Strange metal without magnetic criticality

TL;DR

This paper reports the discovery of a strange metal phase in the heavy fermion superconductor β-YbAlB₄ without any nearby magnetic quantum critical point, challenging the conventional link between non-Fermi liquid behavior and magnetic criticality.

Contribution

It provides experimental evidence of a non-Fermi liquid phase existing independently of magnetic quantum criticality in an ultrapure heavy fermion compound.

Findings

Strange metal behavior observed without magnetic instability.

The phase persists across a wide pressure range.

A Fermi liquid phase separates the strange metal from magnetic transition.

Abstract

A fundamental challenge to our current understanding of metals is the frequent observation of qualitative departures from Fermi liquid behavior. The standard view attributes such non-Fermi liquid phenomena to the scattering of electrons off quantum critical fluctuations of an underlying order parameter. While the possibility of non-Fermi liquid behavior isolated from the border of magnetism has long been speculated, no experimental confirmation has been made. Here we report on the observation of a strange metal region in the absence of a magnetic instability in an ultrapure single crystal. In particular, we show that the heavy fermion superconductor $\beta$-YbAlB$_4$ forms a possible phase with strange metallic behavior across an extensive pressure regime, distinctly separated from a high-pressure magnetic quantum phase transition by a Fermi liquid phase.