The number of holes contained within the Fermi surface volume in underdoped high temperature superconductors

TL;DR

This paper resolves the relationship between Fermi surface reconstruction and hole count in underdoped high-Tc superconductors, showing Coulomb repulsion remains unscreened and quantum oscillations accurately estimate hole numbers.

Contribution

It demonstrates the correspondence between charge-density wave vectors and a small Fermi surface model, clarifying the hole count in underdoped cuprates.

Findings

Charge-density wave vectors match small Fermi surface predictions.

Quantum oscillation frequencies estimate the number of holes accurately.

Coulomb repulsion remains largely unscreened in the pseudogap regime.

Abstract

We bring resolution to the longstanding problem relating Fermi surface reconstruction to the number of holes contained within the Fermi surface volume in underdoped high Tc superconductors. On considering uniaxial and biaxial charge-density wave order, we show that there exists a relationship between the ordering wave vector, the hole doping and the cross-sectional area of the reconstructed Fermi surface whose precise form depends on the volume of the starting Fermi surface. We consider a `large' starting Fermi surface comprising 1+p hole carriers, as predicted by band structure calculations, and a `small' starting Fermi surface comprising p hole carriers, as proposed in models in which the Coulomb repulsion remains the dominant energy. Using the reconstructed Fermi surface cross-sectional area obtained in quantum oscillation experiments in YBa2Cu3O6+x and HgBa2CuO4+x and the established methods for estimating the chemical hole doping, we find the ordering vectors obtained from x-ray scattering measurements to show a close correspondence with those expected for the small starting Fermi surface. We therefore show the Coulomb repulsion to remain largely unscreened throughout the entire underdoped regime where the pseudogap exists and further show that the quantum oscillation frequency and charge-density wave vectors provide accurate estimates for the number of holes contributing to the Fermi surface volume.