Title |
Trion fine structure and coupled spin–valley dynamics in monolayer tungsten disulfide
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Published in |
Nature Communications, September 2016
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DOI | 10.1038/ncomms12715 |
Pubmed ID | |
Authors |
Gerd Plechinger, Philipp Nagler, Ashish Arora, Robert Schmidt, Alexey Chernikov, Andrés Granados del Águila, Peter C.M. Christianen, Rudolf Bratschitsch, Christian Schüller, Tobias Korn |
Abstract |
Monolayer transition-metal dichalcogenides have recently emerged as possible candidates for valleytronic applications, as the spin and valley pseudospin are directly coupled and stabilized by a large spin splitting. The optical properties of these two-dimensional crystals are dominated by tightly bound electron-hole pairs (excitons) and more complex quasiparticles such as charged excitons (trions). Here we investigate monolayer WS2 samples via photoluminescence and time-resolved Kerr rotation. In photoluminescence and in energy-dependent Kerr rotation measurements, we are able to resolve two different trion states, which we interpret as intravalley and intervalley trions. Using time-resolved Kerr rotation, we observe a rapid initial valley polarization decay for the A exciton and the trion states. Subsequently, we observe a crossover towards exciton-exciton interaction-related dynamics, consistent with the formation and decay of optically dark A excitons. By contrast, resonant excitation of the B exciton transition leads to a very slow decay of the Kerr signal. |
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