Speakers
Description
Two-dimensional (2D) materials have the potential to revolutionize the quantum technology industry by enabling the development of quantum information devices [1]. Defect centers in wide-bandgap semiconductors, such as transition metal dichalcogenides (TMDs), have been proposed as quantum bits (qubits) [2] and have been shown to behave as single photon emitters (SPE) [3]. Advances in this field require a microscopic understanding of electron-electron and electron-ion interactions in TMDs with defects, which can be achieved through first-principles simulations. However, the computational cost associated with state-of-the-art ab initio codes for such large systems is prohibitive, leaving significant gaps in the understanding of the interaction between the exciton and the defect site.
We leverage the reduced electronic Wannierized space to build a tight-binding-like two-particle Hamiltonian where the Coulomb interaction can be taken either from first-principles (from codes such as Yambo [4,5]) or from a model potential [6]. This approach allows us to compute optical responses including excitonic effects of large systems [7], bypassing computational bottlenecks related to memory and time. We validate the methodology against a fully first-principles approach by computing the optical absorption of a WS₂ monolayer and exciton dispersion of LiF bulk. We demonstrate its scalability through a study of defective WS₂ systems. Future works include the theoretical development and implementation of a Wannierized electron-electron kernel for the BSE equation, enabling the study of excitonic interactions beyond the Tamm-Dancoff approximation [8].
References
[1] X. Liu and M. Hersam., “2D materials for quantum information science” Nature Reviews Materials, volume 4, pages 669–684 (2019).
[2] A. Srivastava et al., ”Optically active quantum dots in monolayer WSe2” Nature Nanotech, volume 10, pages 491–496 (2015).
[3] He, YM. et al., “Single quantum emitters in monolayer semiconductors”. Nature Nanotech, volume 10, pages 497–502 (2015).
[4] A. Marini et al., “An ab initio tool for excited state calculations” Computer Physics Commmunications, volume 180 (8), pages 1392-1403 (2009).
[5] D. Sangalli et al., “Many-body perturbation theory calculation using the Yambo code” Journal of Physics: Condensed Matter, volume 31, 325902 (2019).
[6] D. Alexandre C et al., “Wantibexos: A Wannier based tight binding code for electronic band structure, excitonic and optoelectronic properties of solids”. Computer Physics Communications, volume 285, (2023).
[7] H. Bethe and E. Salpeter, "A Relativistic Equation for Bound-State Problems". Physical review, volume 84 (6), pages 1232-1242 (1951).
[8] S. Hirata, M. Head-Gordon, “Time-dependent density functional theory within the Tamm–Dancoff approximation”, Chemical Physics Letters, Volume 314, Pages 291-299, (1999).