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UID:UW-Physics-Event-3023
DTSTART:20130520T213000Z
DURATION:PT1H0M0S
DTSTAMP:20260419T225543Z
LAST-MODIFIED:20130516T160700Z
LOCATION:5310 Chamberlin
SUMMARY:Critical quasi-particle theory and scaling near a Quantum Crit
 ical Point of Heavy Fermion metals.\, Condensed Matter Theory Group Se
 minar\, Peter Woelfle\, Visiting Professor\, UW-Madison
DESCRIPTION: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 criti
 cal spin fluctuations induce critical behavior of the electron quasi-p
 articles (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 [1].  We use that the c
 oncept of electron quasi-particles is well-defined as long as the qp w
 idth is less than their excitation energy\, which is still the case in
  the so-called non-Fermi liquid regime.<br>
\n<br>
\nImpurity scatteri
 ng [1\,2] and/or higher order loop processes in the clean system [3] c
 ause a redistribution of the critical scattering at the hot lines all 
 over the Fermi surface\, leading to a weakly momentum dependent critic
 al self-energy. We derive a self-consistent equation for the qp effect
 ive mass which allows for two physical solutions: the usual weak coupl
 ing spin density wave solution and a strong coupling solution featurin
 g 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 exc
 ellent agreement with data for YbRh2Si2 [1\,2]. Results of our theory 
 applied to three-dimensional metals featuring quasi-two-dimensional sp
 in fluctuations will be presented with the aim of explaining the obser
 ved 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[3]. Finally\, the microsco
 pic underpinning of our theory will be addressed\, including the issue
 s of qp renormalization\, vertex corrections\, interaction of bosonic 
 fluctuations in the renormalization group sense\, and higher loop corr
 ections [3].  <br>
\n<br>
\n[1] P. Woelfle\, and E. Abrahams\, Phys. R
 ev. B 84\, 041101 (2011)\; Ann. Phys. (Berlin) 523\, 591 (2011)\; Phys
 . Rev. B 80\, 235112 (2009).  <br>
\n<br>
\n[2] E.Abrahams and P. Woel
 fle\, PNAS \, 3228 (2012).  <br>
\n<br>
\n[3] E. Abrahams\, J. Schmali
 an\, and P.  Woelfle\, to be published. <br>
\n
URL:https://www.physics.wisc.edu/events/?id=3023
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