Charge fluctuations and the tunneling spectra of non-magnetic metallic nanoparticles

We present microscopic transport calculations of the tunneling spectra of non-magnetic metal nanoparticles. We show that charge fluctuations give rise to tunneling resonances of a new type. Positive and negative fluctuations have differing kinetics and thus account for previously unexplained spectral features that are found experimentally under only forward or only reverse applied bias. The observed clustering of tunneling resonances of Al nanoparticles arises naturally from our theory.