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Priority Program SPP 1285
Semiconductor Spintronics
Spintronic > State of Research > Spin control

Spin control and spintronic devices

The third required component for future spintronics is the aimed control of the spin orientation. Datta and Das proposed a device for controlling the spin orientation by an electrical field already in 1990 [49]. This device is today known as Datta-Das spin-field-effect transistor which is based on the Rashba-spin-orbit interaction - an electric field perpendicular to the moving direction causes spin precession. The strength of the electric field is a measure of the structure inversion asymmetry which leads over the spin-orbit interaction to a k-depending effective magnetic field [50, 51]. An efficient electrical control is in principle possible in structures with one dimension. Especially in semiconductors with small bandgap in ballistic regime are predicted 52. First cogent experimental results of spin modulation have been shown in (In0,53Ga0,47)As/(In0,52Al0,48)As-Quantum wells and GaAs/(AlGa)As-2DEG at low temperatures.

A long-ranged aim of spintronics is the evaluation of new devices. The Datta-Das transistor evaluated to a role model because the interplay between spin injection, active spin modulation and spin detection can be exemplarily investigated in this model. Other devices transfer the concept of giant magneto resistance (GMR) from magneto electronics to semiconductor layers and aim to magnetic random access memories (MRAM), magnetic sensors or reprogrammable semiconductor magneto logics 56-58]. For example, a 2000% tunnelling magnetoresistance in a ferromagnetic (Ga,Mn)As nanostructure has been shown [59-61]. But the devices are not limited to magnetoresistive concepts. The already patented spin-LED, for example, emit circular polarized light due to the radiating recombination on spin polarized electrons [62]. It has been shown that the injection of spin polarized electrons reduce the laser threshold in surface emitting microresonator laser. The laser threshold reduction of 23% has been shown experimentally at low temperatures [63]. Calculations based on a simple rate equation model predict a threshold reduction up to 50%. The reduction originates in the selective coupling of spin polarized electrons to photons with a defined helicity. Previous experiments already showed that the intensity and helicity of the spontaneous emission of the so-called spin laser can be switched by the modulation of the spin orientation [64]. The most futuristic devices for spintronics aim for sure on the evaluation of spin quantum computers. The evaluation of those (at least currently) 'academic' devices is inspired by spintronics because the electron spin represents an almost ideal qubit system which is extremely stable and easy to manipulate in semiconductors due to the highly developed technologies [65]. The required operations for quantum computing have already been realized experimentally for single qubits and more sophisticated concepts are theoretically presented [9, 66-68].

Important Dates:

15. Sept. 2013:
Deadline for the special volume semiconductor spintronics (DFG final report) in physica status solidi b
(further information is sent via email)

30. Sept. - 2. Oct. 2013:
final meeting of the priority program "International workshop on semiconductor spintronics" located in the Residenz Würzburg
(further information)

Recent publication(s):

C. Drexler, S.A. Tarasenko, P. Olbrich, J. Karch, M. Hirmer, F. Müller, M. Gmitra, J. Fabian, R. Yakimova, S. Lara-Avila, S. Kubatkin, M. Wang, R. Vajtai, P. M. Ajayan, J. Kono, and S.D. Ganichev :  "Magnetic quantum ratchet effect in graphene" Nature Nanotechnology 8, 104 (2013)

J.H. Buß, J. Rudolph, S. Shvarkov, H. Hardtdegen, A.D. Wieck, and D. Hägele:  "Long electron spin coherence in ion‐implanted GaN: The role of localization" Appl. Phys. Lett. 102, 192102 (2013)

D.J. English, J. Hübner, P.S. Eldridge, D. Taylor, M. Henini, R.T. Harley, and M. Oestreich:  "Effect of symmetry reduction on the spin dynamics of (001)-oriented GaAs quantum wells" Phys. Rev. B 87, 075304 (2013)

V.L. Korenev, I.A. Akimov, S.V. Zaitsev, V.F. Sapega, L. Langer, D.R. Yakovlev, Yu. A. Danilov, and M. Bayer:  "Dynamic spin polarization by orientation-dependent separation in a ferromagnet–semiconductor hybrid" Nature Communications 3, 959 (2012)

M. Althammer, E.-M. Karrer-Müller, S.T.B. Goennenwein, M. Opel, R. Gross:  "Spin transport and spin dephasing in zinc oxide" Appl. Phys. Lett. 101, 082404 (2012)