Speaker
Description
The interest in transition-metal dichalcogenides (TMDs) monolayers
as promising materials for opto-electronics has rapidly increased in the
last few years [1]. The majority of studies has been devoted so far to
group-VI TMDs, with MoS$_\mathrm{2}$ and WS$_\mathrm{2}$ as the most relevant examples
of this material class [1]. Here, we study monolayers of group-IV TMDs
focusing on ZrS$_\mathrm{2}$ and HfS$_\mathrm{2}$. We investigate their electronic and optical
properties in the framework of many-body perturbation theory (GW
and the Bethe-Salpeter equation) as implemented in the all-electron
full-potential code exciting [2]. The optical response of these systems
is characterized by intense peaks in the visible region due to tightlybound
excitons with binding energies of the order of hundreds of meV.
The degeneracy of the hole state at the Γ point with different dispersion
along the M-Γ-K direction and the strong spin-orbit coupling in the
valence band leads to several distinct excitonic states around Γ. Finally
we study van-der-Waals heterostructures obtained by combining ZrS$_\mathrm{2}$
and HfS$_\mathrm{2}$ monolayers in view of understanding how different stacking
patterns influence band alignment and optical excitations.
References
[1] K. F. Mak and J. Shan, Nat. Photon. 10, 216 (2016).
[2] A. Gulans et al., J. Phys.: Condens. Matter 26, 363202 (2014).
