(Poster) Interaction-induced charge and spin pumping through a quantum dot at finite bias

HERNAN L. CALVO; LAURA CLASSEN; JANINE SPLETTSTOESSER; MAARTEN R. WEGEWIJS

Aachen

Workshop; International workshop on Spin-Orbit and Interaction Effects in Nano-Electronics; 2013

We investigate charge and spin transport through an adiabatically driven,strongly interacting quantum dot weakly coupled to two metallic contactswith finite bias voltage. Within a kinetic/master equation approach we identify coefficients of response to the time-dependent external driving and relate these to the concepts of charge and spin emissivities in the time-dependent scattering matrix approach. Expressed in terms of auxiliary vector fields the response coefficients allow for a straightforward analysis of recently predicted interaction-induced pumping under periodic modulation of the gate and bias voltage. We perform a detailed study of this effect and the related adiabatic Coulomb blockade spectroscopy, and, in particular, extend it to spin pumping. Analytic formulas for the pumped charge and spin in the regimes of small and large driving amplitude are provided for arbitrary bias. In the absence of a magnetic field, we obtain a striking, simple relation between the pumped charge at zero bias and at bias equal to the Coulomb charging energy. At finite magnetic field, interaction-induced pure spin pumping is shown to be possible at this finite bias value, and additional features appear in the pumped charge. For large-amplitude adiabatic driving, the magnitude of both the pumped charge and spin at the various resonances saturate at values which are independent of the specific shape of the pumping cycle. Each of these values provide an independent, quantitative measurement of the junction asymmetry.