Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 56: CE: Heavy Fermions

TT 56.2: Vortrag

Donnerstag, 17. März 2011, 16:45–17:00, HSZ 105

Hot lines on quantum critical Fermi surfaces from magneto oscillation measurements — •Lars Fritz and Achim Rosch — Universität zu Köln, Institut für theoretische Physik

Quantum criticality in electronic systems figures prominently in so-called heavy fermion systems. Many of these systems can be driven by either pressure, magnetic field, or chemical doping towards a point, where the anitferromagnetic Néel temperature is suppressed to zero resulting in a quantum critical point. One of the major questions which occur in the context of this quantum critical point is by which mechanism the antiferromagnetic state is converted into the heavy Fermi liquid. There exist two extreme cases: one in which the heavy Fermi liquid state is obtained in the framework of a spin density wave (SDW) scenario in the spirit of the Hertz-Millis-Moriya theory as opposed to a scenario of breakdown of the Kondo effect. On an elementary level, the scenarios also differ in the way the Fermi surface becomes critical. Whereas in a SDW scenario hot lines due to overdamping by spin density wave at certain points of the Fermi surface have to be expected, in more exotic scenarios the whole Fermi surface becomes critical ("hot"). It is thus desirable to have a probe which is sensitive to the existence or nonexistence of hot lines on the Fermi surface. We discuss the possibility to locate hot regions and extract the ordering wave vector in strongly correlated fermionic systems close to a collective instability by means of angle dependent magneto-oscillations measurements of the de-Haas-van-Alphen or Shubnikov-de-Haas type.