybridization in transport properties of the NSN junction, especially how it affects the crossed Andreev reflection (CAR) has been investigated. It has been observed that a rib-like pattern appears in CAR probability profile while examined as a function of angle of incidence and length of the superconductor. Depending on the incoming and reflection or transmission channel, CAR probability can be maneuvered to be higher than 97% under suitable coupling between the two TI surface states along with appropriate gate voltage and doping concentration in the normal region