Nodal Gap in Fe-Based Layered Superconductor LaO_0.9F_{0.1-delta}FeAs Probed by Specific Heat Measurements

TL;DR

This study investigates the superconducting gap structure of LaO_0.9F_{0.1-delta}FeAs using specific heat measurements, revealing nodal behavior and an unconventional superconducting mechanism.

Contribution

First specific heat analysis indicating nodal superconductivity and unconventional pairing in LaO_0.9F_{0.1-delta}FeAs.

Findings

Nonlinear magnetic field dependence of gamma(H) suggests nodal superconductor.

Maximum gap Delta_0 approximately 3.4 meV.

Evidence of an unconventional superconducting mechanism.

Abstract

We report the specific heat measurements on the newly discovered Fe-based layered superconductor LaO_0.9F_{0.1-delta}FeAs with the onset transition temperature T_c \approx 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 Delta_0 \approx 3.4$\pm$0.5 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 T_c. The Debye temperature of our sample was determined to be about 315.7 K. Our results suggest an unconventional mechanism for this new superconductor.