Enhanced Strange Metallicity due to Hubbard-U Coulomb Repulsion

TL;DR

This paper models a strange metal phase emerging from Hubbard-U Coulomb interactions coupled with quantum critical fluctuations, revealing how strong repulsion enhances non-Fermi liquid behavior near a Mott transition.

Contribution

It introduces an extended dynamical mean field theory model showing how Hubbard-U interactions and quantum criticality produce strange metallicity with Planckian decay rates.

Findings

Quantum critical point enhances strange metallic behavior.

Fermi liquid breakdown near Mott transition.

Maximum decay rate bounded by Mott transition.

Abstract

We solve a model of electrons with Hubbard-$U$ Coulomb repulsion and a random Yukawa coupling to a two-dimensional bosonic bath, using an extended dynamical mean field theory scheme. Our model exhibits a quantum critical point, at which the repulsive component of the electron interactions strongly enhances the effects of the quantum critical bosonic fluctuations on the electrons, leading to a breakdown of Fermi liquid physics and the formation of a strange metal with `Planckian' ($\mathcal{O}(k_B T/\hbar)$) quasiparticle decay rates at low temperatures $T\rightarrow 0$. Furthermore, the eventual Mott transition that occurs as the repulsion is increased seemingly bounds the maximum decay rate in the strange metal. Our results provide insight into low-temperature strange metallicity observed in proximity to a Mott transition, as is observed, for instance, in recent experiments on certain moir\'{e} materials.