Abstract
Applications of A15 superconductors have received considerable attention, resulting in a large body of reported research work on A15 superconductors. Nonetheless, studies on this material focusing on its superconducting parameters are scarce. This motivates new efforts toward bulk measurements in typical A15 material V3Ge, which is also the isomorph of V3Si with a superconducting transition temperature at 17 K. In this study, we determined the superconducting parameters of single-phase V3Ge crystals, which crystallize in the A15 structure, through measurements of magnetization, magnetic susceptibility, electrical resistivity, and heat capacity. Our results show that the temperature (Tc) of its superconducting transition is 6.2±0.4 K. Moreover, we conducted electrical resistivity and magnetic susceptibility measurements and found the lower and higher critical fields to be 559 Oe and 39.8 kOe, respectively. The Ginzburg–Landau parameter κGL is determined to be 9.78, which is much greater than 1/2, implying V3Ge Type-II superconductor. The Sommerfeld coefficient γ in the normal state is determined to be 31.2 mJ/K2 mol, which is 50∼100 folds higher compared to that in the normal metal, thereby indicating the enhancement of the density of state at the Fermi energy. The Debye temperature Θ is estimated to be 430 K, and the value of the drastic increase in the specific heat at Tc is approximately 1.33, which is 7% smaller than the weak coupling limit of 1.43 predicted by the Bardeen–Cooper–Schrieffer (BCS) theory. The electron–phonon coupling constant λe−ph is 0.61. These values suggest that V3Ge is a conventional superconductor with s-wave symmetry in the BCS framework, which implies that the high Debye temperature and large density of states at the Fermi energy contribute to the increase in Tc in V3Ge. The superconducting parameters determined in this study provide guidance for the development of a new metal superconductor with high-Tc.
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