Magnetic-field-induced metal-insulator transition in two dimensions

We carried out magnetotransport measurements and scaling analysis to report on a new magnetic-field-induced metal-insulator transition in two dimensions, where the separatrix between insulating and conducting states appears at a critical magnetic field. In the insulating state, a giant magnetoresistance is observed over a wide range of magnetic field. At the transition, the resistance remains nearly constant over two decades of temperature. In the conducting state a quantum Hall plateau is observed at h/2${\mathit{e}}^2$. The critical exponent is in agreement with those of similar transitions in the quantum Hall regime, possibly reflecting a symmetry between the delocalization processes in 2D.