Nodal Gap in Fe-Based Layered Superconductor LaO0.9F0.1-deltaFeAs Probed by Specific Heat Measurements
Abstract
We report the specific heat measurements on the newly discovered Fe-based layered superconductor LaO0.9F0.1-deltaFeAs with the onset transition temperature Tc ≈ 28 K. A nonlinear magnetic field dependence of the electronic specific heat coefficient gamma(H) has been found in the low temperature limit, which is consistent with the prediction for a nodal superconductor. The maximum gap value Delta0 ≈ 3.40.5 meV was derived by analyzing gamma(H) based on the d-wave model. We also detected the electronic specific heat difference between 9 T and 0 T in wide temperature region, a specific heat anomaly can be clearly observed near Tc. The Debye temperature of our sample was determined to be about 315.7 K. Our results suggest an unconventional mechanism for this new superconductor.