Inelastic Electron Backscattering in a Generic Helical Edge Channel

Schmidt, Thomas L.; Rachel, Stephan; Oppen, Felix von; Glazman, L. I.

doi:10.1103/physrevlett.108.156402

Cited by 218 publications

(286 citation statements)

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“…In addition, the edge states do not exhibit significant variation in transport properties for temperatures between 20 mK and 1 K measured. This is in contrast to theoretical studies, which have predicted power law corrections to the edge conductance as a function of temperature due to single particle inelastic [13][14][15], and correlated two-particle backscattering [16], while such corrections vanish for Kondo scattering from a magnetic impurity in a dc limit [17]. The absence of such power laws in the temperature dependence of the edge conductance observed here indicates that spinflip single particle backscattering [14,18] is the dominant edge scattering process in this system.…”

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confidence: 54%

Observation of Edge Transport in the Disordered Regime of Topologically InsulatingInAs/GaSbQuantum Wells

et al. 2014

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We observe edge transport in the topologically insulating InAs=GaSb system in the disordered regime. Using asymmetric current paths we show that conduction occurs exclusively along the device edge, exhibiting a large Hall signal at zero magnetic fields, while for symmetric current paths, the conductance between the two mesoscopicly separated probes is quantized to 2e 2 =h. Both quantized and self-averaged transport show resilience to magnetic fields, and are temperature independent for temperatures between 20 mK and 1 K. DOI: 10.1103/PhysRevLett.112.026602 PACS numbers: 72.25.Dc, 73.23.-b, 73.63.Hs Two-dimensional (2D) topological insulators (TI) are a novel class of materials that are insulating in the bulk but which display uniquely conductive edge channels [1][2][3][4]. These one-dimensional (1D) edge modes are helical, with the spin direction tied to the electron direction of motion, and are protected from backscattering by the time reversal symmetry (TRS) [5,6]. Applying magnetic fields breaks the TRS, removing the topological protection of the 1D helical liquid (HL) from single particle backscattering, resulting in a gap opening in the edge spectrum. Such HL channels were first observed in transport measurements in HgTe=CdTe quantum wells, and much of the HL phenomenology has been confirmed and elucidated in those first experiments [7,8]. Recently, Du et al. reported quantized transport in the inverted regime of Si-doped InAs=GaSb quantum wells in mesoscopic samples [9], where the existence of helical edge states was proposed in Ref.[10] and the first experimental evidence provided in Ref.[11] through scaling arguments due to the presence of residual bulk carriers. Unlike that observed in HgTe=CdTe [7], quantized transport in InAs=GaSb persists to magnetic fields of several Tesla [9,11], challenging the common understanding of 2D TIs in terms of TRS protected edge states and associated Z 2 topological invariant.Much remains to be learned about the nature and robustness of HL, in particular, to TRS breaking and disorder. In addition, edge transport in InAs=GaSb has so far only been indirectly assessed in ballistic samples [9,11]. In this Letter we study TI InAs=GaSb quantum wells in the disordered regime [12], where the total device size is much larger than the ballistic length of the HL, and show that transport in the topological regime manifestly occurs along the sample perimeter and is quantized to values consistent with the existence of a HL. Similar to ballistic regime studies [9,11], the conduction is also seen to be only weakly dependent on externally applied magnetic fields of up to 1 T. We argue that this behavior is due to the reduced effective g factor of the edge states originating from their small Fermi velocity v F . In addition, the edge states do not exhibit significant variation in transport properties for temperatures between 20 mK and 1 K measured. This is in contrast to theoretical studies, which have predicted power law corrections to the edge conductance as a function of temperatur...

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confidence: 54%

Observation of Edge Transport in the Disordered Regime of Topologically InsulatingInAs/GaSbQuantum Wells

et al. 2014

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“…Here, it makes sense to have a common atomic HF coupling for the dipole-dipole-like coupling h n 2 and the orbital to nuclear-spin coupling h n 3 , since the normalization constants for the LCAO lattice functions (13) are numerically approximately equal,…”

Section: The Hf Interactions For P-like Statesmentioning

confidence: 99%

“…10 However, also deviations from perfect conductance have been observed in longer HgTe devices, 6,7,11,12 which could stem from, e.g., inelastic scattering mechanisms. [13][14][15][16][17][18] The effect of external magnetic fields have also been considered. 6,8,[19][20][21][22][23][24] The TI state in HgTe QWs was predicted by Bernevig, Hughes, and Zhang (BHZ) 25 by using a simplified k · p model containing states with S-and P -like symmetries, respectively.…”

Section: Introductionmentioning

confidence: 99%

Hyperfine interactions in two-dimensional HgTe topological insulators

Lunde

Platero

2013

Phys. Rev. B

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We study the hyperfine interaction between the nuclear spins and the electrons in a HgTe quantum well, which is the prime experimentally realized example of a two-dimensional topological insulator. The hyperfine interaction is a naturally present, internal source of broken time-reversal symmetry from the point of view of the electrons. The HgTe quantum well is described by the so-called Bernevig-Hughes-Zhang (BHZ) model. The basis states of the BHZ model are combinations of both S-and P -like symmetry states, which means that three kinds of hyperfine interactions play a role: (i) the Fermi contact interaction, (ii) the dipole-dipole-like coupling, and (iii) the electron-orbital to nuclear-spin coupling. We provide benchmark results for the forms and magnitudes of these hyperfine interactions within the BHZ model, which give a good starting point for evaluating hyperfine interactions in any HgTe nanostructure. We apply our results to the helical edge states of a HgTe two-dimensional topological insulator and show how their total hyperfine interaction becomes anisotropic and dependent on the orientation of the sample edge within the plane. Moreover, for the helical edge states, the hyperfine interaction due to the P -like states can dominate over the S-like contribution in certain circumstances.

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“…However, this would lead to the Anderson localization of the edge states, which is not experimentally observed. Some authors also considered mechanisms of inelastic scattering on a point defect taking into account a strong electron-electron interaction and a violation of the S z symmetry in the edge states by spin-orbit coupling [10]. Apart from the scattering by isolated impurities, a capture of electrons from the edge states into the conducting regions in the bulk of the insulator was also considered in Ref.…”

Section: Introductionmentioning

confidence: 99%

Shot noise in the edge states of 2D topological insulators

Nagaev

Aseev

2017

2017 International Conference on Noise and Fluctuations (ICNF)

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We calculate the resistance and shot noise in the edge states of a two-dimensional topological insulator that result from the exchange of electrons between these states and conducting puddles in the bulk of the insulator. The two limiting cases where the energy relaxation is either absent or very strong are considered. A finite time of spin relaxation in the puddles is introduced phenomenologically. Depending on this time and on the strength of coupling between the edge states and the puddles, the Fano factor F = S I /2eI ranges from 0 to 1/3, which is in an agreement with the available experimental data.

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Inelastic Electron Backscattering in a Generic Helical Edge Channel

Cited by 218 publications

References 21 publications

Observation of Edge Transport in the Disordered Regime of Topologically InsulatingInAs/GaSbQuantum Wells

Observation of Edge Transport in the Disordered Regime of Topologically InsulatingInAs/GaSbQuantum Wells

Hyperfine interactions in two-dimensional HgTe topological insulators

Shot noise in the edge states of 2D topological insulators

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