Characteristic signatures of quantum criticality driven by geometrical frustration

TL;DR

This paper investigates how geometrical frustration in a heavy fermion metal induces quantum criticality, revealing anisotropic critical behavior and a spin-liquid-like state driven by local moments rather than itinerant electrons.

Contribution

It demonstrates that geometrical frustration can drive quantum criticality in metals, with anisotropic thermodynamic responses indicating a local moment spin-liquid-like state.

Findings

Quantum critical point confirmed in CeRhSn via thermodynamic measurements.

Anisotropic thermal expansion reveals frustration-driven criticality.

Discovery of a spin-flop-type metamagnetic crossover.

Abstract

Geometrical frustration describes situations where interactions are incompatible with the lattice geometry and stabilizes exotic phases such as spin liquids. Whether geometrical frustration of magnetic interactions in metals can induce unconventional quantum critical points is an active area of research. We focus on the hexagonal heavy fermion metal CeRhSn where the Kondo ions are located on distorted kagome planes stacked along the c axis. Low-temperature specific heat, thermal expansion and magnetic Gr\"uneisen parameter measurements prove a zero-field quantum critical point. The linear thermal expansion, which measures the initial uniaxial pressure derivative of the entropy, displays a striking anisotropy. Critical and noncritical behaviors along and perpendicular to the kagome planes, respectively, prove that quantum criticality is driven by geometrical frustration. We also discovered a spin-flop-type metamagnetic crossover. This excludes an itinerant scenario and suggests that quantum criticality is related to local moments in a spin-liquid like state.