Abstract
Superconducting transition temperatures of a many-electron system coupled strongly with anharmonic phonons have been studied, to clarify how drastically anharmonicity changes the isotope effect from the harmonic case. The diagonal self-energy of electron as well as the off-diagonal one is determined self-consistently within Migdal's approximation. Typical two types of anharmonicities are studied. The first is a sextic anharmonicity induced by a hard-core repulsion. Isotope shifts become almost zero in this case. When this repulsion is stronger, the shifts are reversed. The second is a small negative quartic anharmonicity in addition to the sextic one, just in the case of a mixture of a hard-core and a soft one. In this case, on the contrary, the shifts are greatly enhanced. Discussion is also given in relation to the observed anomalous isotope effects of newly discovered superconductors.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
