Multiple Quantum Oscillations in the de Haas van Alphen Spectra of the Underdoped High Temperature Superconductor YBa_2Cu_3O_6.5

TL;DR

This study uses high-precision measurements of the de Haas-van Alphen effect to reveal multiple closely spaced frequencies in the Fermi surface of underdoped YBa2Cu3O6.5, challenging previous reports of a larger frequency and suggesting bilayer splitting.

Contribution

The paper provides the first high-precision detection of multiple frequencies in the quantum oscillations of underdoped YBa2Cu3O6.5, indicating bilayer splitting and c-axis coherence.

Findings

Identified three closely spaced frequencies in quantum oscillations.

Refuted the existence of a larger 1650 T frequency previously reported.

Suggested bilayer splitting and warping of a single quasi-2D Fermi surface.

Abstract

By improving the experimental conditions and extensive data accumulation, we have achieved very high-precision in the measurements of the de Haas-van Alphen effect in the underdoped high-temperature superconductor YBa$_{2}$Cu$_{3}$O$_{6.5}$. We find that the main oscillation, so far believed to be single-frequency, is composed of three closely spaced frequencies. We attribute this to bilayer splitting and warping of a single quasi-2D Fermi surface, indicating that \emph{c}-axis coherence is restored at low temperature in underdoped cuprates. Our results do not support the existence of a larger frequency of the order of 1650 T reported recently in the same compound [S.E. Sebastian {\it et al}., Nature {\bf 454}, 200 (2008)].