title: Strong quantum interference in strongly disordered bosonic insulators.
abstract: We study the variable-range hopping of bosons in an array of sites with short-range interactions and a large characteristic coordination number. The latter leads to strong quantum interference phenomena yet allows for their analytical study. We develop a functional renormalization-group scheme that repeatedly eliminates high-energy sites properly renormalizing the tunneling between the low-energy ones. Using this approach we determine the temperature and magnetic field dependence of the hopping conductivity and find a large positive magnetoresistance. With increasing magnetic field the behavior of the conductivity crossovers from the Mott's law to an activational behavior with the activation gap proportional to the magnetic field.
authors.affiliation: Theoretische Physik III, Ruhr-Universität Bochum, 44780 Bochum, Germany.
authors.forename: S V
authors.initials: SV
authors.lastname: Syzranov
authors.forename: A
authors.initials: A
authors.lastname: Moor
authors.forename: K B
authors.initials: KB
authors.lastname: Efetov