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arXiv:1712.08379 · Physical review. B./Physical review. B

Precursors of the insulating state in the square-lattice Hubbard model

Erik G. C. P. van Loon, Hartmut Hafermann, Mikhail I. Katsnelson

Published Feb 13, 2018• 29 citations
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Abstract

We study the two-dimensional square-lattice Hubbard model for small to moderate interaction strengths $1\ensuremath{\le}U/t\ensuremath{\le}4$ by means of the ladder dual fermion approach. The nonlocal correlations beyond dynamical mean-field theory lower the potential energy, lead to a maximum in the uniform susceptibility, and induce a pseudogap in the density of states. While the self-energy exhibits precursors of a possible insulating phase linked to the appearance of long-range fluctuations, the metallic phase persists within the accessible temperature range. Finite-size effects affect results qualitatively. Upper bounds on the crossover temperature are found to be significantly lower than previously reported dynamical vertex approximation results at $U/t=1$.

DOI
10.1103/physrevb.97.085125

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