Mott transition, antiferromagnetism, and unconventional superconductivity in layered organic superconductors

The phase diagram of the organic superconductor kappa-(ET)(2)Cu[N(CN)(2)]Cl has been accurately measured from H-1 NMR and ac susceptibility techniques under helium gas pressure. The domains of stability Bf antiferromagnetic a nd superconducting orders in the pressure vs temperature plane have been de termined. Both phases overlap through a first-order boundary that separates two regions of inhomogeneous phase coexistence. The boundary curve merges with the first-order line of the metal-insulator transition which ends with a critical point at higher temperature. The whole phase diagram features a pointlike region where metallic, insulating, antiferromagnetic, and non-s- wave superconducting phases all meet.