Tunnel coupling in asymmetric semimagnetic double quantum wells

Abstract

The influence of the tunnel coupling on the steady‐state photoluminescence has been studied in Cd(Mg,Mn)Te‐based asymmetric double quantum wells (ADQWs) in a magnetic field up to B = 8 T. As grown structures were annealed to introduce Mn and Mg atoms from the opposite barriers inside pure CdTe quantum wells, resulting in a formation of the magnetic (MW) and nonmagnetic (NMW) wells, respectively. Radiative recombination in the ADQW with a wide barrier (9 nm) shows two bands, corresponding to excitons, localized in two decoupled QWs with a markedly different spin splitting: small splitting in the NMW due to the positive exciton Landé band g ‐factor and large splitting in the MW due to the giant Zeeman effect. Contrary, in the ADQW with a narrow barrier (3 nm) an unusual exciton splitting is observed with a negative value of the exciton g ‐factor and a strong circular polarization of the exciton bands. Simultaneously, a complete reduction of the MW emission is found, indicating strong interwell exciton relaxation. Calculations show that it is a strong electron coupling between the wells which is responsible for the observed behaviour. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Circularly polarized photoluminescence of insulating InGaAs/GaAs heterostructures with a ferromagnetic Mn δ‐layer in the barrier

“…The effect is rather small (jP c ðBÞj < 1%), which is related to a (typical for non-magnetic QWs) slowing down of the spin relaxation with increasing B [20]. This common situation is in agreement with experiments in non-magnetic II-VI QWs [21] and with a theory which predicts long spin relaxation times of carriers at high B, up to the nanosecond time scale for D'yakonov-Perel or long-range exchange spin-flip mechanisms, in both classical [22,23] and quantum limits [24].…”

Electrical spin‐injection and depolarization mechanisms in forward biased ferromagnetic Schottky diodes

“…This common situation is in agreement with experiments (see e.g. [32]) and with a theory that predicts long S τ at high B, up to nanosecond time scale, for the D'yakonov-Perel and the long-range exchange spin-flip mechanisms both in classical [33,34] and quantum limits [35]. Thus, a small growth of C ( ) P B with B in the reference LESD as compared to the case of the thermodynamical equilibrium reflects the suppression of spin relaxation between the Zeeman-split HH levels in the QW.…”