Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 57: Focus Session: Many-body effects in two-dimensional materials

O 57.8: Talk

Wednesday, March 9, 2016, 12:30–12:45, H16

Influence of the spin-orbit splitting on the coupled spin-valley-dynamics in monolayer transition metal dichalcogenides — •Gerd Plechinger, Philipp Nagler, Sven Gelfert, Christian Schüller, and Tobias Korn — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg

Single layers of transition metal dichalcogenides (TMDCs) like MoS₂ and WS₂ can be produced by simple mechanical exfoliation. Offering a direct bandgap at the K-points in the Brillouin zone, they represent promising semiconductor materials for flexible and transparent optoelectronic applications. Due to inversion symmetry breaking together with strong spin-orbit-interaction, the valley and spin degrees of freedom are coupled in monolayer TMDCs. Via circularly polarized optical excitation, an efficient polarization of the K⁺ or the K⁻ valley can be generated. Here, we investigate the dynamics of these coupled spin-valley polarizations in monolayer MoS₂ and WS₂ by means of photoluminescence spectroscopy and time-resolved Kerr rotation (TRKR). The results indicate a maximum achievable spin-valley-lifetime in these materials exceeding one nanosecond at low temperatures. Furthermore, we extract the dependence of the spin-valley lifetime on temperature. By varying the excitation energy, we reveal the excitonic resonances as well as the spin-polarized bandstructure around the K valleys common to monolayer TMDCs.