Electronic Properties and Spin Polarization in Coupled Quantum Dots (original) (raw)

Theory of spin states in coupled quantum dots

physica status solidi (b), 2006

The coherent quantum coupling of carriers in vertically stacked asymmetric pairs of quantum dots in applied electric fields manifests itself in rich photoluminescence spectral patterns of level crossings and anticrossings. These patterns arise from configurations of charges and spins in optically excited coupled quantum dots. We present a theoretical model that provides a useful picture of these optical properties including spin structure in terms of a minimal number of physical parameters.

Spin-spin coupling in electrostatically coupled quantum dots

Physical Review B, 2007

We study the spin-spin coupling between two single-electron quantum dots due to the Coulomb and spin-orbit interactions, in the absence of tunneling between the dots. We find an anisotropic XY spin-spin interaction that is proportional to the Zeeman splitting produced by the external magnetic field. This interaction is studied both in the limit of weak and strong Coulomb repulsion with respect to the level spacing of the dot. The interaction is found to be a non-monotonic function of inter-dot distance a0 and external magnetic field, and, moreover, vanishes for some special values of a0 and/or magnetic field orientation. This mechanism thus provides a new way to generate and tune spin interaction between quantum dots. We propose a scheme to measure this spin-spin interaction based on the spin-relaxation-measurement technique.

Charging energy and spin polarization in artificial atoms and molecules

Journal of Electronic Materials, 1999

We investigate the electronic properties of single and coupled quantum dot systems by a self-consistent solution of Schrödinger and Poisson equations within the density functional theory. The single and coupled quantum dots show remarkable similarities to atoms and molecules. We observe that in the case of single quantum dots with cylindrical symmetry, the electrons in the dot form shells like in atoms. This shell structure is slightly distorted due to the electronelectron interaction, as the number of electrons, N, increases. In the case of coupled quantum dots, we observe that the dots can be driven from a state wherein the individual dots are separate, akin to two isolated atoms, to one in which the dots couple forming an "artificial molecule." By using the local spin density approximation, we observe spin polarization in the double dot for specific values of N.

Interaction-Induced Spin Polarization in Quantum Dots

Physical Review Letters, 2010

The electronic states of lateral many-electron quantum dots in high magnetic fields are analyzed in terms of energy and spin. In a regime with two Landau levels in the dot, several Coulomb-blockade peaks are measured. A zigzag pattern is found as it is known from the Fock-Darwin spectrum. However, only data from Landau level 0 show the typical spin-induced bimodality, whereas features from Landau level 1 cannot be explained with the Fock-Darwin picture. Instead, by including the interaction effects within spin-density-functional theory a good agreement between experiment and theory is obtained. The absence of bimodality on Landau level 1 is found to be due to strong spin polarization.

0 00 42 09 v 1 1 3 A pr 2 00 0 Laterally coupled few-electron quantum dots

2008

We present ground-state calculations for laterally coupled quantum dots containing 2, 4, and 8 electrons. As our emphasis is on spin effects our results are obtained by applying spin-density functional theory (SDFT). By varying the distance between the centers of the coupled quantum dots, the transition from weak to strong coupling situation is realized. For the 2-electron system we also apply the Heitler-London approximation and analytical concepts to check the reliability of SDFT calculations in this case. In addition we discuss the features of the Coulomb staircase of laterally coupled quantum dots in the weak and strong coupling regimes in comparison to that of a circular parabolic quantum dot.

Laterally coupled few-electron quantum dots

2000

Theory of Spin States of Quantum Dot Molecules

AIP Conference Proceedings, 2007

The photoluminescence spectrum of an asymmetric pair of coupled InAs quantum dots in an applied electric field shows a rich pattern of level anticrossings, crossings and fine structure that can be understood as a superposition of charge and spin configurations. We present a theoretical model that provides a description of the energy positions and intensities of the optical transitions in exciton, biexciton and charged exciton states of coupled quantum dots molecules.© 2007 American Institute of Physics

Physical Review B, 1998

Coherent charge transfer in a linear array of tunnel-coupled quantum dots, electrostatically coupled to external gates, is investigated using the Bethe ansatz for a symmetrically biased Hubbard chain. Charge polarization in this correlated system is shown to proceed via two distinct processes: formation of bound states in the metallic phase, and charge-transfer processes corresponding to a superposition of antibound states at opposite ends of the chain in the Mott-insulating phase. The polarizability in the insulating phase of the chain exhibits a universal scaling behavior, while the polarization charge in the metallic phase of the model is shown to be quantized in units of e/2.

Vertically coupled quantum dots in the local spin-density functional theory

Physical Review B, 2001

We have investigated the structure of double quantum dots vertically coupled at zero magnetic field within local spin-density functional theory. The dots are identical and have a finite width, and the whole system is axially symmetric. We first discuss the effect of thickness on the addition spectrum of one single dot. Next, we describe the structure of coupled dots as a function of the interdot distance for different electron numbers. Addition spectra, Hund's rule and molecular-type configurations are discussed. It is shown that self-interaction corrections to the density functional results do not play a very important role in the calculated addition spectra. PACS 71.15Mb, 85.30.Vw, 36.40.Ei, 73.20.Dx Typeset using REVT E X

Spin and charge correlations in quantum dots: An exact solution

2010

The inclusion of charging and spin-exchange interactions within the Universal Hamiltonian description of quantum dots is challenging as it leads to a non-Abelian action. Here we present an exact analytical solution of the probem, in particular, in the vicinity of the Stoner instabilty point. We calculate several observables, including the tunneling density of states (TDOS) and the spin susceptibility. Near the instability point the TDOS exhibits a non-monotonous behavior as function of the tunneling energy, even at temperatures higher than the exchange energy. Our approach is generalizable to a broad set of observables, including the a.c. susceptibility and the absorption spectrum for anisotropic spin interaction. Our results could be tested in nearly ferromagnetic materials.

Electronic Properties and Spin Polarization in Coupled Quantum Dots (original) (raw)

Related papers