Quantum oscillations suggest hidden quantum phase transition in the cuprate superconductor Pr$_{2}$CuO$_{4\pm\delta}$

TL;DR

This study uses high-quality Pr$_{2}$CuO$_{4 ext{±} ext{δ}}$ thin films to investigate quantum oscillations, revealing a hidden quantum phase transition in electron-doped cuprates without chemical doping.

Contribution

It demonstrates that oxygen stoichiometry alone can tune superconductivity and uncover quantum criticality, providing new insights into the electron-doped cuprate phase diagram.

Findings

Observation of magnetic quantum oscillations indicating small hole-like Fermi surface pockets.

Large effective mass enhancement near superconductivity suppression.

Quantum oscillations observed without Ce doping, highlighting oxygen stoichiometry's role.

Abstract

For both electron- and hole-doped cuprates, superconductivity appears in the vicinity of suppressed broken symmetry order, suggesting that quantum criticality plays a vital role in the physics of these systems. A confounding factor in identifying the role of quantum criticality in the electron-doped systems is the competing influence of chemical doping and oxygen stoichiometry. Using high quality thin films of Pr$_{2}$CuO$_{4\pm\delta}$, we tune superconductivity and uncover the influence of quantum criticality without Ce substitution. We observe magnetic quantum oscillations that are consistent with the presence of small hole-like Fermi surface pockets, and a large mass enhancement near the suppression of superconductivity. Tuning these materials using only oxygen stoichiometry allows the observation of quantum oscillations and provides a new axis with which to explore the physics underlying the electron-doped side of the cuprate phase diagram.