Bulg. J. Phys. vol.40 no.2 (2013), pp. 165-175



Excitonic and Vibronic Spectra in 2D Molecular Quadratic Lattice

I.J. Lalov, I. Zhelyazkov
Faculty of Physics, University of Sofia, 1164 Sofia, Bulgaria
Abstract. In this paper, we consider a model of 2D molecular crystal of square symmetry with one molecule per unit cell. Results of the studies of the linear absorption in excitonic and vibronic spectra have been summarized for the following cases: (a) charge-transfer excitons (CTEs) in quadratic lattice; (b) Frenkel excitons (FEs) in that lattice; (c) coupled CTEs and FEs in quadratic lattice. The impact of the anisotropy inside the lattice plane and perpendicular to it on the linear absorption is analytically calculated and numerically simulated. The linear absorption spectra strongly depend upon transition dipole moments of Frenkel and charge-transfer excitons and also on the availability of one-particle and many-particle exciton–phonon states. 2D Van Hove singularities in the excitonic density of states occur in the present model.

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