Quantum critical scaling at the edge of Fermi liquid stability in a cuprate superconductor

TL;DR

This study uncovers quantum critical scaling in electron-doped cuprates, revealing a line of quantum critical points that influence the non-Fermi liquid behavior and potentially underpin the anomalous properties associated with high-temperature superconductivity.

Contribution

It identifies a line of quantum critical points in cuprates that surrounds the superconducting phase, linking quantum criticality to anomalous electronic properties.

Findings

Quantum critical scaling observed in La2-xCexCuO4.

Quantum critical points form a line around the superconducting phase.

Extended non-Fermi liquid behavior linked to quantum criticality.

Abstract

In the high temperature cuprate superconductors, the pervasiveness of anomalous electronic transport properties suggests that violation of conventional Fermi liquid behavior is closely tied to superconductivity. In other classes of unconventional superconductors, atypical transport is well correlated with proximity to a quantum critical point, but the relative importance of quantum criticality in the cuprates remains uncertain. Here we identify quantum critical scaling in the electron-doped cuprate material La2-xCexCuO4 with a line of quantum critical points that surrounds the superconducting phase as a function of magnetic field and charge doping. This zero-temperature phase boundary, which delineates a metallic Fermi liquid regime from an extended non-Fermi liquid ground state, closely follows the upper critical field of the overdoped superconducting phase and gives rise to an expanse of distinct non Fermi liquid behavior at finite temperatures. Together with signatures of two distinct flavors of quantum fluctuations, this suggests that quantum criticality plays a significant role in shaping the anomalous properties of the cuprate phase diagram.