Artificially engineered nanostrain in FeSexTe1-x superconductor thin films for supercurrent enhancement

Abstract

Abstract Although nanoscale deformation, such as nanostrain in iron-chalcogenide (FeSe x Te 1− x , FST) thin films, has attracted attention owing to its enhancement of general superconducting properties, including critical current density ( J c ) and critical transition temperature, the development of this technique has proven to be an extremely challenging and complex process thus far. Herein, we successfully fabricated an epitaxial FST thin film with uniformly distributed nanostrain by injection of a trace amount of CeO 2 inside an FST matrix using sequential pulsed laser deposition. By means of transmission electron microscopy and geometric phase analysis, we verified that the injection of a trace amount of CeO 2 forms nanoscale defects, with a nanostrained region of tensile strain ( ε zz ≅ 0.02) along the c -axis of the FST matrix. This nanostrained FST thin film achieves a remarkable J c of 3.5 MA/cm 2 under a self-field at 6 K and a highly enhanced J c under the entire magnetic field with respect to those of a pristine FST thin film.