Artificial spin superstructures in semimagnetic CdTe/CdMnTe heterostructures
Zusammenfassung der Projektergebnisse
Spin-transistor designs relying on spin-orbit interaction suffer from low signal levels resulting from low spin-injection efficiency and fast spin decay. We present an alternative approach in which spin information is protected by propagating this information adiabatically. We demonstrate the validity of our approach in a cadmium manganese telluride diluted magnetic semiconductor quantum well structure in which efficient spin transport is observed over device distances of 50 micrometers. The device is turned “off” by introducing diabatic Landau-Zener transitions that lead to a backscattering of spins, which are controlled by a combination of a helical and a homogeneous magnetic field. In contrast to other spintransistor designs, we find that our concept is tolerant against disorder. Further we report the observation of the fractional quantum Hall effect in the lowest Landau level of a two-dimensional electron system (2DES), residing in the diluted magnetic semiconductor Cd1−x MnxTe. The presence of magnetic impurities results in a giant Zeeman splitting leading to an unusual ordering of composite fermion Landau levels. In experiment, this results in an unconventional opening and closing of fractional gaps around the filling factor ν =3/2 as a function of an in-plane magnetic field, i.e., of the Zeeman energy. By including the s-d exchange energy into the composite Landau level spectrum the opening and closing of the gap at filling factor 5/3 can be modeled quantitatively. The widely tunable spin-splitting in a diluted magnetic 2DES provides a means to manipulate fractional states.
Projektbezogene Publikationen (Auswahl)
- Science 337, 324 (2012). Spin-Transistor Action via Tunable Landau-Zener Transitions
C. Betthausen, T. Dollinger, H. Saarikoski, V. Kolkovsky, G. Karczewski, T. Wojtowicz, K. Richter, D. Weiss
(Siehe online unter https://doi.org/10.1126/science.1221350) - Phys. Rev. B 90, 115302 (2014). Fractional quantum Hall effect in a dilute magnetic semiconductor
C. Betthausen, P. Giudici, A. Iankilevitch, C. Preis, V. Kolkovsky, M. Wiater, G. Karcezwski, B.A. Piot, J. Kunc, M. Potemski, T. Wojotowicz, D. Weiss
(Siehe online unter https://doi.org/10.1103/PhysRevB.90.115302)
