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| − | =Large Excitation Energy Transfer Dynamics in Nano-Hybrid Systems=
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| − | by Dirk Ziemann, Thomas Plehn and Volkhard May
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| − | Institut für Physik, Humboldt-Universität zu Berlin, Newtonstraße 15, D-12489 Berlin, Germany, EU
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| − | =Introduction=
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| − | Electronic excitation energy transfer (EET) represents an ubiquitous phenomenon in physical chemistry, nanophotonics, plasmonics and other disciplines of nanoscience.
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| − | It interrelates quantum system <math>1</math> with ground state <math>|1g\rangle</math> and excited state <math>|1e\rangle</math> to quantum system <math>2</math> with ground state <math>|\2\bar{g}\rangle</math> and excited state <math>|\2\bar{e}\rangle</math> via the energy exchange matrix element <math>V_{\rm EET}=\langle\2\bar{e}|\langle\1g|\hat{W}|\1e\rangle|\2\bar{g}\rangle</math>[11]. The complete Coulomb-interaction (electrostatic interaction) among the charges of system 1 and system 2 (electrons and nuclei) is denoted by <math>\hat{W}</math>. The formula assumes vanishing wave function overlap between both systems. Thus charge (particle) exchange contributions do not appear. Besides a sufficiently large <math>V_{\rm EET}</math> a further supposition for efficient EET is that the excitation energy <math>E_{1 e} - E_{1 g}</math> of the one system is comparable with the excitation energy <math>E_{2 \bar e} - E_{2 \bar g}</math> of the other system.We also emphasize that this type of EET can be understood as the short distance version of a general quantum electrodynamic photon exchange process (see, for example, [11]).
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| − | The variant of EET which refers to molecules is connected with the name of Förster. Respective rates display the famous <math>\frac{1}{R^{6}}}</math>-dependence (<math>R</math> denotes the intermolecular distance) since the coupling is dominated by molecular electronic transition point dipoles. If the charge distribution in the interacting species is more complex the <math>\frac{1}{R^{6}}}</math>-dependence of the rate undergoes drastic changes. This can be demonstrated, for example, by combining nano-systems of varying composition and shape [13, 14].
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| − | The coupling of molecules to differently shaped semiconductor nano-crystals (NCs) was of particular interest in this respect (c.f., for example,[4] - [10]). In contrast to the extended experimental work, theoretical studies describing molecule-NC EET with an atomistic resolution found less interest.
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| − | A dipyridyl porphyrin interacting with a Cd<math>_{33}</math> Te<math>_{33}</math> NC coated by a Zn<math>_{78}</math>S<math>_{78}</math> shell has been investigated in [7] using a DFT approach.
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