Quantum Critical Behavior in a Concentrated Ternary Solid Solution

TL;DR

This paper demonstrates that concentrated fcc alloys, especially NiCoCrx near x=1, serve as ideal, highly tunable model systems to study quantum critical behavior influenced by chemical disorder, revealing non-Fermi liquid properties.

Contribution

It introduces concentrated fcc alloys as simple, tunable model systems for exploring quantum criticality and disorder effects, filling a gap in experimental platforms.

Findings

Resistivity linear in temperature down to 2 K near x=1

Linear magnetoresistance observed in alloys

Non-Fermi liquid thermodynamic behavior indicating quantum criticality

Abstract

Quantum critical behavior has been associated with some of the most exotic emergent states of matter including high-temperature superconductivity. Much of the research into quantum critical point (QCP) physics has been hampered by the lack of model systems simple enough to be analyzed by theory. Here, we show that the concentrated solid solution fcc alloys, including the so-called high-entropy alloys, are ideal model systems to study the effects of chemical disorder on emergent properties near a quantum critical region. The face centered cubic (fcc) alloy NiCoCrx with x near 1 is found to be close to the Cr concentration where the ferromagnetic transition temperature, Tc, goes to 0. Near this composition these alloys exhibit a resistivity linear in temperature to 2 K, a linear magnetoresistance, an excess -TlnT contribution to the low temperature heat capacity and excess low temperature entropy. All of the low temperature electrical, magnetic and thermodynamic properties of the alloys with compositions near x near 1 are not typical of a Fermi liquid and suggest strong magnetic fluctuations associated with a quantum critical region. The limit of extreme chemical disorder in these simple fcc materials thus provides a novel and unique platform to study quantum critical behavior in a highly tunable system.