S. J. Prado

Manipulation of g-factor in diluted magnetic semiconductors quantum dots: Optical switching control

We propose an optical switch based on a spin tuning mechanism in diluted-magnetic semiconductor quantum dots. At certain critical magnetic field, Bc, the Zeeman spin-splitting energies can cross leading to a zero value of the effective electron g-factor and the Fermi level undergoes a spin-flip transition. Magneto-optical switching is obtained for magnetic fields below and above Bc. Correlations between Bc, confinement shapes, dot sizes, and host material compositions have been established within well-defined temperature and magnetic impurity composition ranges. The generality of the presented theoretical framework allows for its application to magnetic field controlled quantum dot arrays, and spin-injection among others.

Electronic structure in narrow-gap quantum dots

In this work we calculated the electronic structure of spherical quantum dots based on zincblend semiconductor compounds. The strong conduction-valence band coupling in this class of semi-conductors induces a strong mixing of the electronic states which requires a theoretical model to properly take into acount these effects. We have used a full 8 x 8 Kane Hamiltonian in order to include the strong admixture and study the set of symetries associated with these electronic states and their angular momentum in this central force problem. As an application, we have calculated the electronic structure in narrow-gap HgCdTe, InSb and CdTe quantum dots.

Intraband magnetoabsorption as a probing tool for the quantum dot charge

A method of characterizing the quantum dot charge buildup in a magnetic field is proposed based on the far-infrared magneto-optical response properties. The inherent topological symmetry of the nanostructure and several optical configurations are analyzed as key factors determining the appropriate use of intraband transitions as a probing tool for the quantum dot charge buildup.

Zeeman effect and magnetic field induced spin-hybridization in semiconductor quantum dots

We present a systematic theoretical study of the effective Zeeman spin- and non-linear-splitting of a single spherical quantum dot based on the Hamiltonian model. The effect of spin-hybridization on conduction band states is pointed out as the main source of the strong dependence of Lande factors and effective masses on external fields. The topology of the electronic orbitals is highly sensitive to the magnetic field tuning and to the spin polarization. The electron, hole and excitonic g-factors, as well as the diamagnetic coefficient are calculated for CdTe semiconductor quantum dots. Different systematic experimental methods are proposed in order to determine the behaviour of the electronic properties under analysis as a function of magnetic field and confinement geometry. Complementary optical transitions, in Faraday and Voigt configurations, can be used in the determination of electron, hole and exciton Lande factors, effective magnetic masses and diamagnetic coefficients.

Spin‐hybridization effects in quantum dots

A systematic study of spin‐hybridization of states in semiconductor quantum dots under applied magnetic field is presented. The g‐factors for electron, heavy‐ and light‐hole carriers and for excitonic states, as well as the diamagnetic coefficient have been calculated for CdTe quantum dots. Our calculation provides strong evidences that optical spin‐splitting of an exciton is mainly dominated by the Zeeman splitting of the valence band. These findings are in good qualitative agreement with recent experimental results. Optical selection rules for Faraday and Voigt configurations may allow for the direct determination of Lande factors and the diamagnetic coefficient as a function of the quantum dot shape and magnetic field.