Two-phonon process and hyperfine interaction limiting slow hole-spin relaxation time in InAs/GaAs quantum dots

Fras, F.; Eblé, B.; Desfonds, Pascal; Bernardot, F.; Testelin, C.; Chamarro, Maria; Miard, A.; Lemaı̂tre, A.

doi:10.1103/physrevb.86.045306

Cited by 19 publications

(16 citation statements)

References 36 publications

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“…The large dispersion is partly attributed to the different relaxation mechanisms involved in different studies. When the energy splitting between orthogonal spin states is small, hyperfine interaction is the dominant relaxation channel [16,27]. In this case, the lifetime is strongly dependent on the degree of hh-lh mixing.…”

Section: Introductionmentioning

confidence: 99%

“…If the hole state is a pure hh, as in the ground state of flat (quasi-two-dimensional (2D)) QDs, the hyperfine interaction takes an Ising form and spin relaxation is slow, but it rapidly increases in non-flat QDs due to hh-lh mixing [1,7]. On the other hand, when the energy splitting exceeds the nuclear magnetic field, the valence band spin-orbit interaction (SOI) takes over as the main source of relaxation [16,27]. Long hole spin lifetimes have then been observed, reaching up to T h 1 ∼ 0.25 ms, which is only five to ten times shorter than electron spin lifetimes, T e 1 [26].…”

Section: Introductionmentioning

confidence: 99%

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Spin–orbit-induced hole spin relaxation in InAs and GaAs quantum dots

2013

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We study the effect of valence band spin-orbit interactions (SOI) on the acoustic phonon-assisted spin relaxation of holes confined in quantum dots (QDs). Heavy hole-light hole (hh-lh) mixing and all the spin-orbit terms arising from zinc-blende bulk inversion asymmetry (BIA) are considered on equal footing in a fully three-dimensional Hamiltonian. We show that hh-lh mixing and BIA have comparable contributions to the hole spin relaxation in self-assembled QDs, but BIA becomes dominant in gated QDs. Simultaneously accounting for both mechanisms is necessary for quantitatively correct results in quasi-two-dimensional QDs. The dependence of the hole spin relaxation on the QD geometry and spin splitting energy is drastically different from that of electrons, with a non-monotonic behavior which results from the interplay between SOI terms. Our results reconcile contradictory predictions of previous theoretical works and are consistent with experiments. For a qualitative understanding of the geometry dependence of 1/T h 1 , we rewrite the hole states, equation (14), as | h m = J z c m J z |φ m J z |3/2, J z , where |φ m J z = r c m J z ,r |r is the envelope function associated with the periodic Bloch function |3/2, J z . If we restrict to the diagonal components of H h-ph , the matrix element determining the relaxation rate becomes

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spin–orbit-induced hole spin relaxation in InAs and GaAs quantum dots

2013

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“…17 Moreover, this value is almost three times smaller than T h 1 obtained in the same sample at similar magnetic fields. 15 The hyperfine interaction has been identified at the origin of a dephasing time in the nanosecond range in the same sample. 9 In the microsecond range, the coherence time is probably limited by extra nuclear-induced processes 20 and/or impurities and an electrostatic environment of QDs.…”

Section: Hole Spin Mode Locking and Coherent Dynamics In A Largely Inmentioning

confidence: 97%

“…4,[8][9][10][11][12] Several studies have reported a long hole spin relaxation time T h 1 , from μs to ms, under different conditions of temperature and magnetic field. 1,[13][14][15][16] In early single-hole experiments of coherent population trapping, the hole spin coherence time was estimated to be larger than 100 ns. 17 In more recent experiments in time domain, the hole-spin coherence time has been found to be 20 ns, but these single hole-spin measurements were affected by electrical-noise 18,19 or nuclear-spin 20 fluctuations.…”

Section: Hole Spin Mode Locking and Coherent Dynamics In A Largely Inmentioning

confidence: 99%

Hole spin mode locking and coherent dynamics in a largely inhomogeneous ensemble ofp-doped InAs quantum dots

et al. 2012

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In this study, we evidence hole spin mode locking in a largely inhomogeneous p-doped InAs quantum dot (QD) ensemble, g h x /g h x ≈ 34%, which allows us to reveal a long spin coherence time of T h 2 ≈ 0.8 μs. In addition, with a two-pump experiment, we demonstrate, in a low magnetic range 60-120 mT, the possibility to synchronize and tune a single subset of QDs through the distribution. Experiments are supported by an analysis within the density matrix approach.The resident spin of a carrier confined in a quantum dot (QD) is a promising candidate for quantum information systems. Until recently, most theoretical and experimental studies have been centered on the electron spin, and have demonstrated that the ultimate limitation, at low temperature and zero magnetic field, is the hyperfine interaction of an electron with a nuclear-spin ensemble. Due to the limited number of QD nuclei interacting with the electron spin, on the order of 10 5 , random fluctuations of the nuclearspin bath lead to a dephasing time on the order of ns for InAs QDs. Recently, the initialization of hole spin has been demonstrated, 1-7 and it has emerged as a more attractive candidate, with a one-order-of-magnitude weaker hyperfine coupling. 4,[8][9][10][11][12] Several studies have reported a long hole spin relaxation time T h 1 , from μs to ms, under different conditions of temperature and magnetic field. 1,13-16 In early single-hole experiments of coherent population trapping, the hole spin coherence time was estimated to be larger than 100 ns. 17 In more recent experiments in time domain, the hole-spin coherence time has been found to be 20 ns, but these single hole-spin measurements were affected by electrical-noise 18,19 or nuclear-spin 20 fluctuations. Recent spin-echo experiments allow to circumvent the inhomogeneous decoherence and measure a much longer hole-spin coherence time T h 2 , in the microsecond range between 6 and 10 T. 18 This value is of the same order of magnitude as for electrons 21 and represents an upper bound on the free-induction decay time of hole spin coherence. 22 For electron spins, the possibility to go beyond the ensemble inhomogeneities and to measure a long coherence time by using a periodic train of circularly polarized pulses has been demonstrated. A single pulse creates an ensemble of electron spins along its propagation direction and perpendicular to an external magnetic field (Voigt geometry). Each electron spin precesses about the field and, due to the inhomogeneity of the precession frequencies, the phase coherence is quickly lost. The train of pulses allows the phase synchronization of subsets of the whole spin ensemble, for which the precession frequency is a multiple of the laser repetition rate. This effect was called "electron spin mode locking." 23,24 It has allowed the measurement of an electron spin coherence time of 600 ns at 2 T, 25 and 3 μs at 6 T, 23 in an ensemble of InGaAs QDs with a relative dispersion of the in-plane electron Landé factor g e x /g e x ≈ 1%.Holes are more sensitive than...

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“…In contrast to unstrained or uniformly strained systems, where the SO effects are characterized by usual Rashba [25] or Dresselhaus [26] couplings, in strained self-assembled QDs the situation is more complex and the SO effect that predominantly affects spin relaxation is induced by shear strain [27,28]. While the measured hole spin relaxation times vary from experiment to experiment, the observed upper limit seems to reach hundreds of microseconds [23,[29][30][31][32]. These hole spin life times are shorter than those for electrons because of the much stronger SO coupling in the valence band.…”

Section: Introductionmentioning

confidence: 99%

Spin–orbit-induced hole spin relaxation in a quantum dot molecule: the effect of s-p coupling

Kawa¹,

Machnikowski²

2019

J. Phys.: Condens. Matter

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We study the effect of the coupling between the hole s shell of one quantum dot and the p shell in the other dot forming a quantum dot molecule on the spin relaxation between the sublevels of the hole s state. Using an effective model that captures the spin-orbit effects in the p shell irrespective of their origin, we show that the strong spin mixing in the p shell can be transferred to the s shell of the other dot, leading to enhanced spin relaxation in a certain energy range around the s-p resonance if the dots are misaligned and the magnetic field is tilted from the sample plane. arXiv:1902.09161v1 [cond-mat.mes-hall]

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Two-phonon process and hyperfine interaction limiting slow hole-spin relaxation time in InAs/GaAs quantum dots

Cited by 19 publications

References 36 publications

Spin–orbit-induced hole spin relaxation in InAs and GaAs quantum dots

Spin–orbit-induced hole spin relaxation in InAs and GaAs quantum dots

Hole spin mode locking and coherent dynamics in a largely inhomogeneous ensemble ofp-doped InAs quantum dots

Spin–orbit-induced hole spin relaxation in a quantum dot molecule: the effect of s-p coupling

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