Quantum Critical Point revisited by the Dynamical Mean Field Theory

TL;DR

This paper employs dynamical mean field theory to analyze the quantum critical point in the doped Hubbard model, revealing universal scaling and spin density wave instabilities, and highlighting differences with the Spin-Fermion model.

Contribution

It introduces a detailed DMFT analysis of the QCP in the doped Hubbard model, emphasizing the importance of frequency-dependent vertices and contrasting with existing models.

Findings

Universal scaling form of the self energy at QCP

Identification of spin density wave instability at incommensurate wave vector

Significant differences from Spin-Fermion model calculations

Abstract

Dynamical mean field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low energy kink and the high energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high energy antiferromagnetic paramagnons. We use the frequency dependent four-point correlation function of spin operators to calculate the momentum dependent correction to the electron self energy. Our results reveal a substantial difference with the calculations based on the Spin-Fermion model which indicates that the frequency dependence of the the quasiparitcle-paramagnon vertices is an important factor.