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SUMMARY:de Haas-van Alphen studies of the YbRh2Si2 Fermi surface: Lifshitz
  transition at H0 ~ 10 T - Patrick Rourke\, University of Bristol
DTSTART:20090429T101500Z
DTEND:20090429T111500Z
UID:TALK17021@talks.cam.ac.uk
CONTACT:Michael Sutherland
DESCRIPTION:The heavy fermion compound YbRh2Si2 has a rich temperature - m
 agnetic field phase diagram\, including an antiferromagnetic field-induced
  quantum critical point. The nature of the YbRh2Si2 Fermi surface\,\nparti
 cularly its inclusion or exclusion of the Yb 4f quasihole degrees of freed
 om in various regions of the phase diagram\, is of central importance to u
 nderstanding the physics of this material.\n\nIn order to directly determi
 ne the field dependence of the YbRh2Si2 Fermi surface\, we have performed 
 de Haas-van Alphen effect measurements in the magnetic field range 8 T <= 
 H <= 16 T [1\, 2]. Our data reveal a continuous change of the extremal Fer
 mi surface areas\nthrough H0 ~ 10 T\, supporting the theory of a Lifshitz 
 transition at H0. In such a scenario\, a low-field "large" Fermi surface\,
  including the 4f degrees of freedom\, is increasingly spin split until a\
 nmajority-spin branch disappears [3]. Combined with Luttinger's theorem\, 
 our measurements are inconsistent with the proposal of 4f localization in 
 this field range\, in which the 4f degrees of freedom drop out of the Ferm
 i surface at H0.\n\n[1] P.M.C. Rourke et al.\, Phys. Rev. Lett. 101\, 2372
 05 (2008).\n[2] P.M.C. Rourke et al.\, J. Phys.: Conf. Ser. 150\, 042165 (
 2009).\n[3] S. Viola Kusminskiy et al.\, Phys. Rev. B 77\, 094419 (2008).\
 n\n\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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