S. V. Kravchenko

Metallic behavior and related phenomena in two dimensions

For about twenty years, it has been the prevailing view that there can be no metallic state or metal-insulator transition in two dimensions in zero magnetic field. In the last several years, however, unusual behavior suggestive of such a transition has been reported in a variety of dilute two-dimensional electron and hole systems. The physics behind these observations is presently not understood. We review and discuss the main experimental findings and suggested theoretical models.

Possible metal-insulator transition at B=0 in two dimensions.

We have studied the zero magnetic field resistivity of unique high- mobility two-dimensional electron system in silicon. At very low electron density (but higher than some sample-dependent critical value,

Metal-insulator transition in two-dimensional electron systems

n_{cr}\sim 10^{11}

Electric Field Scaling at a B=0 Metal-Insulator Transition in Two Dimensions.

cm

Sharp increase of the effective mass near the critical density in a metallic two-dimensional electron system

^{-2}

Indication of the ferromagnetic instability in a dilute two-dimensional electron system.

), CONVENTIONAL WEAK LOCALIZATION IS OVERPOWERED BY A SHARP DROP OF RESISTIVITY BY AN ORDER OF MAGNITUDE with decreasing temperature below 1--2 K. No further evidence for electron localization is seen down to at least 20 mK. For

Electric Field Scaling at a {ital B={bold 0}} Metal-Insulator Transition in Two Dimensions

n_s<N_{cr}

Spin-Independent Origin of the Strongly Enhanced Effective Mass in a Dilute 2D Electron System

, the sample is insulating. The resistivity is empirically found to SCALE WITH TEMPERATURE BOTH BELOW AND ABOVE

Colloquium: Transport in strongly correlated two dimensional electron fluids

n_{cr}

Pauli spin susceptibility of a strongly correlated two-dimensional electron liquid

WITH A SINGLE PARAMETER which approaches zero at