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arXiv · 1505.07006

Assessing the orbital selective Mott transition with variational wave functions

Luca F. Tocchio·Federico Arrigoni·Sandro Sorella·Federico Becca
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Abstract

We study the Mott metal-insulator transition in the two-band Hubbard model with different hopping amplitudes $t_1$ and $t_2$ for the two orbitals on the two-dimensional square lattice by using {\it 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 $R=t_2/t_1$ 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 $U$'s, 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 $R$.

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Luca F. Tocchio, Federico Arrigoni, Sandro Sorella, Federico Becca. 2015-05-26. Assessing the orbital selective Mott transition with variational wave functions. https://doi.org/10.1088/0953-8984/28/10/105602

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