Abstract
We study non-equilibrium current and occupation probabilities of a two-orbital quantum dot. The couplings to the leads are allowed to be asymmetric and orbital dependent as is generically the case in transport experiments on molecules and nanowires. Starting from a two-orbital Anderson model, we perform a generalised Schrieffer-Wolff transformation to derive an effective Kondo model. This generates an orbital potential scattering contribution which is of the same order as the spin exchange interaction. In a first perturbative analysis we identify a regime of negative differential conductance and a cascade resonance in the presence of an external magnetic field, which both originate from the non-equilibrium occupation of the orbitals. We then study the logarithmic enhancement of these signatures by means of a renormalisation-group treatment. We find that the orbital potential scattering qualitatively changes the renormalisation of the spin exchange couplings and strongly affects the differential conductance for asymmetric couplings.
| Original language | English |
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| Journal | EPL |
| Volume | 92 |
| Pages (from-to) | 10002 |
| Number of pages | 7 |
| ISSN | 0295-5075 |
| DOIs | |
| Publication status | Published - 19 Oct 2010 |