QUROPE Quantum Information Processing and Communication in Europe

We construct a real time current-conserving functional renormalization group (RG) scheme on the Keldysh contour to study frequency-dependent transport and noise through a quantum dot in the local moment regime. We find that the current vertex develops a nontrivial nonlocal structure in time that is governed by a new set of RG equations. Solving these RG equations, we compute the complete frequency and temperature dependence of the noise spectrum. For voltages that are large compared to the Kondo temperature (i.e., eV≫kBTK), two sharp antiresonances are found in the noise spectrum at frequencies ℏω=±eV and, correspondingly, two Kondo-assisted peaks appear in the ac conductance through the dot.