Exciton spectrum in two-dimensional transition metal dichalcogenides: The role of Diracness

33rd International Conference on the Physics of Semiconductors

Trushin, Maxim^1 ; Goerbig, Mark Oliver^2 ; Belzig, Wolfgang^1

University of Konstanz, Fachbereich Physik, Konstanz

D-78457, Germany^1

Laboratoire de Physique des Solides, Univ. Paris-Sud, Universit e Paris-Saclay, CNRS, UMR 8502, Orsay

F-91405, France^2

关键词: Ab initio calculations;    Coulomb attraction;    Dirac equations;    Electron hole pairs;    Exciton spectra;    Quantum mechanical;    Spectroscopic measurements;    Transition metal dichalcogenides;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/864/1/012033/pdf
DOI  :  10.1088/1742-6596/864/1/012033

来源: IOP

【 摘 要 】

The physics of excitons, electron-hole pairs that are bound together by their mutual Coulomb attraction, can to great extent be understood in the framework of the quantum-mechanical hydrogen model. This model has recently been challenged by spectroscopic measurements on two-dimensional transition-metal dichalchogenides that unveil strong deviations from a hydrogenic spectrum. Here, we show that this deviation is due to the particular relativistic character of electrons in this class of materials. Indeed, their electrons are no longer described in terms of a Schrödinger but a massive Dirac equation that intimately links electrons to holes. Dirac excitons therefore inherit a relativistic quantum spin-1/2 that contributes to the angular momentum and thus the exciton spectrum. Most saliently, the level spacing is strongly reduced as compared to the hydrogen model, in agreement with spectroscopic measurements and ab-initio calculations.