title: Direct transition between a singlet Mott insulator and a superconductor.
abstract: We argue that a normal Fermi liquid and a singlet, spin-gapped Mott insulator cannot be continuously connected, and that some intermediate phase must intrude between them. By explicitly working out a case study where the singlet insulator is stabilized by orbital degeneracy and an inverted Hund's rule coupling, mimicking a Jahn-Teller effect, we find that the intermediate phase is a superconductor.
authors.affiliation: International School for Advanced Studies (SISSA), and Istituto Nazionale per la Fisica della Materia (INFM) Unità Trieste-SISSA, Via Beirut 2-4, I-34014 Trieste, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Capone
authors.forename: M
authors.initials: M
authors.lastname: Fabrizio
authors.forename: E
authors.initials: E
authors.lastname: Tosatti