Into the flat land: Transport studies of ultra-dilute GaAs two-dimensional hole systems in zero field – Jian Huang

Date: Mon. October 1st, 2012, 12:30 pm-1:30 pm
Location: Rockefeller 221

Low temperature charge transport studies of high purity electron systems encompass fundamental subjects of disorder and electron-electron interaction. 50 years after Anderson’s theory of localization for non-interacting electrons, the question on whether and how electron-electron interaction qualitatively alters the picture is still unsettled. Fascinating subjects on interaction-driven phenomena such as Wigner crystallization of electrons (for the quantum scenario) have never been demonstrated. Experimentally, high-purity semiconductor bulk materials offer a desirable tunability of charge density down to ultra-dilute limits where both new frontiers of physics and important applications such as quantum information technologies can be explored. However, such a transition is often overshadowed by the substantial disorder which competes with or even dominates over interaction by rendering the system into an Anderson insulator. We report findings obtained through measuring ultra-high-purity GaAs two-dimensional hole systems with dilute charge concentrations down to 8\times 10^8/cm^2. The measurement of the charge density and temperature dependence of the conductivity provides evidence for the interaction-driven many-body characteristics in contrast to the disorder-dominated situations. Moreover, some striking discontinuous behaviors observed for charge densities below 4\times 10^9/cm^2 suggest a possible phase transition which will be discussed.