Field Dependence of π-Band Superconducting Gap in MgB₂ Thin Films from Point-Contact Spectroscopy

We present the results of point-contact spectroscopy measurements on High-quality epitaxial MgB₂ thin films with injected current along the c-axis. The temperature and field dependences of π-band properties with the field parallel to (H_⊥) or perpendicular to (H_|| the c-axis are investigated in detail. When a magnetic field is applied, either parallel or perpendicular to the c-axis, the density of the quasiparticle state (DOS) of the π-band proliferates quickly with increasing field, while the gap amplitude of the π-band decreases slowly, which is different from the recent theoretical calculations, showing a field dependent competition between the interband scattering and the pair-breaking effects.