Magnetic-Field Induced Metal-Insulator Transition in SrTiO_3−δ

Metallic samples of SrTiO_3−δ with charge-carrier concentrations of n = 8.6 × 10¹⁶ cm⁻³ and 2.0 × 10¹⁷ cm⁻³ are shown to exhibit magnetic-field-induced metal-insulator transitions. Landau levels emerge in the magnetic field, and their energy spacing is comparable to the Fermi and thermal energies. The convergence of these energy scales plays an important role in the observed behavior. A simple parallel-conduction model represents the data below the metal-insulator transition well.