TitleGiant Spin-Splitting and Gap Renormalization Driven by Trions in Single-Layer WS2/H-Bn Heterostructures
Publication TypeJournal Article
Year of Publication2018
AuthorsKatoch J., Ulstrup S., Koch R.J, Moser S., McCreary K.M, Singh S., Xu J.S, Jonker B.T, Kawakami R.K, Bostwick A., Rotenberg E., Jozwiak C.
JournalNature Physics
Date Published04/2018

In two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs), new electronic phenomena such as tunable bandgaps(1-3) and strongly bound excitons and trions emerge from strong many-body effects(4-6), beyond the spin and valley degrees of freedom induced by spin-orbit coupling and by lattice symmetry(7). Combining single-layer TMDs with other 2D materials in van der Waals heterostructures offers an intriguing means of controlling the electronic properties through these many-body effects, by means of engineered interlayer interactions(8-10). Here, we use micro-focused angle-resolved photoemission spectroscopy (microARPES) and in situ surface doping to manipulate the electronic structure of single-layer WS2 on hexagonal boron nitride (WS2/h-BN). Upon electron doping, we observe an unexpected giant renormalization of the spin-orbit splitting of the single-layer WS2 valence band, from 430 meV to 660 meV, together with a bandgap reduction of at least 325 meV, attributed to the formation of trionic quasiparticles. These findings suggest that the electronic, spintronic and excitonic properties are widely tunable in 2D TMD/h-BN heterostructures, as these are intimately linked to the quasiparticle dynamics of the materials(11-13).