Abstract-Magnetic quantum ratchet effect in (Cd,Mn)Te- and CdTe-based quantum well structures with a lateral asymmetric superlattice

P. Faltermeier, G. V. Budkin, J. Unverzagt, S. Hubmann, A. Pfaller, V. V. Bel'kov, L. E. Golub, E. L. Ivchenko, Z. Adamus, G. Karczewski, T. Wojtowicz, V. V. Popov, D. V. Fateev, D. A. Kozlov, D. Weiss, S. D. Ganichev

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.155442

We report on the observation of magnetic quantum ratchet effect in (Cd,Mn)Te- and CdTe-based quantum well structures with an asymmetric lateral dual grating gate superlattice subjected to an external magnetic field applied normal to the quantum well plane. A dc electric current excited by cw terahertz laser radiation shows $1/B$ oscillations with an amplitude much larger as compared to the photocurrent at zero magnetic field. We show that the photocurrent is caused by the combined action of a spatially periodic in-plane potential and the spatially modulated radiation due to the near-field effects of light diffraction. Magnitude and direction of the photocurrent are determined by the degree of the lateral asymmetry controlled by the variation of voltages applied to the individual gates. The observed magneto-oscillations with enhanced photocurrent amplitude result from Landau quantization and, for (Cd,Mn)Te at low temperatures, from the exchange enhanced Zeeman splitting in diluted magnetic heterostructures. Theoretical analysis, considering the magnetic quantum ratchet effect in the framework of semiclassical approach, describes quite well the experimental results.

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Abstract-Terahertz Radiation from Magnetic Excitations in Diluted Magnetic Semiconductors

R. Rungsawang¹, F. Perez^2,*, D. Oustinov¹, J. Gómez^2,†, V. Kolkovsky³, G. Karczewski³, T. Wojtowicz³, J. Madéo¹,N. Jukam¹, S. Dhillon¹, and J. Tignon^1 
1Laboratoire Pierre Aigrain, Ecole Normale Supérieure, CNRS (UMR 8551), Université Pierre et Marie Curie, Université D. Diderot, 75231 Paris Cedex 05, France
²Institut des Nanosciences de Paris, CNRS (UMR7588), Université Paris VI, Paris 75005, France
³Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland


http://prl.aps.org/abstract/PRL/v110/i17/e177203

We probed, in the time domain, the THz electromagnetic radiation originating from spins in CdMnTe diluted magnetic semiconductor quantum wells containing high-mobility electron gas. Taking advantage of the efficient Raman generation process, the spin precession was induced by low power near-infrared pulses. We provide a full theoretical first-principles description of spin-wave generation, spin precession, and of emission of THz radiation. Our results open new perspectives for improved control of the direct coupling between spin and an electromagnetic field, e.g., by using semiconductor technology to insert the THz sources in cavities or pillars.

© 2013 American Physical Society

Abstract-Terahertz radiation from magnetic excitations in diluted magnetic semiconductors

R. Rungsawang, F. Perez, D. Oustinov, J. Gómez, V. Kolkovsky, G. Karczewski, T. Wojtowicz, J. Madéo, N. Jukam, S. Dhillon, and J. Tignon
http://prl.aps.org/accepted/c1072Y88G3019b3ce3be8a80c1ecd8d7ec5bd5683
We probed in the time domain, the THz electromagnetic radiation originating from spins in CdMnTe diluted magnetic semiconductors quantum wells containing high mobility electron gas. Taking advantage of the efficient Raman generation process, the spin precession was induced by low power near-infrared pulses. We provide a full theoretical first-principles description of spin-waves generation, spin precession and of emission of the THz radiation. Our results open new perspectives for improved control of the direct coupling between spins and electromagnetic field, e.g. by using semiconductor technology to insert the THz sources in cavities or pillars.