7 research outputs found
Radiation induced zero-resistance states in GaAs/AlGaAs heterostructures: Voltage-current characteristics and intensity dependence at the resistance minima
High mobility two-dimensional electron systems exhibit vanishing resistance
over broad magnetic field intervals upon excitation with microwaves, with a
characteristic reduction of the resistance with increasing radiation intensity
at the resistance minima. Here, we report experimental results examining the
voltage - current characteristics, and the resistance at the minima vs. the
microwave power. The findings indicate that a non-linear V-I curve in the
absence of microwave excitation becomes linearized under irradiation, unlike
expectations, and they suggest a similarity between the roles of the radiation
intensity and the inverse temperature.Comment: 3 color figures; publishe
Magnetoresistive response of a high mobility 2DES under electromagnetic wave excitation
Oscillations of the resistance observed under electromagnetic wave excitation
in the high mobility GaAs/AlGaAs 2DES are examined as a function of the
radiation frequency and the power, utilizing an empirical lineshape based on
exponentially damped sinusoids. The fit-analysis indicates the resistance
oscillation frequency, F, increases with the radiation frequency, n, at the
rate dF/dn = 2.37 mTesla/GHz; the damping parameter, a, is approximately
independent of n at constant power; and the amplitude, A, of the oscillations
grows slowly with the incident power, at a constant temperature and frequency.
The lineshape appears to provide a good description of the data.Comment: presented at the 26th International Conference on the Physics of
Semiconductors, Edinburgh, Scotland, 29 July - 2 August 200
Demonstration of a 1/4 cycle phase shift in the radiation-induced oscillatory-magnetoresistance in GaAs/AlGaAs devices
We examine the phase and the period of the radiation-induced
oscillatory-magnetoresistance in GaAs/AlGaAs devices utilizing in-situ magnetic
field calibration by Electron Spin Resonance of DiPhenyl-Picryl-Hydrazal. The
results confirm a -independent 1/4 cycle phase shift with respect to the condition for , and they also suggest a small
( 2%) reduction in the effective mass ratio, , with respect
to the standard value for GaAs/AlGaAs devices.Comment: 4 pages, 4 color figure
Radiation induced oscillatory Hall effect in high mobility GaAs/AlGaAs devices
We examine the radiation induced modification of the Hall effect in high
mobility GaAs/AlGaAs devices that exhibit vanishing resistance under microwave
excitation. The modification in the Hall effect upon irradiation is
characterized by (a) a small reduction in the slope of the Hall resistance
curve with respect to the dark value, (b) a periodic reduction in the magnitude
of the Hall resistance, , that correlates with an increase in the
diagonal resistance, , and (c) a Hall resistance correction that
disappears as the diagonal resistance vanishes.Comment: 4 pages text, 4 color figure
Radiation-induced oscillatory magnetoresistance as a sensitive probe of the zero-field spin splitting in high mobility GaAs/AlGaAs devices
We suggest an approach for characterizing the zero-field spin splitting of
high mobility two-dimensional electron systems, when beats are not readily
observable in the Shubnikov-de Haas effect. The zero-field spin splitting and
the effective magnetic field seen in the reference frame of the electron is
evaluated from a quantitative study of beats observed in radiation-induced
magnetoresistance oscillations.Comment: 4 pages, 4 color figure
Nonlinear effects in microwave photoconductivity of two-dimensional electron systems
We present a model for microwave photoconductivity of two-dimensional
electron systems in a magnetic field which describes the effects of strong
microwave and steady-state electric fields. Using this model, we derive an
analytical formula for the photoconductivity associated with photon- and
multi-photon-assisted impurity scattering as a function of the frequency and
power of microwave radiation. According to the developed model, the microwave
conductivity is an oscillatory function of the frequency of microwave radiation
and the cyclotron frequency which turns zero at the cyclotron resonance and its
harmonics. It exhibits maxima and minima (with absolute negative conductivity)
at the microwave frequencies somewhat different from the resonant frequencies.
The calculated power dependence of the amplitude of the microwave
photoconductivity oscillations exhibits pronounced sublinear behavior similar
to a logarithmic function. The height of the microwave photoconductivity maxima
and the depth of its minima are nonmonotonic functions of the electric field.
It is pointed to the possibility of a strong widening of the maxima and minima
due to a strong sensitivity of their parameters on the electric field and the
presence of strong long-range electric-field fluctuations. The obtained
dependences are consistent with the results of the experimental observations.Comment: 9 pages, 6 figures Labeling of the curves in Fig.3 correcte