Unconventional quantum vortex matter state hosts quantum oscillations in the underdoped high-temperature cuprate superconductors

TL;DR

This paper reveals an unconventional quantum vortex matter state in underdoped cuprate superconductors that exhibits quantum oscillations, challenging traditional models of the pseudogap ground state and suggesting new theoretical frameworks.

Contribution

It uncovers an unusual quantum vortex matter state in underdoped cuprates that hosts quantum oscillations without significant damping, prompting a new model of the pseudogap ground state.

Findings

Observation of quantum oscillations in vortex matter state

Evidence of non-ohmic electrical transport and magnetic hysteresis

Quantum oscillations occur without large damping despite a big superconducting gap

Abstract

A central question in the underdoped cuprates pertains to the nature of the pseudogap ground state. A conventional metallic ground state of the pseudogap region has been argued to host quantum oscillations upon destruction of the superconducting order parameter by modest magnetic fields. Here we use low applied measurement currents and millikelvin temperatures on ultra-pure single crystals of underdoped YBa$_2$Cu$_3$O$_{6+x}$ to unearth an unconventional quantum vortex matter ground state characterized by vanishing electrical resistivity, magnetic hysteresis, and non-ohmic electrical transport characteristics beyond the highest laboratory accessible static fields. A new model of the pseudogap ground state is now required to explain quantum oscillations that are hosted by the bulk quantum vortex matter state without experiencing sizeable additional damping in the presence of a large maximum superconducting gap; possibilities include a pair density wave.