AVERAGE PERSISTENT CURRENT IN A MESOSCOPIC RING

We present a microscopic calculation of the disorder-averaged persistent current for a mesoscopic ring with a fixed number of electrons. Using an idea by Imry, we show that the even Fourier components of the average current dominate and are related to the typical single-level current (I2p)D-proportional-<i(p)2D>/I0, which can be calculated by a Green's-function-averaging technique. For the small even harmonics p, the result simplifies to <I2p>D almost-equal-to I0/2piM, where M is the number of transverse channels. Its relevance to multiring experiments is discussed.