Persistent currents in mesoscopic copper rings

Abstract

At sufficiently low temperature, the total magnetization of an ensemble of 10 7 isolated mesoscopic copper rings oscillates as a function of the enclosed magnetic flux with a period of half a flux quantum, h/2 e. The amplitude of the oscillatory moment is ≈1.2×10 -15 A m 2 and decreases exponentially with increasing temperature on the scale of the correlation energy E c = π 2ℏ D/ L 2. This isevidence for a flux periodic persistent current in each ring of average value 3×10 -3 ev F/ L. Single-particle effects only give rise to an h/2 e periodicity in a closed system where the variations of the chemical potential are correlated to the variation of the density of states with magnetic flux. On the other hand, electron-electron interactions always give rise to persistent currents periodic in h/2 e whether the system is open or closed.