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Optical spin control and coherence properties of acceptor bound holes in strained GaAs

Xiayu Linpeng, Todd Karin, Mikhail V. Durnev, Mikhail M. Glazov, Rüdiger Schott, Andreas D. Wieck, Arne Ludwig, and Kai-Mei C. Fu
Phys. Rev. B 103, 115412 – Published 8 March 2021
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  • INTRODUCTION
  • SAMPLE DESCRIPTION AND EXPERIMENTAL…
  • INDUCED STRAIN AND PHOTOLUMINESCENCE…
  • OPTICAL PUMPING AND T1 MEASUREMENT
  • COHERENT POPULATION TRAPPING AND THE…
  • THEORY OF THE HEAVY-HOLE LONGITUDINAL…
  • CONCLUSION
  • ACKNOWLEDGMENTS
  • APPENDICES
    • References

    Abstract

    Hole spins in semiconductors are a potential qubit alternative to electron spins. In nuclear-spin-rich host crystals like GaAs, the hyperfine interaction of hole spins with nuclei is considerably weaker than that for electrons, leading to potentially longer dephasing times. Here we demonstrate optical pumping and coherent population trapping for acceptor-bound holes in a strained GaAs epitaxial layer. We find μs-scale longitudinal spin relaxation time T1 and an inhomogeneous dephasing time T2* of ∼7 ns. We attribute the spin relaxation mechanism to the combined effect of a hole-phonon interaction through the deformation potentials, and heavy-hole–light-hole mixing in an in-plane magnetic field. We attribute the short T2* to g-factor broadening due to strain inhomogeneity. T1 and T2* are calculated based on these mechanisms and compared with the experimental results. While the hyperfine-mediated decoherence is mitigated, our results highlight the important contribution of strain to relaxation and dephasing of acceptor-bound hole spins.

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    • Received 15 December 2020
    • Revised 20 February 2021
    • Accepted 22 February 2021

    DOI:https://doi.org/10.1103/PhysRevB.103.115412

    ©2021 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Spin coherenceSpin relaxation
    1. Physical Systems
    III-V semiconductors
    1. Properties
    Spin
    Condensed Matter, Materials & Applied PhysicsQuantum Information, Science & Technology

    Authors & Affiliations

    Xiayu Linpeng1, Todd Karin2, Mikhail V. Durnev3, Mikhail M. Glazov3,4, Rüdiger Schott5, Andreas D. Wieck5, Arne Ludwig5, and Kai-Mei C. Fu1,6

    • 1Department of Physics, University of Washington, Seattle, Washington 98195, USA
    • 2Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
    • 3Ioffe Institute, 194021 St.-Petersburg, Russia
    • 4Spin Optics Laboratory, Saint Petersburg State University, 198504 St. Petersburg, Russia
    • 5Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44870 Bochum, Germany
    • 6Department of Electrical Engineering, University of Washington, Seattle, Washington 98195, USA

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    Issue

    Vol. 103, Iss. 11 — 15 March 2021

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    Images

    • Figure 1
      Figure 1

      (a) Optical microscope image of the GaAs epitaxial layer transferred to the MgO substrate. (b) PL spectra of the GaAs epitaxial layer before and after the ELO process at 1.5 K and 0 T. Excitation at 1.653 eV with 80 nW power. The laser spot diameter is ∼1μm. The inset shows the illustrated model of the acceptor systems and how the energies of A0 and A0X change with strain. In the illustrated diagram, “A” denotes the acceptor center, “h” denotes hole, and “e” denotes electron. (c) Single-laser and two-laser PLE spectra at 1.5 K and 4.77 T. The single-laser PLE spectrum is taken by scanning a laser across all four transitions and collecting the signal from two-hole transitions (THT). A typical THT spectrum is shown in Appendix pp2. The two-laser PLE spectrum is taken with a second laser fixed at the energy of transition 1. Δf is the detuning of the scanning laser with respect to the energy of transition 1. We have used background subtraction on both the single-laser and two-laser PLE spectra, where we use the PLE intensity at large Δf as the background. All lasers are at 1 µW power and 45∘ polarization. The laser spot diameter is ∼1μm. The inset shows the energy structure of the acceptor system. Transitions 1 and 4 (2 and 3) are polarized in the horizontal (vertical) direction.

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    • Figure 2
      Figure 2

      (a) An optical pumping curve at 1.5 K and 1.9 T. The frequency of the laser is set on resonance with transition 1, and the laser power is 45 nW. The PL from transition 2 is collected with a single photon counting module. The laser spot diameter is ∼1μm. The insets show the energy diagram and the laser sequence. The detection is on all the time during the laser sequence. (b) A population recovery curve at 1.5 K and 1.9 T. The energy of the laser and detection are the same as in (a). A single exponential curve is used to fit for the T1. T1=0.51±0.04μs for these data. The inset shows the laser sequence. The detection window is 0.8μs. (c) T1 as a function of the magnetic fields. Different colors represent different locations on the sample. The dashed line shows the curve from theoretical calculation, Eq. (12).

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    • Figure 3
      Figure 3

      (a) Energy diagram of the CPT experiment. The frequency of the control laser is fixed at transition 1 and the frequency of the probe laser is scanned across transition 2. (b) CPT with different probe laser power. Each curve is a two-laser PLE spectrum where Δf is the detuning of the probe laser compared to the energy of transition 2. The solid curves are from a simultaneous fit of the data at all different probe laser powers using the three-level density matrix model. The frequency of the control laser is fixed at transition 1 with a slight detuning of about 0.2 GHz, and the power is 3 µW. The polarization of both lasers is set at 45∘. The laser spot diameter is ∼1μm. The temperature is 1.5 K and the magnetic field is 7 T. We note that we have used background subtraction on all CPT curves where we use the signal at large Δf as the background.

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    • Figure 4
      Figure 4

      (a) Spectrum of the n=2 and 3 THTs. The excitation is on resonance with the acceptor transition at 1.512 eV and the power is at 0.9 µW. The temperature is at 2 K and the magnetic field is at 0 T. (b) The corresponding spectrum of the main acceptor transitions. Excitation at 1.653 eV with 13 nW power. The laser has a spot size of ∼1μm. The spectra are taken in the sample before the ELO process.

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    • Figure 5
      Figure 5

      (a) Electron and hole Zeeman splitting as a function of the in-plane magnetic field. (b) PL spectra with horizontal and vertical polarization in collection. The magnetic field is at 7 T and the temperature is at 1.5 K. Excitation at 1.53 eV with 200 nW power. The electron and hole splittings are marked in the spectra.

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    • Figure 6
      Figure 6

      (a) Geometry of the experiment. x (H) is the horizontal direction (parallel to the magnetic field B⃗) and y (V) is the vertical direction (perpendicular to the magnetic field B⃗). ĉ is the direction of the optical axis, which is parallel to the [001] axis of the GaAs epilayer. (b) Energy diagram and selection rules of the acceptor system under magnetic fields.

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    • Figure 7
      Figure 7

      Energy diagram of the Λ system.

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