Deviations from Fermi-liquid behavior above $T_c$ in 2D short coherence length superconductors

TL;DR

This paper investigates the normal state properties of 2D short coherence length superconductors, revealing a spin-charge separation and deviations from Fermi-liquid behavior above the critical temperature using quantum Monte Carlo simulations.

Contribution

It demonstrates the existence of spin-charge separation and anomalous behavior above Tc in 2D superconductors, supported by quantum Monte Carlo results.

Findings

Pseudogap appears above Tc with depleted density of states.

Spin susceptibility and spectral weight follow the pseudogap behavior.

Charge compressibility remains temperature independent despite spin anomalies.

Abstract

We show that there are qualitative differences between the temperature dependence of the spin and charge correlations in the normal state of the 2D attractive Hubbard model using quantum Monte Carlo simulations. The one-particle density of states shows a pseudogap above $\tc$ with a depleted $N(0)$ with decreasing $T$. The susceptibility $\cs$ and the low frequency spin spectral weight track $N(0)$, which explains the spin-gap scaling: $1/T_1T \sim \cs(T)$. However the charge channel is dominated by collective behavior and the compressibility $dn/d\mu$ is $T$-independent. This anomalous ``spin-charge separation'' is shown to exist even at intermediate $|U|$ where the momentum distribution $n(\bk)$ gives evidence for degenerate Fermi system.