Universal conductance fluctuations and direct observation of crossover of symmetry classes in topological insulators

Abstract

A key feature of topological insulators (TI) is symplectic symmetry of the Hamiltonian which changes to unitary when time reversal symmetry is lifted and the topological phase transition occurs. However, such a crossover has never been explicitly observed, by directly probing the symmetry class of the Hamiltonian. In this report, we have probed the symmetry class of topological insulators by measuring the mesoscopic conductance fluctuations in the TI Bi${}_{1.6}$Sb${}_{0:4}$Te${}_2$Se, which shows an exact factor of two reduction on application of a magnetic field due to crossover from symplectic to unitary symmetry classes. The reduction provides an unambiguous proof that the fluctuations arise from the universal conductance fluctuations (UCF), due to quantum interference and persists from T = 22 mK to 4.2 K. We have also compared the phase breaking length (l${}_{\varphi }$) extracted from both magneto-conductivity and UCF which agree well within a factor of two in the entire temperature and gate voltage range. Our experiment confirms UCF as the major source of fluctuations in mesoscopic disordered topological insulators, and the intrinsic preservation of time reversal symmetry in these systems.

arXiv comment6 pages, 4 figures

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Cited by in corpus (8)

• Low temperature saturation of phase coherence length in topological insulators
• Spontaneous time reversal symmetry breaking at individual grain boundaries in graphene
• Influence of magnetic and electric fields on universal conductance fluctuations in thin films of the Dirac semi-metal Cd3As2
• Mechanism of Universal Conductance Fluctuations
• Signature of pseudo-diffusive transport in mesoscopic topological insulators
• Quantum Transport Reservoir Computing
• Fermi energy sensitive universal conductance fluctuations in anisotropic materials
• Spectral analysis of universal conductance fluctuations