Spin-valley qubit in nanostructures of monolayer semiconductors: Optical control and hyperfine interaction

Abstract

We investigate the optical control possibilities of spin-valley qubit carried by single electrons localized in nanostructures of monolayer TMDs, including small quantum dots formed by lateral heterojunction and charged impurities. The quantum controls are discussed when the confinement induces valley hybridization and when the valley hybridization is absent. We show that the bulk valley and spin optical selection rules can be inherited in different forms in the two scenarios, both of which allow the definition of spin-valley qubit with desired optical controllability. We also investigate nuclear spin induced decoherence and quantum control of electron-nuclear spin entanglement via intervalley terms of the hyperfine interaction. Optically controlled two-qubit operations in a single quantum dot are discussed.

Discrete quantum dot like emitters in monolayer MoSe2: Spatial mapping, magneto-optics, and charge tuning

“…An open question is whether the QD like emitters inherit the valley selection rules. 5,6 Concerning spin manipulation, the reduced hyperfine interaction with the nuclear spin bath for states at the K-points (direct gap) as compared to electronic states in III-V semiconductor quantum dots will be an advantage. 4,6,52 The control of the emission properties of these quantum dot like emitters paves the way for further engineering of the light matter interaction in these atomically thin materials.…”

“…In a charge tunable sample, we record discrete jumps on the meV scale as charges are added to the emitter when changing the applied voltage. [4][5][6] The 2D host materials have the advantage of being cost efficient, with highly tunable properties 3,7 and optical access to the electron valley index in momentum space, 8,9 an additional degree of freedom compared to other solid state qubits in III-V quantum dots (QDs) or NV centres in diamond, for example. There are several approaches to achieve 3D quantum confinement, such as patterning TMD MLs, 10 chemically synthesized TMD nano-crystals, [11][12][13][14][15][16] and defect engineering.…”

Spin-degenerate regimes for single quantum dots in transition metal dichalcogenide monolayers

“…TMDCs are characterised by the chemical composition MX 2 , where M denotes the transition metal (Mo or W) and X denotes the chalcogenide (S or Se). The presence of a direct band gap and spin-valley coupling in a two-dimensional material allows for a number of interesting electronic, spintronic and valleytronic applications including room temperature quantum spin Hall insulators, optically pumped valley polarisation, long lived exciton spin polarisation and 2D quantum dots (QDs) [11][12][13][14][15][16] .…”

Interplay of valley polarization and dynamic nuclear polarization in 2D transition metal dichalcogenides

“…For our calculations, we include only the hyperfine interaction with the M atom, which is dominant, based on the combination of natural abundance and hyperfine strength 33 . Going beyond this approximation would only result in small quantitative corrections.…”

“…In TMDs, both the transition element M and the chalcogen X have stable elemental isotopes with nonzero nuclear spin, and therefore one expects interesting electron-nuclear spin dynamics to occur in these materials. Apart from the nuclear spins acting as a decoherence channel, the possibility of optical control of the electron-nuclear spin entanglement has also been pointed out recently in TMD-based quantum dot systems 33 . However, the (b) Hyperfine interaction causes nuclear spins to polarize, however at a much slower time scale.…”