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 (T_m ≃ 70 mK). Since T_m increases with decreasing unit cell volume (increasing hydrostatic pressure), one expects to get even closer to the QCP (T_m → 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.