We report the electrical, magnetic and thermal measurements on a layered cobalt oxyhydrate Na0.31CoO2·1.3H2O. Bulk superconductivity at 4.3 K has been confirmed, however, the measured superconducting fraction is relatively low probably due to the sample's intrinsic two-dimensional characteristic. The compound exhibits weak-coupled and extreme type-II superconductivity with the average energy gap ∆a(0) and the Ginzburg-Landau parameter κ of ∼ 0.50 meV and ∼ 140, respectively. The normalized electronic specific heat data in the superconducting state well fit the T 3 dependence, suggesting point nodes for the superconducting gap structure.

We report the measurements of in-plane resistivity, Hall effect, and Nernst effect in Zn doped YBa2Cu3O 7−δ epitaxial thin films grown by pulsed laser deposition technique. The pseudogap temperature, T * , determined from the temperature dependence of resistivity, does not change significantly with Zn doping. Meanwhile the onset temperature (T ν ) of anomalous Nernst signal above Tc0, which is interpreted as evidence for vortex-like excitations, decreases sharply as the superconducting transition temperature Tc0 does. A significant decrease in the maximum of vortex Nernst signal in mixed state is also observed, which is consistent with the scenario that Zn impurities cause a decrease in the superfluid density and therefore suppress the superconductivity. The phase diagram of T * , T ν , and Tc0 versus Zn content is presented and discussed.

We report the measurements of thermopower, electrical resistivity and thermal conductivity in a complex cobalt oxide Li0.48Na0.35CoO2, whose crystal structure can be viewed as an intergrowth of the O3 phase of LixCoO2 and the P2 phase of NayCoO2 along the c axis. The compound shows large room-temperature thermopower of ∼180 µV/K, which is substantially higher than those of LixCoO2 and NayCoO2. The figure of merit for the polycrystalline sample increases rapidly with increasing temperature, and it achieves nearly 10 −4 K −1 at 300 K, suggesting that LixNayCoO2 system is a promising candidate for thermoelectric applications.

The temperature dependence of the resistivity and magnetoresistance (MR) of quasi-one-dimensional NbSe3 was studied. The sharp increase of the positive MR in the lower charge-density wave (CDW) phase is consistent with previous reports, and the violation of Kohler’s rule is obvious. We found that the MR data can be fitted very well with a modified two-band model, and the temperature dependence of the resulting parameters was discussed. The MR, the effect of magnetic field on the CDW gap, and the thermoelectric power of NbSe3 can be coherently understood within this model.

Single crystals of two-dimensional 2H-NbSe2, which undergoes a superconducting transition at Tc = 7.2 K and a charge-density wave (CDW) transition at TCDW = 30 K, were synthesized. Measurements of the resistivity, Hall coefficient and magnetoresistance (MR) versus temperature were performed on NbSe2 crystals with different resistance residual ratios (RRR = R(300 K)/R(8 K)), chosen from different batches. The superconducting transition temperature hardly changes with the RRR, while the MR and Hall coefficient are strongly dependent on the RRR values of the samples. Moreover, the temperature and field dependence of the MR violate Kohler’s rule, indicating that the scattering times of the charge carriers are no longer isotropic. A steep decrease of the Hall coefficient RH below 50 K is only observed for the high quality sample; this can be interpreted in terms of a drastic increase of the mean free path for the electron-type charge carriers. The effect of the CDW transition on the Hall coefficient is discussed using a two-band model and a sharp change in the scattering rate on an electron-like orbit below TCDW is suggested.