Arabi Seshappan

UC Merced

“Optical excitation energies and spin studies of charged Co@S defect of WS2 computed with the spin-flip Bethe-Salpeter equation approach”

Defected transition metal dichalcogenides are exciting materials for quantum information science (QIS) applications as potential single photon emitters, quantum light sources, and room-temperature solid-state quantum bits (qubits). To fully understand the potential applications of these materials, it is important to understand the excitonic interactions within these materials. Monolayer cobalt-at-sulfur-site substituted WS2 (Co@S:WS2) has an open-shell electronic structure due to the spin of the cobalt atom, as found from our DFT calculations. While quasi-particle energies for open-shell systems have been calculated previously–and are known to have multiplet solutions–there is at present no similar approach available for the Bethe-Salpeter equation in open-shell systems. Instead, we investigate the vertical excitation energies through the Spin-Flip Bethe-Salpeter equation approach [arXiv:2207.04549], which allows for the simultaneous calculation of ground- and excited-state energies for multiconfigurational open-shell systems. In this work, I show a first-pass at calculating the optical excitation energies for Co@S:WS2 – the first time this method has been used to study 2D (atomically thin) materials.


Quantum Information Science (QIS) holds the promise to transform our world, revolutionizing fields from computing to communication—leading to a future of unparalleled technological possibilities. QIS could provide unbreakable encryption methods, making digital communication virtually impervious to hackers; it could supercharge computing, with quantum computers that could solve in seconds what would take conventional computers millennia; and it could even improve medical diagnostics, through quantum sensing as highly detailed and less invasive medical imaging techniques. In this poster, I describe computational investigation of a promising QIS candidate material.

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