Absence of a zero-temperature vortex solid phase in strongly disordered superconducting Bi films

We present low-temperature measurements of the resistance in magnetic field of superconducting ultrathin amorphous Bi films with normal-state sheet resistances, R-N, near the resistance quantum, R-Q=h/e(2). For R-N less than R-Q, the tails of the resistive transitions show the thermally activated flux flow signature characteristic of defect motion in a vortex solid with a finite correlation length. When R-N exceeds R-Q, the tails become nonactivated. We conclude that in films where R-N greater than R-Q there is no vortex solid and, hence, no zero resistance state in magnetic field. We describe how disorder induced quantum and/or mesoscopic fluctuations can eliminate the vortex solid and also discuss implications for the magnetic-field-tuned superconductor-insulator transition.