Interplay of Electron and Nuclear Spin Noise inn-Type GaAs

Abstract

We present spin-noise spectroscopy measurements on an ensemble of donor-bound electrons in ultrapure GaAs:Si covering temporal dynamics over 6 orders of magnitude from milliseconds to nanoseconds. The spin-noise spectra detected at the donor-bound exciton transition show the multifaceted dynamical regime of the ubiquitous mutual electron and nuclear spin interaction typical for III-V-based semiconductor systems. The experiment distinctly reveals the finite Overhauser shift of an electron spin precession at zero external magnetic field and a second contribution around zero frequency stemming from the electron spin components parallel to the nuclear spin fluctuations. Moreover, at very low frequencies, features related with time-dependent nuclear spin fluctuations are clearly resolved making it possible to study the intricate nuclear spin dynamics at zero and low magnetic fields. The findings are in agreement with the developed model of electron and nuclear spin noise. DOI: 10.1103/PhysRevLett.115.176601 PACS numbers: 72.25.Rb, 72.70.+m, 78.47.db, 85.75.-d Harnessing coherence is one of the central topics in current research and attracts high interest due to the complex fundamental physics bridging quantum mechanics and statistics as well as due to prospective applications for information processing [1][2][3]. The solid state quantum states based upon the spin degree of freedom of confined carriers in semiconductors are at the forefront of many current research activities in this field. In this respect, optically addressable electron and hole spin quantum states in III-V-based semiconductor systems bear the beauty of efficient options for initialization, manipulation, and readout by light in combination with exceptional sample quality [4]. Currently, a promising system for these tasks are donorbound electrons in ultrahigh quality, very weakly n-doped GaAs since the widely spaced, quasi-isolated electrons act as an ensemble of identical, individually localized atoms [5,6]. However, the ostensible catch of this approach is the inherent interaction with the nuclear spin bath which has been addressed in many different systems so far [7][8][9][10][11].In principle, there are different approaches to deal with the decoherence imposed via the hyperfine interaction. On the first sight, the most obvious way is to replace the isotopes carrying a nuclear spin with spinless isotopes like in 28 Si [12] but silicon has the drawback of an indirect gap. Direct semiconductors with spinless isotopes like, e.g., isotopically purified II-VI systems have yet the drawback of inferior sample quality. In single III-V-based quantum dots, the hyperfine interaction can be reduced by either moving on to hole spins which show a diminished hyperfine interaction [13][14][15] or by polarizing the nuclei in order to make them less effective [16,17]. Besides that, the mutual interaction between carrier and nuclear spins is also strain dependent and strongly varying coupling strengths in such nanostructures result in a row of widely discussed pr...

Longitudinal spin relaxation of donor-bound electrons in direct band-gap semiconductors

“…Our result is consistent with prior works [19,20] and suggests additional, unknown mechanisms may be at play, such as an inhomogeneous donor distribution resulting in the formation of clusters with a relatively high donor density, and short τ c .…”

“…(4), we determine a correlation time τ c ≈ 25 ns for the GaAs-2 sample. Such a value of the correlation time is consistent with previous studies of GaAs samples with similar donor densities [19,20]. A somewhat longer τ c of ∼ 40 ns is determined for the InP-2 sample, where the hyperfine interaction is dominated by 115 In isotopes with I In = 9/2.…”

“…In this situation, spin precession is randomized due to the finite electron correlation time at each donor site [18,19]. Although the mechanism for the extremely-short correlation time τ c (τ c,GaAs 25 ns, τ c,InP 40 ns) is not completely clear, our measurement is consistent with prior works [19,20]. Our results show that the nuclear-spin environment, known to be the dominant factor in spin dephasing [2,12], plays an important role in longitudinal relaxation even at low doping densities (∼10 14 cm −3 ) and moderate magnetic fields (up to several tesla).…”

Electron g‐factor fluctuations in highly n‐doped GaAs at high temperatures detected by ultrafast spin noise spectroscopy

“…During the past decade the nearly perturbation free method of spin noise spectroscopy (SNS) has become a versatile and powerful tool for the investigation of the spin dynamics of a vast number of semiconductor systems. The applicability spans from spin coherence times of millisecond and microsecond of nuclear host spins and single holes in quantum dots over nanoseconds for the electron spin dynamics in quantum wells up to picoseconds for the very fast dynamics of free electron spins in high magnetic fields and at high temperatures . Extremely short spin dephasing times are measured by ultrafast spin noise spectroscopy (USNS) which has been proposed in 2008 and demonstrated experimentally recently .…”

“…The homogeneous and inhomogeneous spin dephasing rates yield together the effective total spin dephasing rate γ s which dependence on magnetic field and which can be well approximated by the inverse of 1 Elastic electron-electron scattering is neglected since the corresponding momentum scattering times are long compared to ionized impurity scattering and electron-plasmon scattering times, e.g., about 2 ns at 160 K [12] versus ≈100 fs. 2 The factor 1/ √ 2 has to be considered for a Gaussian g-factor distribution and a definition of T 2 after Pines and Slichter [18].…”