A Local Quantum Phase Transition in YFe$_{2}$Al$_{10}$

TL;DR

This study reveals a novel local quantum phase transition in YFe₂Al₁₀, where quantum fluctuations diverge without spatial correlations, challenging traditional phase transition paradigms.

Contribution

It introduces a new paradigm of local quantum phase transition driven by the creation of moments, differing from conventional spatially correlated transitions.

Findings

Quantum fluctuations diverge at low energies and temperatures.

Fluctuating moments lack spatial correlations.

Zero temperature order arises from a local transition.

Abstract

A phase transition occurs when correlated regions of a new phase grow to span the system and the fluctuations within the correlated regions become long-lived. Here we present neutron scattering measurements showing that this conventional picture must be replaced by a new paradigm in \boldmath$\mathrm{YFe}_2\mathrm{Al}_{10}$, a compound that forms naturally very close to a \boldmath$T=0$ quantum phase transition. Fully quantum mechanical fluctuations of localized moments are found to diverge at low energies and temperatures, however the fluctuating moments are entirely without spatial correlations. Zero temperature order in \boldmath$\mathrm{YFe}_2\mathrm{Al}_{10}$ is achieved by a new and entirely local type of quantum phase transition that may originate with the creation of the moments themselves.