Proximity to valence transition in heavy fermion superconductor CeCu2Si2 under pressure
DPMC - Université de Genève - Quai Ernest Ansermet 24, 1211 Geneva 4, Switzerland
2 Centre de Physique Théorique, École Polytechnique, CNRS - 91128 Palaiseau Cedex, France, EU
3 Collège de France - 11 place Marcelin Berthelot, 75005 Paris, France, EU
Accepted: 14 March 2012
The first heavy fermion superconductor CeCu2Si2 is still only partially understood. At high pressures, superconductivity is supposed to be mediated by a different mechanism than at ambient pressure, where spin fluctuations most likely act as pairing glue. We have obtained and analyzed new resistivity data up to 7 GPa on a good quality CeCu2Si2 single crystal with an unprecedented high transition temperature. For the first time, we establish quantitatively that CeCu2Si2 lies in proximity to a valence transition: the critical end point could be located at 4.5±0.2 GPa and a slightly negative temperature, and the corresponding valence cross-over line has been added to the p-T phase diagram. This outcome is essential for the theoretically predicted critical valence fluctuations scenario, and opens new routes for further investigations in other Ce-based compounds.
PACS: 75.20.Hr – Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions / 74.62.Fj – Effects of pressure / 74.25.fc – Electric and thermal conductivity
© EPLA, 2012