title: Assessing the orbital selective Mott transition with variational wave functions.
abstract: We study the Mott metal-insulator transition in the two-band Hubbard model with different hopping amplitudes t1 and t2 for the two orbitals on the two-dimensional square lattice by using non-magnetic variational wave functions, similarly to what has been considered in the limit of infinite dimensions by dynamical mean-field theory. We work out the phase diagram at half filling (i.e. two electrons per site) as a function of R = t2/t1 and the on-site Coulomb repulsion U, for two values of the Hund's coupling J = 0 and J/U = 0.1. Our results are in good agreement with previous dynamical mean-field theory calculations, demonstrating that the non-magnetic phase diagram is only slightly modified from infinite to two spatial dimensions. Three phases are present: a metallic one, for small values of U, where both orbitals are itinerant; a Mott insulator, for large values of U, where both orbitals are localized because of the Coulomb repulsion; and the so-called orbital-selective Mott insulator (OSMI), for small values of R and intermediate Us, where one orbital is localized while the other one is still itinerant. The effect of the Hund's coupling is two-fold: on one side, it favors the full Mott phase over the OSMI; on the other side, it stabilizes the OSMI at larger values of R.
authors.affiliation: Democritos National Simulation Center, Istituto Officina dei Materiali del CNR, and SISSA-International School for Advanced Studies, Via Bonomea 265, I-34136 Trieste, Italy.
authors.forename: Luca F
authors.initials: LF
authors.lastname: Tocchio
authors.forename: Federico
authors.initials: F
authors.lastname: Arrigoni
authors.forename: Sandro
authors.initials: S
authors.lastname: Sorella
authors.forename: Federico
authors.initials: F
authors.lastname: Becca