Spin dephasing of doped electrons in charge-tunable InP quantum dots: Hanle-effect measurements

Abstract

The spin dephasing relaxation in single-electron-doped InP quantum dots was studied by means of Hanle measurements. When an InP quantum dot is doped with one electron on average, a narrow Lorentzian dip with half-width of 4.6 mT appeared and was superposed on two Lorentzians with half-widths of 1.54 and 128 mT in the Hanle curve. The half-widths 1.54 T, 128 mT, and 4.6 mT are ascribed to spin-dephasing relaxation of holes, electron-hole pairs, and doped electrons consistuting negative trions, respectively. The corresponding spin coherence time of the doped electrons at 5 K is 1.7 ns, which is determined by the frozen fluctuation of nuclear spins in the quantum dots. With increase of temperature, the spin-dephasing rate of the doped electrons increases.

Resonant spin orientation at the exciton level anticrossing in InP quantum dots

“…The decrease of the spin relaxation time s at the elevated temperature was reported in our preceding papers. 18,19 In longitudinal magnetic field ͑ =0°͒, bright excitons do not mix with dark excitons in the frame of the present spin Hamiltonian. Then, crossing does not give any change of the polarization on the theoretical model.…”

Nuclear-spin effects in singly negatively charged InP quantum dots

“…Negative circularly polarized PL Our measurements of polarization-resolved PL spectra under quasiresonant excitation (E x = 1.77 eV) of singly negatively charged InP QDs show that the degree of circular polarization ρ c is negative 5,6,19,20 in the spectral region 1.7-1.735 eV, for which ∆E = (E x − E d ) lies between 70-35 meV [ Fig. 1(inset)].…”

Optical initialization of hole spins inp-doped quantum dots: Orientation efficiency and loss of coherence

“…To compare it to other processes occurring in systems of this type one can use the only characteristics available, namely the total decrease of coherence and the duration of dephasing process which is equal to the laser pulse duration (here, sub-picosecond). Comparing the latter to timescales of other relevant processes occurring in discussed system, like the phonon-assisted 23,24 or hyperfine hole-nuclei coupling driven hole spin relaxation 25 , electron spin dephasing [26][27][28] or relaxation of the positive trion 29 (ranging from hundreds of picoseconds to a few microseconds), we find it to be at least three orders of magnitude shorter. This fact allows us to consider it separately and treat the dynamical spin dephasing as instantaneous on the background of the whole optical spin initialization process.…”