Events at Physics
Impurity scattering [1,2] and/or higher order loop processes in the clean system  cause a redistribution of the critical scattering at the hot lines all over the Fermi surface, leading to a weakly momentum dependent critical self-energy. We derive a self-consistent equation for the qp effective mass which allows for two physical solutions: the usual weak coupling spin density wave solution and a strong coupling solution featuring a power law divergence of the effective mass as a function of energy scale. The resulting spin excitation spectrum obeys E/T scaling with dynamical exponent z=4 and correlation length exponent nu=1/3, in excellent agreement with data for YbRh2Si2 [1,2]. Results of our theory applied to three-dimensional metals featuring quasi-two-dimensional spin fluctuations will be presented with the aim of explaining the observed properties of the AFM quantum critical point of CeCu(6-x)Aux , in particular the E/T scaling exhibited by inelastic neutron scattering data. In that case we find z=8/3 and nu=3/7. Finally, the microscopic underpinning of our theory will be addressed, including the issues of qp renormalization, vertex corrections, interaction of bosonic fluctuations in the renormalization group sense, and higher loop corrections .
 P. Woelfle, and E. Abrahams, Phys. Rev. B 84, 041101 (2011); Ann. Phys. (Berlin) 523, 591 (2011); Phys. Rev. B 80, 235112 (2009).
 E.Abrahams and P. Woelfle, PNAS , 3228 (2012).
 E. Abrahams, J. Schmalian, and P. Woelfle, to be published.