Study of inter-band pair transfer and density of states on isotope effect in TTF[Ni (dmit)2]2 organic superconductor

Abstract

The present work deals with the influence of the inter-band pair transfer process and density of states on the isotope effect in layered TTF[Ni(dmit)2]2 organic superconductors. The model Hamiltonian is based on two chains tight binding Hubbard model that includes the electron coupled intra and intermolecular vibrations in the presence of electron Coulomb energy and the electron transfer energy between the chains. The expressions for superconducting order parameter, transition temperature and finally the isotope effect coefficient (α) are calculated in the BCS-framework of Green's function equations of motion approach. The numerical computation predicts that pair transfer processes and density of states controls the isotope effect coefficient in a significant way. More rigorous experimental investigations are needed to understand the microscopic origin of superconductivity and isotope effect in these organic superconductors.