Contrast between spin and valley degrees of freedom

Gokmen, Tayfun; Padmanabhan, Medini; Shayegan, M.

doi:10.1103/physrevb.81.235305

Cited by 26 publications

(29 citation statements)

References 41 publications

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“…Considering the band values m * ∼ = 0.2 and g * ∼ = 0.65, 53 this implies an enhancement of g * m * by a factor of about 1.5. Such an enhancement is about a factor of two smaller than the g * m * enhancement reported for 2D electrons in Si-MOSFETs, 15 GaAs, 19 or AlAs 27 at comparable values of r s . The reason for this absence of enhancement might again be the holes' band structure and large effective spin.…”

Section: Spin Susceptibility Of Dilute 2d Holesmentioning

confidence: 58%

“…This is surprising. Previous studies on 2D electron systems confined to Si-MOSFETs, 15 to GaAs, 21,22 or to narrow (width < 5 nm) AlAs quantum wells 27 have reported an enhancement of m * by about 50% over the band value for a comparable value of r s (∼ 6). The reason for the lack of m * enhancement in 2D holes is not obvious but is possibly related to the holes' band structure and effective spin j = 3/2, as discussed in Ref.…”

Section: Discussion Of Effective Mass Datamentioning

confidence: 99%

“…[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Besides r s , the spin and/or valley degrees of freedom also play an important role in the re-normalization of m * and χ * since they modify the exchange interaction. 5,6,17,[24][25][26][27] In particular, it was recently demonstrated that when a 2D electron system is fully spin and valley polarized, m * is suppressed compared to its band value. [24][25][26][27] This suppression was reproduced in subsequent, numerical theoretical work.…”

mentioning

confidence: 99%

“…5,6,17,[24][25][26][27] In particular, it was recently demonstrated that when a 2D electron system is fully spin and valley polarized, m * is suppressed compared to its band value. [24][25][26][27] This suppression was reproduced in subsequent, numerical theoretical work. 28,29 In this work we present measurements of m * in a dilute 2D hole system (2DHS) confined to a (311)A GaAs quantum well.…”

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confidence: 99%

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Effective mass and spin susceptibility of dilute two-dimensional holes in GaAs

et al. 2011

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We report effective hole mass (m * ) measurements through analyzing the temperature dependence of Shubnikov-de Haas oscillations in dilute (density p ∼ 7 × 10 10 cm −2 , rs ∼ 6) two-dimensional (2D) hole systems confined to a 20 nm-wide, (311)A GaAs quantum well. The holes in this system occupy two nearly-degenerate spin subbands whose m * we measure to be ∼ 0.2 (in units of the free electron mass). Despite the relatively large rs in our 2D system, the measured m * is in reasonably good agreement with the results of our energy band calculations which do not take interactions into account. We then apply a sufficiently strong parallel magnetic field to fully depopulate one of the spin subbands, and measure m * for the populated subband. We find that this latter m * is close to the m * we measure in the absence of the parallel field. We also deduce the spin susceptibility of the 2D hole system from the depopulation field, and conclude that the susceptibility is enhanced by about 50% relative to the value expected from the band calculations.

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Section: Spin Susceptibility Of Dilute 2d Holesmentioning

confidence: 58%

Section: Discussion Of Effective Mass Datamentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Effective mass and spin susceptibility of dilute two-dimensional holes in GaAs

et al. 2011

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“…Finally, there is an extensive amount of experimental phenomenology associated with the spin physics. Phase transitions as a function of the Zeeman energy have been measured in various semiconductor based two-dimensional systems [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] , and recently also in graphene by Feldman et al…”

Section: Introductionmentioning

confidence: 99%

Fractional quantum Hall effect in graphene: Quantitative comparison between theory and experiment

et al. 2015

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The observation of extensive fractional quantum Hall states in graphene brings out the possibility of more accurate quantitative comparisons between theory and experiment than previously possible, because of the negligibility of finite width corrections. We obtain accurate phase diagram for differently spin-polarized fractional quantum Hall states, and also estimate the effect of Landau level mixing using the modified interaction pseudopotentials given in the literature. We find that the observed phase diagram is in good quantitative agreement with theory that neglects Landau level mixing, but the agreement becomes significantly worse when Landau level mixing is incorporated assuming that the corrections to the energies are linear in the Landau level mixing parameter λ. This implies that a first order perturbation theory in λ is inadequate for the current experimental systems, for which λ is typically on the order of or greater than one. We also test the accuracy of the composite-fermion theory and find that it is very accurate for the states of the form n/(2n + 1) but for the states at n/(2n − 1) the results are sensitive to the lowest Landau level projection method. An earlier prediction of an absence of spin transitions for the n/(4n + 1) states is confirmed by more rigorous calculations, and new predictions are made regarding spin physics for the n/(4n − 1) states.

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Quantum Hall Effect in Electron-Doped Black Phosphorus Field-Effect Transistors

et al. 2018

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The advent of black phosphorus field-effect transistors (FETs) has brought new possibilities in the study of two-dimensional (2D) electron systems. In a black phosphorus FET, the gate induces highly anisotropic 2D electron and hole gases. Although the 2D hole gas in black phosphorus has reached high carrier mobilities that led to the observation of the integer quantum Hall effect, the improvement in the sample quality of the 2D electron gas (2DEG) has however been only moderate; quantum Hall effect remained elusive. Here, we obtain high quality black phosphorus 2DEG by defining the 2DEG region with a prepatterned graphite local gate. The graphite local gate screens the impurity potential in the 2DEG. More importantly, it electrostatically defines the edge of the 2DEG, which facilitates the formation of well-defined edge channels in the quantum Hall regime. The improvements enable us to observe precisely quantized Hall plateaus in electron-doped black phosphorus FET. Magneto-transport measurements under high magnetic fields further revealed a large effective mass and an enhanced Landé g-factor, which points to strong electron-electron interaction in black phosphorus 2DEG. Such strong interaction may lead to exotic many-body quantum states in the fractional quantum Hall regime.

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Contrast between spin and valley degrees of freedom

Cited by 26 publications

References 41 publications

Effective mass and spin susceptibility of dilute two-dimensional holes in GaAs

Effective mass and spin susceptibility of dilute two-dimensional holes in GaAs

Fractional quantum Hall effect in graphene: Quantitative comparison between theory and experiment

Quantum Hall Effect in Electron-Doped Black Phosphorus Field-Effect Transistors

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