Disorder Effects In Topological Insulator Nanowires

Three-dimensional topological insulator (TI) nanowires with quantized surface subband spectra are studied as a main component of Majorana bound states (MBS) devices. However, such wires are known to have large concentration N similar to 10(19) cm(-3) of Coulomb impurities. It is believed that a MBS device can function only if the amplitude of long-range fluctuations of the random Coulomb potential Gamma is smaller than the subband gap Delta. Here we calculate Gamma for recently experimentally studied large-dielectric-constant (Bi1-xSbx)(2)Te-3 wires in a small-dielectric-constant environment (no superconductor). We show that provided by such a dielectric-constant contrast, the confinement of electric field of impurities within the wire allows more distant impurities to contribute into Gamma, leading to Gamma similar to 3 Delta. We also calculate a TI wire resistance as a function of the Fermi level and carrier concentration due to scattering on Coulomb and neutral impurities and do not find observable discrete subband-spectrum-related oscillations at N greater than or similar to 10(18) cm(-3).