Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 25: Correlated Electrons - Poster Session

TT 25.82: Poster

Mittwoch, 29. März 2006, 14:30–18:30, P1

Possible critical pressure-induced valence fluctuation in EuCu₂Ge₂ — •Gabriel Alejandro Dionicio¹, Heribert Wilhelm¹, Zakir Hossain², and Christoph Geibel¹ — ¹Max-Planck-Institute for Chemical Physics of Solids, 01187 Dresden, Germany — ²Department of Physics, Indian Institute of Technology, Kanpur-208016, India

By means of electrical resistivity measurements under pressure, we investigated the possibility of inducing a valence fluctuating regime in EuCu₂Ge₂ at low temperatures. The results are discussed in terms of a possible scenario for unconventional superconductivity driven by virtual exchange fluctuation of the charge density [1]. This mechanism was proposed to explain the high pressure superconducting dome in CeCu₂(Si_0.9Ge_0.1)₂ [2]. Our porpuse is to look for further candidates where this model might be apply. Some Eu-compounds with the ThCr₂Si₂ structure have shown a thermal activated continuous crossover from a divalent to a trivalent state, due to the degeneracy of the f⁷ and f⁶ configuration. We would like to address the question whether such a degenerated state can be induced by pressure at very low temperatures in EuCu₂Ge₂, taking into account that this situation seems to be achieved in EuCu₂(Si_0.7Ge_0.3)₂. The electrical resistivity measurements were performed up to 10 GPa in the temperature range 100 mK < T < 300 K. A tentative phase diagram is presented and the results are compared with the studies peformed in the alloy CeCu₂(Si_xGe_1−x)₂.

[1] K. Miyake, H. Maebashi; J. Phys. Soc. Jpn. 71 (2002) 1007

[2] H. Q. Yuan et al; Science 302 (2003) 2104