Magnetic oscillations measure interlayer coupling in cuprate superconductors

TL;DR

This paper proposes that magnetic oscillations in YBCO high-temperature superconductors reveal interlayer electronic coupling rather than small Fermi surface pockets, challenging previous interpretations and aligning with ARPES data.

Contribution

It introduces a new interpretation of magnetic oscillations as a measure of interplanar coupling, not Fermi surface reconstruction, supported by analysis of peak intensities and angular dependence.

Findings

Magnetic oscillations reflect interlayer coupling in cuprates.

Oscillation frequencies are larger than Fermi surface areas.

Strong correlations lead to non-linear frequency mixing.

Abstract

The magnetic oscillations in YBCO high-temperature superconductors have been widely studied over the last decade and consist of three equidistant low frequencies with a central frequency several times more intense than its two shoulders. This remains a puzzle in spite of numerous attempts to explain the corresponding small Fermi-surface pockets. Furthermore the ARPES data indicate only four Fermi-arcs with bilayer splitting, and show no sign of such small areas in the Fermi surface. Here we argue that the magnetic oscillations measured in under-doped bilayer high temperature superconductors, in particular YBa$_{2}$Cu$_{3}$O$_{6+\delta }$, provide a measure of the interplanar electronic coupling rather than the areas of fine-grain reconstruction of the Fermi surfaces coming from induced charge density waves. This identification is based on the relative intensities of the different peaks, as well as their angular dependence, which points to an effective Fermi surface that is larger than the oscillation frequencies, and is compatible with several indications from ARPES. The dominance of such frequencies with respect to the fundamental frequencies from the Fermi surface is natural for a strongly correlated quasi-two dimensional electronic systems where non-linear mixings of frequencies are more resistant to sample inhomogeneity.