Nernst effect of a new iron-based superconductor LaO1-xFxFeAs

We report the first Nernst effect measurement on a new iron-based superconductor LaO1-xFxFeAs (x = 0(1). In the normal state, the Nernst signal is negative and very small. Below T-c, a large positive peak caused by vortex motion is observed. The flux flowing regime is quite large compared to the conventional type-II superconductors. The sharp decrease in the Nernst signal at the depairing magnetic field H-c2 is not obvious even for temperatures close to T-c. Furthermore, a clear deviation of the Nernst signal from normal state background and an anomalous suppression of off-diagonal thermoelectric current in the normal state between T-c and 50K are observed. We argue that this anomaly in the normal state Nernst effect could correlate with the spin-density wave (SDW) fluctuations although the contribution of superconducting fluctuations cannot be excluded.