Extended Metal-Insulator Crossover with Strong Antiferromagnetic Spin Correlation in Half-Filled 3D Hubbard Model
arxiv(2024)
摘要
The Hubbard model at temperature above the Néel transition, despite of
being a paramagnet, can exhibit rich physics due to the interplay of Fermi
surface, on-site interaction U and thermal fluctuations. Nevertheless, the
understanding of the crossover physics remains only at a qualitative level,
because of the intrinsically smooth behavior. Employing an improved variant of
the numerically exact auxiliary-field quantum Monte Carlo algorithm
equipped with numerical analytic continuation, we obtain a broad variety of
static and dynamical properties of the three-dimensional (3D) Hubbard model at
half filling, quantitatively determine the crossover boundaries, and observe
that the metal-insulator crossover state, in which antiferromagnetic spin
correlations appear strongest, exists over an extended regime in between the
metallic state for small U and the Mott insulator for large U. In
particular, the Widom line, corresponding to the most rapid suppression of
double occupancy as U increases, is found to fully reside in the metallic
Fermi liquid regime, in contrast to the conventional intuition that it is a
representative feature for entering the Mott insulator. Beside providing a
reliable methology for numerical study of crossover physics, our work can serve
as a timely and important guideline for the most recent optical lattice
experiments.
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