Heavy fermion superconductor CeCu2Si2 under high pressure: Multiprobing the valence crossover

G. Seyfarth, A.-S. Rüetschi, K. Sengupta, A. Georges, D. Jaccard, S. Watanabe, and K. Miyake
Phys. Rev. B 85, 205105 – Published 3 May 2012

Abstract

The first heavy fermion superconductor CeCu2Si2 has not revealed all its striking mysteries yet. At high pressures, superconductivity is supposed to be mediated by valence fluctuations, in contrast to ambient pressure, where spin fluctuations most likely act as pairing glue. We have carried out a multiprobe (electric transport, thermopower, ac specific heat, Hall and Nernst effects) experiment up to 7GPa on a high-quality CeCu2Si2 single crystal. For the first time, the resistivity data make it possible quantitatively to draw the valence crossover line within the pT plane and to locate the critical end point at 4.5±0.2GPa and a slightly negative temperature. In the same pressure region, remarkable features have also been detected in the other physical properties, presumably acting as further signatures of the Ce valence crossover and the associated critical fluctuations: We observe maxima in the Hall and Nernst effects and a sign change and a strong sensitivity on magnetic field in the thermopower signal.

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  • Received 20 November 2011

DOI:https://doi.org/10.1103/PhysRevB.85.205105

©2012 American Physical Society

Authors & Affiliations

G. Seyfarth*, A.-S. Rüetschi, K. Sengupta, A. Georges, and D. Jaccard

  • DPMC-Université de Genève, 24 Quai Ernest Ansermet, 1211 Geneva 4, Switzerland

S. Watanabe

  • Quantum Physics Section, Kyushu Institute of Technology, Fukuoka 804-8550, Japan

K. Miyake

  • Graduate School of Engineering Science, Osaka University, Toyonaka 560-0043, Japan

  • *gabriel@seyfarth.net
  • Also at Centre de Physique Théorique, École Polytechnique, CNRS, 91128 Palaiseau Cedex, France; Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France.

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Vol. 85, Iss. 20 — 15 May 2012

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