Role of electronic structure in photoassisted transport through atomic-sized contacts

Departamento de F´isica Te´orica de la Materia Condensada,Universidad Aut´onoma de Madrid, E-28049 Madrid, Spain(Dated: February 6, 2008)We study theoretically quantum transport through laser-irradiated metallic atomic-sized contacts.The radiation field is treated classically, assuming its effect to be the generation of an ac voltageover the contact. We derive an expression for the dc current and compute the linear conductancein one-atom thick contacts as a function of the ac frequency, concentrating on the role played byelectronic structure. In particular, we present results for three materials (Al, Pt, and Au) with verydifferent electronic structures. It is shown that, depending on the frequency and the metal, theradiation can either enhance or diminish the conductance. This can be intuitively understood interms of the energy dependence of the transmission of the contacts in the absence of radiation.