Subgap Two-Photon States in Polycyclic Aromatic Hydrocarbons: Evidence for Strong Electron Correlations

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Aryanpour, K. ; Roberts, A. ; Sandhu, A. ; Rathore, R. ; Shukla, A. ; Mazumdar, S. (2013)
  • Related identifiers: doi: 10.1021/jp410793r
  • Subject: Condensed Matter - Strongly Correlated Electrons
    arxiv: Physics::Chemical Physics

Strong electron correlation effects in the photophysics of quasi-one-dimensional $\pi$-conjugated organic systems such as polyenes, polyacetylenes, polydiacetylenes, etc., have been extensively studied. Far less is known on correlation effects in two-dimensional $\pi$-conjugated systems. Here we present theoretical and experimental evidence for moderate repulsive electron-electron interactions in a number of finite polycyclic aromatic hydrocarbon molecules with $D_{6h}$ symmetry. We show that the excited state orderings in these molecules are reversed relative to that expected within one-electron and mean-field theories. Our results reflect similarities as well as differences in the role and magnitude of electron correlation effects in these two-dimensional molecules compared to those in polyenes.
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