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The field of semiconductor spintronics is well-established. However, the realization of semiconductor devices utilizing spin remains problematic. A search for the solutions of the known problems is now focused on low-dimensional nanostructures, for which the spatial scale of the potential profile matches the characteristic length for the quantum tunneling. The combination of spin effects and resonant tunneling leads to a number of new phenomena discussed in the talk.
Tunneling between 2D layers separated by a potential barrier is essentially resonant. The energy and in-plane momentum conservation allow the tunneling only at zero bias between the layers so that the differential conductance exhibits a sharp resonance. Such behavior has been experimentally observed for heterostructures with two quantum wells (QW). With account for spin-orbit interaction (SOI) in the 2D layers the tunneling becomes more intriguing. We have shown theoretically that SOI would manifest itself in the complicated pattern of I-V tunnel characteristic and appears to be very sensitive to the SOI parameters. The phenomenon opens a way to use the 2D-2D tunneling as a highly sensitive spin-orbit spectroscopy tool [1].
The essentially resonant character of the transport between 2D systems also leads to an effective spin injection and high tunnelling magnetoresistance. For the two 2D ferromagnetic layers with the spin split subbands the tunneling is allowed only when the same spin subbands of the two layers are matched, i.e. when the magnetizations of the layers are parallel. Analogously, for the tunneling from a 2D layer with the spin split band into a non-magnetic 2D channel the tunneling is allowed for one spin projection and blocked for the opposite, thus leading to an efficient spin injection. We believe this mechanism of the spin injection can be realized in GaMnAs heterostructures [2].
We also propose a mechanism for the dynamic spin injection in semiconductor heterostructures with a QW and a magnetic impurity layer spatially separated from the QW. The spin polarization of the carriers in a QW originates from spin-dependent tunneling recombination at impurity states in the magnetic layer. The developed theory allowed us to explain the kinetics of photoexcited electrons in experiments with time-resolved photoluminescence in Mn-doped InGaAs heterostructures [3] and study the influence of the Coulomb correlations at the impurity site on the spin injection [4].
[1] I. V. Rozhansky, N. S. Averkiev, E. Lahderanta, Phys.Rev. B 93, 195405 (2016).
[2] M. Buchner, T. Kuczmik, M. Oltscher et.al., Phys. Rev. B 95, 035304 (2017).
[3] I.V. Rozhansky, K.S. Denisov, N.S. Averkiev et.al., Phys. Rev. B 92, 25428 (2015).
[4] N.S. Maslova, I.V. Rozhansky, V.N. Mantsevich et.al., arXiv:1802.06352 (2018).
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