Proper definitions of persistent currents in mesoscopic Aharonov-Bohm interferometers

We introduce a long-standing ambiguity in the persistent currents (PCs), addressed by Buttiker in 1985 and by Jayannavar and Deo in 1995, of a mesoscopic loop connected to two electron reservoirs. In order to clarify the ambiguity, we investigated the PCs in Aharonov-Bohm (AB) interferometers. We show that there are two types of PCs. One can be induced by the quantum interference originating from the asymmetries of the upper and the lower interferometer arms for nonequilibrium. The other is induced by the AB flux. A proper current expression for each type is presented as a function of the AB flux. By applying the expressions for a one-dimensional AB loop interferometer, we find an anomalously giant PC induced by AB flux and show it to be a unique characteristic behavior in open mesoscopic loop systems be observed experimentally with current nanotechnologies.