Signature of pseudogap formation in the density of states of underdoped cuprates

TL;DR

This paper investigates the pseudogap in underdoped cuprates using a resonating valence bond model, revealing how it affects the density of states and matches recent experimental data.

Contribution

It demonstrates how the pseudogap introduces asymmetry in the density of states and distinguishes it from superconductivity effects, aligning with tunneling spectroscopy observations.

Findings

Pseudogap causes asymmetry in the density of states.

The low-energy density of states slope remains nearly constant in underdoped cuprates.

The model's predictions qualitatively agree with recent experimental data.

Abstract

The resonating valence bond spin liquid model for the underdoped cuprates has as an essential element, the emergence of a pseudogap. This new energy scale introduces asymmetry in the quasiparticle density of states because it is associated with the antiferromagnetic Brillouin zone. By contrast, superconductivity develops on the Fermi surface and this largely restores the particle-hole symmetry for energies below the superconducting energy gap scale. In the highly underdoped regime, these two scales can be separately identified in the density of states and also partial density of states for each fixed angle in the Brillouin zone. From the total density of states, we find that the pseudogap energy scale manifests itself differently as a function of doping for positive and negative bias. Furthermore, we find evidence from recent scanning tunneling spectroscopy data for asymmetry in the positive and negative bias of the extracted $\Delta(\theta)$ which is in qualitative agreement with this model. Likewise, the slope of the linear low energy density of states is nearly constant in the underdoped regime while it increases significantly with overdoping in agreement with the data.