부산대학교 도서관

Low-temperature heat capacity C(T) of the weakly electron-correlated SrNi2Ge2 122-layer compound undergoes a superconducting transition with onset at 1.4 K and a bulk Tc=0.75 K, where heat-capacity jump ratio ΔC(Tc)/γTc=0.88–1.05. A small average superconducting energy gap Eg(ave)=2.21 kTc=0.14 meV is derived for this multi-gap superconductor. Similar results for isostructural SrPd2Ge2 include Tc(onset)=3.5 K, bulk Tc of 2.92 K, ΔC(Tc)/γTc=0.70 and Eg(ave)=2.54 kTc=0.64 meV. The higher Tc onset could be associated with stoichiometric 1:2:2 grains in the polycrystalline samples. In addition, deviations of Eg/kTc from the BCS ratio of 3.5 suggest that, just like their iron-based counterpart, these 122-layer germanides may also exhibit an unconventional, fully-opened multi-gap s-wave superconductivity.