# Dresden 2014 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 88: Graphene-like materials: Silicene, MoS_{2} and relatives (with DY/MA/O/TT)

### HL 88.8: Vortrag

### Donnerstag, 3. April 2014, 12:00–12:15, POT 081

**Spin-orbit coupling, quantum dots, and qubits in transition metal dichalcogenides** — •Andor Kormanyos^{1}, Viktor Zolyomi^{2}, Neil Drummond^{2}, and Guido Burkard^{1} — ^{1}Universität Konstanz — ^{2}Lancaster University

We derive an effective Hamiltonian describing the dynamics of electrons in the conduction band of
transition metal dichalcogenides (TMDC) in the presence of perpendicular electric and magnetic fields.
We discuss both the intrinsic and Bychkov-Rashba spin-orbit coupling (SOC) induced by an external electric field.
We identify a new term in the Hamiltonian of the Bychkov-Rashba SOC which does not exist in III-V semiconductors.
We point out important differences in the spin-split conduction band between different TMDC compounds.
A significant consequence of the strong intrinsic SOC is an effective out-of-plane *g*-factor for the electrons
which differs from the free-electron *g*-factor *g*≃ 2. Using first-principles calculations, we give
estimates of the various parameters appearing in the theory. Finally, we consider quantum dots (QDs)
formed in TMDC materials and derive an effective Hamiltonian allowing us to calculate the magnetic
field dependence of the bound states in the QDs. We find that all states
are both valley and spin split, which suggests that these QDs could be used as valley-spin filters.
We explore the possibility of using spin and valley states in TMDCs as quantum bits, and conclude that,
due to the relatively strong intrinsic SOC in the conduction band, the most realistic option appears to be a
combined spin-valley (Kramers) qubit at low B fields.