Wydarzenia

Seminarium Międzynarodowego Laboratorium Silnych Pól Magnetycznych i Niskich Temperatur PAN

Persistent currents and magnetic properties of some mesoscopic systems

Nail Suleimanov

Zavoisky Physical Technical Institute of Russian Academy of Sciences, Kazan, Russian Federation

Persistent currents are the unique feature of aromatic hydrocarbon molecules and mesoscopic metal rings. The ring currents that flow in aromatic molecules in response to applied magnetic field are often likened to electrical conductivity and superconductivity. A conventional resistance measurement is far too insensitive to establish infinite conductivity, a much better method consists in inducing a current in a ring and determining the decay rate of the produced magnetic field. The moment from an individual ring  is at the sensitivity limit of the best magnetic detectors.  Unfortunately, an ensemble measurement with many rings could not overcome this low signal problem, because each ring is expected to contribute a moment with a random sign. Another fundamental peculiarity of persistent currents in mesoscopic rings, which distinguishes them from superconducting currents, is that the direction of the induced current depends on the number of electrons in the ring as well as the interaction between them. In contrast, persistent currents in superconducting rings (at low enough fields) are always diamagnetic. In this presentation, the approach is developed which will allow hopefully to determine the amplitude of the ring current in individual benzene ring that is in a single molecule, to estimate some critical temperature below which the current will not dissipate if the applied external magnetic field will be decreased or removed, and to answer would be it possible  the transition from persistent current regime to the superconductivity in molecular systems like benzene and others.