2020/05/28 by Lorenz Maximilian Schneider, Shanece Esdaille, Schneider, Lorenz Maximilian +9
Engineering · Materials Science · Physics and Astronomy · #2D Materials and Applications #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Molecular Junctions and Nanostructures #Semiconductor Quantum Structures and Devices #Strong Light-Matter Interactions
paper · pdf · doi:10.48550/arxiv.2005.13900
openalex publication_date 2020/05/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Several theoretical predictions have claimed that the neutral exciton of\nTMDCs splits into a transversal and longitudinal exciton branch, with the\nlongitudinal one, which is the upper branch, exhibiting an extraordinary strong\ndispersion in the meV range within the light cone. Historically, this was\nlinked for semiconductor quantum wells to strong far-field optical dipole\ncoupling, or strong electronic long-range exchange interactions, describing two\nsides of the same coin. Recently, experiments utilizing Fourier-space\nspectroscopy have shown that the exciton (exciton-polariton) dispersion can\nindeed be measured for high-quality hexagonal-BN-encapsulated WSe2 monolayer\nsamples and can confirm the energy scale. Here, the exciton fine-structure's\npseudo-spin and the valley polarization are investigated as a function of the\ncentre-of-mass-momentum and excitation-laser detuning. For quasi-resonant\nexcitation, a strong dispersion featuring a pronounced momentum-dependent\nhelicity is observed. By increasing the excitation energy step-wise towards and\nthen above the electronic band gap, the dispersion and the helicity\nsystematically decrease due to contributions of incoherent excitons and\nemission from plasma. The decline of the helicity with centre-of-mass momentum\ncan be phenomenologically modelled by the Maialle-Silva-Sham mechanism using\nthe exciton splitting as the source of an effective magnetic field.\n