Topological Surface Dirac Fermion in BiTeCl-Based Heterostructures

Inversion asymmetric topological insulator promises great potential to realize many intriguing phenomena such as intrinsic topological p-n junctions, pyroelectricity and novel topological magneto-electric effects that require inversion asymmetry. Recently, gapless helical surface Dirac fermions were observed in inversion-asymmetric BiTeCl crystal. However, heavy debate about whether BiTeCl is a topological insulator and controversial experimental results of the electronic structure of BiTeCl exist. In this work, through ab-initio calculations, we discovered that a BiTeCl-dominant BiTeCl/Bi₂Te₃ heterostructure can give rise to the observed band structures with a single surface Dirac fermion. Interestingly, we further suggest that such a BiTeCl/Bi₂Te₃ heterostructure could be naturally formed by annealing pure BiTeCl single crystals. Our results not only resolve the discrepancy between the previous experiments on heat treated samples and theoretical investigations, but also point out a pathway to design novel materials with sophisticated properties.