Length scale of puddle formation in compensation-doped semiconductors and topological insulators

Bömerich, Thomas; Lux, Jonathan; Feng, Qingyufei Terenz; Rosch, Achim

doi:10.1103/physrevb.96.075204

Cited by 25 publications

(26 citation statements)

References 19 publications

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“…3). We speculate that they arise from time-dependent conductance fluctuations due to charge traps or mobile scattering centers, similar to those observed in metallic nanowires of similar mesoscopic size 24 , but they may also be affected by the presence of electron-hole puddles [25][26][27] . Averaging over several gate-voltage sweeps suppresses type II fluctuations while type I fluctuations remain unaffected, see Supplementary Note 4.…”

Section: Resultsmentioning

confidence: 58%

Quantum confinement of the Dirac surface states in topological-insulator nanowires

et al. 2021

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The non-trivial topology of three-dimensional topological insulators dictates the appearance of gapless Dirac surface states. Intriguingly, when made into a nanowire, quantum confinement leads to a peculiar gapped Dirac sub-band structure. This gap is useful for, e.g., future Majorana qubits based on TIs. Furthermore, these sub-bands can be manipulated by a magnetic flux and are an ideal platform for generating stable Majorana zero modes, playing a key role in topological quantum computing. However, direct evidence for the Dirac sub-bands in TI nanowires has not been reported so far. Here, using devices fabricated from thin bulk-insulating (Bi1−xSbx)2Te3 nanowires we show that non-equidistant resistance peaks, observed upon gate-tuning the chemical potential across the Dirac point, are the unique signatures of the quantized sub-bands. These TI nanowires open the way to address the topological mesoscopic physics, and eventually the Majorana physics when proximitized by an s-wave superconductor.

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Section: Resultsmentioning

confidence: 58%

Quantum confinement of the Dirac surface states in topological-insulator nanowires

et al. 2021

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“…for ∆/E C → ∞. The same behavior but with a smaller prefactor is found for l s [30]. Under the assumption that the surface carriers screen like a perfect metal, i.e., large |µ|, Bömerich et al predict l s ≈ 7−12/N 1/3 def in the range relevant to us, i.e., ∆/E C = 50 − 75.…”

Section: Discussionmentioning

confidence: 59%

Charge puddles in the bulk and on the surface of the topological insulator BiSbTeSe2 studied by scanning tunneling microscopy and optical spectroscopy

et al. 2017

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The topological insulator BiSbTeSe2 corresponds to a compensated semiconductor in which strong Coulomb disorder gives rise to the formation of charge puddles, i.e., local accumulations of charge carriers, both in the bulk and on the surface. Bulk puddles are formed if the fluctuations of the Coulomb potential are as large as half of the band gap. The gapless surface, in contrast, is sensitive to small fluctuations but the potential is strongly suppressed due to the additional screening channel provided by metallic surface carriers. To study the quantitative relationship between the properties of bulk puddles and surface puddles, we performed infrared transmittance measurements as well as scanning tunneling microscopy measurements on the same sample of BiSbTeSe2, which is close to perfect compensation. At 5.5 K, we find surface potential fluctuations occurring on a length scale rs = 40 − 50 nm with amplitude Γ = 8 − 14 meV which is much smaller than in the bulk, where optical measurements detect the formation of bulk puddles. In this nominally undoped compound, the value of Γ is smaller than expected for pure screening by surface carriers, and we argue that this arises most likely from a cooperative effect of bulk screening and surface screening. arXiv:1708.09166v1 [cond-mat.mes-hall]

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“…Yet, strong compositional disorder combined with the small band-gap of these materials leads to the formation of bulk and surface electron-hole puddles, as recently confirmed by scanning tunneling microscopy and optical conductivity experiments [16][17][18][19][20]. Hybridization between topological surface states and defect state potentials have also been shown to generate strong resonances that can form diffusive impurity bands [21].…”

Section: Introductionmentioning

confidence: 99%

Spatially varying electronic dephasing in three-dimensional topological insulators

et al. 2018

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Information processing devices operating in the quantum mechanical regime strongly rely on the quantum coherence of charge carriers. Studies of electronic dephasing in conventional metallic and semiconductor systems have not only paved the way towards high coherence quantum electronics, but also led to fundamental new insights in condensed matter physics. In this work, we perform a spatially resolved study of electronic dephasing in three dimensional topological insulators by exploiting an edge versus surface contacted measurement scheme. Unlike conventional two dimensional systems that are characterized by a single dephasing mechanism, we find that dephasing in our samples evolves from a variable-range-hopping type mechanism on the sample surface to a Nyquist type electron-electron interaction mechanism in the sub-surface layers. This is confirmed independently by the temperature and chemical potential dependence of the dephasing length, and gate dependent suppression/enhancement of the weak anti-localization effect. Our devices are fabricated using bulk insulating topological insulator BiSbTe 1.25 Se 1.75 capped with hexagonal-Boron Nitride in an inert environment, ruling out any extrinsic effects and confirming the topological surface state origin of our results. Our work introduces the idea of spatially resolved electronic dephasing and reveals a new regime of coherent transport in perhaps the most important topological insulator discovered so far. Our edge-vs-surface scheme may be applied to dephasing studies in a wide class of 2D materials.

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Length scale of puddle formation in compensation-doped semiconductors and topological insulators

Cited by 25 publications

References 19 publications

Quantum confinement of the Dirac surface states in topological-insulator nanowires

Quantum confinement of the Dirac surface states in topological-insulator nanowires

Charge puddles in the bulk and on the surface of the topological insulator BiSbTeSe2 studied by scanning tunneling microscopy and optical spectroscopy

Spatially varying electronic dephasing in three-dimensional topological insulators

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