Microwave Radiation Induced Magnetoresistance Oscillations Research Articles

Power dependence of the amplitude of the microwave radiation induced magneto-Resistance oscillations and linear polarisation

We have studied the power dependence of the amplitude of the microwave radiation induced magneto resistance oscillations and the linear polarization sensitivity of these oscillations. For the power dependence, some experimental results have indicated that the amplitude of the microwave radiation induced oscillations increase nonlinearly with the microwave power as the radiation driven electron orbit model has theoretically confirmed a nonlinear power relation. The microwave polarization dependence is concerned; the microwave radiation induced oscillations are in dependent of the polarization orientation for both linearly and circularly polarized microwaves. Microwave radiation induced oscillations are independent of the polarization orientation for both linearly and circularly polarized microwaves. Microwave radiation induces oscillation amplitudes do depend on the polarization angle of linearly polarized microwaves and that they follow a cosine square function of the polarization angle. We found that microwave photo excited electrons are scattered by impurities and this gives rise to an additional current density due to radiation. The inelastic model for magneto oscillations in the photo conductivity of the two dimensional which is governed by the microwave induced change in the distribution function, suggests a linear dependence in the amplitude with the microwave power that is independent of the linear microwave polarization.

Evolution of the frequency-dependent polarization-angle phase-shift in the microwave radiation-induced magnetoresistance oscillations

We report the evolution of the phase shift, θ0, extracted from traces of the diagonal resistance, Rxx, vs. the linear polarization angle, θ, at oscillatory extrema of the microwave radiation induced magnetoresistance oscillations over the 36 ≤ f ≤ 40 GHz band in GaAs/AlGaAs system. A reference phase shift for the linear polarization angle in the vicinity of the specimen is obtained with the help of a sensitive carbon resistor. We fit an empirical cosine square law to the sinusoidal responses of Rxx vs. θ to extract the phase shift θ0. The quasi-continuous variation θ0 vs. f trace suggests a preferable polarization orientation for the specimen, and the f− and B− independence of overall average of θ0.

Behaviour of Bichromatic Microwave Induced Magnetoresistance Oscillations in the High Mobility GaAs/AlGaAs 2D electron System

Microwave radiation-induced magneto-resistance oscillations are examined under bichromatic excitation for various frequency combinations in order to obtain a better understanding of the lineshape observed in the dual excitation experiment of the high mobility GaAs/AlGaAs 2D electron system. Here, we examine superposition- or lack thereof- in the lineshape observed in the bichromatic experiment, and report a trend observed between the monochromatic and bichromatic responses of the oscillatory diagonal resistance.

Extraction of overlapping radiation-induced magnetoresistance oscillations and bell-shaped giant magnetoresistance in the GaAs/AlGaAs 2DES using a multiconduction model

We present an experimental study aimed at extracting the microwave radiation-induced magnetoresistance oscillations from the bell-shape giant magnetoresistance in high mobility GaAs/AlGaAs devices using a multi-conduction model. The results show that the multi-conduction model describes the observed giant magnetoresistance effect and the model helps to extract radiation-induced magnetoresistance oscillations, over a wider parameter space.

Comparative study of microwave radiation-induced magneto-resistance oscillations induced by circularly- and linearly- polarized microwaves

A systematic comparative study of radiation-induced magneto-resistance oscillations using circularly polarized- and linearly polarized microwaves was carried out on the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES). The results showed that, the sinusoidal sensitivity in the amplitude of the radiation-induced magnetoresistance oscillations observed under launcher rotation for linearly polarized microwaves, is remarkably absent in the similar experiment carried out with circularly polarized microwaves.

Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation.

A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ.

Evolution of the linear-polarization-angle-dependence of the radiation-induced magnetoresistance-oscillations with microwave power

We examine the role of the microwave power in the linear polarization angle dependence of the microwave radiation induced magnetoresistance oscillations observed in the high mobility GaAs/AlGaAs two dimensional electron system. The diagonal resistance Rxx was measured at the fixed magnetic fields of the photo-excited oscillatory extrema of Rxx as a function of both the microwave power, P, and the linear polarization angle, θ. Color contour plots of such measurements demonstrate the evolution of the lineshape of Rxx versus θ with increasing microwave power. We report that the non-linear power dependence of the amplitude of the radiation-induced magnetoresistance oscillations distorts the cosine-square relation between Rxx and θ at high power.

Remote sensor response study in the regime of the microwave radiation-induced magnetoresistance oscillations

A concurrent remote sensing and magneto-transport study of the microwave excited two dimensional electron system (2DES) at liquid helium temperatures has been carried out using a carbon detector to remotely sense the microwave activity of the 2D electron system in the GaAs/AlGaAs heterostructure during conventional magneto-transport measurements. Various correlations are observed and reported between the oscillatory magnetotransport and the remotely sensed reflection. In addition, the oscillatory remotely sensed signal is shown to exhibit a power law type variation in its amplitude, similar to the radiation-induced magnetoresistance oscillations.

Effect of rotation of the polarization of linearly polarized microwaves on the radiation-induced magnetoresistance oscillations

Light-matter coupling is investigated by rotating, by an angle \theta, the polarization of linearly polarized microwaves with respect to the long-axis of GaAs/AlGaAs Hall-bar electron devices. At low microwave power, P, experiments show a strong sinusoidal variation in the diagonal resistance R_{xx} vs. \theta at the oscillatory extrema, indicating a linear polarization sensitivity in the microwave radiation-induced magnetoresistance oscillations. Surprisingly, the phase shift \theta_{0} for maximal oscillatory R_{xx} response under photoexcitation appears dependent upon the radiation-frequency f, the extremum in question, and the magnetic field orientation or sgn(B).

Comparative Study of Microwave Radiation-Induced Magnetoresistance Oscillations in GaAs/AlGaAs Devices

We examine the inverse magnetic field periodic, radiation-induced magnetoresistance oscillations in GaAs/AlGaAs heterostructures prepared in W. Wegscheider's group, compare their characteristics with similar oscillations in V. Umansky's material, and describe the lineshape variation versus the radiation power P in the two systems. We find that there is a good consistency between the results obtained in the different material.