Two-dimensional fluctuations at the quantum-critical point of CeCu_{6-x}Au_x

TL;DR

This study investigates the quantum critical fluctuations in CeCu_{6-x}Au_x at x=0.1, revealing two-dimensional magnetic fluctuations that serve as precursors to three-dimensional magnetic order, shedding light on non-Fermi-liquid behavior.

Contribution

The paper provides the first direct evidence of two-dimensional quantum critical fluctuations in a heavy-fermion system at its quantum critical point.

Findings

Identification of rod-like features indicating 2D fluctuations

Observation of 3D magnetic peaks at higher doping levels

Linking 2D fluctuations to non-Fermi-liquid behavior

Abstract

The heavy-fermion system CeCu_{6-x}Au_x exhibits a quantum critical point at x_c = 0.1 separating nonmagnetic and magnetically ordered ground states. The pronounced non-Fermi-liquid behavior at x_c calls for a search for the relevant quantum critical fluctuations. Systematic measurements of the inelastic neutron scattering cross section S(q,omega) for x = 0.1 reveal rod-like features in the reciprocal ac plane translating to two-dimensional (2d) fluctuations in real space. We find 3d magnetic ordering peaks for x = 0.2 and 0.3 located on these rods which hence can be viewed as 2d precursors of the 3d order.