First-principles study of exchange-induced valley splitting in transition metal dichalcogenide monolayers
ORAL
Abstract
Monolayer transition metal dichalcogenides (TMDs) with spin-valley coupling are an emerging class of materials for valleytronics applications. Magnetic substrates have been shown to produce larger valley splitting than magnetic fields. In this work, we develop intuition for the physical mechanism driving valley splitting via magnetic substrates by performing first-principles density functional theory calculations for a series of Fe-decorated WSe2 and MoS2 monolayers. The valley splitting is computed as a function of different Fe heights above the TMD surface, different Fe alignment, and different Fe coverages. The non-Zeeman-like behavior of the valence band eigenvalues in the presence of variable magnetic atom position are rationalized using a magnetic impurity Hamiltonian, where the DFT trends in valley splitting can be recovered to second-order in the magnetic exchange coupling, a term that is strongly sensitive to TMD 4d/5d-Fe 3d orbital overlap. These computed trends are used to rationalize prior experiments involving magnetic exchange coupling-induced valley splitting, and are used to suggest new substrates to achieve large valley splitting.
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Presenters
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Elizabeth Peterson
Lawrence Berkeley National Laboratory
Authors
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Elizabeth Peterson
Lawrence Berkeley National Laboratory
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Jeffrey Neaton
Lawrence Berkeley National Laboratory, Physics, University of California at Berkeley, Physics, University of California, Berkeley, University of California, Berkeley; Lawrence Berkeley National Lab; Kavli Energy NanoScience Institute at Berkeley, Department of Physics, University of California Berkeley, University of California, Berkeley, Physics, University of California, Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Molecular Foundry, Lawrence Berkeley National Laboratory, University of California Berkeley