Inverted valley polarization in optically excited transition metal dichalcogenides

Berghäuser, Gunnar,1983Chalmers tekniska högskola,Chalmers University of Technology (författare)

Large spin-orbit coupling in combination with circular dichroism allows access to spin-polarized and valley-polarized states in a controlled way in transition metal dichalcogenides. The promising application in spin-valleytronics devices requires a thorough understanding of intervalley coupling mechanisms, which determine the lifetime of spin and valley polarizations. Here we present a joint theory-experiment study shedding light on the Dexter-like intervalley coupling. We reveal that this mechanism couples A and B excitonic states in different valleys, giving rise to an efficient intervalley transfer of coherent exciton populations. We demonstrate that the valley polarization vanishes and is even inverted for A excitons, when the B exciton is resonantly excited and vice versa. Our theoretical findings are supported by energy-resolved and valley-resolved pump-probe experiments and also provide an explanation for the recently measured up-conversion in photoluminescence. The gained insights might help to develop strategies to overcome the intrinsic limit for spin and valley polarizations.

Bernal, Ivan,1984Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)bivan (författare)
Schmidt, RobertWestfaelische Wilhelms-Universität Münster,University of Münster (författare)
Schneider, R.Westfaelische Wilhelms-Universität Münster,University of Münster (författare)
Niehues, IrisWestfaelische Wilhelms-Universität Münster,University of Münster (författare)
Erhart, Paul,1978Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)erhart (författare)
de Vasconcellos, S. M.Westfaelische Wilhelms-Universität Münster,University of Münster (författare)
Bratschitsch, R.Westfaelische Wilhelms-Universität Münster,University of Münster (författare)
Knorr, A.Technische Universität Berlin (författare)
Malic, Ermin,1980Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)ermin (författare)
Chalmers tekniska högskolaWestfaelische Wilhelms-Universität Münster (creator_code:org_t)

Ingår i:Nature Communications: Springer Science and Business Media LLC9:12041-17232041-1723

Av författaren/redakt...: Berghäuser, Gunn ...; Bernal, Ivan, 19 ...; Schmidt, Robert; Schneider, R.; Niehues, Iris; Erhart, Paul, 19 ...; visa fler...; de Vasconcellos, ...; Bratschitsch, R.; Knorr, A.; Malic, Ermin, 19 ...; visa färre...

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