New Reentrant Insulating Phases in Strongly Interacting 2D Systems with Low Disorder

Abstract

The apparent metal-insulator transition (MIT) in two-dimension (2D) was discovered by Kravchenko et al. [1] more than two decades ago in strongly interacting 2D electrons residing in a Si-metal-oxide-semiconductor field-effect transistor (Si-MOSFET). Its origin remains unresolved. Recently, low magnetic field reentrant insulating phases (RIPs), which dwell between the zero-field (B=0) metallic state and the integer quantum Hall (QH) states where the Landau-level filling factor υ > 1, have been observed in strongly correlated 2D GaAs hole systems with large interaction parameter rs (~20-40) and high purity. A new complex phase diagram was proposed, which includes zero field MIT, low magnetic field RIPs, integer QH states, fractional QH states, high field RIPs and insulating phases (HFIPs) with υ < 1 in which the insulating phases are explained by the formation of Wigner crystal. Furthermore, evidences of new intermediate phases were reported. All contribute to the further understandings of the puzzle. This review article serves the purpose of summarizing those recent experimental findings and theoretical endeavors, to foster future research efforts.

Recent Developments in the Field of the Metal-Insulator Transition in Two Dimensions

“…In summary, we have reviewed the exciting properties of strongly interacting fermions in 2D electron and hole systems, in particular, transport and thermodynamic data on the metallic side of the B = 0 metal-insulator transition and recent advances in our understanding of the low-density state on the insulating side of the transition. A complementary review [61] of the low-density state is available in the same volume.…”

“…[6,57] and references therein). The observation of broad-band voltage noise at the threshold I − V curves [50][51][52], as well as the attempts to probe the low-density state in perpendicular magnetic fields [53,[58][59][60][61], also have not yielded information that allows a choice between the depinning of the electron solid or traditional mechanisms [6,57]. Much confusion was introduced by the fact that many authors chose to interpret their data in terms of Wigner crystal [62][63][64][65][66], ignoring mundane interpretations.…”

Recent Developments in the Field of the Metal-Insulator Transition in Two Dimensions

“…[6,57] and references therein). The observation of broad-band voltage noise at the threshold I − V curves [50][51][52] as well as the attempt to probe the low-density state in perpendicular magnetic fields [53,[58][59][60][61] also have not provided information that allows a choice between the depinning of the electron solid or traditional mechanisms [6,57]. It is worth noting that much confusion was introduced by the fact that many authors chose to interpret their data in terms of Wigner crystal [62][63][64][65][66], ignoring mundane interpretations.…”