Spin-dependent transport through multi-level quantum dots in phase-coherent and/or nonequilibrium conditions

We plan to study spin-dependent transport through multi-level quantum dots under phase-coherent and/or nonequilibrium conditions, aiming to achieve a unified description of both few- and many-level quantum dots. For quantum dots, the interplay of spin and Coulomb charging effects leads to a rich but complex set of phenomena. We will study (A) phase-coherent transport for dots embedded in Aharonov-Bohm interferometers, and (B) steady-state nonequilibrium transport for dots connected to two leads at different chemical potentials. A combination of numerical and analytical methods will be used: Jan von Delft (JvD) will focus on quantum dots with comparatively large level spacings (modeled by few-level Anderson impurity models), mainly using numerical matrix-product-state methods. Yuval Gefen (YG) will pursue analytical studies (based on the so-called universal Hamiltonian), mainly using a non-Abelian effective action that describes spin-charge correlations beyond a mean-field level. The results of this method will be checked against the numerical results of JvD for few-level models, but it also applies to many-level dots. By combining both approaches, we will thus achieve a unified description of both few- and many-level models.