Detection of Single Spin Decoherence in a Quantum Dot via Charge Currents

We consider a quantum dot attached to leads in the Coulomb blockade regime that has a spin 1 / 2 ground state. We show that, by applying an ESR field to the dot spin, the stationary current in the sequential tunneling regime exhibits a new resonance peak whose linewidth is determined by the single spin decoherence time T₂. The Rabi oscillations of the dot spin are shown to induce coherent current oscillations from which T₂ can be deduced in the time domain. We describe a spin inverter which can be used to pump current through a double dot via spin flips generated by ESR.