Hidden magnetism at the pseudogap critical point of a high temperature superconductor

TL;DR

This study reveals hidden antiferromagnetic order in cuprate superconductors below a critical doping level by suppressing superconductivity with magnetic fields, indicating a quantum phase transition at the pseudogap boundary.

Contribution

It uncovers the true magnetic ground state in La2-xSrxCuO4 by revealing glassy antiferromagnetic order hidden by superconductivity, highlighting a quantum phase transition at p*.

Findings

Glassy antiferromagnetic order exists up to p* ~ 0.19

Quantum phase transition occurs at the pseudogap boundary p*

Doped Mott insulator physics persists throughout the pseudogap regime

Abstract

The mysterious pseudogap phase of cuprate superconductors ends at a critical hole doping level p* but the nature of the ground state below p* is still debated. Here, we show that the genuine nature of the magnetic ground state in La2-xSrxCuO4 is hidden by competing effects from superconductivity: applying intense magnetic fields to quench superconductivity, we uncover the presence of glassy antiferromagnetic order up to the pseudogap boundary p* ~ 0.19, and not above. There is thus a quantum phase transition at p*, which is likely to underlie highfield observations of a fundamental change in electronic properties across p*. Furthermore, the continuous presence of quasi-static moments from the insulator up to p* suggests that the physics of the doped Mott insulator is relevant through the entire pseudogap regime and might be more fundamentally driving the transition at p* than just spin or charge ordering.