M. A. Zudov

Evidence for a new dissipationless effect in 2D electronic transport.

In an ultraclean 2D electron system (2DES) subjected to crossed millimeterwave (30-150 GHz) and weak (B<2 kG) magnetic fields, a series of apparently dissipationless states emerges as the system is detuned from cyclotron resonances. Such states are characterized by an exponentially vanishing low-temperature diagonal resistance and a classical Hall resistance. The activation energies associated with such states exceed the Landau level spacing by an order of magnitude. Our findings are likely indicative of a collective ground state previously unknown for 2DES.

Observation of microwave-induced zero-conductance state in Corbino rings of a two-dimensional electron system

Using Corbino samples we have observed oscillatory conductance in a high-mobility two-dimensional electron system subjected to crossed microwave and magnetic fields. On the strongest of the oscillation minima the conductance is found to be vanishingly small, possibly indicating an insulating state associated with these minima.

Nonequilibrium phenomena in high Landau levels

Developments in the physics of 2D electron systems during the last decade have revealed a new class of nonequilibrium phenomena in the presence of a moderately strong magnetic field. The hallmark of these phenomena is magnetoresistance oscillations generated by the external forces that drive the electron system out of equilibrium. The rich set of dramatic phenomena of this kind, discovered in high mobility semiconductor nanostructures, includes, in particular, microwave radiation-induced resistance oscillations and zero-resistance states, as well as Hall field-induced resistance oscillations and associated zero-differential resistance states. We review the experimental manifestations of these phenomena and the unified theoretical framework for describing them in terms of a quantum kinetic equation. The survey contains also a thorough discussion of the magnetotransport properties of 2D electrons in the linear response regime, as well as an outlook on future directions, including related nonequilibrium phenomena in other 2D electron systems.

Superradiant decay of cyclotron resonance of two-dimensional electron gases

We report on the observation of collective radiative decay, or superradiance, of cyclotron resonance (CR) in high-mobility two-dimensional electron gases in GaAs quantum wells using time-domain terahertz magnetospectroscopy. The decay rate of coherent CR oscillations increases linearly with the electron density in a wide range, which is a hallmark of superradiant damping. Our fully quantum mechanical theory provides a universal formula for the decay rate, which reproduces our experimental data without any adjustable parameter. These results firmly establish the many-body nature of CR decoherence in this system, despite the fact that the CR frequency is immune to electron-electron interactions due to Kohns theorem.

Ultradense phosphorous delta layers grown into silicon from PH3 molecular precursors

Phosphorous δ-doping layers were fabricated in silicon by PH3 deposition at room temperature, followed by low-temperature Si epitaxy. Scanning tunneling microscope images indicate large H coverage, and regions of c(2×2) structure. Hall data imply full carrier activation with mobility <40 cm2/V s when the surface coverage is ≲0.2 ML. Conductivity measurements show a ln(T) behavior at low temperatures, characteristic of a high-density two-dimensional conductor. Possible future applications to atom-scale electronics and quantum computation are briefly discussed.

Multiphoton processes in microwave photoresistance of two-dimensional electron systems

We extend our studies of microwave photoresistance of ultra-high mobility two-dimensional electron system (2DES) into the high-intensity, non-linear regime employing both monochromatic and bichromatic radiation. Under high-intensity monochromatic radiation

Temperature Dependence of Microwave Photoresistance in 2D Electron Systems

\omega

Magnetotransport in a two-dimensional electron system in dc electric fields

we observe new zero-resistance states (ZRS) which correspond to rational values of

Bichromatic microwave photoresistance of a two-dimensional electron system.

\epsilon=\omega/\omega_C

Period and phase of microwave-induced resistance oscillations and zero-resistance states in two-dimensional electron systems

(