Latest Developments in the Field of the Metal-Insulator Transition in Two Dimensions
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Abstract
Ignited by the discovery of the metal-insulator transition, the behavior of low-disorder two-dimensional (2D) electron systems is currently the focus of a great deal of attention. In the strongly-interacting limit, electrons are expected to crystallize into a quantum Wigner crystal (Wigner, 1934), but no definitive evidence for this effect has been obtained despite much experimental effort over the years. Now we have found two-threshold voltage-current characteristics with a dramatic increase in noise between the two threshold voltages.
This behavior cannot be described within existing traditional models.
On the other hand, it is strikingly similar to that observed for the collective depinning of the vortex lattice in Type-II superconductors. Adapting the model used for vortexes to the case of an electron solid yields good agreement with our experimental results, favoring the quantum electron solid as the origin of the low-density state.
Bio
Professor Kravchenko is studying low temperature (millikelvin) properties of low-dimensional electron systems by means of transport, capacitance, thermopower, and magnetization measurements. His primary interest is to understand the nature of the metal-insulator transition in strongly interacting two-dimensional electron systems, discovered by him and his collaborators, and to determine its phase diagram. This discovery was subject of numerous editorial papers in Physics Today, Nature, Science, Science Daily, The Economist, and elsewhere, and was listed on the American Physical Society timeline “A Century of Mesoscopic Physics (1899-1999)” as one of 50 main discoveries of the last century, together with the discovery of the superconductivity, the quantum Hall effect, etc. The experiments include studies of Si metal-oxide-semiconductor field-effect transistors, p-SiGe heterostructures, GaAs/AlGaAs heterostructures, and SiGe/Si/SiGe quantum wells at temperatures down to 20 millikelvin and at magnetic fields up to 10 tesla.
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Physics, Room 203, Purdue University, West Lafayette, IN