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 $\frac{1}{2}$ 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 $T_2$. The Rabi oscillations of the dot spin are shown to induce coherent current oscillations from which $T_2$ 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.