Structural phase transition, precursory electronic anomaly, and strong-coupling superconductivity in quasi-skutterudite (Sr1−xCax)3Ir4Sn13 and Ca3Rh4Sn13*

Project supported by the National Natural Science Foundation of China (Grant Nos. 11674377 and 11634015), the National Key R&D Program of China (Grant Nos. 2017YFA0302904 and 2016YFA0300502), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020200). J. Y. is supported by the Youth Innovation Promotion Association of CAS.

Luo Jun1, 2, Yang Jie1, †, Maeda S3, Li Zheng1, 2, Zheng Guo-Qing1, 2, 3, ‡
       

(color online) The crystal structure of (Sr1−xCax)3Ir4Sn13 and Ca3RH4Sn13 that contain two different Sn sites, and the 119Sn-NMR spectra for (Sr1−xCax)3Ir4Sn13 (x = 0, 0.5, 1) and Ca3RH4Sn13 at 250 K. The horizontal coordinate represents the reduced frequency f/f0, with f0 = γH0/2π. The blue and red dotted lines are Gaussian fittings to the obtained spectra with area ratio of 1 : 12. The solid lines are the sum of the two Gaussian functions.