[13p-B408-1~16] 11.1 基礎物性

▲ [13p-B408-6] First Principles Calculations of Superconducting Transition Temperature of ThCr$_2$Si$_2$-type Structure

〇(M1)Gewinner Senderanto Sinaga¹、Keishu Utimura¹、Kousuke Nakano²、Kenta Hongo^2,3,4,5、Ryo Maezono^2,6 (1.Mater. Sci., JAIST、2.Info. Sci., JAIST、3.RCACI, JAIST、4.NIMS、5.PRESTO、6.RIKEN)

キーワード：superconductivity, first-principles calculations, ThCr2Si2-type structure

High superconducting transition temperature (T_c) superconductors have a great potential in many industrial applications. However, discovering a compound having high T_c is still remaining a big challenge for experimental approach due to time-consuming and high cost. In this talk, we focus on ThCr₂Si₂-type compounds with a I4/mmm symmetry and predict their T_c values by combining first-principles phonon simulations with models based on the Bardeen-Cooper-Schrieffer (BCS) theory [1]. Although thousand compounds belong to this structure, no comprehensive and systematic study has been done so far. Referring to the NIMS database [2], our T_c results showed a fairly good agreement with the experimental data. Finally, our exploration within the ThCr₂Si₂ family revealed that ThCu₂Si₂ and ThAu₂Si₂ could be newly possible conventional superconductors having T_c around 3.88 K and 4.27 K, respectively [3]. Here our first principles phonon simulations confirmed that both of compounds have non-negative frequencies indicating the dynamical stability of the compounds at ambient temperature. In addition, we found that Fe or Co based compounds could not be explained just by electron-phonon interaction. This discrepancy between theory and experiment implies that those compounds are unconventional superconductors.
[1] K. Nakano, K. Hongo, and R. Maezono, Sci. Rep. 6, 29661 (2016).
[2] “Superconducting material database (supercon),” https://supercon.nims.go.jp/supercon/material_search, accessed: 2019-11-17
[3] G.S Sinaga, K. Uchimura, K. Nakano, K. Hongo, and R. Maezono, arXiv:1911.10716