Spin polarized photocurrents generated by coherently trapping

Tu-P.178
Tu-P.178
Spin polarized photocurrents generated by coherently trapping spins in a
magnetically doped semiconductor heterostructure
Nelson Studart1,2, Pedro H. Pereira3, Anibal T. Bezerra4, Paulo F. Farinas2, Marcelo Maialle5,
and Marcos Degani5
DISSE, Instituto Nacional de Ciência e Tecnologia de Dispositivos Semicondutores, Brazil
1
Centro de Ciências Naturais e Humanas, UFABC, 09210-580, Santo André, SP Brazil
2
Departamento de Física, UFSCar, 13565-905, São Carlos, SP, Brazil
3
Departamento de Engenharia Elétrica, PUC-Rio, 22451-900, Rio de Janeiro, RJ Brazil
4
Departamento de Física, UNIFAL, 37130-000, Alfenas, MG, Brazil
5
Faculdade de Ciências Aplicadas, UNICAMP, 13484-350, Limeira, SP Brazil
Calculated results are obtained from time-dependent simulations of optical devices idealized
from choices of layer thicknesses and x, in GaAs/AlxGa1-xAs/MnxGa1-xAs semiconductor
heterostructures. Such parameters are known to control the resulting static potential profile
experienced by an electron moving in the growth direction of these systems. The choices,
made by using realistic parameters taken from the literature [1], are thought to yield two
quantum wells, one of them Mn doped, separated by a AlxGa1-xAs barrier. This leads to
formation of two low energy states, |1> in the first well and |2> in the Mn-doped well, with a
relativelly small energy difference between them, forming the so called Λ configuration [2]
with the continuum, whose subspace span we label |3>. The design is tuned to allow
transitions 1
3 and 2
3 but forbid 1
2. In addition, by properly tuning of the Mn
doping in one of the layers, the 2
3 transition is made to have distinct frequencies (due to
the “giant Zeeman splitting” [3]) for the two different spins when a static magnetic field of a
few T is present. Two oscillating (laser) fields are applied to the resulting structure, and the
dynamics of a single electron initially placed in the lowest energy state (|1>) is studied. Our
numerical simulations show that a dark state is formed near the resonance and since there are
two different resonances, one for each spin, it is possible to select the escape of only one of
the spins from the structure by simply switching the frequency of the field assotiated to the 2
3 transition. The resulting photocurrent is calculated and shown to have a spin polarization
that can be reversed by changing the control field frequency. Besides providing potential
means to generate spin polarized currents in quantum well structures, such an optical control
of the spin polarization may yield relatively fast switching times.
[1] H. Lee, L. Juravel, J. Woolley, and A. Thorpe, Phys. Rev. B 21, 659 (1980)
[2] C. Cohen-Tannoudji, Phys. Scr. 90, 088013 (2015)
[3] J.K. Furdyna, J. Appl. Phys. 64, R29 (1988)