Nanoscale mapping of local superconductivity in FeTe_1-xSe_x thin films

The iron-based superconductors FeTe_1-xSe_x have recently been found to be a promising candidate for topological superconductivity, which attracts significant research interests because of the possible realization of Majorana bound states and potential application in topological quantum computers. Beyond its topological aspects, FeTe_1-xSe_x exhibits a complex interplay between magnetism, electronic correlations, and superconductivity, which can be sensitively influenced by the local chemical composition—particularly the selenium concentration. Here we employ our newly developed BOlometric Superconducting Optical Nanoscopy (BOSON) technique to probe the nanoscale distribution of the superconducting transition in FeTe_1-xSe_x thin films. This capability provides an unprecedented window into the microscopic landscape of superconductivity in FeTe_1-xSe_x, linking compositional fluctuations and electronic inhomogeneity to superconducting coherence. Such insight is crucial for understanding how topological and trivial superconducting regions coexist and interact—an essential step toward engineering and controlling Majorana modes in this material platform. More broadly, this work establishes BOSON as a powerful nanoscale probe for studying emergent quantum phenomena in inhomogeneous and strongly correlated superconductors.