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Signatures of long-range-correlated disorder in the magnetotransport of ultrathin topological insulators

Title
Signatures of long-range-correlated disorder in the magnetotransport of ultrathin topological insulators
Authors
D. NandiB. SkinnerLee Gil-HoK.-F. HuangK. ShainCui-Zu ChangY. OuS.-P. LeeJ. WardJ. S. MooderaP. KimB. I. HalperinA. Yacoby
POSTECH Authors
Lee Gil-Ho
Date Issued
Dec-2018
Publisher
AMER PHYSICAL SOC
Abstract
In an ultrathin topological insulator (TI) film, a hybridization gap opens in the TI surface states, and the system is expected to become either a trivial insulator or a quantum spin Hall insulator when the chemical potential is within the hybridization gap. Here we show, however, that these insulating states are destroyed by the presence of a large and long-range-correlated disorder potential, which converts the expected insulator into a metal. We perform transport measurements in ultrathin dual-gated topological insulator films as a function of temperature, gate voltage, and magnetic field, and we observe a metalliclike nonquantized conductivity, which exhibits a weak antilocalizationlike cusp at low magnetic fields and gives way to a nonsaturating linear magnetoresistance at large fields. We explain these results by considering the disordered network of electron- and hole-type puddles induced by charged impurities. We argue theoretically that such disorder can produce an insulator-to-metal transition as a function of increasing disorder strength, and we derive a condition on the band gap and the impurity concentration necessary to observe the insulating state. We also explain the linear magnetoresistance in terms of strong spatial fluctuations of the local conductivity using both numerical simulations and a theoretical scaling argument.
In an ultrathin topological insulator (TI) film, a hybridization gap opens in the TI surface states, and the system is expected to become either a trivial insulator or a quantum spin Hall insulator when the chemical potential is within the hybridization gap. Here we show, however, that these insulating states are destroyed by the presence of a large and long-range-correlated disorder potential, which converts the expected insulator into a metal. We perform transport measurements in ultrathin dual-gated topological insulator films as a function of temperature, gate voltage, and magnetic field, and we observe a metalliclike nonquantized conductivity, which exhibits a weak antilocalizationlike cusp at low magnetic fields and gives way to a nonsaturating linear magnetoresistance at large fields. We explain these results by considering the disordered network of electron- and hole-type puddles induced by charged impurities. We argue theoretically that such disorder can produce an insulator-to-metal transition as a function of increasing disorder strength, and we derive a condition on the band gap and the impurity concentration necessary to observe the insulating state. We also explain the linear magnetoresistance in terms of strong spatial fluctuations of the local conductivity using both numerical simulations and a theoretical scaling argument.
URI
http://oasis.postech.ac.kr/handle/2014.oak/94619
DOI
10.1103/PhysRevB.98.214203
ISSN
1098-0121
Article Type
Article
Citation
PHYSICAL REVIEW B, vol. 98, no. 21, 2018-12
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