Regensburg 2000 – scientific programme

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TT: Tiefe Temperaturen

TT 20: Quantenphasenüberg
änge

TT 20.2: Talk

Thursday, March 30, 2000, 12:30–12:45, H18

Anomalous Low Temperature States in CeNi₂Ge₂ and YbRh₂Si₂ — •M. Grosche¹, S. Mederle¹, P. Agarwal², O. Trovarelli¹, S. Julian², P. Gegenwart¹, C. Langhammer¹, J. Sichelschmidt¹, R. Borth¹, C. Geibel¹, G. Sparn¹, G. Lonzarich², and F. Steglich¹ — ¹MPI-CPfS, Bayreuther Str. 40, 01187 Dresden — ²Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK

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. The pure compounds CeNi₂Ge₂ and YbRh₂Si₂ display nearly linear temperature dependences of the resistivity and a strongly temperature-dependent C/T over a wide range even at ambient pressure and are therefore particularly suited for a detailed investigation of this curious low temperature state. Both materials undergo further phase transitions under pressure or chemical substitution, which give rise to rich and interesting phase diagrammes. The normal state in the two materials and its evolution with hydrostatic pressure and magnetic field are discussed in the light of current theories of quantum critical behaviour.