Influence of inter-dot coupling on spin polarization of carriers in double quantum dots

Abstract

We have performed magneto-photoluminescence (PL) experiments on a self-assembled coupled double quantum dot (QD) system consisting of adjacent CdSe and CdZnSe QD layers. We have observed well-separated two PL peaks in such a double layer QD system, corresponding to the CdSe and the CdZnSe QDs. The PL signal was studied using circularly polarized detection. The intensities of the two PL peaks exhibited significant differences for the two circular polarizations when a magnetic field applied, in contrast to the behaviour shown by single layer CdSe or CdZnSe QD systems, which show nearly identical polarization dependence on the field. The observed behaviour can be interpreted in terms of interaction between carriers localized in pairs of QDs that are electronically coupled.

Antiferromagnetic interaction in coupled CdSe/ZnMnSe quantum dot structures

“…Instead, it should arise from an anti-parallel spin interaction between the CdSe QDs and the DMS. Anti-parallel interaction has been reported earlier in a number of coupled quantum layer structures, [15][16][17][18][19] which was suggested to originate from AFC of photo-generated carriers/excitons spins between the QDs and DMS. Up to now, a direct proof for the suggested model is still lacking.…”

“…Several observations of antiferromagnetic coupling (AFC) between nonmagnetic CdSe QDs and adjacent layers, including DMS quantum wells (QW), 15,16 DMS QDs (Refs. 17 and 18), and also nonmagnetic QDs, 19 have been reported in the past years. The suggested underlying physical mechanism 18 in the case of coupling to magnetic layers involves acceleration of exciton spin relaxation in the CdSe QDs due to magnetic coupling to photo-generated carriers in the nearby DMS layer, based on continuous-wave (CW) magneto-photoluminescence (PL) measurements.…”

Inter‐dot spin exchange interaction in coupled II–VI semiconductor quantum dots

“…Detailed calculations in Ref. [2,4] reveal that in a QD pair with inter-QD interactions the energy levels are lower than they would be in the same configuration if the inter-QD coupling were absent. Such virtual hopping process between the coupled dots can thus occur only in the anti-parallel spin configurations due to the Pauli exclusion principle.…”

“…In order to realize multi-bits gate using the spin property, the inter-dot spin exchange interaction must be understood in coupled QD structures. The double layer QD structures are especially important, in this context, to understand the nature of inter-dot spin exchange interaction since they constitute the simplest and at the same time the most informative QD system for studying spin interactions in a highly-localized geometry [2][3][4]. The II-VI based QD systems have significant advantages over III-V based QD systems for studying such spin-related phenomena, since magnetic ions such as Mn 2+ can be easily incorporated into II-VI materials.…”

Coupled II–VI semiconductor quantum dots: manipulation of spin polarization by inter‐dot exchange interaction

“…Detailed calculations in Ref. [17] reveal that in a QD pair with inter-QD interactions the energy levels are lower than they would be in the same configuration if the inter-QD coupling were absent. Such virtual hopping process between the coupled dots can thus occur only in the spin configurations (b) and (c) in Fig.…”