We investigate the phase diagram of the square lattice bilayer Hubbard model at half-filling with the variational Monte Carlo method for both the magnetic and the paramagnetic case as a function of the interlayer hopping tτ and on-site Coulomb repulsion U. With this study we resolve some discrepancies in previous calculations based on the dynamical mean-field theory, and we are able to determine the nature of the phase transitions between metal, Mott insulator and band insulator. In the magnetic case we find only two phases: an antiferromagnetic Mott insulator at small tτ for any value of U and a band insulator at large tτ . At large U values we approach the Heisenberg limit. The paramagnetic phase diagram shows at small tτ a metal to Mott insulator transition at moderate U values and a Mott to band insulator transition at larger U values. We also observe a re-entrant Mott insulator to metal transition and metal to band insulator transition for increasing tτ in the range of 5.5t < U < 7.5t. Finally, we discuss the phase diagrams obtained in relation to findings from previous studies based on different many-body approaches.© 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

The phase diagram of the square lattice bilayer Hubbard model: a variational Monte Carlo study

Tocchio, Luca Fausto;
2014

Abstract

We investigate the phase diagram of the square lattice bilayer Hubbard model at half-filling with the variational Monte Carlo method for both the magnetic and the paramagnetic case as a function of the interlayer hopping tτ and on-site Coulomb repulsion U. With this study we resolve some discrepancies in previous calculations based on the dynamical mean-field theory, and we are able to determine the nature of the phase transitions between metal, Mott insulator and band insulator. In the magnetic case we find only two phases: an antiferromagnetic Mott insulator at small tτ for any value of U and a band insulator at large tτ . At large U values we approach the Heisenberg limit. The paramagnetic phase diagram shows at small tτ a metal to Mott insulator transition at moderate U values and a Mott to band insulator transition at larger U values. We also observe a re-entrant Mott insulator to metal transition and metal to band insulator transition for increasing tτ in the range of 5.5t < U < 7.5t. Finally, we discuss the phase diagrams obtained in relation to findings from previous studies based on different many-body approaches.© 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
16
3
1
16
033010
10.1088/1367-2630/16/3/033010
https://arxiv.org/abs/1311.6504
Rüger, R.; Tocchio, Luca Fausto; Valenti, R.; Gros, C.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11767/32772
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