Interface-induced superconductivity and strain-dependent spin density waves in FeSe/SrTiO sub(3) thin films

• Published in: Nature materials 2013-07, Vol.12 (7), p.634-640
• Main Authors: Tan, Shiyong, Zhang, Yan, Xia, Miao, Ye, Zirong, Chen, Fei, Xie, Xin, Peng, Rui, Xu, Difei, Fan, Qin, Xu, Haichao, Jiang, Juan, Zhang, Tong, Lai, Xinchun, Xiang, Tao, Hu, Jiangping, Xie, Binping, Feng, Donglai
• Format: Article
• Language: English
• Subjects: Iron; Lattice parameters; Phase diagrams; Spin density waves; Strontium titanates; Superconductivity; Thin films; Transition temperature; Tuning
• ISSN: 1476-1122
• DOI: 10.1038/nmat3654

The record superconducting transition temperature (T sub(c)) for the iron-based high-temperature superconductors (Fe-HTS) has long been 56K. Recently, in single-layer FeSe films grown on SrTiO sub(3) substrates, indications of a new record of 65K have been reported. Using in situ photoemission measurements, we substantiate the presence of spin density waves (SDWs) in FeSe films-a key ingredient of Fe-HTS that was missed in FeSe before-and we find that this weakens with increased thickness or reduced strain. We demonstrate that the superconductivity occurs when the electrons transferred from the oxygen-vacant substrate suppress the otherwise pronounced SDWs in single-layer FeSe. Beyond providing a comprehensive understanding of FeSe films and directions to further enhance its T sub(c), we map out the phase diagram of FeSe as a function of lattice constant, which contains all the essential physics of Fe-HTS. With the simplest structure, cleanest composition and single tuning parameter, monolayer FeSe is an ideal system for testing theories of Fe-HTS.