Edge transport in InAs and InAs/GaSb quantum wells

Mueller, Susanne; Mittag, Christopher; Tschirky, Thomas; Charpentier, Christophe; Wegscheider, Werner; Ensslin, Klaus; Ihn, Thomas

doi:10.1103/physrevb.96.075406

Cited by 43 publications

(34 citation statements)

References 35 publications

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“…Then we find that the total resistance is proportional to the length of the edge, R = Ln imp |∆G|/G 2 0 , in accordance with experimental observations of Refs. [11,13,15,20,22]. This estimate for R holds under assumptions that the impurities are uncorrelated, 1/n imp > L T = v/T .…”

Section: Discussionmentioning

confidence: 88%

Helical edge transport in the presence of a magnetic impurity: The role of local anisotropy

Kurilovich

Burmistrov

et al. 2019

Phys. Rev. B

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Helical edge modes of 2D topological insulators are supposed to be protected from time-reversal invariant elastic backscattering. Yet substantial deviations from the perfect conductance are typically observed experimentally down to very low temperatures. To resolve this conundrum we consider the effect of a single magnetic impurity with arbitrary spin on the helical edge transport. We consider the most general structure of the exchange interaction between the impurity and the edge electrons. We take into the account the local anisotropy for the impurity and show that it strongly affects the backscattering current in a wide range of voltages and temperatures. We show that the sensitivity of the backscattering current to the presence of the local anisotropy is different for half-integer and integer values of the impurity spin. In the latter case the anisotropy can significantly increase the backscattering correction to the current. arXiv:1808.03084v2 [cond-mat.mes-hall]

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Section: Discussionmentioning

confidence: 88%

Helical edge transport in the presence of a magnetic impurity: The role of local anisotropy

Kurilovich

Burmistrov

et al. 2019

Phys. Rev. B

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“…In a helical edge, however, the position of the electronic gap opened in the edge state spectrum depends on the ± sign in Eq. (23). Provided that the edge states consist of R ↓ and L ↑ electrons and the Fermi level is placed above the Dirac point at q = 0, the order with the positive sign, Ĩ + , would mix R ↓ (q + 2k F ) and L ↑ (q), and therefore gap out the electrons at the Magnon energy E mag as a function of the momentum q in an infinitely long edge.…”

Section: A Rkky Interaction and Spiral Nuclear Spin Ordermentioning

confidence: 99%

Effects of nuclear spins on the transport properties of the edge of two-dimensional topological insulators

et al. 2018

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The electrons in the edge channels of two-dimensional topological insulators can be described as a helical Tomonaga-Luttinger liquid. They couple to nuclear spins embedded in the host materials through the hyperfine interaction, and are therefore subject to elastic spin-flip backscattering on the nuclear spins. We investigate the nuclear-spin-induced edge resistance due to such backscattering by performing a renormalization-group analysis. Remarkably, the effect of this backscattering mechanism is stronger in a helical edge than in nonhelical channels, which are believed to be present in the trivial regime of InAs/GaSb quantum wells. In a system with sufficiently long edges, the disordered nuclear spins lead to an edge resistance which grows exponentially upon lowering the temperature. On the other hand, electrons from the edge states mediate an anisotropic Ruderman-Kittel-Kasuya-Yosida nuclear spin-spin interaction, which induces a spiral nuclear spin order below the transition temperature. We discuss the features of the spiral order, as well as its experimental signatures. In the ordered phase, we identify two backscattering mechanisms, due to charge impurities and magnons. The backscattering on charge impurities is allowed by the internally generated magnetic field, and leads to an Anderson-type localization of the edge states. The magnon-mediated backscattering results in a power-law resistance, which is suppressed at zero temperature. Overall, we find that in a sufficiently long edge the nuclear spins, whether ordered or not, suppress the edge conductance to zero as the temperature approaches zero.

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“…In contrast, in InAs the surface pinning occurs in the conduction band [21,22], which implies that in heterostructures the edge potential is bent downward so the electron density increases near the edge. While this is advantageous for superconducting junctions, it gives rise to trivial edge conduction with no topological origin at zero magnetic field [15,[23][24][25][26]. In a quantizing magnetic field, this suggests that the Fermi level can cross Landau levels extra times (see the inset to Fig.…”

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confidence: 99%

Counterflowing edge current and its equilibration in quantum Hall devices with sharp edge potential: Roles of incompressible strips and contact configuration

et al. 2019

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We report the observation of counterflowing edge current in InAs quantum wells which leads to the breakdown of quantum Hall (QH) effects at high magnetic fields. Counterflowing edge channels arise from the Fermi-level pinning of InAs and the resultant sharp edge potential with downward bending. By measuring the counterflow conductance for varying edge lengths, we determine the effective number N C of counterflowing modes and their equilibration length λ eq at bulk integer filling factor ν = 1-4. λ eq increased exponentially with magnetic field B, reaching 200 µm for ν = 4 at B ≥ 7.6 T. Our data reveal important roles of the innermost incompressible strip with even filling in determining N C and λ eq and the impact of the contact configuration on the QH effect breakdown. Our results show that counterflowing edge channels manifest as transport anomalies only at high fields and in short edges. This in turn suggests that, even in the integer QH regime, the actual microscopic structure of edge states can differ from that anticipated from macroscopic transport measurements, which is relevant to various systems including atomic-layer materials.

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Edge transport in InAs and InAs/GaSb quantum wells

Cited by 43 publications

References 35 publications

Helical edge transport in the presence of a magnetic impurity: The role of local anisotropy

Helical edge transport in the presence of a magnetic impurity: The role of local anisotropy

Effects of nuclear spins on the transport properties of the edge of two-dimensional topological insulators

Counterflowing edge current and its equilibration in quantum Hall devices with sharp edge potential: Roles of incompressible strips and contact configuration

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