NMR Study of the Mott Transitions to Superconductivity in the Two Cs3C60 Phases

We report a NMR and magnetometry study on the expanded intercalated fulleride ${\mathrm{Cs}}_3{C}_{60}$ in both its $A15$ and face centered cubic structures. NMR allowed us to evidence that both exhibit a first-order Mott transition to a superconducting state, occurring at distinct critical pressures $p_c$ and temperatures $T_c$. Though the ground state magnetism of the Mott phases differs, their high $T$ paramagnetic and superconducting properties are found similar, and the phase diagrams versus unit volume per $C_{60}$ are superimposed. Thus, as expected for a strongly correlated system, the interball distance is the relevant parameter driving the electronic behavior and quantum transitions of these systems.

Reproduced with permission. Copyright 2010, American Physical Society