Massless Dirac Fermions, Gauge Fields, and Underdoped Cuprates

TL;DR

This paper models underdoped cuprates using 2+1D massless Dirac fermions coupled to a U(1) gauge field, revealing logarithmic enhancements in susceptibility and specific heat, and explaining the susceptibility drop below T_c.

Contribution

It introduces a gauge field framework for underdoped cuprates, explaining experimental observations with gauge fluctuation effects.

Findings

Logarithmic enhancement of susceptibility and specific heat coefficient.

Good agreement with experimental data in the spin gap phase.

Suppression of gauge fluctuations explains susceptibility drop below T_c.

Abstract

We study 2+1 dimensional massless Dirac fermions and bosons coupled to a U(1) gauge field as a model for underdoped cuprates. We find that the uniform susceptibility and the specific heat coefficient are logarithmically enhanced (compared to linear-in-T behavior) due to the fluctuation of transverse gauge field which is the only massless mode at finite boson density. We analyze existing data, and find good agreement in the spin gap phase. Within our picture, the drop of the susceptibility below the superconducting T_c arises from the suppression of gauge fluctuations.