Indications of topological transport by universal conductance fluctuations in Bi2Te2Se microflakes

Universal conductance fluctuations (UCFs) are extracted in the magnetoresistance responses in bulk-insulating Bi2Te2Se microflakes. Their two-dimensional character is demonstrated by field-tilting magnetoresistance measurements. Their origin from the surface electrons is determined by the fact that the UCF amplitudes remain unchanged while applying an in-plane field to suppress the coherence of bulk electrons. After considering the ensemble average in a batch of micrometer-sized samples, the intrinsic UCF magnitude of over 0.37 e2/h is obtained. This agrees with the theoretical prediction on topological surface states. All the lines of evidence point to the successful observation of the UCF of topological surface states.