FisMat2017 - Submission - View

Abstract's title: Hidden Mott transition and large-U superconductivity in the two-dimensional Hubbard model
Submitting author: Luca Fausto Tocchio
Affiliation: Politecnico di Torino
Affiliation Address: Institute for condensed matter physics and complex systems, DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino
Country: Italy
Oral presentation/Poster (Author's request): Oral presentation
Other authors and affiliations: Sandro Sorella (International School for Advanced Studies (SISSA) and CNR-IOM, Trieste, Italy)

We consider the one-band Hubbard model on the square lattice by using variational and Green's function Monte Carlo methods, where the variational states contain Jastrow and backflow correlations on top of an uncorrelated wave function that includes BCS pairing and magnetic order. At half-filling, where the ground state is antiferromagnetically ordered for any value of the on-site interaction U, we can identify a hidden critical point UMott, above which a finite BCS pairing is stabilized in the wave function. The existence of this point is reminiscent of the Mott transition in the paramagnetic sector and determines a separation between a Slater insulator (at small values of U), where magnetism induces a potential energy gain, and a Mott insulator (at large values of U), where magnetic correlations drive a kinetic energy gain. Most importantly, the existence of UMott has crucial consequences when doping the system: We observe a tendency for phase separation into hole-rich and hole-poor regions only when doping the Slater insulator, while the system is uniform by doping the Mott insulator. Superconducting correlations are clearly observed above UMott, leading to the characteristic dome structure in doping. Furthermore, we show that the energy gain due to the presence of a finite BCS pairing above UMott shifts from the potential to the kinetic sector by increasing the value of the Coulomb repulsion.

LF. Tocchio, F. Becca, and S. Sorella, Phys. Rev. B 94, 195126 (2016).