Abstract-Sign-alternating photoconductivity and magnetoresistance oscillations induced by terahertz radiation in HgTe quantum wells

M. Otteneder, I. A. Dmitriev, S. Candussio, M. L. Savchenko, D. A. Kozlov, V. V. Bel'kov, Z. D. Kvon, N. N. Mikhailov, S. A. Dvoretsky, S. D. Ganichev

https://arxiv.org/abs/1807.10663

We report on the observation of terahertz radiation induced photoconductivity and of terahertz analog of the microwave-induced resistance oscillations (MIRO) in HgTe-based quantum well (QW) structures of different width. The MIRO-like effect has been detected in QWs of 20 nm thickness with inverted band structure and a rather low mobility of about 3 × 105 cm2/V s. In a number of other structures with QW widths ranging from 5 to 20 nm and lower mobility we observed an unconventional non-oscillatory photoconductivity signal which changes its sign upon magnetic field increase. This effect was observed in structures characterized by both normal and inverted band ordering, as well as in QWs with critical thickness and linear dispersion. In samples having Hall bar and Corbino geometries an increase of the magnetic field resulted in a single and double change of the sign of the photoresponse, respectively. We show that within the bolometric mechanism of the photoresponse these unusual features imply a non-monotonic behavior of the transport scattering rate, which should decrease (increase) with temperature for magnetic fields below (above) the certain value. This behavior is found to be consistent with the results of dark transport measurements of magnetoresistivity at different sample temperatures. Our experiments demonstrate that photoconductivity is a very sensitive probe of the temperature variations of the transport characteristics, even those that are hardly detectable using standard transport measurements

Abstract-Magnetoresistance oscillations induced by high-intensity terahertz radiation

T. Herrmann, Z. D. Kvon, I. A. Dmitriev, D. A. Kozlov, B. Jentzsch, M. Schneider, L. Schell, V. V. Bel’kov, A. Bayer, D. Schuh, D. Bougeard, T. Kuczmik, M. Oltscher, D. Weiss, and S. D. Ganichev

https://journals.aps.org/prb/accepted/7a079Oe8S5a1573025948ef2a7974268293e8629a

We report on observation of pronounced terahertz radiation-induced magneto-resistivity oscillations in AlGaAs/GaAs two-dimensional electron systems, the THz analog of the microwave induced resistivity oscillations (MIRO). Applying high power radiation of a pulsed molecular laser we demonstrate that MIRO, so far observed at low power only, are not destroyed even at very high intensities. Experiments with radiation intensity ranging over five orders of magnitude from 0.1 W/cm2 to 104 W/cm2 reveal high-power saturation of the MIRO amplitude, which is well described by an empirical fit function I/(1+I/I_s)^\beta with \beta~\sim 1. The saturation intensity I_s is of the order of tens of W/cm2and increases by six times by increasing the radiation frequency from 0.6 to 1.1~THz. The results are discussed in terms of microscopic mechanisms of MIRO and compared to nonlinear effects observed earlier at significantly lower excitation frequencies.

Abstract-Magneto-resistance oscillations induced by high-intensity terahertz radiation

T. Herrmann, Z. D. Kvon, I. A. Dmitriev, D. A. Kozlov, B. Jentzsch, M. Schneider, L. Schell, V. V. Bel'kov, A. Bayer, D. Schuh, D. Bougeard, T. Kuczmik, M. Oltscher, D. Weiss, S. D. Ganichev

(Submitted on 22 Jun 2017)

https://arxiv.org/abs/1706.07239

We report on observation of pronounced terahertz radiation-induced magneto-resistivity oscillations in AlGaAs/GaAs two-dimensional electron systems, the THz analog of the microwave induced resistivity oscillations (MIRO). Applying high power radiation of a pulsed molecular laser we demonstrate that MIRO, so far observed at low power only, are not destroyed even at very high intensities. Experiments with radiation intensity ranging over five orders of magnitude from 0.1 W/cm2 to 104 W/cm2 reveal high-power saturation of the MIRO amplitude, which is well described by an empirical fit function I/(1+I/Is)β with β∼1. The saturation intensity Is is of the order of tens of W/cm2 and increases by six times by increasing the radiation frequency from 0.6 to 1.1 THz. The results are discussed in terms of microscopic mechanisms of MIRO and compared to nonlinear effects observed earlier at significantly lower excitation frequencies.