Spin-orbit coupled particle in a spin bath

We consider a spin-orbit coupled particle confined in a quantum dot in a bath of impurity spins. We investigate the consequences of spin-orbit coupling on the interactions that the particle mediates in the spin bath. We show that in the presence of spin-orbit coupling, the impurity-impurity interactions are no longer spin conserving. We quantify the degree of this symmetry breaking and show how it relates to the spin-orbit coupling strength. We identify several ways how the impurity ensemble can in this way relax its spin by coupling to phonons. A typical resulting relaxation rate for a self-assembled Mn-doped ZnTe quantum dot populated by a hole is 1 $\mu$s. We also show that decoherence arising from nuclear spins in lateral quantum dots is still removable by a spin echo protocol, even if the confined electron is spin-orbit coupled.

Figure 1

Effective interaction between impurities (encircled in red/gray) mediated by a confined particle (red/gray lines). (a) Electron is excited from the ground state of spin $+\frac{1}{2}$ into the closest spin-$\frac{1}{2}$ state (up by the Zeeman energy ${\Delta }_z$) upon flipping one of the impurities and deexcited back upon flipping another one. (b) Hole spectrum comprises heavy-hole- (hh) and light-hole- (lh) like states, the latter displaced by light-heavy–hole splitting ${\Delta }_{lh}$.