Quantum oscillations from nodal bilayer magnetic breakdown in the underdoped high temperature superconductor YBa2Cu3O6+x

TL;DR

This study reports quantum oscillations in underdoped YBa2Cu3O6.56, revealing multiple frequencies caused by nodal bilayer coupling and magnetic breakdown, consistent with photoemission measurements, advancing understanding of Fermi surface reconstruction in high-Tc superconductors.

Contribution

It demonstrates that nodal bilayer coupling and magnetic breakdown explain observed quantum oscillation frequencies in underdoped YBa2Cu3O6.56, providing a quantitative link to photoemission data.

Findings

Three distinct quantum oscillation frequencies observed.

Nodal bilayer coupling causes frequency splitting and beat patterns.

Amplitude ratios match photoemission measurements.

Abstract

We report quantum oscillations in underdoped YBa2Cu3O6.56 over a significantly large range in magnetic field extending from 24 to 101 T, enabling three well-spaced low frequencies at 440 T, 532 T, and 620 T to be clearly resolved. We show that a small nodal bilayer coupling that splits a nodal pocket into bonding and antibonding orbits yields a sequence of frequencies, F0 - {\Delta}F, F0, and F0 + {\Delta}F and accompanying beat pattern similar to that observed experimentally, on invoking magnetic breakdown tunneling at the nodes. The relative amplitudes of the multiple frequencies observed experimentally in quantum oscillation measurements are shown to be reproduced using a value of nodal bilayer gap quantitatively consistent with that measured in photoemission experiments in the underdoped regime.