Quantum Critical Point of Itinerant Antiferromagnet in the Heavy Fermion Ce(Ru_{1-x}Rh_x)_2Si_2

TL;DR

This study investigates the quantum critical point of an itinerant antiferromagnet in a heavy fermion system, revealing it is governed by a spin density wave fixed point in three dimensions through neutron scattering experiments.

Contribution

The paper provides experimental evidence that the AFM QCP in Ce(Ru_{1-x}Rh_x)_2Si_2 is an SDW type in three dimensions, supporting theoretical models with a critical exponent of 3/2.

Findings

The dynamical susceptibility fits a Lorentzian profile.

The inverse correlation time scales as T^{3/2}.

The QCP is consistent with SDW theory in three dimensions.

Abstract

A focus of recent experimental and theoretical studies on heavy fermion systems close to antiferromagnetic (AFM) quantum critical points (QCP) is directed toward revealing the nature of the fixed point, i.e., whether it is an itinerant antiferromagnet [spin density wave (SDW)] type or a locally-critical fixed point. The relevance of the local QCP was proposed to explain the E/T-scaling with an anomalous exponent observed for the AFM QCP of CeCu_{5.9}Au_{0.1}. In this work, we have investigated an AFM QCP of another archetypal heavy fermion system Ce(Ru_{1-x}Rh_x)_2Si_2 with x = 0 and 0.03 (sim x_c) using single-crystalline neutron scattering. Accurate measurements of the dynamical susceptibility Im[chi(Q,E)] at the AFM wave vector Q = 0.35 c^* have shown that Im[chi(Q,E)] is well described by a Lorentzian and its energy width Gamma(Q), i.e., the inverse correlation time depends on temperature as Gamma(Q) = c_1 + c_2 T^{3/2 +- 0.1}, where c_1 and c_2 are x dependent constants, in low temperature ranges.This critical exponent 3/2 proves that the QCP is controlled by the SDW QCP in three space dimensions studied by the renormalization group and self-consistent renormalization theories.