Affiliation
INSA Toulouse
Title
Control of the Exciton and Spin/Valley Properties in Transition Metal Dichalcogenide Monolayers
Abstract
Encapsulation of Transition Metal Dichalcogenides (TMD) monolayers in hexagonal Boron Nitride (hBN) yields narrow optical transitions approaching the homogeneous exciton linewidth [1-3]. The exciton radiative rate in these van der Waals heterostructures can be tailored by a simple change of the hBN encapsulation layer thickness as a consequence of the Purcell effect [4].
We also measured the exciton fine structure by magneto-photoluminescence spectroscopy in magnetic fields up to 30 T [5-6]. I will show that the bright-dark exciton splitting can be tuned by a few meV, as a result of a significant Lamb shift of the optically active exciton which arises from emission and absorption of virtual photons triggered by the vacuum fluctuations of the electromagnetic field [7].
Finally I will present recent experimental results on spin/valley pumping of resident electrons in WSe2 and WS2 monolayers [8]. Using a spatially-resolved optical pump-probe experiment, we measured the lateral transport of spin/valley polarized electrons over very long distances (tens of micrometers) [9]. These results highlight the key role played by the spin-valley locking effect in TMD monolayers on the pumping efficiency and the polarized electron transport.
[1] G. Wang et al, Rev. Mod. Phys. 90, 021001 (2018)
[2] F. Cadiz et al, Phys. Rev. X 7, 021026 (2017)
[3] G. Wang et al, Phys. Rev. Lett. 119, 047401 (2017)
[4] H. Fang et al, Phys. Rev. Lett. 123, 067401 (2019)
[5] C. Robert et al, Phys. Rev. Lett . 126, 067403 (2021)
[6] C. Robert et al, Nature Com. 11, 4037 (2020)
[7] L. Ren et al, Arxiv 2303.17880 (2023)
[8] C. Robert et al, Nature Com. 12, 5455 (2021)
[9] C. Robert et al, Phys. Rev. Lett. 129, 027402 (2022)