著者

Inada Yasuzi Nasu Keiichiro

出版者

一般社団法人日本物理学会

雑誌

Journal of the Physical Society of Japan (ISSN:00319015)

巻号頁・発行日

vol.61, no.12, pp.4511-4520, 1992-12-15

被引用文献数

8

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Superconducting transition temperatures of a many-electron system coupledstrongly w'ith anharmonic PIIOIIOIIS have been studied, to clarify how drasticallyanlaarmonicity changes tlae isotope effect from the harmonic case. The diagonal self-energy of electron as well as tlte off-diagonal one is determined self-consistentlywitlain Migdal's approxinaation. Typical two types of anharmonicities are studied.The first is a sextic anharmonicity induced by a hard-core repulsion. Isotope shiftsbecome almost zero in this case. Whena Thais repulsion is stronger, the shifts are re-versed. The second is a small negative quartic anharmonicity in additiora to the sexticone, just in tlae case of a mixture of a hard-core and a soft one. In this case, on thecontrary, the slaifts are greatly enhancecl. Discussion is also given in relation to the ob-served anomalous isotope effects of newly discovered superconductors[isotope effect, superconductivity, N4igda1-Eliashberg theory, anharmonic ll phononl