Equilibrium and nonequilibrium electron tunneling via discrete quantum states

We analyze quantitatively the resonance energies, widths, and amplitudes for electron tunneling via the quantum levels of a metal nanoparticle. We consider both the regime where only one quantum state is accessible for tunneling and the nonequilibrium regime where additional states are made accessible one by one. For tunneling through one state, our results agree with expectations for sequential tunneling, but in the nonequilibrium regime the resonances are broadened and shift with temperature in ways that require taking into account electron interactions and relaxation.