Transport in Two Dimensional Electronic Micro-emulsions

In two dimensional electron systems with Coulomb or dipolar interactions, a direct transition, whether first or second order, from a liquid to a crystalline state is forbidden. As a result, between these phases there must be other (microemulsion) phases which can be viewed as a meso-scale mixture of the liquid and crystalline phases. We investigate the transport properties of these new electronic phases and present arguments that they are responsible for the various transport anomalies that have been seen in experiments on the strongly correlated 2DEG in high mobility semiconductor devices with low electron densities

Giant magnetoresistance in the variable range hopping regime

We predict the universal power law dependence of localization length on magnetic field in the strongly localized regime. This effect is due to the orbital quantum interference. Physically, this dependence shows up in an anomalously large negative magnetoresistance in the hopping regime. The reason for the universality is that the problem of the electron tunneling in a random media belongs to the same universality class as directed polymer problem even in the case of wave functions of random sign. We present numerical simulations which prove this conjecture. We discuss the existing experiments that show anomalously large magnetoresistance. We also discuss the role of localized spins in real materials and the spin polarizing effect of magnetic field.Comment: 21 pages, 16 figures, 52 citations, pdflate

Is there a linewidth theory for semiconductor lasers?

Semiconductor laser generation begins at a critical injection when the gain and loss spectra touch each other at a singular frequency. In the framework of the standard (Schawlow-Townes-Lax-Henry) theory, the finite linewidth results from the account of fluctuations associated with the random spontaneous emission processes. This approach is based on the assumption that in the mean-field approximation the singular frequency generation persists for injection levels higher than critical. We show that this assumption in the framework of the Boltzmann kinetic equation for electrons and photons is invalid and therefore the standard description of semiconductor laser linewidth lacks theoretical foundation. Experimental support of the standard theory is also questionable