The heavy-fermion metal YbRh2Si2 is a weak antiferromagnet below
TN=0.07 K. Application of a low magnetic field Bc=0.06 T (⊥c) is sufficient to continuously suppress the antiferromagnetic (AF) order.
Below T≈10 K, the Sommerfeld coefficient of the electronic specific
heat γ(T) exhibits a logarithmic divergence. At T<0.3 K, γ(T)∼T−ϵ (ϵ:0.3−0.4), while the electrical resistivity
ρ(T)=ρ0+aT (ρ0: residual resistivity). Upon
extrapolating finite-T data of transport and thermodynamic quantities to T=0, one observes (i) a vanishing of the "Fermi surface crossover" scale
T∗(B), (ii) an abrupt jump of the initial Hall coefficient RH(B) and
(iii) a violation of the Wiedemann Franz law at B=Bc, the field-induced
quantum critical point (QCP). These observations are interpreted as evidence of
a critical destruction of the heavy quasiparticles, i.e., propagating Kondo
singlets, at the QCP of this material.Comment: 20 pages, 8 figures, SCES 201