Radiation-Induced “Zero-Resistance State” and the Photon-Assisted Transport

Abstract

We demonstrate that the radiation induced "zero-resistance state" observed in a two-dimensional electron gas is a result of the non-trivial structure of the density of states of the systems and the photon assisted transport. A toy model of a structureless quantum tunneling junction where the system has oscillatory density of states catches most of the important features of the experiments. We present a generalized Kubo-Greenwood conductivity formula for the photon assisted transport in a general system, and show essentially the same nature of the transport anomaly in a uniform system. The recent discovery of the "zero-resistance state" in a twodimensional (2D) electron gas (2DEG) presents a surprise to the physics community [1,2,3,4,5,6]. In these experiments [1,2,3], the magneto-resistance of a 2DEG under the influence of a microwave radiation exhibits strong oscillations vs. magnetic field. Unlike the well known Shubnikov-de Hass oscillation, the period of such oscillation is determined by the frequency of the microwave radiation, and the resistance shows minima near ω/ω c = n + 1/4, where ω is the frequency of the microwave radiation and ω c is the cyclotron frequency of electron in the magnetic field. When the microwave radiation is strong enough, the "zero-resistance states" are observed around the resistance minima. Durst et al. proposed a theory [4] which successfully explains the period and the phase of the magneto-resistance oscillation and also yields the negative resistance at the positions where the "zero-resistance state" was observed in the experiments. Andreev et al. [5] pointed out that such negative resistance state is essential to understanding the "zero-resistance state" , because the negative resistance is unstable in nature and could be interpreted as the "zero-resistance" by the measurement techniques employed in those experiments. A similar conclusion is also reached in Ref. 6. In essence, the existence of the negative resistance state is crucial in the current stage of theoretical understanding of the phenomenon.In this Letter, we show that such negative resistance state is the result of the non-trivial structure of the density of states of the 2DEG system and the photon assisted transport. The similar effect of photon assisted transport could be observed in other systems. A generalized Kubo-Greenwood formula is presented to provide a formal theory for such phenomena.To demonstrate our point in a clear and simple way, we first consider the transport through a quantum tunneling junction. Such a toy model catches most of the qualitative feature of the 2DEG experiments [1,2,3]. At the same time, the simplicity of the model provides us a clear view to the origin of the transport anomaly. Then we will present a generalized KuboGreenwood formula to calculate the conductivity of a general system under the influence of radiation, and provide a natural explanation of the success of the simple toy model.The structure of the toy model is shown in Fig. 1. We define the two systems across the junction...

Zero-Differential Resistance State of Two-Dimensional Electron Systems in Strong Magnetic Fields

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Microwave photoconductivity of a modulated two-dimensional electron gas due to intra-Landau-level transitions

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Calculation of the nonlinear free-carrier absorption of terahertz radiation in semiconductor heterostructures

“…[1][2][3][4][5][6][7][8] The discovery of a new magnetoresistance oscillation and zero-resistance state in high-mobility electronic systems [9][10][11] has stimulated new theoretical interest in the transport properties of electrons under electromagnetic radiation. [12][13][14][15] A satisfactory understanding of the observed dc magnetoresistance oscillation has been achieved. 12,14,15 There are three different theoretical methods of calculating the electrical transport under a radiation.…”