Collapse of the charge gap in random Mott insulators

Effects of randomness on interacting fermionic systems in one dimension are investigated by quantum Monte Carlo techniques. At first, interacting spin less fermions are studied whose ground state shows charge ordering. Quantum phase transition due to randomness is observed associated with the collaps e of the charge ordering. We also treat random Hubbard model focusing on th e Mott gap. Although the randomness closes the Mott gap and low-lying state s are created, which is observed in the charge compressibility, no (quasi-) Fermi-surface singularity is formed. It implies localized nature of the low -lying states. [S0163-1829(98)00748-6].