Sign reversal and light controlled tuning of circular polarization in semimagnetic CdMnSe quantum dots

Abstract

Circularly polarized luminescence of CdMnSe quantum dots in magnetic fields up to 5 T is studied for nominal Mn concentrations of 0%, 1%, and 2% by using a photoelastic modulator technique. The exciton g factors as well as spin relaxation times were determined from the polarized luminescence taking into account the exciton lifetimes, which were also extracted by means of time-resolved photoluminescence spectroscopy. For quantum dots without Mn and with 2% Mn exciton g factors of −1.62 and +1.32, respectively, were found. The quantum dots with 1% Mn show a vanishing small value of g for small excitation powers. For this structure the polarization properties are dominated by the optical orientation. Interestingly, for the 1% Mn quantum dots with increasing excitation power considerable changes of the polarization and the exciton g factor were observed which are interpreted in terms of heating effects. From the power dependence indirect heating via phonons and above a critical value direct heating due to photocarriers were identified to result in drastic changes of the circular polarized quantum dot emission.

Mn2+‐Doped CdSe Quantum Dots: New Inorganic Materials for Spin‐Electronics and Spin‐Photonics

“…[2,10,13,16,18,[20][21][22] Although the focus of this article is on colloidal materials, the extremely rich body of literature describing these self-assembled QDs provides an invaluable reference point for studies of the analogous colloidal materials (Sections 4-7).…”

“…[2][3][4][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] These so-called self-assembled QDs have led to remarkable demonstrations of new physics, particularly when combined with single-particle measurements. In parallel, direct chemical methods for synthesis of analogous colloidal doped semiconductor nanocrystals have advanced considerably in recent years.…”

Magnetic field dependence of the many-electron states in a magnetic quantum dot: The ferromagnetic-antiferromagnetic transition

“…Diluted magnetic II-VI and III-V semiconductor (DMS) quantum dots were fabricated with single-electron control 2,3 . A rich variety of different magnetic and optical properties were discovered 4,5,6,7,8,9,10 . In such structures one can explore the physical properties coming from inter-carrier interactions and the interaction of the carriers with the magnetic ion.…”

Carrier Dynamics and Magneto-Optical Properties of Cd1-xMnxS Nanoparticles

“…The Zeeman energy splitting in the electronic structure of the NPs is also other important effect caused by the increasing in the magnetic field. It is well known that in DMS structures the Zeeman energy splitting can be considerably altered by the exchange interaction between the carrier spins and the substitutional doping magnetic ions [46]. Thus, in our Cd1-xMnxS NP samples, it is quite expected different Zeeman energy splitting for QDs and bulklike NCs with the increase in the magnetic field.…”