Nuclear polarization in quantum point contacts in an in-plane magnetic field

Ren, Yuan; Yu, Wing Wa; Frolov, Sergey; Folk, J. A.; Wegscheider, Werner

doi:10.1103/physrevb.81.125330

Cited by 9 publications

(14 citation statements)

References 27 publications

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“…The value of dI/dV sd increases continuously over a period of 150 s. The long time required to change dI/dV sd in Fig. 3(a) is in accordance with the typical time scale for building up a DNP in GaAs [10][11][12][13][14][15][16][17] , suggesting the occurrence of the DNP in the present QD.…”

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confidence: 81%

Resistive detection of nuclear spins in a single quantum dot under Kondo effect regime

et al. 2013

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We study dynamic polarization and resistive detection of nuclear spins in a semiconductor quantum dot (QD) under the Kondo effect regime. We find that the differential conductance spectra of the QD exhibit hysteresis under the Kondo effect regime in magnetic fields. Relevance of nuclear spins to the hysteresis is confirmed by the detection of nuclear magnetic resonance signals by monitoring the differential conductance. We attribute the origin of the hysteresis to the dynamic nuclear spin polarization (DNP) induced in the QD. Using the DNP, we demonstrate nuclear spin relaxation rate measurements in the QD under the Kondo effect regime.PACS numbers: 73.63. Kv, 72.10.Fk, The Kondo effect, arising from the interaction between a localized spin and itinerant spins at the Fermi energy, is one of the most fundamental many-body phenomena observed in semiconductor quantum dot (QD) systems 1-4 . The differential conductance (dI/dV sd ) spectrum of the QD exhibits a sharp zero-bias conductance peak (ZBCP), which reflects the Kondo resonance at the Fermi energy. In the presence of an external magnetic field B, the energy for the Kondo resonance shifts away from the Fermi energy by ±|g * |µ B B due to the Zeeman splitting of the electronic state in the QD 1 , where g * is the effective gfactor for electrons and µ B is the Bohr magneton. Consequently, the dI/dV sd spectrum splits into two peaks at finite bias voltages. The peak-to-peak voltage V p−p , defined as the difference in the bias voltage between the split differential conductance peaks, is given by twice the Zeeman energyBecause an electron spin S in a semiconductor device can interact with a nuclear spin I of the host material through the contact hyperfine interaction H hyp = A I · S = A(I + S − + I − S + )/2 + AI z S z , where A is the hyperfine coupling constant, a dynamic nuclear spin polarization (DNP) can be build by driving electron spins using optical or electrical means 5,6 . The polarized nuclear spins modify the Zeeman energy for electrons through an effective magnetic field B N = A I z /g * µ B [ Fig. 1(a)]. In a QD under the Kondo effect regime, the modification of the Zeeman energy is expected to change the peakto-peak voltage V p−p between the split dI/dV sd peaks to V p−p = 2|g * |µ B (B + B N )/e, as shown schematically in Fig. 1(b). Therefore a small change in the nuclear spin polarization can be sensitively detected by measuring the dI/dV sd spectrum. However, to the best of our knowledge, effects of nuclear spins on transport properties of a QD under the Kondo effect regime have not been addressed experimentally. In addition, establishment of a novel technique for the resistive detection of nuclear spins has a potential to open a way for studying electron spin Schematic of differential conductance spectra in a QD under the Kondo effect regime. Application of an external magnetic field B causes the splitting of the dI/dV sd spectrum. The peak-to-peak voltage between the split dI/dV sd peaks is further modified by BN.properties in a QD through nucl...

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confidence: 81%

Resistive detection of nuclear spins in a single quantum dot under Kondo effect regime

et al. 2013

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“…However, it is an experimentally well established fact that the electrons are dominant in providing the dissipation channel for nuclear spins. Namely, the nuclear spin order can be maintained over hours or days if the hyperfine interaction is absent, even at room temperature [68][69][70]. Therefore, spin polarization of electrons will have strong influence on dynamics of the nuclear order.…”

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confidence: 99%

Helical nuclear spin order in a strip of stripes in the quantum Hall regime

et al. 2014

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We investigate nuclear spin effects in a two-dimensional electron gas in the quantum Hall regime modeled by a weakly coupled array of interacting quantum wires. We show that the presence of hyperfine interaction between electron and nuclear spins in such wires can induce a phase transition, ordering electrons and nuclear spins into a helix in each wire. Electron-electron interaction effects, pronounced within the one-dimensional stripes, boost the transition temperature up to tens to hundreds of millikelvins in GaAs. We predict specific experimental signatures of the existence of nuclear spin order, for instance for the resistivity of the system at transitions between different quantum Hall plateaus.

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“…Note that, in the presence of a large Zeeman splitting, electron spins may be injected with a high degree of polarization [17,18]. However, such magneticallyinduced spin injection is symmetric in the magnetic field B, and therefore does not lead to magnetic-fieldinversion asymmetry.…”

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Detection of spin injection into a double quantum dot: Violation of magnetic-field-inversion symmetry of nuclear polarization instabilities

Rudner

Rashba

2011

Phys. Rev. B

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In mesoscopic systems with spin-orbit coupling, spin-injection into quantum dots at zero magnetic field is expected under a wide range of conditions. However, up to now, a viable approach for experimentally identifying such injection has been lacking. We show that electron spin injection into a spin-blockaded double quantum dot is dramatically manifested in the breaking of magneticfield-inversion symmetry of nuclear polarization instabilities. Over a wide range of parameters, the asymmetry between positive and negative instability fields is extremely sensitive to the injected electron spin polarization and allows for the detection of even very weak spin injection. This phenomenon may be used to investigate the mechanisms of spin transport, and may hold implications for spin-based information processing. arXiv:1011.2247v1 [cond-mat.mes-hall]

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Nuclear polarization in quantum point contacts in an in-plane magnetic field

Cited by 9 publications

References 27 publications

Resistive detection of nuclear spins in a single quantum dot under Kondo effect regime

Resistive detection of nuclear spins in a single quantum dot under Kondo effect regime

Helical nuclear spin order in a strip of stripes in the quantum Hall regime

Detection of spin injection into a double quantum dot: Violation of magnetic-field-inversion symmetry of nuclear polarization instabilities

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