Abstract
Single spins localized in semiconductor nanostructures have been consideredas carriers of qubits in quantum computing and quantum spintronics.Recently, monolayer transition metal dichalcogenides (TMDs) have attracted vast interest as a new class of two-dimensional (2D) semiconductors with extraordinary properties including the direct band gap, the strong spin-orbit coupling, and the additional valley degree of freedom for localized electrons (holes).
In this talk, we investigate the possibility of realizing optically controllable spin-valley qubit carried by single localized electrons in monolayer TMDs nanostructures, including small quantum dots and impurity systems. We propose schemes of optical quantum controls for two scenarios: (a) in presence of valley hybridization caused by the confinement; (b) in the absence of valley hybridization. With lattice nuclear spins being the ultimate environment for spin qubit at low temperature, we have also investigated the hyperfine interplay with nuclear spins. The forms of hyperfine interaction between the electron and hole with the lattice nuclear spins are derived in the envelope function approximation. We analyze the symmetry properties of the hyperfine interaction between electron (hole) and nuclear spins in monolayer TMDs nanostructures and numerically estimate the hyperfine interaction strength by using band edge Bloch functions obtained from: (a) the Rothaan-Hatree-Fock atomic orbitals; (b) first principle Abinit all electron wavefunction calculation. We also investigate the feedback control schemes of the nuclear field for the spin-valley qubit in monolayer TMDs quantum dots. A negative feedback control process of the nuclear field is found to suppress the statistical fluctuation of the nuclear configurations. The positive feedback scheme is also discussed and we give the critical conditions for these two feedback scenarios.