Two relaxation mechanisms observed in transport between spin-split edge states at high imbalance

Deviatov, E. V.; Würtz, A.; Lorke, Axel; Mel'nikov, M. Yu.; Dolgopolov, V. T.; Reuter, D.; Wieck, A. D.

doi:10.1103/physrevb.69.115330

Cited by 33 publications

(52 citation statements)

References 19 publications

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“…Here, HF-induced spin-flip transitions between the unidirectional edge states can create nuclear spin polarization locally at the boundary of the 2D sample. [54][55][56][57][58][59][60] Recently, we have predicted a similar phenomenon for a 2D TI, namely that embedded fixed spins such as the nuclear spins in a 2D TI can polarize locally at the boundary due to a current through the HESs. 61 Interestingly, the 2D TI with localized spins remains ballistic, 61,62 except if additional spin-flip mechanisms for the localized spins are present.…”

Section: Fig 1 (Color Online)mentioning

confidence: 72%

“…Nevertheless, other anisotropic HF interactions are present for P -like states such as the dipole-dipole-like HF interaction, [47][48][49][50][51] which can play a significant role, e.g., for the decoherence of a hole confined in a quantum dot. 47,48,51,52 HF interactions and dynamical nuclear spin polarization have also been investigated in the context of integer quantum Hall systems, [53][54][55][56][57][58][59][60] which contain unidirectional edge states. Here, HF-induced spin-flip transitions between the unidirectional edge states can create nuclear spin polarization locally at the boundary of the 2D sample.…”

Section: Fig 1 (Color Online)mentioning

confidence: 99%

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Hyperfine interactions in two-dimensional HgTe topological insulators

Lunde

Platero

2013

Phys. Rev. B

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We study the hyperfine interaction between the nuclear spins and the electrons in a HgTe quantum well, which is the prime experimentally realized example of a two-dimensional topological insulator. The hyperfine interaction is a naturally present, internal source of broken time-reversal symmetry from the point of view of the electrons. The HgTe quantum well is described by the so-called Bernevig-Hughes-Zhang (BHZ) model. The basis states of the BHZ model are combinations of both S-and P -like symmetry states, which means that three kinds of hyperfine interactions play a role: (i) the Fermi contact interaction, (ii) the dipole-dipole-like coupling, and (iii) the electron-orbital to nuclear-spin coupling. We provide benchmark results for the forms and magnitudes of these hyperfine interactions within the BHZ model, which give a good starting point for evaluating hyperfine interactions in any HgTe nanostructure. We apply our results to the helical edge states of a HgTe two-dimensional topological insulator and show how their total hyperfine interaction becomes anisotropic and dependent on the orientation of the sample edge within the plane. Moreover, for the helical edge states, the hyperfine interaction due to the P -like states can dominate over the S-like contribution in certain circumstances.

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Section: Fig 1 (Color Online)mentioning

confidence: 72%

Section: Fig 1 (Color Online)mentioning

confidence: 99%

Hyperfine interactions in two-dimensional HgTe topological insulators

Lunde

Platero

2013

Phys. Rev. B

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“…65 The Overhauser field is generally inhomogeneous and therefore often different in the two dots. DNP is also studied in optical [66][67][68][69][70][71][72][73][74][75] and quantum Hall [76][77][78][79][80][81][82][83][84][85][86] systems. It is important to emphasize that even though the HFinduced spin-relaxation do flip a nuclear spin, it will not always change the average nuclear polarization in the steady state of the SB regime.…”

Section: -63mentioning

confidence: 99%

Temperature-dependent dynamical nuclear polarization bistabilities in double quantum dots in the spin-blockade regime

et al. 2013

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The interplay of dynamical nuclear polarization (DNP) and leakage current through a double quantum dot in the spin-blockade regime is analyzed. A finite DNP is built up due to a competition between hyperfine (HF) spin-flip transitions and another inelastic escape mechanism from the triplets, which block transport. We focus on the temperature dependence of the DNP for zero energy-detuning (i.e. equal electrostatic energy of one electron in each dot and a singlet in the right dot). Our main result is the existence of a transition temperature, below which the DNP is bistable, so a hysteretic leakage current versus external magnetic field B appears. This is studied in two cases: (i) Close to the crossing of the three triplet energy levels near B = 0, where spin-blockade is lifted due to the inhomogeneity of the effective magnetic field from the nuclei. (ii) At higher B-fields, where the two spin-polarized triplets simultaneously cross two different singlet energy levels. We develop simplified models leading to different transition temperatures Tc,tt and Tc,st for the crossing of the triplet levels and the singlet-triplet level crossings, respectively. We find Tc,tt analytically to be given solely by the HF couplings, whereas Tc,st depends on various parameters and Tc,st > Tc,tt. The key idea behind the existence of the transition temperatures at zero energy-detuning is the suppression of energy absorption compared to emission in the inelastic HF transitions. Finally, by comparing the rate equation results with Monte Carlo simulations, we discuss the importance of having both HF interaction and another escape mechanism from the triplets to induce a finite DNP.

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“…The electron's spin flip is not necessary in this case, so the transfer process is partially coherent in two neighbor interaction regions. The interference paths are formed by transport across the edge 19,20,22 in the interaction regions and by the transport along the outer borders of the incompressible strips 25,26 between the interaction regions, see Fig. 1 (b) and Appendix.…”

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confidence: 99%

Interference effects in transport across a single incompressible strip at the edge of the fractional quantum Hall system

et al. 2009

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We experimentally investigate interference effects in transport across a single incompressible strip at the edge of the quantum Hall system by using a Fabry-Perot type interferometer. We find the interference oscillations in transport across the incompressible strips with local filling factors νc = 1, 4/3, 2/3 even at high imbalances, exceeding the spectral gaps. In contrast, there is no sign of the interference in transport across the principal Laughlin νc = 1/3 incompressible strip. This indicates, that even at fractional νc, the interference effects are caused by "normal" electrons. The oscillation's period is determined by the effective interferometer area, which is sensitive to the filling factors because of screening effects.

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Two relaxation mechanisms observed in transport between spin-split edge states at high imbalance

Cited by 33 publications

References 19 publications

Hyperfine interactions in two-dimensional HgTe topological insulators

Hyperfine interactions in two-dimensional HgTe topological insulators

Temperature-dependent dynamical nuclear polarization bistabilities in double quantum dots in the spin-blockade regime

Interference effects in transport across a single incompressible strip at the edge of the fractional quantum Hall system

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