Theory of single electron spin relaxation in Si/SiGe lateral coupled quantum dots

Abstract

We investigate the spin relaxation induced by acoustic phonons in the presence of spin-orbit interactions in single electron Si/SiGe lateral coupled quantum dots. The relaxation rates are computed numerically in single and double quantum dots, in in-plane and perpendicular magnetic fields. The deformation potential of acoustic phonons is taken into account for both transverse and longitudinal polarizations and their contributions to the total relaxation rate are discussed with respect to the dilatation and shear potential constants. We find that in single dots the spin relaxation rate scales approximately with the seventh power of the magnetic field, in line with a recent experiment. In double dots the relaxation rate is much more sensitive to the dot spectrum structure, as it is often dominated by a spin hot spot. The anisotropy of the spin-orbit interactions gives rise to easy passages, special directions of the magnetic field for which the relaxation is strongly suppressed. Quantitatively, the spin relaxation rates in Si are typically 2 orders of magnitude smaller than in GaAs due to the absence of the piezoelectric phonon potential and generally weaker spinorbit interactions.

Theory of spin relaxation in two-electron laterally coupled Si/SiGe quantum dots

“…34,35,50,53,54,[56][57][58][59][60][61][62][63][64][65][66][67] Our work completes these findings by a global, quantitative understanding of two-electron lateral silicon double quantum dots. We investigate the spin-orbit and hyperfine-induced relaxation rate as a function of interdot coupling, detuning, and the magnitude and orientation of the external magnetic field for zero and finite temperatures, and for natural and isotopically purified silicon.…”

Singlet-triplet relaxation in SiGe/Si/SiGe double quantum dots

“…[1][2][3][4] Recently, silicon QDs have attracted much attention due to their outstanding spin-related properties. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Specifically, the hyperfine interaction can be reduced by isotopic purification. 25 The Dresselhaus spinorbit coupling (SOC) 26 is absent thanks to the bulk-inversion symmetry, and the SOC induced by the interface-inversion asymmetry (IIA) is rather weak.…”

“…30,31 Nowadays, spin qubits in silicon single and double QDs have been actively investigated. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] In silicon single QDs, we have studied the singlet-triplet (ST) relaxation by explicitly including the electron-electron Coulomb interaction and the multivalley effect. Our results in the Voigt configuration agree quite well with the recent experiment by Xiao et al 16 Silicon double QDs, which have been proven very useful in exploiting the spin Coulomb blockade, 32 have also attracted much attention.…”

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

“…[36][37][38][39][40][41][42][43][44][45][46][47][48] Theoretical research on Si QDs has also evolved at a brisk pace. [49][50][51][52][53][54][55][56][57][58][59][60][61] Concomitantly, QDs in other group IV elements are being explored for QC: carbon, 62-67 including nitrogen-vacancy centers in diamond, 68 and Ge. 69 Group IV materials (C, Si, Ge) are notable for having equivalent conduction band minima known as valleys.…”