Characterization of single crystals of CeCu2Si2. A source of new perspectives

Abstract

We report the first thorough characterization of single crystals of Ce${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$. Measurements on these flux-grown crystals, which are not superconducting above 0.050 K, include ac susceptibility, resistivity, Hall effect, and specific heat. A review of other measurements is given, and the implications of our single-crystal data are discussed. Specifically, our data are consistent with superconductivity in Ce${\mathrm{Cu}}_2$ ${\mathrm{Si}}_2$ being destroyed by having too low a Kondo temperature, although $T_{\mathrm{Kondo}}$ is not found to be inversely proportional to $\gamma$ as previously claimed. The entropy associated with the low-temperature specific-heat anomaly is found to be only $0.66R \ln 2$, in contrast to the previous result of $R \ln 2$ for polycrystalline material. The lack of superconductivity in our single crystals does not appear to be due to poor stoichiometry to ±5%, as proposed previously for single crystals grown by a Bridgman technique. The possibility of charge-density waves suppressing superconductivity in strain-free material is discussed, although no experimental verification is found.