Effect of antiferromagnetic ordering on temperature dependent superconducting gap in ErNi2B2C: Laser-photoemission spectroscopy

We have performed temperature ( T )-dependent laser-photoemission spectroscopy of antiferromagnetic (AF) superconductor ErNi 2 B 2 C to study the electronic structure, especially the effect of AF ordering in T -dependent superconducting (SC) gap. To estimate the values of T -dependent SC gap, we fitted the experimental data by Dynes function having an anisotropic s -wave SC gap. From the fitting results, we find a sudden deviation from the BCS prediction just below T N . This observation can be well explained by the theoretical model, indicating that the origin of anomalous T -dependence is competition between rapid evolution of AF molecular field and SC condensation energy.