de Haas-van Alphen oscillations in the underdoped cuprate YBa$_2$Cu$_3$O$_{6.5}$

TL;DR

This study reports the observation of de Haas-van Alphen quantum oscillations in underdoped YBa2Cu3O6.5, providing thermodynamic evidence for a coherent Fermi surface in the pseudogap phase of cuprates.

Contribution

It is the first thermodynamic detection of quantum oscillations in underdoped cuprates, confirming a well-defined Fermi surface in the pseudogap phase.

Findings

Quantum oscillations observed above 30 T magnetic field.

Oscillation frequency of 540 T and cyclotron mass of 1.76 m_e.

Oscillations follow Lifshitz-Kosevich theory, indicating Fermi-liquid behavior.

Abstract

The de Haas-van Alphen effect was observed in the underdoped cuprate YBa$_2$Cu$_3$O$_{6.5}$ via a torque technique in pulsed magnetic fields up to 59 T. Above an irreversibility field of $\sim$30 T, the magnetization exhibits clear quantum oscillations with a single frequency of 540 T and a cyclotron mass of 1.76 times the free electron mass, in excellent agreement with previously observed Shubnikov-de Haas oscillations. The oscillations obey the standard Lifshitz-Kosevich formula of Fermi-liquid theory. This thermodynamic observation of quantum oscillations confirms the existence of a well-defined, close and coherent, Fermi surface in the pseudogap phase of cuprates.