Superconductivity in Uncollapsed Tetragonal LaFe2As2

• Published in: The journal of physical chemistry letters 2019-03, Vol.10 (5), p.1018-1023
• Main Authors: Iyo, Akira, Ishida, Shigeyuki, Fujihisa, Hiroshi, Gotoh, Yoshito, Hase, Izumi, Yoshida, Yoshiyuki, Eisaki, Hiroshi, Kawashima, Kenji
• Format: Article
• Language: English
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.9b00321

We report synthesis, crystal structure, and superconductivity in ThCr2Si2-type LaFe2As2 (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 CaFe2As2 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 CaFe2As2 under pressure.