Abstract
We study the relaxation of a single electron spin in a circular quantum dot in a transition-metal dichalcogenide monolayer defined by electrostatic gating. Transition-metal dichalcogenides provide an interesting and promising arena for quantum dot nano-structures due to the combination of a band gap, spin-valley physics and strong spin–orbit coupling. First we will discuss which bound state solutions in different B-field regimes can be used as the basis for qubits states. We find that at low B-fields combined spin-valley Kramers qubits to be suitable, while at large magnetic fields pure spin or valley qubits can be envisioned. Then we present a discussion of the relaxation of a single electron spin mediated by electron–phonon interaction via various different relaxation channels. In the low B-field regime we consider the spin-valley Kramers qubits and include impurity mediated valley mixing which will arise in disordered quantum dots. Rashba spin–orbit admixture mechanisms allow for relaxation by in-plane phonons either via the deformation potential or by piezoelectric coupling, additionally direct spin-phonon mechanisms involving out-of-plane phonons give rise to relaxation. We find that the relaxation rates scale as B6 for both in-plane phonons coupling via deformation potential and the piezoelectric effect, while relaxation due to the direct spin-phonon coupling scales independant to B-field to lowest order but depends strongly on device mechanical tension. We will also discuss the relaxation mechanisms for pure spin or valley qubits formed in the large B-field regime.
Highlights
In recent years two-dimensional semiconductoring monolayers of transition-metal dichalcogenides (TMDs) have become the subject of immense study, due to their intriguing electronic and optical properties [1]
We find that the relaxation rates scale as ∝B6 for both in-plane phonons coupling via deformation potential and the piezoelectric effect, while relaxation due to the direct spin-phonon coupling scales independant to B-field to lowest order but depends strongly on device mechanical tension
We find that the relaxation due to phonons arising from both deformation potential and piezoelectric effect varies with the sixth power of the perpendicular magnetic field
Summary
In recent years two-dimensional semiconductoring monolayers of transition-metal dichalcogenides (TMDs) have become the subject of immense study, due to their intriguing electronic and optical properties [1] These atomically thin materials have a direct band gap in the optical frequency range [2] and a large spin– orbit coupling [3, 4]. Ates the situation in QDs, that the level spacing due to confinement is much smaller than the spin splitting EL Eso, in stark contrast to GaAs, Silicon and carbon nano-structures This combined with the valley physics opens up new regimes and opportunities for spin and valley qubits.
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