Hole spin relaxation in quantum dots

Abstract

We present results for relaxation of the spin of a hole in a cylindrical quantum dot due to acoustic phonon assisted spin flips at low temperatures with an applied magnetic field. The hole dispersion is calculated by numerical diagonalization of the Luttinger Hamiltonian and applying perturbation theory with respect to the magnetic field, and the hole-phonon coupling is described by the Bir-Pikus Hamiltonian. We find that the decoherence time for hole spins for dots Շ20 nm is on the order of 10 Ϫ8 s. This is several orders smaller than the decoherence time due to phonon assisted processes for electron spins in similar dots and is comparable to the total decoherence time of an electron spin in a quantum dot, which is controlled by the hyperfine interaction with nuclei. We obtain the dependence of the relaxation rate of the hole spin on dot size and hole mass.

Hole-spin initialization and relaxation times in InAs/GaAs quantum dots

“…We note that in the DTS technique we measure the PCD(13 ns), i.e., at a fixed time that is comparable to, or larger than, the hole-dephasing time T h , which is why DTS measurements give information, essentially, on the slow hole-spin dynamics, and they are very few affected by the fast initial hole-spin decay. Concerning slow dynamics, theoretical papers predict a nonexponential spin relaxation; 7,31,42 here the measured Fourier components are analyzed assuming an exponential decay, and in this sense our experiments give a characteristic time but do not give details of the complex relaxation of the hole spin.…”

“…That is why the electron spin relaxation and decoherence sources in QDs have been intensively studied in the last few years; some more limited number of studies have centered on the hole spin. The main conclusions of these studies are that in moderate magnetic fields (1-10 T) and at low temperature, the electron T e 1 and the hole T h 1 spin-relaxation times are governed by the same mechanism, i.e., the spin-orbitmediated single-phonon scattering, [4][5][6][7][8] which leads to relatively slow relaxation times in the range of milliseconds [9][10][11][12][13] with T h 1 five or ten times smaller than T e 1 . 12 However, the electron-and hole-spin coherence times T e,h 2 have been found to be in the microsecond range up to 15 K, [14][15][16][17] and for higher temperatures T e 2 has shown a sharp decrease 16 related to the modulation by phonons of the hyperfine (hf) interaction with the random fluctuating host nuclear spins.…”

Optical control over electron g factor and spin decoherence in (In,Ga)As∕GaAs quantum dots

“…Therefore, the hole spins do not precess and sh is enhanced up to several orders of magnitude. [13][14][15] The fact that the first minimum reaches nearly zero signal indicates that equal amounts of electron and hole spins are present in the system with comparable decay times. Apart from the coherent peak, the full time response can be well described by the following fitting function:…”

Origin of two-hole triplet splitting in circular quantum dots

“…[24] The suitability of positively charged trions is not clear a priori, as the valence band spin-orbit interaction can lead to significant hole spin mixing. [14,25,26] To address this question we calculate the expectation value of the hole spin in single-hole and two-hole states. The results are shown in Fig.…”