The spin–orbit splitting in monolayer transition-metal dichalcogenides is a key energy scale for spin and valley dynamics, the bright–dark exciton hierarchy, and spintronic applications. Its magnitude is controlled not only by atomic spin–orbit coupling, but also by Coulomb interactions and the microscopic orbital composition of the band edge. In monolayer MoS₂, this makes the splitting unusually sensitive to many-body and band-structure corrections: standard DFT calculations give only a few meV, whereas magnetotransport in high-mobility hBN-encapsulated devices indicates a substantially larger value.

This talk discusses how conduction-band spin–orbit splittings are renormalised in monolayer TMDs, using MoS₂ as a concrete benchmark. Magnetotransport provides the experimental context through the threshold density n* = 4.2 × 1012 cm−2 for occupation of the upper spin-orbit-split conduction band [2], which is far above the value expected from conventional DFT parameters. I will show that electron–electron exchange in the finite-density electron gas enhances the apparent spin–orbit splitting and explains roughly half of the difference [1].

The part of the conduction-band splitting not accounted for by exchange is traced to the microscopic orbital composition of the conduction-band edge. Refined DFT+U+V calculations modify the relevant metal–chalcogen hybridisation, with MoS₂ providing a clear example through the balance between sulphur p-orbital and molybdenum d-orbital contributions. Together, exchange renormalisation and the corrected band structure bring the calculated conduction-band spin–orbit splitting and related band-edge parameters into agreement with the observed density scale. The talk connects these interaction and hybridisation effects to the conduction-band spin–valley structure of monolayer TMDs, guided by magnetotransport measurements in monolayer MoS₂.

[1] I. Rozhansky and V. Fal’ko, Phys. Rev. B 110, L161404 (2024).

[2] I. Rozhansky, M. Masseroni, R. Pisoni, S. Alshammari, X. Li, T. Ihn, K. Ensslin, J. McHugh and V. Fal’ko, Nano Lett. 26, 5901–5908 (2026).