Charge Rearrangement and Screening in a Quantum Point Contact

Lüscher, Silvia; Moore, Lindsay; Rejec, T.; Meir, Yigal; Shtrikman, Hadas; Goldhaber‐Gordon, David

doi:10.1103/physrevlett.98.196805

Cited by 40 publications

(81 citation statements)

References 19 publications

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“…Then, it decreases at a slow rate for U 0 5.75 meV, when the QPC channel becomes more populated with electrons. This pinning effect is a consequence of the compressibility peak in the 1D electron gas, in agreement with previous works [28][29][30] . It also occurs when U eff crosses the Fermi level on both sides of the QPC when the 1D channel is still closed, and is responsible for the "kink" observed in the barrier profile ( Fig.…”

Section: Resultssupporting

confidence: 93%

“…In the constriction, the gate-induced potential leads to a downward shift of the 2DEG subbands. Our model, based on a transmission matrix technique, predicts an anomaly in the range 0.3G 0 < G < 0.6G 0 , during the rise to the first conductance plateau at T = 0 K. This anomaly is caused by a change of slope in the variation of the effective potential with the external gate voltage due to the charging of the 1D channel at the compressibility peak, in agreement with previous observations [28][29][30] . Our model also predicts an anomaly enhancement in the case of anti-ferromagnetic interaction in the QPC as the attractive exchange interaction lowers the potential barrier, thereby disqualifying the presence of any spontaneous spin polarization.…”

Section: Discussionsupporting

confidence: 88%

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Temperature modulation of the transmission barrier in quantum point contacts

Sánchez

Leburton

2013

Phys. Rev. B

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We investigate near-equilibrium ballistic transport through a quantum point contact (QPC) along a GaAs/AlGaAs heterojunction with a transfer matrix technique, as a function of temperature and the shape of the potential barrier in the QPC. Our analysis is based on a three-dimensional (3D) quantum-mechanical variational model within the Hartree-Fock approximation that takes into account the vertical depletion potential from ionized acceptors in GaAs and the gate-induced transverse confinement potential that reduce to an effective slowly-varying one-dimensional (1D) potential along the narrow constriction. The calculated zero-temperature transmission exhibits a shoulder ranging from 0.3 to 0.6 depending on the length of the QPC and the profile of the barrier potential. The effect is a consequence of the compressibility peak in the 1D electron gas and is enhanced for anti-ferromagnetic interaction among electrons in the QPC, but is smeared out once temperature is increased by a few tenths of a kelvin.

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Section: Resultssupporting

confidence: 93%

Section: Discussionsupporting

confidence: 88%

Temperature modulation of the transmission barrier in quantum point contacts

Sánchez

Leburton

2013

Phys. Rev. B

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“…Similar effects of the pinch-off for the screening were obtained in Ref. [37], in which the transconductance was not disussed. The present paper indicates their consequences for asymmetry of the transconductance lines.…”

Section: Interaction Effectssupporting

confidence: 80%

Transconductance and effective Landé factors for quantum point contacts: Spin-orbit coupling and interaction effects

2016

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We analyze the effective g * factors and their dependence on the orientation of the external magnetic field for a quantum point contact defined in the two-dimensional electron gas. The paper simulates the experimental procedure for evaluation of the effective Landé factors from the transconductance of a biased device in external magnetic field. The contributions of the orbital effects of the magnetic field, the electron-electron interaction and spin-orbit (SO) coupling are studied. The anisotropy of the g * factors for the in-plane magnetic field orientation, which seems counterintuitive from the perspective of the effective SO magnetic field, is explained in an analytical model of the constriction as due to the SO-induced subband mixing. The asymmetry of the transconductance as a function of the gate voltage is obtained in agreement with the experimental data and the results are explained as due to the depletion of the electron gas within the quantum point contact constriction and the related reduction of the screening as described within the DFT approach. The results for transconductance and the g * factors are in a good agreement with the experimental data [Phys. Rev. B 81, 041303, 2010]. arXiv:1508.04287v1 [cond-mat.mes-hall]

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“…a large negative mass −m 0 , which is of order of the lattice cutoff. This operator satisfies the Ginsparg-Wilson relation [14], D ov γ 5 + γ 5 D ov = D ov γ 5 D ov /m 0 , through which the exact chiral symmetry on the lattice can be defined [15]. The operator (2) has a singularity due to the sign function, when an eigenvalue of H W (−m 0 ) crosses zero as the background gauge field varies.…”

Section: Introductionmentioning

confidence: 99%

Finite temperature study of the axial U(1) symmetry on the lattice with overlap fermion formulation

Cossu

Aoki²,

Fukaya³

et al. 2013

Phys. Rev. D

112

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We examine the axial U (1) symmetry near and above the finite temperature phase transition in two-flavor QCD using lattice QCD simulations. Although the axial U (1) symmetry is always violated by quantization, i.e. the chiral anomaly, the correlation functions may manifest effective restoration of the symmetry in the high temperature phase. We explicitly study this possibility by calculating the meson correlators as well as the Dirac operator spectral density near the critical point. Our numerical simulations are performed on a 16 3 × 8 lattice with two flavors of dynamical quarks represented by the overlap fermion formalism. Chiral symmetry and its violation due to the axial anomaly is manifestly realized with this formulation, which is a prerequisite for the study of the effective restoration of the axial U (1) symmetry. In order to avoid discontinuity in the gauge configuration space, which occurs for the exactly chiral lattice fermions, the simulation is confined in a fixed topological sector. It induces finite volume effect, which is well described by a formula based on the Fourier transform from the θ-vacua. We confirm this formula at finite temperature by calculating the topological susceptibility in the quenched theory. Our two flavor simulations show degeneracy of the meson correlators and a gap in the Dirac operator spectral density, which implies that the axial U (1) symmetry is effectively restored in the chirally symmetric phase.PACS numbers:

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Charge Rearrangement and Screening in a Quantum Point Contact

Cited by 40 publications

References 19 publications

Temperature modulation of the transmission barrier in quantum point contacts

Temperature modulation of the transmission barrier in quantum point contacts

Transconductance and effective Landé factors for quantum point contacts: Spin-orbit coupling and interaction effects

Finite temperature study of the axial U(1) symmetry on the lattice with overlap fermion formulation

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