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arXiv · 1912.04918

Dynamical resilience to disorder: the dilute Hubbard model on the Lieb lattice

L. Oliveira-Lima·N. C. Costa·J. Pimentel de Lima·R. T. Scalettar·R. R. dos Santos
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Abstract

In itinerant systems, electron-electron interactions may lead to the formation of local magnetic moments and their effective exchange coupling, which in turn gives rise to long-range magnetic order. Therefore, when moment formation is weakened, such as in the single-band Hubbard model on a square lattice with the on-site repulsion being randomly switched off on a fraction $x$ of sites, magnetic order is suppressed beyond some critical $x_c$, which was found to lie below the classical percolation threshold, $x_c^\text{(perc,sq)}$. Here we study dilute magnetism in flat band systems, namely in the Hubbard model on a `Lieb' lattice. Interestingly, we show that magnetic order persists to $x$ almost twice as large as the classical percolation threshold for the lattice, thus emphasizing the central role of electron itinerancy to the magnetic response. The analysis of the orbital-resolved order parameters reveals that the contribution of the four-fold coordinated `d' sites to magnetism is dramatically affected by dilution, while the localized `p' states of the flat band provide the dominant contribution to long-range correlations. We also examine the transport properties, which suggest the existence of an insulator-to-metal transition in the same range of the critical magnetic dilution.

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L. Oliveira-Lima, N. C. Costa, J. Pimentel de Lima, R. T. Scalettar, R. R. dos Santos. 2020-04-09. Dynamical resilience to disorder: the dilute Hubbard model on the Lieb lattice. https://doi.org/10.1103/physrevb.101.165109

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