Inelastic cotunneling current and shot noise of an interacting quantum dot with ferromagnetic correlations

We explore inelastic cotunneling through a strongly Coulomb-blockaded quantum dot attached to two ferromagnetic leads in the weak coupling limit using a Langevin equation approach.$^1$ We first develop a Bloch-type equation to describe the cotunneling-induced spin relaxation dynamics, and then derive explicit analytical expressions for the local magnetization, current, and its fluctuations. On this basis, we predict a novel zero-bias anomaly of the differential conductance in the absence of a magnetic field for the anti-parallel configuration, and asymmetric peak splitting in a magnetic field, which are ascribed to rapid spin-reversal due to underlying spin-flip cotunneling.$^2$\\ $^1$ B. Dong, N. J. M. Horing, and H. L. Cui, Phys. Rev. B {\bf 72}, 165326 (2005).\\ $^2$ B. Dong, X. L. Lei, and N. J. M. Horing, cond-mat/0509098.