Iyo Akira, Ishida Shigeyuki, Fujihisa Hiroshi, Gotoh Yoshito, Hase Izumi, Yoshida Yoshiyuki, Eisaki Hiroshi, Kawashima Kenji
National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Umezono , Tsukuba , Ibaraki 305-8568 , Japan.
IMRA Material R&D Co., Ltd. , 2-1 Asahi-machi , Kariya , Aichi 448-0032 , Japan.
J Phys Chem Lett. 2019 Mar 7;10(5):1018-1023. doi: 10.1021/acs.jpclett.9b00321. Epub 2019 Feb 20.
We report synthesis, crystal structure, and superconductivity in ThCrSi-type LaFeAs (La122). La122 was synthesized at 960 °C for 1.5 h under a pressure of 3.4 GPa. An as-synthesized La122 (nonsuperconductor) had a collapsed tetragonal structure with a short c-axis length of 11.0144(4) Å as observed in CaFeAs under pressure. The collapsed tetragonal structure transformed into an uncollapsed tetragonal structure by annealing the as-synthesized La122 at 500 °C. The c-axis length remarkably extended to 11.7317(4) Å, and superconductivity emerged at 12.1 K in the uncollapsed tetragonal La122. A cylindrical hole-like Fermi surface around the Γ point that plays an important role for an s± wave pairing in iron-based superconductors was missing in the uncollapsed tetragonal La122 because of heavy electron doping. Superconductivity in La122 may be closely related to that induced in CaFeAs under pressure.
我们报道了ThCrSi型LaFeAs（La122）的合成、晶体结构及超导性。La122在3.4 GPa压力下于960 °C合成1.5小时。合成后的La122（非超导体）具有一种塌缩的四方结构，其c轴短长度为11.0144(4) Å，这与在压力下的CaFeAs中观察到的情况相同。通过将合成后的La122在500 °C退火，塌缩的四方结构转变为未塌缩的四方结构。c轴长度显著延长至11.7317(4) Å，并且在未塌缩的四方La122中于12.1 K出现了超导性。由于重电子掺杂，在未塌缩的四方La122中，在铁基超导体中对s±波配对起重要作用的围绕Γ点的圆柱状孔状费米面缺失。La122中的超导性可能与在压力下CaFeAs中诱导出的超导性密切相关。
