Specific Heat and de Haas-van Alphen Experiments on the Heavy-Fermion Superconductor CePt_3Si(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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Specific heat and de Haas-van Alphen (dHvA) measurements were performed on a high-quality single crystal of CePt_3Si without inversion symmetry in the tetragonal crystal structure. We observed distinct peaks in the specific heat C at the superconducting transition temperature T_c=0.46K and the antiferromagnetic ordering temperature T_N=2.25K, compared to the previous data, indicating an improvement of the sample quality. The temperature dependence of the electronic specific heat coefficient C_e/T below about 0.3K is well described by the equation of C_e/T=γ_s+β_sT with γ_s=34.1mJ/(K^2-mol) and β_s=1290mJ/(K^3-mol), evidencing the existence of line nodes in the super-conducting energy gap. Furthermore, the electronic specific heat coefficient γ_s in the superconducting state indicates a nonlinear magnetic field dependence γ_s(H) ∝ √<H>, which also supports the presence of line nodes. We did not observe a discontinuous change of the Fermi surface at P_<AF>=0.6 GPa where the Neel temperature becomes zero, but observed a new dHvA branch above 1.5 GPa of which the cyclotron effective mass decreased steeply as a function of pressure from 19m_0 at 2.0 GPa to 11m_0 at 2.7 GPa.
社団法人日本物理学会の論文
2007-01-15