Superconductivity in potassium and ammonia co-intercalated Fe[Se .sub.-x] [Te.sub.x]

• Published in: Science China. Physics, mechanics & astronomy Vol. 62; no. 4
• Main Authors: Xiao, BinBin, Wang, NaiZhou, Shang, Chao, Meng, FanBao, Ding, JianWen, Lei, Bin, Luo, XiGang
• Format: Journal Article
• Language: English
• Published: Springer 01.04.2019
• Subjects: Ammonia; Superconductors
• ISSN: 1674-7348; 1869-1927
• DOI: 10.1007/s11433-018-9302-6

The origin of the ~40 and ~30 K superconducting phases in the metal-intercalated FeSe superconductors is still unclear. We report the synthesis of [K.sub.0.3] [(N[H.sub.3]).sub.y] [(Fe[Se.sub.1-x] [Te.sub.x]).sub.2] and [K.sub.0.6] [(N[H.sub.3]).sub.y] [(Fe[Se.sub.1-x] [Te.sub.x]).sub.2] with x=0-0.6 by using the liquid ammonia method at room temperature. The superconducting transition temperature [T.sub.c] of the former remains about 43 K for all the nominal Te content less than 0.3, while that of the latter is about 30 K and obviously decreases with Te doping. Superconductivity disappears for x [greater than or equal to] 0.4 in both systems. Except for the different chemical pressure induced by substitution of Te for Se in both systems, we also observed distinct external pressure effect on superconductivity for both systems, with much more efficiency of suppressing [T.sub.c] by external pressure in the former system. These dramatic differences of both chemical and external pressure effects on [T.sub.c] between the ~30 and ~40 K superconducting phases revealed that the existence of the two superconducting phases can be ascribed to the moderate and negligible coupling between FeSe layers, respectively. pnictides and chalcogenides, properties of superconductors, effects of pressure, methods of materials synthesis and materials processing PACS number(s): 74.70.Xa, 81.20.-n, 74.10.+v, 74.62.Fj