title: Supersolid phase accompanied by a quantum critical point in the intermediate coupling regime of the Holstein model.
abstract: We reveal that electron-phonon systems described by the Holstein model on a bipartite lattice exhibit, away from half filling, a supersolid (SS) phase characterized by coexisting charge order (CO) and superconductivity (SC), and an accompanying quantum critical point (QCP). The SS phase, demonstrated by the dynamical mean-field theory with a quantum Monte Carlo impurity solver, emerges in the intermediate-coupling regime, where the peak of the Tc dome is located and the metal-insulator crossover occurs. On the other hand, in the weak- and strong-coupling regimes the CO-SC boundary is of first order with no intervening SS phases. The QCP is associated with the continuous transition from SS to SC and characterized by a reentrant behavior of the SS around it. We further show that the SS-SC transition is hallmarked by diverging charge fluctuations and a kink (peak) in the superfluid density.
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Murakami
authors.affiliation: Department of Physics, University of Fribourg, 1700 Fribourg, Switzerland.
authors.forename: Philipp
authors.initials: P
authors.lastname: Werner
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Tsuji
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Aoki