Isotope Effect and Phonon Softening in Superconducting Borocarbides and Boronitrides

Authors : Tuğrul HAKİOĞLU

Pages : 863-872

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Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :The isotope effect in the recently disvovered class o superconductors LuNi2B2C and La3Ni2B2N3 is investigated in the context of electron-squezed phonon interaction renormalizing the Ni-d electron-electron correlations. Squeezed phonon mode originates from the anharmonic character of the tetragonal Ni-B structure and is polarized in the vortical direction to the Ni layers. The isotope effect arises as a result of the zero point motion of the Ni-Ni d-electron hopping amplitude dominantly due to this vertical phonon mode. Within this model the isotope exponent is calculated to be aB \leq 0.20 as compared to the recently found experimental value aBexp = 0.27 \mp 0.10. Finally, the phonon frequency softening predicted by our model eletron-phonon interaction is discussed within the context of recent experiments on the relevant boron A1g softening.
Keywords : Turk J Phys, 22, 1998, 863 872 Turk J Phys, vol 22, iss 9