Mapping of the energetically lowest exciton in bulk 1T-HfS2
Research output: Contribution to journal › Research article › Contributed › peer-review
Contributors
Abstract
By combining electron energy-loss spectroscopy and state-of-the-art computational methods, we were able to provide an extensive picture of the excitonic processes in 1T-HfS2. The results differ significantly from the properties of the more scrutinized group VI semiconducting transition metal dichalcogenides such as MoS2 and WSe2. The measurements revealed a parabolic exciton dispersion for finite momentum q parallel to the Gamma K direction which allowed the determination of the effective exciton mass. The dispersion decreases monotonically for momentum exchanges parallel to the Gamma M high symmetry line. To gain further insight into the excitation mechanisms, we solved the ab initio Bethe-Salpeter equation for the system. The results matched the experimental loss spectra closely, thereby confirming the excitonic nature of the observed transitions, and produced the momentum-dependent binding energies. The simulations also demonstrated that the excitonic transitions for q parallel to Gamma M occur exactly along that particular high symmetry line. For q parallel to Gamma K on the other hand, the excitations traverse the Brillouin zone crossing various high symmetry lines. A particular interesting aspect of our findings was that the calculation of the electron probability density revealed that the exciton assumes a six-pointed star-like shape along the real space crystal planes indicating a mixed Frenkel-Wannier character.
Details
Original language | English |
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Pages (from-to) | 155204-1 - 155204-9 |
Number of pages | 9 |
Journal | Physical Review B |
Volume | 98 |
Issue number | 15 |
Publication status | Published - 11 Oct 2018 |
Peer-reviewed | Yes |
External IDs
Scopus | 85054876586 |
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Keywords
Keywords
- Transition-metal dichalcogenides, Electron-energy-loss, Transmission spectra, Optical-transitions, Loss spectroscopy, Group-iva, Photoemission, Monolayer, Zirconium, Titanium