Mott Transition vs Multicritical Phenomenon of Superconductivity and Antiferromagnetism —Application to κ-(BEDT-TTF)₂X—

Abstract

Interplay between Mott transition and the multicritical phenomenon of d-wave superconductivity (SC) and antiferromagnetism (AF) is studied theoretically. We describe the Mott transition, which is analogous to a liquid–gas phase transition, in terms of an Ising-type order parameter η. We reveal possible mean-field phase diagrams produced by this interplay. Renormalization group analysis up to one-loop order gives flows of coupling constants, which in most cases lead to fluctuation-induced first-order phase transitions even when the SO(5) symmetry exists betwen the SC and AF. Behaviors of various physical quantities around the Mott critical point are predicted. Experiments on κ-(BEDT-TTF)₂X are discussed from this viewpoint.