Heavy-Fermion Superconductivity in CeAgSi --Interplay of Spin and Valence Fluctuations--
arXiv:1711.02965 · doi:10.1016/j.physb.2017.09.120
Abstract
We present the pressure-temperature phase diagram of the antiferromagnet CeAgSi established via resistivity and calorimetry measurements under quasi-hydrostatic conditions up to 22.5~GPa. With increasing pressure, the Néel temperature [~K] slowly increases up to ~K at 9.4~GPa and then vanishes abruptly at the magnetic critical pressure ~GPa. For the first time, heavy fermion superconductivity is observed in CeAgSi . Superconductivity emerges at ~GPa and persists over roughly 10~GPa. Partial- and bulk-transition temperatures are highest at ~GPa, with a maximal ~K. In the pressure region of superconductivity, Kondo and crystal-field splitting energies become comparable and resistivity exhibits clear signatures of a Ce-ion valence crossover. The crossover line is located at a rapid collapse in resistivity as function of pressure and extrapolates to a valence transition critical endpoint at critical pressure and temperature of ~GPa and , respectively. Both critical spin and valence fluctuations may build up superconductivity in CeAgSi.
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