Electronic States and Superconductivity in Alkali-Intercalated Fullerides: 13C-NMR Study in Na2RbC60, Na2CsC60, K3C60, K2RbC60, K2CsC60, KRbCsC60, Rb2CsC60 and RbCs2C60

Yutaka Maniwa; Takahito Saito; Atushi Ohi; Kenji Mizoguchi; Kiyoshi Kume; Koichi Kikuchi; Isao Ikemoto; Shinzo Suzuki; Yohji Achiba; Mayumi Kosaka; Katsumi Tanigaki; Thomas W. Ebbesen

doi:10.1143/jpsj.63.1139

Electronic States and Superconductivity in Alkali-Intercalated Fullerides: ¹³C-NMR Study in Na₂RbC₆₀, Na₂CsC₆₀, K₃C₆₀, K₂RbC₆₀, K₂CsC₆₀, KRbCsC₆₀, Rb₂CsC₆₀ and RbCs₂C₆₀

Yutaka Maniwa, Takahito Saito, Atushi Ohi, Kenji Mizoguchi, Kiyoshi Kume, Koichi Kikuchi, Isao Ikemoto, Shinzo Suzuki, Yohji Achiba, Mayumi Kosaka, Katsumi Tanigaki, Thomas W. Ebbesen

Author information

Yutaka Maniwa
Department of Physics, Tokyo Metropolitan University, Minami–osawa, Hachioji, Tokyo 192–03
Takahito Saito
Department of Physics, Tokyo Metropolitan University, Minami–osawa, Hachioji, Tokyo 192–03
Atushi Ohi
Department of Physics, Tokyo Metropolitan University, Minami–osawa, Hachioji, Tokyo 192–03
Kenji Mizoguchi
Department of Physics, Tokyo Metropolitan University, Minami–osawa, Hachioji, Tokyo 192–03
Kiyoshi Kume
Department of Physics, Tokyo Metropolitan University, Minami–osawa, Hachioji, Tokyo 192–03
Koichi Kikuchi
Department of Chemistry, Tokyo Metropolitan University, Minami–osawa, Hachioji, Tokyo 192–03
Isao Ikemoto
Department of Chemistry, Tokyo Metropolitan University, Minami–osawa, Hachioji, Tokyo 192–03
Shinzo Suzuki
Department of Chemistry, Tokyo Metropolitan University, Minami–osawa, Hachioji, Tokyo 192–03
Yohji Achiba
Department of Chemistry, Tokyo Metropolitan University, Minami–osawa, Hachioji, Tokyo 192–03
Mayumi Kosaka
Fundamental Research Laboratory, NEC Corporation, Tsukuba 305
Katsumi Tanigaki
Fundamental Research Laboratory, NEC Corporation, Tsukuba 305
Thomas W. Ebbesen
Fundamental Research Laboratory, NEC Corporation, Tsukuba 305

Keywords: C₆₀, fullerene, NMR, superconductivity, spin-lattice relaxation, BCS theory, Knight shift, T₁

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1994 Volume 63 Issue 3 Pages 1139-1148

DOI https://doi.org/10.1143/jpsj.63.1139

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Abstract

A systematic ¹³C NMR experiment is reported in alkali-fullerides A₃C₆₀ (where A₃ is alkali-metals) between superconducting transition temperature T_c and -- 100, K. Careful ¹³C NMR spin-lattice relaxation time study clarified the properties of the conduction electron wave functions at Fermi surface. An upper limit of Stoner exchange parameter was estimated to be -- 3, eV/(spin-carbon), which is far from spin-wave instability criterion. Based on these studies, a variation of the density of states at Fermi level, N(E_f), with T_c was deduced. The results were analyzed in terms of McMillan formula, leading to weak or medium electron-phonon coupling constants and relevant phonon energy larger than 600, K. It was strongly suggested that the A₃C₆₀ superconductor is described within a framework of the conventional phonon-mediated BCS superconductivity.

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