Experimental lattice dependence of the density of states in alkali fullerides

Abstract

Using electron-spin resonance, we measured conduction-electron-spin susceptibility versus temperature for three alkali-fulleride compounds in the normal state. Converting the observed Pauli-spin susceptibility into density of states at the Fermi level $N(0)$ and using the temperature dependence of the lattice parameter we fit the experimental variation of $N(0)$ as a function of the inter-${\mathrm{C}}_{60}$ distance $d$ with an exponential functional form. Assuming a universal ${T}_{c}$ dependence on the lattice constant for every alkali fulleride, we used the value $N(0)=f(d)$ in the McMillan formula to fit the ${(T}_{c},d)$ data points taken from the literature.