期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：7
页码：1937-1940
DOI：10.1073/pnas.1418994112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceTo clarify the mechanism of superconductivity in iron-based superconductors, it is crucial to investigate FeSe1-xTex, which has the simplest crystal structure among them. There is, however, a serious obstacle to the understanding of its superconductivity; phase separation occurs in the region of [IMG]f1.gif" ALT="Formula" BORDER="0">, and thus a whole phase diagram has not been available. Here we report the successful fabrication of FeSe1-xTex films with [IMG]f2.gif" ALT="Formula" BORDER="0">. This is, to our knowledge, the first demonstration of the suppression of the phase separation. What is more notable is that a giant enhancement of [IMG]f3.gif" ALT="Formula" BORDER="0"> is observed in the "phase-separation region." The complete phase diagram that we present provides a previously unidentified perspective for the mechanism of superconductivity of this material. We demonstrate the successful fabrication on CaF2 substrates of FeSe1-xTex films with [IMG]f2.gif" ALT="Formula" BORDER="0">, including the region of [IMG]f1.gif" ALT="Formula" BORDER="0">, which is well known to be the "phase-separation region," via pulsed laser deposition that is a thermodynamically nonequilibrium method. In the resulting films, we observe a giant enhancement of the superconducting transition temperature, [IMG]f3.gif" ALT="Formula" BORDER="0">, in the region of [IMG]f1.gif" ALT="Formula" BORDER="0">: The maximum value reaches 23 K, which is [~]1.5 times as large as the values reported for bulk samples of FeSe1-xTex. We present a complete phase diagram of FeSe1-xTex films. Surprisingly, a sudden suppression of [IMG]f3.gif" ALT="Formula" BORDER="0"> is observed at [IMG]f4.gif" ALT="Formula" BORDER="0">, whereas [IMG]f3.gif" ALT="Formula" BORDER="0"> increases with decreasing x for [IMG]f5.gif" ALT="Formula" BORDER="0">. Namely, there is a clear difference between superconductivity realized in [IMG]f6.gif" ALT="Formula" BORDER="0"> and in [IMG]f7.gif" ALT="Formula" BORDER="0">. To obtain a film of FeSe1-xTex with high [IMG]f3.gif" ALT="Formula" BORDER="0">, the controls of the Te content x and the in-plane lattice strain are found to be key factors.
关键词：FeSe1− x Te x ; thin-film growth ; compressive strain ; complete phase diagram
