Yale University

Title: Kondo Physics and the Lamb Shift in the Single Electron Box

Abstract: We measure the average charge on a single-electron box as a function of an externally applied potential, or the Coulomb staircase, with an accuracy of two thousandths of an electron. At this accuracy, we observe "fine structure" on the staircase due to quantum fluctuations of charge, or the fact that tunneling strongly couples the charge states to quasiparticle degrees of freedom. The effects of the fluctuations have analogies with both Kondo physics and the Lamb shift. We find excellent agreement between our measurements and a theory that treats the quantum fluctuations of charge perturbatively, in a comparison with no adjustable parameters.