Interface-enhanced superconductivity in multi-grain (FeSe)η(SrTiO3)1-η composites

• Published in: Superconductor science & technology 2021-03, Vol.34 (3), p.35002
• Main Authors: Zhang, Huimin, Dong, Wenfeng, Meng, Qing-Long, Yin, Nan, Liu, Zhengmao, Lu, Xiaowei, Ge, Binghui, Li, Yuanzhao, Shi, Quan, Wang, Lili, Xue, Qi-Kun, Jiang, Peng, Bao, Xinhe
• Format: Article
• Language: English
• Subjects: FeSe/SrTiO; interface superconductivity; multi-grain composite; percolation; spark-plasma-sintering
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/1361-6668/abd28f

Interface superconductivity, realized in multiple artificial crystalline heterostructures, is one of the most exciting directions to search for high-temperature superconductivity. In this work, we prepare bulk (FeSe)η(SrTiO3)1−η multi-grain composites by a simple facile liquid-phase compaction method using a spark-plasma-sintering technique. Combining transmission electron microscopy/scanning electron microscopy and x-ray diffraction investigations, we demonstrate that the composites consist of micron-scale SrTiO3 grains surrounded by [001]-compressed β-FeSe grains. Transport measurements for the composites with FeSe mole fraction η > 0.06 reveal that two superconducting channels, one Tc ∼ 13 K phase from FeSe/SrTiO3 interfaces and another Tc ∼ 7 K phase from FeSe grains, cooperatively induce macroscopic superconducting behavior with isotropic upper critical fields above 40 T. This work points out a straightforward method to enhance Tc in the multi-grain (FeSe)η(SrTiO3)1−η composites by reducing the crystalline grains to nanoscale and finely tuning the stoichiometries of FeSe and SrTiO3.