Optical saturation driven by exciton confinement in molecular chains: a time-dependent density-functional theory approach |
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Authors: | Varsano Daniele Marini Andrea Rubio Angel |
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Institution: | National Center on nanoStructures and Biosystems at Surfaces (S3) of INFM-CNR, Via Campi 231/A, 41100 Modena, Italy. |
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Abstract: | We identify excitonic confinement in one-dimensional molecular chains (i.e., polyacetylene and H2) as the main driving force for the saturation of the chain polarizability as a function of the number of molecular units. This conclusion is based on first principles time-dependent density-functional theory calculations using a recently developed exchange-correlation kernel that accounts for excitonic effects. The failure of simple local and semilocal functionals is shown to be linked to the lack of memory effects, spatial ultranonlocality, and self-interaction corrections. These effects get smaller as the gap reduces, in which case such simple approximations do perform better. |
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