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Title: Exchange interaction between the triplet exciton and the localized spin in copper-phthalocyanine

Triplet excitonic state in the organic molecule may arise from a singlet excitation and the following inter-system crossing. Especially for a spin-bearing molecule, an exchange interaction between the triplet exciton and the original spin on the molecule can be expected. In this paper, such exchange interaction in copper-phthalocyanine (CuPc, spin-1/2 ) was investigated from first-principles by using density-functional theory within a variety of approximations to the exchange correlation, ranging from local-density approximation to long-range corrected hybrid-exchange functional. The magnitude of the computed exchange interaction is in the order of meV with the minimum value (1.5 meV, ferromagnetic) given by the long-range corrected hybrid-exchange functional CAM-B3LYP. This exchange interaction can therefore give rise to a spin coherence with an oscillation period in the order of picoseconds, which is much shorter than the triplet lifetime in CuPc (typically tens of nanoseconds). This implies that it might be possible to manipulate the localized spin on Cu experimentally using optical excitation and inter-system crossing well before the triplet state disappears.
Authors:
 [1]
  1. London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT (United Kingdom)
Publication Date:
OSTI Identifier:
22420112
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 97 MATHEMATICAL METHODS AND COMPUTING; APPROXIMATIONS; COPPER COMPLEXES; DENSITY FUNCTIONAL METHOD; EXCHANGE INTERACTIONS; EXCITATION; HYBRIDIZATION; MEV RANGE; MOLECULES; OSCILLATIONS; PHTHALOCYANINES; SPIN; TRIPLETS