The main focus of our research is the exotic collective behavior of low dimensional electronic systems in semiconductors. Of special interest are single- and multilayer two-dimensional electron systems in ultra-clean GaAs/AlGaAs heterostructures grown by molecular beam epitaxy (MBE). Experimental probes include electrical transport, tunneling spectroscopy, and thermodynamic measurements at low temperatures (down to 10mK) and high magnetic fields (up to 17 Tesla).
Two-dimensional electron systems have been the source of some of the most spectacular discoveries in physics over the last 25 years. The integer and fractional quantized Hall effects are perhaps the best known, but dramatic findings continue to be made. For example, in conventional single layer 2D systems, recent research of our and other groups have revealed the existence of a whole new class of 2D electronic phases that resemble molecular liquid crystals. There is also a growing body of experimental evidence suggesting that under appropriate conditions, a double layer 2D electron system can condense into a remarkable new kind of superfluid state. This new state is analogous to a superconductor, only the "Cooper pairs" are excitons which consist of an electron in one layer bound to a hole in the other. Excitonic superfluidity has been sought for 40 years.
The fundamental reason that such qualitatively important results continue to be obtained is that the technique of MBE crystal growth continues to be improved. Indeed, the synergy between fundamental physics research and industrially important materials science is a key feature of our work.