Events at Physics
Events on Monday, May 20th, 2013
- Cosmology Journal Club
- An Informal discussion about a broad variety of arXiv papers related to Cosmology
- Time: 12:30 pm
- Place: 5242 Chamberlin Hall
- Abstract: Please visit the following link for more details:
Please feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Le Zhang (email@example.com)
- Host: Peter Timbie
- Condensed Matter Theory Group Seminar
- Critical quasi-particle theory and scaling near a Quantum Critical Point of Heavy Fermion metals.
- Time: 4:30 pm
- Place: 5310 Chamberlin
- Speaker: Peter Woelfle, Visiting Professor, UW-Madison
- Abstract: We recently developed a theory of the critical properties of a heavy fermion metal near an antiferromagnetic (AFM) quantum phase transition governed by three-dimensional spin fluctuations. The critical spin fluctuations induce critical behavior of the electron quasi-particles (qp) as seen in a diverging effective mass, leading, e.g., to a diverging specific heat coefficient. This in turn gives rise to a modification of the spin excitation spectrum . We use that the concept of electron quasi-particles is well-defined as long as the qp width is less than their excitation energy, which is still the case in the so-called non-Fermi liquid regime.
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.
- Host: Perkins