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

Islam, Saurav and Bhattacharyya, Semonti and Nhalil, Hariharan and Elizabeth, Suja and Ghosh, Arindam (2018) Universal conductance fluctuations and direct observation of crossover of symmetry classes in topological insulators. In: PHYSICAL REVIEW B, 97 (24).

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Abstract

A key feature of topological insulators (TIs) is symplectic symmetry of the Hamiltonian which changes to unitary when time-reversal symmetry is lifted and a topological phase transition occurs. However, such a crossover has yet to be explicitly observed by directly probing the symmetry class of the Hamiltonian. In this Rapid Communication, we have probed the symmetry class of topological insulators by measuring the mesoscopic conductance fluctuations in the TI Bi1.6Sb0.4Te2Se, which shows an exact factor of 2 reduction on application of a magnetic field due to a crossover from symplectic to unitary symmetry classes. The reduction provides an unambiguous proof that the fluctuations arise from the universal conductance fluctuations (UCFs), due to quantum interference, and persists from T similar to 22 mK to 4.2 K. We have also compared the phase breaking length l(phi) extracted from both magnetoconductance and UCFs which agree well within a factor of 2 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.

Item Type:	Journal Article
Publication:	PHYSICAL REVIEW B
Publisher:	AMER PHYSICAL SOC, ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
Additional Information:	Copyright of this article belong to AMER PHYSICAL SOC, ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
Department/Centre:	Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering Division of Physical & Mathematical Sciences > Physics
Date Deposited:	19 Jul 2018 14:54
Last Modified:	19 Jul 2018 14:54
URI:	http://eprints.iisc.ac.in/id/eprint/60239

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