Gunnarsson O., Rainer D., Zwicknagl G.
The authors study the screening for C60 in the random phase approximation. For a free molecule they find a substantial reduction of the interaction between close atoms but an 'antiscreening' of the interaction between distant atoms. For a C60 solid there is an efficient screening of the intraband Coulomb interaction (U approximately 0.05 eV), leading to mu =UN(0) approximately 0.4, where N(0) is the density of states per spin and molecule. The authors then study the renormalization of the Coulomb pseudo-potential mu * due to higher subbands in a simple two-band model. They find that the renormalization is small, although a traditional approach, summing ladder diagrams is the screened interaction, predicts a large renormalization. This suggests that mu * may not be much smaller than mu approximately 0.4 in C60. To obtain reasonable transition temperatures, Tc, this value of mu *( approximately 0.4) requires values of the electron-phonon coupling constant lambda , which are not very much larger than what has been calculated.
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