Effect of Randomness on Charge Density Wave and Superconductivity in Strong Coupling Electron Systems

Effects of randomness in the strong coupling electron systems, where the real space pairings of electrons have an important contribution are investigated in (quasi-) one-dimensional systems. For weak randomness, it is discussed that the nature of the ground state of purely one-dimensional systems does not necessarily reflect the low temperature properties of three-dimensional systems with quasi-one-dimensional anisotropy. In particular, the commensurate charge density wave and superconducting long range order persist for weak randomness. In the bipolaronic or biexcitonic region, Monte Carlo results show that the charge density wave is more strongly suppressed by randomness than superconductivity. The suppression of the CDW phase by impurities allows superconductivity to occur in parameter regime which were in a CDW phase for a pure system.