Universal conductance fluctuations in a Bi_1.5Sb_0.5Te_1.8Se_1.2 topological insulator nano-scaled Hall bar structure

We present low-temperature magnetotransport measurements characterizing the promising quaternary Bi1.5Sb0.5Te1.8Se1.2 topological insulator material. The measurements performed on a nano-Hall bar grown by selective-area molecular beam epitaxy revealed pronounced universal conductance fluctuations. It is shown that these fluctuations originate from phase-coherent loops within the topologically protected surface states. Furthermore, the decay of the fluctuation amplitude with increasing temperatures suggests a quasi one-dimensional transport regime.