title: Quantum criticality and incipient phase separation in the thermodynamic properties of the Hubbard model.
abstract: Transport measurements on the cuprates suggest the presence of a quantum critical point (QCP) hiding underneath the superconducting dome near optimal hole doping. We provide numerical evidence in support of this scenario via a dynamical cluster quantum Monte Carlo study of the extended two-dimensional Hubbard model. Single-particle quantities, such as the spectral function, the quasi-particle weight and the entropy, display a crossover between two distinct ground states: a Fermi liquid at low filling and a non-Fermi liquid with a pseudo-gap at high filling. Both states are found to cross over to a marginal Fermi-liquid state at higher temperatures. For finite next-nearest-neighbour hopping t', we find a classical critical point at temperature T(c). This classical critical point is found to be associated with a phase-separation transition between a compressible Mott gas and an incompressible Mott liquid corresponding to the Fermi liquid and the pseudo-gap state, respectively. Since the critical temperature T(c) extrapolates to zero as t' vanishes, we conclude that a QCP connects the Fermi liquid to the pseudo-gap region, and that the marginal Fermi-liquid behaviour in its vicinity is the analogue of the supercritical region in the liquid-gas transition.
authors.affiliation: Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LO 70803, USA. dimitris.galanakis@gmail.com
authors.forename: D
authors.initials: D
authors.lastname: Galanakis
authors.forename: E
authors.initials: E
authors.lastname: Khatami
authors.forename: K
authors.initials: K
authors.lastname: Mikelsons
authors.forename: A
authors.initials: A
authors.lastname: Macridin
authors.forename: J
authors.initials: J
authors.lastname: Moreno
authors.forename: D A
authors.initials: DA
authors.lastname: Browne
authors.forename: M
authors.initials: M
authors.lastname: Jarrell