Special Condensed Matter Seminar

Jian Huang
Princeton University

Wednesday, December 6, 2006 Note different date and time!
2:30 pm in SPL 38 Note different room!

Novel transport behaviors in strongly correlated two-dimensional holes

Abstract: I will present experimental results on the transport of 2D holes in the GaAs/AlGaAs heterojunction-insulated-gate field-effect-transistors (HIGFET). The advantage of such HIGFET devices is the absence of the dopants which could significantly lower the sample quality. This ultra-clean environment allows probing transport of 2D holes, with extremely low carrier densities down to a record low value of 6 x 108cm-2 (with an averaged carrier spacing ~ 0.5 micron), in a regime where the Coulomb interaction effects are pronounced (rs ~100). In contrast to the insulating behavior anticipated for such low densities, we have observed a remarkable non-activated power-law-like T-dependence of the conductivity at sufficiently low temperatures. Moreover, the exponent of the power law is found to systematically vary with a dimensionless parameter a/d (a-Wigner Seitz radius and d-distance from the 2D layer to the gate), indicating an important role played by electron-electron interaction. [Phys. Rev. B 74, 201302(R) (2006) and Cond-mat/0610320]. If time permits, I shall also report some new results on the “metallic” side of the so called metal-insulator transition.