  We theoretically reveal the possibility of specular Andreev reflection in a
thin film topological insulator normal-superconductor (N/S) junction in the
presence of a gate electric field. The probability of specular Andreev
reflection increases with the electric field, and electron-hole conversion with
unit efficiency happens in a wide experimentally accessible range of the
electric field. We show that perfect specular Andreev reflection can occur for
all angles of incidence with a particular excitation energy value. In addition,
we find that the thermal conductance of the structure displays exponential
dependence on the temperature. Our results reveal the potential of the proposed
topological insulator thin-film-based N/S structure for the realization of
intraband specular Andreev reflection.
