Fermi surface pockets in ortho-II YBa$_2$Cu$_3$O$_{6.5}$: the origin of quantum oscillations?

TL;DR

This study investigates whether conventional density functional theory can explain the quantum oscillation signals in ortho-II YBa₂Cu₃O₆.₅, revealing sensitive Fermi surface features that match experimental observations.

Contribution

It demonstrates that small band shifts in DFT calculations can produce Fermi surface pockets consistent with quantum oscillation data in YBa₂Cu₃O₆.₅.

Findings

Fermi surface pockets emerge with ~30 meV band shifts.

Calculated pocket areas and masses align with experiments.

Fermi surface sensitivity explains quantum oscillation signals.

Abstract

In this paper we explore whether the quantum oscillation signals recently observed in ortho-II YBa$_2$Cu$_3$O$_{6.5}$ may be explained by conventional density functional band-structure theory. Our calculations show that the Fermi surface of YBa$_2$Cu$_3$O$_{6.5}$ is extremely sensitive to small shifts in the relative positions of the bands. With rigid band shifts of around 30 meV small tubular pockets of Fermi surface develop around the Y point in the Brillouin zone. The cross-sectional areas and band masses of the quantum oscillatory orbits on these pockets are close to those observed. The difference between the bandstructure of YBa$_2$Cu$_3$O$_{6.5}$ and YBa$_2$Cu$_4$O$_{8}$ are discussed.