The normal-state charge transport is studied systematically in high-quality single crystals of BaFe2(As1−xPx)2 (0 ≤ x ≤ 0.71). By substituting isovalent P for As, the spin-density-wave (SDW) state is suppressed and the dome-shaped superconducting phase (Tc 31 K) appears. Near the SDW end point (x ≈ 0.3), we observe striking linear temperature (T ) dependence of resistivity in a wide T -range, and remarkable low-T enhancement of Hall coefficient magnitude from the carrier number estimates. We also find that the magnetoresistance apparently violates the Kohler's rule and is well scaled by the Hall angle ΘH as ∆ρxx/ρxx ∝ tan 2 ΘH . These non-Fermi liquid transport anomalies cannot be attributed to the simple multiband effects. These results capture universal features of correlated electron systems in the presence of strong antiferromagnetic fluctuations.

No abstract

The thermal conductivity of the heavy-fermion superconductor CeCoIn5 has been studied in a magnetic field rotating within the 2D planes. A clear fourfold symmetry of the thermal conductivity which is characteristic of a superconducting gap with nodes along the ( +/- pi,+/- pi) directions is resolved. The thermal conductivity measurement also reveals a first-order transition at H(c2), indicating a Pauli limited superconducting state. These results indicate that the symmetry most likely belongs to d(x(2)-y(2)), implying that the anisotropic antiferromagnetic fluctuation is relevant to the superconductivity.

We observed de Haas-van Alphen (dHvA) oscillation in both the normal and superconducting mixed states of a heavy-fermion superconductor CeCoIn5. The Fermi surfaces are found to consist of nearly cylindrical Fermi surfaces and small ellipsoidal ones, reflecting the unique tetragonal crystal structure. The detected cyclotron masses of 5-87 m0 for these Fermi surfaces are extremely large, and correspond to a large electronic specific heat coefficient of about 1000 mJ K-2 mol-1. The cyclotron masses are also found to be field dependent in both the normal and mixed states.

No abstract