Magnetic-Field Induced Quantum Critical Point in YbRh$_2$Si$_2$

TL;DR

This study investigates a magnetic-field-induced quantum critical point in YbRh₂Si₂, revealing divergence in quasiparticle mass and singular scattering, indicating a new type of quantum criticality in heavy-fermion systems.

Contribution

It provides experimental evidence for a novel quantum critical point driven by magnetic field in a heavy-fermion metal, characterized by divergent quasiparticle mass and singular scattering.

Findings

Divergence of the coefficient A(B) near the critical field Bc0.

Observation of a T² resistivity dependence above Bc0.

Identification of a new quantum critical point separating weak antiferromagnetic and polarized Fermi-liquid states.

Abstract

We report low-temperature calorimetric, magnetic and resistivity measurements on the antiferromagnetic (AF) heavy-fermion metal YbRh$_2$Si$_2$ (${T_N =}$ 70 mK) as a function of magnetic field $B$. While for fields exceeding the critical value ${B_{c0}}$ at which ${T_N\to0}$ the low temperature resistivity shows an ${AT^2}$ dependence, a ${1/(B-B_{c0})}$ divergence of ${A(B)}$ upon reducing $B$ to ${B_{c0}}$ suggests singular scattering at the whole Fermi surface and a divergence of the heavy quasiparticle mass. The observations are interpreted in terms of a new type of quantum critical point separating a weakly AF ordered from a weakly polarized heavy Landau-Fermi liquid state.