Microscopic origin of the ‘0.7-anomaly’ in quantum point contacts

Bauer, F.; Heyder, Jan; Schubert, E.; Borowsky, David; Taubert, D.; Bruognolo, Benedikt; Schuh, Dieter; Wegscheider, Werner; Delft, Jan von; Ludwig, Stefan

doi:10.1038/nature12421

Cited by 99 publications

(196 citation statements)

References 42 publications

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“…Similarly, for a magnetic field along B X (Fig 5c,d) In conclusion we achieved substantial improvements in electrical transport measurements of InSb nanowires by using a high quality hBN dielectric and clearly demonstrated conductance quantization at zero magnetic field, as well as degenerate sub-bands at magnetic field above 1 T. In the future these, improvements will allow the more detailed investigation of features in the 1 st plateau, such as signatures of a helical gap, 38,39 or the presence of a 0.7 anomaly. 40,41,42 The large SOI in our InSb nanowire strongly influences the electron dispersion relation and the tunability with magnetic field could add new insight into the underlying physics. 43 We did not see any clear features related to the 0.7-anomaly in our devices.…”

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confidence: 99%

Conductance Quantization at Zero Magnetic Field in InSb Nanowires

et al. 2016

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Ballistic electron transport is a key requirement for existence of a topological phase transition in proximitized InSb nanowires. However, measurements of quantized conductance as direct evidence of ballistic transport have so far been obscured due to the increased chance of backscattering in one dimensional nanowires. We show that by improving the nanowiremetal interface as well as the dielectric environment we can consistently achieve conductance quantization at zero magnetic field. Additionally, studying the sub-band evolution in a rotating magnetic field reveals an orbital degeneracy between the second and third sub-bands for perpendicular fields above 1 T.

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confidence: 99%

Conductance Quantization at Zero Magnetic Field in InSb Nanowires

et al. 2016

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“…We emphasize that by employing the Very recently, SGM experiments pointing in this direction were reported on quasi-1D constrictions [13] where fluctuations in the conductance maps were Another route could be an SGM investigation of the effects of the barrier geometry on the 0.7-anomaly. Such an experiment could effectively test the scenario involving a "van Hove ridge" in the density of states of a QPC [14]. In this model, the sample geometry is extremely important for the precise way in which the density of states affects the conductance.…”

Section: Resultsmentioning

confidence: 99%

“…Even very recently, two papers provided evidence for the Kondo scenario, based on the formation of a quasi-bound state at the constriction [12,13]. On the other hand, another recently proposed model involves a "van Hove ridge" in the density of states of the QPC that strongly enhances interaction effects for subopen QPCs without needing spin-polarization or quasi-bound states [14].…”

Section: Introductionmentioning

confidence: 99%

Scanning gate imaging of quantum point contacts and the origin of the 0.7 anomaly

et al. 2014

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The origin of the anomalous transport feature appearing at conductance G ≈ 0.7 x (2e 2 /h) in quasi-1D ballistic devices − the so-called 0.7 anomaly − represents a long standing puzzle. Several mechanisms were proposed to explain it, but a general consensus has not been achieved. Proposed explanations are based on quantum interference, Kondo effect, Wigner crystallization, and more. A key open issue is whether point defects that can occur in these low-dimensional devices are the physical cause behind this conductance anomaly. Here we adopt a scanning gate microscopy technique to map individual impurity positions in several quasi-1D constrictions and correlate these with conductance characteristics. Our data demonstrate that the 0.7 anomaly can be observed irrespective of the presence of localized defects, and we conclude that the 0.7 anomaly is a fundamental property of low-dimensional systems.

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“…However, this precondition has been put into question, particularly for clean QPCs. More recent works following this type of argument have appeared [11][12][13]19].…”

Section: Kondo Physics In a Qpcmentioning

confidence: 99%

“…In the current literature both 0.7 and ZBA features have been explained [11,12] by either: amplification of interaction effects when a smeared van-Hove singularity of the local density of states (DOS) (at the bottom of the lowest 1D sub-band) crosses the chemical potential; or by an emergent localized state contributing to the formation of a collective (many-body) state arising from the Kondo effect in electron transport through the localized state. Another work, [13], develops a similar idea based on Kondo physics.…”

Section: Introductionmentioning

confidence: 99%

Conductance anomalies in quantum point contacts and 1D wires

Das

Green

2017

Adv. Nat. Sci: Nanosci. Nanotechnol.

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Over the last decade, interest in 1D charge transport has progressed from the seminal discovery of Landauer quantization of conductance, as a function of carrier density, to finerscale phenomena at the onset of quantization. This has come to be called the '0.7 anomaly', rather connoting a theoretical mystery of some profundity and universality, which remains open to date. Its somewhat imaginative appellation may tend to mislead, since the anomaly manifests itself over a range of conductance values: anywhere between 0.25-0.95 Landauer quanta. In this paper we offer a critique of the 0.7 anomaly and discuss the extent to which it represents a deep question of physics.

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Microscopic origin of the ‘0.7-anomaly’ in quantum point contacts

Cited by 99 publications

References 42 publications

Conductance Quantization at Zero Magnetic Field in InSb Nanowires

Conductance Quantization at Zero Magnetic Field in InSb Nanowires

Scanning gate imaging of quantum point contacts and the origin of the 0.7 anomaly

Conductance anomalies in quantum point contacts and 1D wires

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