Evidence for a Kondo destroying quantum critical point in YbRh2Si2

Abstract

The heavy-fermion metal YbRh${}_2$Si${}_2$ is a weak antiferromagnet below $T_N=0.07$ K. Application of a low magnetic field $B_c=0.06$ T ($\perp c$) is sufficient to continuously suppress the antiferromagnetic (AF) order. Below $T\approx 10$ K, the Sommerfeld coefficient of the electronic specific heat $\gamma (T)$ exhibits a logarithmic divergence. At $T<0.3$ K, $\gamma (T)\sim T^{-\epsilon }$ ($\epsilon :0.3-0.4$), while the electrical resistivity $\rho (T)={\rho }_0+aT$ (${\rho }_0$: 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 $T^{\ast }(B)$, (ii) an abrupt jump of the initial Hall coefficient $R_H(B)$ and (iii) a violation of the Wiedemann Franz law at $B=B_c$, 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.

20 pages, 8 figures, SCES 2013

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• Transport Spectroscopy of the Field Induced Cascade of Lifshitz Transitions in YbRh2Si2
• Non-Fermi liquid behavior and quantum criticality in cubic heavy fermion systems with non-Kramers multipolar local moments
• Intermediate valence in single crystalline Yb${}_2$Si${}_2$Al
• Microstructuring YbRh2Si2 for resistance and noise measurements down to ultra-low temperatures
• Quantum impurity model for two-stage multipolar ordering and Fermi surface reconstruction
• Kondo Effect of a Jahn-Teller Ion Vibrating in a Cubic Anharmonic Potential
• CeCu${}_2$Si${}_2$ and YbRh${}_2$Si${}_2$: Strange Cases of Heavy-Fermion Superconductivity