Backscattering of Dirac Fermions in HgTe Quantum Wells with a Finite Gap

Tkachov, G.; Thienel, Cornelius; Pinneker, V.; Büttner, Bastian; Brüne, C.; Buhmann, H.; Molenkamp, L. W.; Hankiewicz, Ewelina M.

doi:10.1103/physrevlett.106.076802

Cited by 49 publications

(51 citation statements)

References 17 publications

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“…Although the zero-field dc bulk conductivity may significantly exceed the surface one, the surface contribution can still be detected through anomalous magnetic field dependencies of electrodynamic responses, revealing the underlying broken time-reversal symmetry. With appropriate modifications our findings can be extended to HgTe quantum wells which also support single-valley Dirac fermions [25][26][27][28][29] and show a pronounced Faraday effect. 30 …”

Section: Discussionmentioning

confidence: 99%

Anomalous galvanomagnetism, cyclotron resonance, and microwave spectroscopy of topological insulators

2011

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The surface quantum Hall state, magneto-electric phenomena and their connection to axion electrodynamics have been studied intensively for topological insulators. One of the obstacles for observing such effects comes from nonzero conductivity of the bulk. To overcome this obstacle we propose to use an external magnetic field to suppress the conductivity of the bulk carriers. The magnetic field dependence of galvanomagnetic and electromagnetic responses of the whole system shows anomalies due to broken time-reversal symmetry of the surface quantum Hall state, which can be used for its detection. In particular, we find negative linear dc magnetoresistivity and a quadratic field dependence of the Hall angle, shifted rf cyclotron resonance, nonanalytic microwave transmission coefficient and saturation of the Faraday rotation angle with increasing magnetic field or wave frequency.

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Section: Discussionmentioning

confidence: 99%

Anomalous galvanomagnetism, cyclotron resonance, and microwave spectroscopy of topological insulators

2011

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“…This regime can be identified from the carrier-density dependence of the QW mobility. 17 As to the dependence on the gap M , it can be extracted from sample-to-sample measurements. The band structure of MBE grown HgTe QWs is controllable to a great extent.…”

Section: Overview Of the Resultsmentioning

confidence: 99%

Weak antilocalization in HgTe quantum wells and topological surface states: Massive versus massless Dirac fermions

Tkachov

Hankiewicz

2011

Phys. Rev. B

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HgTe quantum wells and surfaces of three-dimensional topological insulators support Dirac fermions with a single-valley band dispersion. In the presence of disorder they experience weak antilocalization, which has been observed in recent transport experiments. In this work we conduct a comparative theoretical study of the weak antilocalization in HgTe quantum wells and topological surface states. The difference between these two single-valley systems comes from a finite band gap (effective Dirac mass) in HgTe quantum wells in contrast to gapless (massless) surface states in topological insulators. The finite effective Dirac mass implies a broken internal symmetry, leading to suppression of the weak antilocalization in HgTe quantum wells at times larger than certain τM, inversely proportional to the Dirac mass. This corresponds to the opening of a relaxation gap τ −1 M in the Cooperon diffusion mode which we obtain from the Bethe-Salpeter equation including relevant spin degrees of freedom. We demonstrate that the relaxation gap exhibits an interesting nonmonotonic dependence on both carrier density and band gap, vanishing at a certain combination of these parameters. The weak-antilocalization conductivity reflects this nonmonotonic behavior which is unique to HgTe QWs and absent for topological surface states. On the other hand, the topological surface states exhibit specific weak-antilocalization magnetoconductivity in a parallel magnetic field due to their exponential decay in the bulk.

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“…In a related paper from the same group, Tkachov et al 132 presented a theoretical and experimental study of the mobility of 5-12 nm-wide HgTe quantum wells with a finite gap. Whereas semiconductor heterostructures exhibit an increase in mobility with carrier density, a mobility maximum is seen in HgTe quantum wells.…”

Section: Transport Experimentsmentioning

confidence: 99%

Transport in three-dimensional topological insulators: Theory and experiment

Culcer

2012

Physica E: Low-dimensional Systems and Nanostructures

143

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This article reviews recent theoretical and experimental work on transport due to the surface states of three-dimensional topological insulators. The theoretical focus is on longitudinal transport in the presence of an electric field, including Boltzmann transport, quantum corrections and weak localization, as well as longitudinal and Hall transport in the presence of both electric and magnetic fields and/or magnetizations. Special attention is paid to transport at finite doping, to the π-Berry phase, which leads to the absence of backscattering, Klein tunneling and half-quantized Hall response. Signatures of surface states in ordinary transport and magnetotransport are clearly identified. The review also covers transport experiments of the past years, reviewing the initial obscuring of surface transport by bulk transport, and the way transport due to the surface states has increasingly been identified experimentally. Current and likely future experimental challenges are given prominence and the current status of the field is assessed.

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Backscattering of Dirac Fermions in HgTe Quantum Wells with a Finite Gap

Cited by 49 publications

References 17 publications

Anomalous galvanomagnetism, cyclotron resonance, and microwave spectroscopy of topological insulators

Anomalous galvanomagnetism, cyclotron resonance, and microwave spectroscopy of topological insulators

Weak antilocalization in HgTe quantum wells and topological surface states: Massive versus massless Dirac fermions

Transport in three-dimensional topological insulators: Theory and experiment

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