Cyclic depopulation of edge states in a large quantum dot

Baer, Stephan; Rössler, C.; Ihn, Thomas; Ensslin, Klaus; Reichl, Christian; Wegscheider, Werner

doi:10.1088/1367-2630/15/2/023035

Cited by 19 publications

(32 citation statements)

References 32 publications

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“…This was interpreted initially as a signature of the anti-Pfaffian or SU (2) 2 state. Subsequent experiments [8,19] in other sample geometries produced g between 0.37 and 0.42 as the best fits at fixed e * = e/4. This supports the case for the 331 state.…”

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confidence: 96%

“…Spin polarization data are controversial: optical experiments [13,14] were interpreted as a sign of zero polarization while resistively-detected NMR points [15,16] at 100% polarization. Thermoelectric response [17] shows qualitative agreement with a non-Abelian state but an Abelian state may exhibit similar behavior, if it has different types of quasiparticles of close or equal energy.Several groups [8,18,19] performed tunneling experiments which measured the quasiparticle current through a narrow constriction. At low temperatures the zerobias conductance scales as T 2g−2 , where the exponent g depends on the topological order and is universal in the absence of long-range interactions [2].…”

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confidence: 99%

“…This made it impossible to select the correct theory of the 5/2-liquid. The last few years have seen considerable accumulation of the new experimental results [6][7][8][11][12][13][14][15][16][17][18][19]. They provide tight constraints on the topological order at ν = 5/2.…”

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confidence: 99%

“…Several groups [8,18,19] performed tunneling experiments which measured the quasiparticle current through a narrow constriction. At low temperatures the zerobias conductance scales as T 2g−2 , where the exponent g depends on the topological order and is universal in the absence of long-range interactions [2].…”

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confidence: 99%

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Experimental constraints and a possible quantum Hall state atν=5/2

Yang

Feldman

2014

Phys. Rev. B

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Several topological orders have been proposed to explain the quantum Hall plateau at ν = 5/2. The observation of an upstream neutral mode on the sample edge supports the non-Abelian antiPfaffian state. On the other hand, tunneling experiments favor the Halperin 331 state which exhibits no upstream modes. No proposed ground states agree with both types of experiments. We find a topological order, compatible with the results of both experiments. That order allows both finite and zero spin polarizations. It is Abelian but its signatures in Aharonov-Bohm interferometry can be similar to those of the Pfaffian and anti-Pfaffian states.Fractional quantum Hall effect (QHE) exhibits remarkably rich phenomenology. More than 70 filling factors have been discovered. Some of them are well understood but many are not. In particular, the nature of the fragile states in the second Landau level remains a puzzle.The quantum Hall plateaus at the filling factors [1] ν = 5/2 and ν = 7/2 are particularly interesting. Almost all known filling factors have odd denominators. Such quantum Hall states can be explained in a natural way within the Haldane-Halperin hierarchy [2] and the composite fermion picture [3]. Even-denominator filling factors require additional ideas. It was argued that electrons form pairs [4] at ν = 5/2, i.e., the 5/2 state is a topological superconductor. Paring implies that the lowest-charge quasiparticles carry one quarter of an electron charge [1,5]. This was indeed observed in several experiments [6][7][8]. At the same time, the nature of pairing remains an open problem.The investigations of the ν = 5/2 QHE liquid have focused on its topological order which is robust to small variations of sample parameters [2]. This led to a striking proposal of non-Abelian statistics [1,5]. In contrast to ordinary fermions, bosons and Abelian anyons, systems of non-Abelian quasiparticles possess numerous degenerate ground states at fixed quasiparticle positions. This may be useful for quantum computing [1]. Theoretically proposed non-Abelian Pfaffian, anti-Pfaffian, SU (2) 2 and anti-SU (2) 2 states have attracted much interest as possible candidates to explain the QHE plateau at ν = 5/2 (for a review of the proposed states see Refs. 9 and 10). At the same time, one can also construct Abelian states with the same filling factor, such as the Halperin 331, K = 8 and anti-331 states [9,10].Most above-mentioned states were invented before experimental information beyond the existence of the 5/2 QHE plateau and the value of its energy gap became available. This made it impossible to select the correct theory of the 5/2-liquid. The last few years have seen considerable accumulation of the new experimental results [6][7][8][11][12][13][14][15][16][17][18][19]. They provide tight constraints on the topological order at ν = 5/2. We argue that all previously proposed ground state wave functions are excluded by those constraints. To explain the 5/2 plateau we propose a different topological order that satisfies the experimental constrai...

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confidence: 96%

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confidence: 99%

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Experimental constraints and a possible quantum Hall state atν=5/2

Yang

Feldman

2014

Phys. Rev. B

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“…Experimental investigation of the non-Abelian statistics of the ν = 5/2 fractional quantum Hall state can be performed by Fabry-Perot interferometry (FPI) of quasiparticles, leaning on the Aharonov-Bohm (AB) phase 12,13 . Recently, there have been advances in realising quantum Hall edge-state based interferometers at fractional filling factors at the lowest LL 14,15 . Much of the attention has been focused on the filling factor ν = 5/2 state in quantum dots (QDs) which consist of the two LLs [16][17][18] .…”

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confidence: 99%

Formation of spin droplet atν=52in an asymmetric quantum dot under quantum Hall conditions

Atci

Siddiki

2017

Phys. Rev. B

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In this work, a quantum dot that is defined asymmetrically by electrostatic means induced on a GaAs/AlGaAs heterostructure is investigated to unravel the effect of geometric constrains on the formation of spin droplets under quantised Hall conditions. The incompressibility of exciting ν = 5/2 state is explored by solving the Schrödinger equation within spin density functional theory, where the confinement potential is obtained self-consistently utilising the Thomas-Fermi approximation. Our numerical investigations show that the spatial distribution of the ν = 2 incompressible strips and electron occupation in the second lowest Landau level considerably differ from the results of the laterally symmetric quantum dots. Our findings yield two important consequences, first the incompressibility of the intriguing ν = 5/2 state is strongly affected by the asymmetry, and second, since the Aharonov-Bohm interference patterns depend on the velocity of the particles, asymmetry yields an additional parameter to adjust the oscillation period, which imposes a boundary condition dependency in observing quasi-particle phases.

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Integer and Fractional Quantum Hall States in QPCs

Baer

Ensslin

2015

Transport Spectroscopy of Confined Fractional Quantum Hall Systems

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Cyclic depopulation of edge states in a large quantum dot

Cited by 19 publications

References 32 publications

Experimental constraints and a possible quantum Hall state atν=5/2

Experimental constraints and a possible quantum Hall state atν=5/2

Formation of spin droplet atν=52in an asymmetric quantum dot under quantum Hall conditions

Integer and Fractional Quantum Hall States in QPCs

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