Controlling valley splitting and polarization of dark- and bi-excitons in monolayer WS 2 by a tilted magnetic field
| Autor: | Railson Vasconcelos, Hao Zeng, Fujun Liu, Shijie Xie, Helena Bragança, Fanyao Qu |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Materials science
Exciton FOS: Physical sciences Astrophysics::Cosmology and Extragalactic Astrophysics 02 engineering and technology 01 natural sciences Mesoscale and Nanoscale Physics (cond-mat.mes-hall) 0103 physical sciences Monolayer General Materials Science 010306 general physics Biexciton Condensed Matter - Materials Science Condensed Matter - Mesoscale and Nanoscale Physics Condensed matter physics Condensed Matter::Other Mechanical Engineering Materials Science (cond-mat.mtrl-sci) General Chemistry Condensed Matter::Mesoscopic Systems and Quantum Hall Effect 021001 nanoscience & nanotechnology Condensed Matter Physics Polarization (waves) Magnetic field Mechanics of Materials 0210 nano-technology |
| Zdroj: | 2D Materials. 6:045014 |
| ISSN: | 2053-1583 |
| Popis: | We developed a comprehensive theoretical framework focusing on many-body effects of exciton species in monolayer WS$_2$, including bright and dark excitons, and intra- and inter-valley biexcitons, to investigate valley dynamics in monolayer WS$_2$ subjected to a tilted magnetic field B. In particular, the evolution of the exciton population densities and the many-body particle scatterings are considered to calculate the valley polarization (V P ) as a function of the magnetic field. We found valley splittings for the dark exciton and biexciton energy levels that are larger than those of bright excitons, of -0.23 meV/T. For example, -0.46 meV/T for dark excitons and -0.69 meV/T for bright-dark intra-valley biexcitons. Furthermore, inter-valley bright-dark excitons have an opposite valley energy splittings of +0.23 meV/T. For the samples pumped by linearly polarized light, V P exhibits distinct magnetic field dependence for different types of many-body particle states. Among them, the V P of the intra-valley bright-dark biexcitons increases with increasing magnetic field and reaches nearly 50% at B=65 T. The brightened dark exciton, on the other hand, exhibits vanishing VP, indicating long valley relaxation time. Remarkably, the inter-valley bright-dark biexciton shows unconventional behavior with an inverted VP. The opposite VP for intra- and inter-valley bright-dark biexcitons, coupled with their large valley splitting and long valley lifetime may facilitate their coherent manipulation for quantum computing. |
| Databáze: | OpenAIRE |
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