Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 75: Ultrafast Electron and Spin Dynamics

O 75.6: Vortrag

Mittwoch, 22. März 2017, 16:15–16:30, TRE Phy

Spin and Valley Dynamics of Free Carriers in Epitaxial Single-Layer WS₂ — •Antonija Grubisic-Cabo¹, Soren Ulstrup², Deepnarayan Biswas³, Jonathon M. Riley³, Maciej Dendzik¹, Charlotte E. Sanders¹, Marco Bianchi¹, Cephise Cacho⁴, Dan Matselyukh⁴, Richard T. Chapman⁴, Emma Springate⁴, Phil D. C. King³, Jill A. Miwa¹, and Philip Hofmann¹ — ¹Aarhus University, DK — ²ALS Berkeley, USA — ³University of St. Andrews, UK — ⁴CLF, STFC Rutherford Appleton Laboratory, UK

The semiconducting single-layer (SL) transitional metal dichalcogenides (TMDCs) have been identified as ideal materials for accessing and manipulating spin- and valley-degrees of freedom. The current understanding of the valley properties and excited carrier dynamics relies largely on a photoluminescence and differential absorption measurements. Since excitons dominate the optical response of SL TMDCs, studies of free carriers can only be made indirectly. Here, we use time-resolved ARPES to directly measure free carriers in epitaxial SL WS₂ grown on Ag(111). We observe that the optically generated free carrier density in a single valley can be increased by a factor of 2 using circularly polarized light. Moreover, by varying the photon energy of the excitation, we can tune the free carrier density in a given spin-split band. This allows us to selectively excite free electron-hole pairs with a given spin and within a single valley.