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Hamburg 2001 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 16: Postersitzung II: Amorphe und Tunnelsysteme, Mesoskopische Systeme, Schwere Fermionen, Kernmagnetismus

TT 16.37: Poster

Dienstag, 27. März 2001, 14:30–17:00, Rang S\ 3

Unconventional metallic state in YbRh2Si2 – a high pressure study — •S. Mederle, R. Borth, J. Custers, P. Gegenwart, C. Geibel, M. Grosche, M. Lang, C. Langhammer, R. Schleser, G. Sparn, O. Trovarelli, and F. Steglich — Max–Planck–Institute for the Chemical Physics of Solids, Nöthnitzer Str. 40, D–01187 Dresden, Germany

The study of 3d– and 4f–electron compounds on the threshold of magnetism has brought to light a number of "strange" metals which appear to defy the conventional description of the metallic state in terms of well–defined fermionic and bosonic excitations. One of these compounds is YbRh2Si2, which shows a nearly linear temperature dependence of the resistivity and a strongly temperature–dependent C/T ratio over a wide range in temperature above a low lying (presumably antiferro–) magnetic phase transition (Tm ≃ 70 mK). Since Tm increases with decreasing unit cell volume (increasing hydrostatic pressure), one expects to get even closer to the QCP (Tm → 0) when increasing the unit cell volume. Indeed no indication of a magnetic phase transition can be observed down to T ≃ 10 mK when substituting Si with 5% of Ge (which has a larger ionic radius).

We present results of a detailed study of the electrical resistivity and the specific heat over a wide range of pressure and temperature and discuss the results in the light of current theories of quantum critical behaviour and in comparison to the isostructural compound YbCo2Ge2.

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