Phase diagram and quasiparticle properties of the Hubbard model within cluster two-site DMFT

TL;DR

This paper uses a cluster two-site dynamical mean-field approach to study the Hubbard model, revealing how magnetism, Fermi surface distortions, and pseudogap phenomena evolve with electron filling and interaction strength.

Contribution

It extends Potthoff's two-site method to a cluster DMFT, providing new insights into Fermi surface evolution and pseudogap formation near the Mott transition.

Findings

Fermi surface changes from electron-like to hole-like near half-filling.

Anisotropic gap opening around the Fermi surface near the Mott transition.

Presence of Fermi arcs and pockets with small quasiparticle residue.

Abstract

We present a cluster dynamical mean-field treatment of the Hubbard model on a square lattice to study the evolution of magnetism and quasiparticle properties as the electron filling and interaction strength are varied. Our approach for solving the dynamical mean-field equations is an extension of Potthoff's "two-site" method [Phys. Rev. B. 64, 165114 (2001)] where the self-consistent bath is represented by a highly restricted set of states. As well as the expected antiferromagnetism close to half filling, we observe distortions of the Fermi surface. The proximity of a van Hove point and the incipient antiferromagnetism lead to the evolution from an electron-like Fermi surface away from the Mott transition, to a hole-like one near half-filling. Our results also show a gap opening anisotropically around the Fermi surface close to the Mott transition (reminiscent of the pseudogap phenomenon seen in the cuprate high-Tc superconductors). This leaves Fermi arcs which are closed into pockets by lines with very small quasiparticle residue.