Leggett's conjecture for a mesoscopic ring

Persistent currents in a carbon nanotube torus encapsulated with a carbon ring

A toroidal carbon nanowire (TCNW) model is proposed for an ideal one-dimensional mesoscopic ring, consisting of a toroidal carbon nanotube (TCN) and an encapsulated carbon ring, of which the electronic structure and thus the persistent current (I(pc)) are investigated within the tight-binding formalism. The tube-ring interactions lead to a charge transfer from the inner ring to the outer TCN, and thus the Fermi level rises and the band overlaps in a certain flux range. In zigzag TCNWs with a metallic TCN, the actual magnetic response, the amplitude and the period of I(pc) in the primary carbon ring are concealed by those in the resultant TCNW; in zigzag TCNWs with a semiconducting TCN, I(pc) exhibits the same behavior as that in their primary carbon rings. The results show that I(pc) in the sample ring depends strongly on the surrounding environment and thus a semiconducting or insulating matrix may provide a desired environment for measuring persistent current in mesoscopic rings.