通过微量锰掺杂直接合成体超导的Fe(Te,Se)单晶

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

无砷的铁硒基超导体Fe(Te,Se)在高场应用方面具有广阔的前景,但至今仍缺乏制备体超导块材的有效方法.本文通过微量的Mn掺杂,一步法直接合成了无间隙铁的厘米尺寸高性能体超导单晶.通过电阻、磁化率与比热表征,发现Mn掺杂浓度为1%时,样品具有最好的体超导电性,且上临界场和临界电流密度相比未掺杂时显著提高.最佳掺杂样品在2 K时自场下的临界电流密度高达4.5×10^(5)A cm^(-2),且在高场下衰减很小.利用扫描隧道显微镜观测,证实了微量锰掺杂有效消除了层间的间隙铁原子.本工作首次提供了一种大规模制备高性能Fe(Te,Se)超导块材的实用方法,为其未来高场应用奠定了基础.

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 centimetersized 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 undoped sample,the optimally doped one shows a significantly enhanced upper critical field,and a large self-field critical current density J_(c) of 4.5×10^(5)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.