Authors: J. Martinek, M. Sindel, L. Borda, J. Barnas, R. Bulla,
J. König, G. Schön, S. Maekawa, and J. von Delft
Journal:
Phys. Rev. B 72, 121302(R) (2005)
The effect of a gate voltage (Vg) on the spin-splitting of an electronic level in a quantum dot (QD) attached to ferromagnetic leads is studied in the Kondo regime using a generalized numerical renormalization group technique. We find that the Vg-dependence of the QD level spin-splitting strongly depends on the shape of the density of states (DOS). For one class of DOS shapes there is nearly no Vg-dependence, for another, Vg can be used to control the magnitude and sign of the spin-splitting, which can be interpreted as a local exchange magnetic field. We find that the spin-splitting acquires a new type of logarithmic divergence. We give an analytical explanation for our numerical results and explain how they arise due to spin-dependent charge fluctuations.