Comment on "Zeeman-Driven Lifshitz Transition: A Model for the   Experimentally Observed Fermi-Surface Reconstruction in YbRh2Si2"
  In Phys. Rev. Lett. 106, 137002 (2011), A. Hackl and M. Vojta have proposed to explain the quantum critical behavior of YbRh2Si2 in terms of a Zeeman-induced Lifshitz transition of an electronic band whose width is about 6 orders of magnitude smaller than that of conventional metals. Here, we note that the ultra-narrowness of the proposed band, as well as the proposed scenario per se, lead to properties which are qualitatively inconsistent with the salient features observed in YbRh2Si2 near its quantum critical point. 
S. Friedemann, S. Paschen, C. Geibel, S. Wirth, F. Steglich, S.   Kirchner, E. Abrahams, Q. Si
cond-mat.str-el