Tight-binding<i>g</i>-factor calculations of CdSe nanostructures

Schrier, Joshua; Whaley, K. Birgitta

doi:10.1103/physrevb.67.235301

Cited by 27 publications

(36 citation statements)

References 30 publications

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“…Simple model studies based on the effective mass approximation 15,22 or a multi-band k · pmodel 23,24,25 describe the QD by a confinement potential caused by the band offsets, for instance; they give qualitative insights into the formation of bound (hole and electron) states, but they are too crude for quantitative, material specific results or predictions. More suitable for a microscopic description are empirical pseudopotential methods 26,27,28,29 as well as empirical tight-binding models 30,31,32,33,34,35,36,37,38,39,40,41 . The empirical pseudopotential methods allow for a detailed variation of the wave functions on the atomic scale.…”

Section: Introductionmentioning

confidence: 99%

Tight-binding model for semiconductor nanostructures

Schulz

Czycholl

2005

Phys. Rev. B

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An empirical scp 3 a tight-binding (TB) model is applied to the investigation of electronic states in semiconductor quantum dots. A basis set of three p-orbitals at the anions and one s-orbital at the cations is chosen. Matrix elements up to the second nearest neighbors and the spin-orbit coupling are included in our TB-model. The parametrization is chosen so that the effective masses, the spinorbit-splitting and the gap energy of the bulk CdSe and ZnSe are reproduced. Within this reduced scp 3 a TB-basis the valence (p-) bands are excellently reproduced and the conduction (s-) band is well reproduced close to the Γ-point, i.e. near to the band gap. In terms of this model much larger systems can be described than within a (more realistic) sp 3 s * -basis. The quantum dot is modelled by using the (bulk) TB-parameters for the particular material at those sites occupied by atoms of this material. Within this TB-model we study pyramidal-shaped CdSe quantum dots embedded in a ZnSe matrix and free spherical CdSe quantum dots (nanocrystals). Strain-effects are included by using an appropriate model strain field. Within the TB-model, the strain-effects can be artifically switched off to investigate the infuence of strain on the bound electronic states and, in particular, their spatial orientation. The theoretical results for spherical nanocrystals are compared with data from tunneling spectroscopy and optical experiments. Furthermore the influence of the spin-orbit coupling is investigated.

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Section: Introductionmentioning

confidence: 99%

Tight-binding model for semiconductor nanostructures

Schulz

Czycholl

2005

Phys. Rev. B

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“…It also appears unlikely from these exact calculation of g-factors that the cancellation will become more complete for large-size nanocrystals since the difference between g z and g increases for larger nanocrystals having aspect ratio approximately unity. As a result a true quasi-spherical regime as predicted by an analysis perturbative in spin 12,14 in which the electron g-factors become isotropic may never reached. Under certain growth conditions it is possible to synthesis CdSe nanostructures with zincblende structure.…”

Section: A Electron G-factormentioning

confidence: 99%

“…The same structures have been used in previous time-independent tight-binding studies. 14,19,21 We remove the dangling bonds on the surface by shifting the energies of the corresponding hybrid orbitals well above the conduction band edge. The spin-orbit interaction is included in the Hamiltonian.…”

Section: A Tight-binding Model Of Cdse Nanostructurementioning

confidence: 99%

“…13,14 In general, the effective mass approximation (EMA) type calculation is inadequate for nanostructures at small sizes ( ≤ 30Å ) because the atomic nature and surface effects become more prominent as the size of the nanostructure decreases. Because of its atomic nature, the tight-binding model is ideal to study the electronic and optical properties of nanostructures in this size range.…”

Section: Introductionmentioning

confidence: 99%

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Magneto-optical response of CdSe nanostructures

Chen

Whaley

2004

Phys. Rev. B

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We present theoretical calculations of the Landé g-factors of semiconductor nanostructures using a time-dependent empirical tight-binding method. The eigenenergies and eigenfunctions of the band edge states are calculated as a function of an external magnetic field with the electromagnetic field incorporated into the tight-binding Hamiltonian in a gauge-invariant form. The spin-orbit interaction and magnetic field are treated non-perturbatively. The g-factors are extracted from the energy splitting of the eigenstates induced by the applied magnetic field. Both electron and hole gfactors are investigated for CdSe nanostructures. The size and aspect ratio dependence of g-factors is studied. We observe that the electron g-factors are anisotropic and find that the calculated values agree quantitatively with experimental data. We conclude that the two distinct g-factor values extracted from time resolved Faraday rotation experiments should be assigned to the anisotropic in plane (g ) and out of plane (gz) electron g-factors, rather than to isotropic electron and exciton g-factors. We find that the anisotropy in the electron g-factor depends on the aspect ratio of the nanocrystal. The g-factor anisotropy derived from the wurtzite structure and from the non-unity aspect ratio may cancel each other in some regime. We observe that hole g-factors oscillate as a function of size, due to size dependent mixing between the heavy hole-light hole components of the valence band edge states. Extension to the calculation of exciton g-factors is discussed.

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“…This modified magnetic moment also controls the spin dynamics in nanostructures, and is usually parametrized in the literature as a shape, size and composition dependent g tensor defined by μ ¼ g · S, where S represents the electron spin [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Despite the central nature of g tensors to high-speed spin manipulation [12][13][14][15]17,18], spin lifetimes [19,20], and quantum computation [21], the spatial structure of the spin-correlated orbital currents that determine these g tensors has not been investigated.…”

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confidence: 99%

Spin-Orbit-Induced Circulating Currents in a Semiconductor Nanostructure

et al. 2014

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Circulating orbital currents produced by the spin-orbit interaction for a single electron spin in a quantum dot are explicitly evaluated at zero magnetic field, along with their effect on the total magnetic moment (spin and orbital) of the electron spin. The currents are dominated by coherent superpositions of the conduction and valence envelope functions of the electronic state, are smoothly varying within the quantum dot, and are peaked roughly halfway between the dot center and edge. Thus the spatial structure of the spin contribution to the magnetic moment (which is peaked at the dot center) differs greatly from the spatial structure of the orbital contribution. Even when the spin and orbital magnetic moments cancel (for g = 0) the spin can interact strongly with local magnetic fields, e.g. from other spins, which has implications for spin lifetimes and spin manipulation.

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Tight-bindingg-factor calculations of CdSe nanostructures

Cited by 27 publications

References 30 publications

Tight-binding model for semiconductor nanostructures

Tight-binding model for semiconductor nanostructures

Magneto-optical response of CdSe nanostructures

Spin-Orbit-Induced Circulating Currents in a Semiconductor Nanostructure

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