I. A. Dmitriev

Cyclotron-resonance harmonics in the ac response of a 2D electron gas with smooth disorder.

The frequency-dependent conductivity

Nonequilibrium phenomena in high Landau levels

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Theory of fractional microwave-induced resistance oscillations.

of 2D electrons subjected to a transverse magnetic field and smooth disorder is calculated. The interplay of Landau quantization and disorder scattering gives rise to an oscillatory structure that survives in the high-temperature limit. The relation to recent experiments on photoconductivity by Zudov {\it et al.} and Mani {\it et al.} is discussed.

Oscillatory ac conductivity and photoconductivity of a two-dimensional electron gas: Quasiclassical transport beyond the Boltzmann equation

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.

Compressibility of a two-dimensional electron gas under microwave radiation

We develop a systematic theory of microwave-induced oscillations in magnetoresistivity of a 2D electron gas in the vicinity of fractional harmonics of the cyclotron resonance, observed in recent experiments. We show that in the limit of well-separated Landau levels the effect is dominated by a change of the distribution function induced by multiphoton processes. At moderate magnetic field, a single-photon mechanism originating from the microwave-induced sidebands in the density of states of disorder-broadened Landau levels becomes important.

Theory of microwave-induced photocurrent and photovoltage magneto-oscillations in a spatially nonuniform two-dimensional electron gas

We have analyzed the quasiclassical mechanism of magneto-oscillations in the ac conductivity and photoconductivity, related to non-Markovian dynamics of disorder-induced electron scattering. While the magnetooscillations in the photoconductivity are found to be weak, the effect manifests itself much more strongly in the ac conductivity, where it may easily dominate over the oscillations due to the Landau quantization. We argue that the damping of the oscillatory photoconductivity provides a reliable method of measuring the homogeneous broadening of Landau levels (single-particle scattering rate ) in high-mobility structures.

Quantum magneto-oscillations in the ac conductivity of disordered graphene

Microwave irradiation of a two-dimensional electron gas (2DEG) produces a non-equilibrium distribution of electrons, and leads to oscillations in the dissipative part of the conductivity. We show that the same nonequilibrium electron distribution induces strong oscillations in the 2DEG compressibility, measured by local probes. Local probe measurements of the compressibility are expected to provide information about the domain structure of the zero resistance state of a 2DEG under microwave radiation.

Relaxation of optically excited carriers in graphene: Anomalous diffusion and Levy flights

Received 23 June 2009; revised manuscript received 21 August 2009; published 21 September 2009 Recent experiment S. I. Dorozhkin et al., Phys. Rev. Lett. 102, 036602 2009 on quantum Hall structures with strongly asymmetric contact configuration discovered microwave-induced photocurrent and photovoltage magneto-oscillations in the absence of dc driving. We show that in an irradiated sample the Landau quantization leads to violation of the Einstein relation between the dc conductivity and diffusion coefficient. Then, in the presence of a built-in electric field in a sample, the microwave illumination causes photogalvanic signals which oscillate as a function of magnetic field with the period determined by the ratio of the microwave frequency to the cyclotron frequency, as observed in the experiment.

Emergence of domains and nonlinear transport in the zero-resistance state.

The dynamic conductivity

Negative conductivity and anomalous screening in two-dimensional electron systems subjected to microwave radiation

\ensuremath{\sigma}(\ensuremath{\omega})