  The gas-liquid transition is a first-order transition terminating at a
finite-temperature critical point with diverging density fluctuations. Mott
transition, a metal-insulator transition driven by Coulomb repulsion between
electrons, has been identified with this textbook transition. However, the
critical temperature of the Mott transition can be suppressed, resulting in
unusual quantum criticality. It accounts for non-Fermi-liquid-like properties,
and strongly momentum dependent quasiparticles as in many materials near the
Mott insulator. Among all, the mode-coupling theory of the density fluctuations
supports d-wave superconductivity at the order of a hundred Kelvin for relevant
parameters of the copper oxide superconductors.
