Mapping of the energetically lowest exciton in bulk 1T-HfS2

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Carsten Habenicht - , Leibniz Institute for Solid State and Materials Research Dresden (First author)
  • Lorenzo Sponza - , Université Paris-Saclay (Author)
  • Roman Schuster - , Leibniz Institute for Solid State and Materials Research Dresden (Author)
  • Martin Knupfer - , Leibniz Institute for Solid State and Materials Research Dresden (Author)
  • Bernd Büchner - , Chair of Experimental Solid State Physics, Center for Transport and Devices of Emergent Materials (CTD), Leibniz Institute for Solid State and Materials Research Dresden (Last author)

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 languageEnglish
Pages (from-to) 155204-1 - 155204-9
Number of pages9
JournalPhysical Review B
Volume98
Issue number15
Publication statusPublished - 11 Oct 2018
Peer-reviewedYes

External IDs

Scopus 85054876586

Keywords

Keywords

  • Transition-metal dichalcogenides, Electron-energy-loss, Transmission spectra, Optical-transitions, Loss spectroscopy, Group-iva, Photoemission, Monolayer, Zirconium, Titanium