Metal-insulator transition in the 2D Hubbard model: dual fermion approach with the Lanczos exact diagonalization

Abstract

In this study the metal-insulator transition in the square-lattice Hubbard model at half-filling is revisited in relation to the DOS and spectral functions by means of the ladder dual fermion approximation (LDFA). For this purpose, a new expression of the two-body Green's function in the form of resolvents is proposed, which provides tractable and efficient means to calculate the local vertex function with the Lanczos exact diagonalization (ED) method. This makes it possible to use the Lanczos ED method as a solver of the effective impurity Anderson model for LDFA, opening up the way to access low temperatures for these perturbative extensions of the dynamical mean field theory and to obtain accurate DOS and spectral functions on the real frequency axis by a new variant of the maximum entropy method. It is found that for $U\le 3.5t$, as temperature decreases, the pseudogap formation due to antiferromagnetic correlations in the quasiparticle peak of the spectral function occurs at the X point $[k=(\pi ,0)]$, spreads through the Fermi surface and ends at the M${}_2$ point $[k=(\pi /2,\pi /2)]$. The almost simultaneous creation of the pseudogap and the loss of the Fermi liquid feature is consistent with that expected in the Slater regime. Although the pseudogap still appears in the quasi-particle-like single peak for $U\ge 4.0t$, the Fermi-liquid feature is partially lost on the Fermi surface already at higher temperatures as expected in the Mott-Heisenberg regime, in which local spins are preformed at high temperatures. A sharp crossover from a pseudogap phase to a Mott insulator at finite $U^{\ast }\approx 4.7t$ is found to occur below the temperature of the pseudogap formation similar to a previous study with the non-linear $\sigma$ model approach.

24 pages, 16 figures

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• Efficient evaluation of the polarization function in dynamical mean-field theory
• Exceptional points in the one-dimensional Hubbard model
• Parametrizations of local vertex corrections from weak to strong coupling: importance of the Hedin three-leg vertex
• Local and nonlocal electronic correlations at the metal-insulator transition in the Hubbard model in two dimensions
• Mott-Anderson Metal-Insulator Transitions from Entanglement
• Fluctuation diagnostics of the finite temperature quasi-antiferromagnetic regime of the 2D Hubbard model
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• Local moments versus itinerant antiferromagnetism: magnetic phase diagram and spectral properties of the anisotropic square lattice Hubbard model
• Modified $GW$ Method in Electronic Systems
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• Quantum entanglement, local indicators and effect of external fields in the Kugel-Khomskii model
• Overcomplete intermediate representation of two-particle Green's functions and its relation to partial spectral functions
• Pseudogap and strange metal states in the square-lattice Hubbard model: A comprehensive study