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Résumé |
Organic pi-conjugated polymers have been studied for many years in the context of optoelectronic
applications such as solar cells, LEDs and sensors, and remain a highly promising class of materials for
cheap, non-toxic and flexible light-matter coupling devices. Recently, on-surface synthesis techniques
have allowed novel quasi-1D molecular polymers to be fabricated whose electronic and optical properties
can be controlled via the connectivity and composition of the monomer units. For polymers based on
acene units, Cirera et al. have shown that varying the size of the acene unit causes the polymer band gap
to close and reopen, as the system passes from a trivial to a topologically non-trivial electronic phase [1].
In this talk, I will present our recent exploration of the behaviour of the strongly bound excitonic
excitations of acene polymers as they pass through this transition. Using self-consistent GW and Bethe
Salt-Peter techniques, we show that the presence of the topological transition and the related band
flattening and inversion lead to a range of rich, measureable and functionally exploitable properties of
singlet and triplet excitons, including negative dispersions and the possibility of spontaneous fission of
singlets into entangled triplet pairs.
[1] Cirera et al., Nature Nanotechnology, 15, 437–443 (2020)
Zoom link https://us06web.zoom.us/j/87504784241?pwd=eDJsSUpYU01tTGNieVlodUtHYllLQT09 |
