Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 11: Transition-metal dichalcogenides and boron nitride (with O)

HL 11.3: Talk

Monday, March 16, 2015, 12:15–12:30, ER 270

Coupled spin-valley-dynamics in singlelayer transition metal dichalcogenides — •Gerd Plechinger, Nicola Paradiso, Philipp Nagler, Sven Gelfert, Christoph Strunk, Christian Schüller, and Tobias Korn — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany

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 a promising semiconductor material 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 singlelayer TMDCs. Via circularly polarized optical excitation, an efficient polarization of the K⁺ or the K⁻ valley can be generated. Here, we optically investigate the dynamics of these coupled spin-valley polarizations in singlelayer MoS₂ and singlelayer WS₂ by means of time-resolved Kerr rotation (TRKR) and display the dependence of the spin lifetime on the temperature and the excitation energy. Moreover, we probe the influence of mild annealing on the lifetimes.