Perfect and imperfect conductance quantization and transport resonances of two-dimensional topological-insulator quantum dots with normal conducting leads and contacts

A minimal tight-binding model of the two-dimensional topological-insulator bismuthene on SiC that accurately describes its experimentally determined low-energy electronic band structure is presented. Two-terminal electron transport through quantum dots described by this model with Ohmic normal conductor contacts and leads is studied within Landauer theory. Depending on the configuration of the leads and contacts, quantized conductances exactly or approximately equal to the conductance quantum 2e2/h, or conductance resonances are found at zero temperature if the Fermi level is within the topological-insulator bulk band gap. Interface states formed at the normal contact–topological-insulator boundary and their role in electron transport are discussed. Disorder along the normal contact–topological-insulator interfaces is found to improve the accuracy of the conductance quantization due to Anderson localization of the interface states.