Wednesday, November 7, 2018
Based on the famous 1979 paper by Abrahams, Anderson, Licciardello and Ramakrishnan [Phys. Rev. Lett. 42, 673 (1979)], as well as several carefully executed experiments on different materials, it was assumed for many years that no metallic phase can exist and a metal-insulator transition (MIT) does not occur in a two-dimensional electron/hole system. It was therefore a surprise when experimental studies in the 1990's appeared to show that such a transition does take place in low disorder, dilute 2D electron systems when strong electron interactions rather than the kinetic energy are dominant and determine the behavior of the system [PRB 50, 8039 (1994); PRB 51, 7038 (1995); PRL 77, 4938 (1996)]. In addition to the dramatic change in resistivity that signals the onset of a conducting phase as the electron density is increased, unusually interesting behavior in voltage-current characteristics and magnetoresistance have also been studied.
Following a brief review of earlier experiments, I will report on two interesting new developments: (A) Recent studies of the V-I characteristics and broadband noise spectrum at a temperature down to 60mK have provided transport evidence for the (zero field) Wigner Crystal as the origin of the low-density state in the strongly interacting electron system in Si-MOSFETs, and (B) Recent studies of the in-plane magnetic field Bsat (above which the magnetoresistance becomes essentially constant) have provided evidence for the formation of a mixed micro-emulsion phase composed of Fermi liquid and Wigner crystallites near the 2D metal-insulator transition.