Optical Switching of Charge Transmission through a Single Molecule: Effects of Contact Excitations and Molecule Heating

Photoinduced changes of the current voltage (IV) characteristics of a single molecule attached to a left and a right electrode are revisited including the inevitable photon absorption by the leads due to electron-hole pair generation. To determine the related nonequilibrium electron distribution, a method is Utilized based on the indtroduction of in effective electron temperature T-el in the Fermi distribution. By varying T-el, possible excitation conditions ill the experiments are modeled. Heating of the molecule is well as the effect of intramolecular vibrational energy redistribution (IVR) is also accounted for. An intermediate excitation regime call be identified where the Optical current switch is dominated by molecular excitations and less by an electron-hole pair generation in the leads. Vibrational distributions in the molecule induced due to either current formation or optical excitation are found to strongly deviate from thermal equilibrium. To observe the current switch, it is essential that these distributions are only slightly affected by IVR.