Unusual insulating phase at low temperature in thin indium films

We have prepared a series of thin indium films whose disorder is systematically introduced, and measured the temperature-dependent and magnetic-field-dependent Hall resistance ${\mathit{R}}_{\mathit{x}\mathit{y}}$ as well as the longitudinal resistance ${\mathit{R}}_{\mathit{x}\mathit{x}}$ at low temperatures. By increasing the field at fixed disorder, we have found, in addition to a usual critical field ${\mathit{B}}_{\mathit{x}\mathit{x}\mathit{C}}$ where ${\mathit{R}}_{\mathit{x}\mathit{x}}$(T→0)→∞, another critical field ${\mathit{B}}_{\mathit{x}\mathit{y}\mathit{C}}$ (≳${\mathit{B}}_{\mathit{x}\mathit{x}\mathit{C}}$) where ${\mathit{R}}_{\mathit{x}\mathit{y}}$(T→0) diverges. With increasing disorder, ${\mathit{B}}_{\mathit{x}\mathit{x}\mathit{C}}$ decreases faster than ${\mathit{B}}_{\mathit{x}\mathit{y}\mathit{C}}$, thus the region ${\mathit{B}}_{\mathit{xxC}}$<B<${\mathit{B}}_{\mathit{xyC}}$ as the critical disorder is approached. We suggest a possibility that the region ${\mathit{B}}_{\mathit{xxC}}$<B<${\mathit{B}}_{\mathit{xyC}}$ corresponds to the Bose-insulator phase.