Bulk superconductivity in one-step grown Fe(Te,Se) crystals free of interstitial iron by minor Mn doping

Abstract

The iron-based nontoxic chalcogenide superconductor Fe(Te,Se) has great potential for high magnetic field applications while it lacks a reliable method to produce bulk superconductor so far. Here we report a one-step synthesis method to grow high-quality Fe(Te,Se) single crystals free of interstitial iron atoms through minor Mn doping. Bulk superconductivity is revealed in the as-grown centimeter-sized crystals with the optimal doping level of 1% Fe atoms substituted by Mn, which is systematically demonstrated by sharp electrical resistivity and magnetic susceptibility transitions, and large specific heat jumps. Compared with the un-doped sample, the optimally doped one shows a significantly enhanced upper critical field, and a large self-field critical current density Jc of 4.5 × 105 A cm−2 at 2 K (calculated by the Bean model), which maintains large values under high fields. The absence of interstitial iron atoms is testified by the scanning tunneling microscopy, and the effect of Mn doping is discussed. Our results provide a practical method by minor Mn doping to directly synthesize high-performance Fe(Te,Se) bulks that allow for future high-field superconducting applications.