MAGNETIC-FIELD-INDUCED METAL-INSULATOR-TRANSITION IN 2 DIMENSIONS

We carried out magnetotransport measurements and scaling analysis to r eport on a new magnetic-field-induced metal-insulator transition in tw o dimensions, where the separatrix between insulating and conducting s tates appears at a critical magnetic field. In the insulating state, a giant magnetoresistance is observed over a wide range of magnetic fie ld. At the transition, the resistance remains nearly constant over two decades of temperature. In the conducting state a quantum Hall platea u is observed at h/2e2. The critical exponent is in agreement with tho se of similar transitions in the quantum Hall regime, possibly reflect ing a symmetry between the delocalization processes in 2D.