Ion-Beam-Induced Metal-Insulator Transition in YBa sub 2 Cu sub 3 O sub 7- sigma : A Mobility Edge

We have studied the temperature-dependent resistivity and Hall coefficient of epitaxial YBa sub 2 Cu sub 3 O sub 7- sigma films as a function of ion-beam-induced damage. At low ion fluences the films behave like typical metals above the superconducting transition. At higher ion fluences, the material goes continuously through the metal-insulator transition with a resistivity that varies like exp(T sup -1/2 ) but with a Hall coefficient that changes very little.