Magnetic quantum oscillations and multiple holon pockets in underdoped YBa$_2$Cu$_3$O$_{6+y}$

TL;DR

This paper demonstrates that underdoped YBa$_2$Cu$_3$O$_{6+y}$ exhibits multiple holon pockets causing various quantum oscillation frequencies, linked to a quantum phase transition associated with magnetic order onset.

Contribution

It identifies multiple holon pockets in underdoped YBa$_2$Cu$_3$O$_{6+y}$ and connects their properties to magnetic quantum oscillation data and a quantum phase transition.

Findings

Multiple holon pockets with different areas cause multiple oscillation frequencies.

The effective mass divergence indicates a quantum phase transition at y≈0.48.

The transition correlates with the onset of incommensurate magnetic order.

Abstract

We show that lightly doped YBa$_2$Cu$_3$O$_{6+y}$ has multiple holon pockets with different areas, which lead to multiple frequencies of magnetic quantum oscillations. Using neutron scattering data on incommensurate spin ordering we determine these areas, which yields frequencies in good agreement with experiments. Divergence of the effective mass observed in magnetic quantum oscillations indicates a quantum phase transition at the oxygen content $y\approx 0.48$. We argue that the transition is the onset of quasistatic incommensurate magnetic order predicted by theory and observed in neutron scattering.