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Bester, Gabriel; Zunger, Alex; Shumway, John

doi:10.1103/physrevb.71.075325

Cited by 146 publications

(157 citation statements)

References 33 publications

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“…We are thus free from the need to pre-judge at the outset which 3D bands will couple in nanostructrues, a judgment needed in the truncation of the k · p expansion. This method has been tested extensively over the past two decades for a broad range of spectroscopic quantities in self-assembled as well as colloidal nanostructures 4,10,[27][28][29][30][31][32][33] . The well known k · p approaches can also be in principle accurate at the limit of a large number (possibly infinite) of band basis functions 18 .…”

Section: Theoretical Methodologymentioning

confidence: 99%

Supercoupling between heavy-hole and light-hole states in nanostructures

2015

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The heavy-hole (HH) and light-hole (LH) components of the valence states in 3D bulk semiconductors can mix quantum mechanically as the dimensionality is reduced in forming 2D, 1D nanostructures and 0D quantum dots (QDs). This coupling controls the tuning of the excitonic fine structure splitting, provides an efficient channel for the spin coherence, and leads to polarization anisotropy of light emission, central to several quantum information schemes. Current understanding is that the mixing scales with the square of δV HL /∆ HL , where δV HL and ∆ HL are the coupling matrix elements of the crystal potential and the energy separation between the primary HH0 and LH0 states, respectively. We discuss two classes of HH-LH coupling mechanisms.First, coupling factors occurring through the numerator δV HL , referred to as "direct coupling", including the well-known (1) quantum confinement, (2) built-in strain, and (3) shape elongation, as well as three additional direct coupling mechanisms discussed here: (4) the intrinsic C 2v crystal field effect, (5) the local symmetry of the interface, and (6) the alloy disorder. We quantify these 6 direct HH-LH coupling effects by performing atomistic pseudopotential calculations on a range of strained and unstrained QDs of different morphologies. We find that in unstrained self-assembled QDs such as GaAs/AlGaAs effects (1)-(6) contribute 0%, 0%, 0%, 0%, 40%, and 60%, respectively, whereas in strained self-assembled QDs such as InGaAs/GaAs they contribute 0%, 0%, 78%, 0%, 8%, and 14%, respectively, to the direct HH-LH coupling δV HL . These relative contributions to direct HH-LH coupling differ significantly from what was previously believed.Second, we discover an unexpected HH-LH coupling that effectively reduces the denominator ∆ HL by the presence of a dense ladder of intermediate states between the HH0 and LH0 states (analogous to super-exchange in magnetism). Supercoupling amplifies and propagates the HH-LH interaction and is the dominant source of HH-LH mixing in strained nanostructures where ∆ HL is fairly large, so by the direct coupling mechanism alone δV HL /∆ HL would be expected to be rather small. Supercoupling explains a number of outstanding puzzles including the surprising fact that in strained (InAs/GaAs) QDs the mixing is very strong despite the fact that ∆ HL is large, and offers a new way to manipulate HH-LH mixing and hence associated properties in nanostructures.

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Section: Theoretical Methodologymentioning

confidence: 99%

Supercoupling between heavy-hole and light-hole states in nanostructures

2015

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“…This entails that we disregard phenomena such as piezoelectricity and atomistic anisotropic effects. 32,33 The atomistic anisotropic effects have been investigated by Bester and Zunger 34 showing that they lead among other things to a splitting of states which in our model are degenerate. This splitting is however less pronounced for cylindrical shaped quantum dots as studied here.…”

Section: B Band Structurementioning

confidence: 99%

Optical properties and optimization of electromagnetically induced transparency in strained InAs/GaAs quantum dot structures

et al. 2009

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“…The symmetry of a pyramidal InAs/GaAs quantum dot when a full atomistic structure is considered is C 2v and is lower than the symmetry of the dot's geometrical shape 13 . Due to the computational complexity of the pseudopotential methods that take into account the atomistic nature of the structure, one often employs the k · p method which is considered to be a reliable tool for modeling the electronic structure of quantum dots despite its known limitations 8 .…”

Section: Introductionmentioning

confidence: 99%

“…A range of theoretical approaches has been used so far to calculate the energy levels in self-assembled quantum dots -effective mass 4,5,6,7 , k · p 8,9,10,11 and the pseudopotential method 12,13 . In quantum dots with cylindrical symmetry, symmetry considerations have been applied to effectively reduce the geometry of the problem from three-dimensional to two-dimensional, both in the effective mass and the k · p method (within the axial approximation) 14 .…”

Section: Introductionmentioning

confidence: 99%

Symmetry ofk∙pHamiltonian in pyramidalInAs∕GaAsquantum dots: Application to the

et al. 2005

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A method for the calculation of the electronic structure of pyramidal self-assembled InAs/GaAs quantum dots is presented. The method is based on exploiting the C 4 symmetry of the 8-band k · p Hamiltonian with the strain taken into account via the continuum mechanical model. The operators representing symmetry group elements were represented in the plane wave basis and the group projectors were used to find the symmetry adapted basis in which the corresponding Hamiltonian matrix is block diagonal with four blocks of approximately equal size. The quantum number of total quasi-angular momentum is introduced and the states are classified according to its value. Selection rules for interaction with electromagnetic field in the dipole approximation are derived. The method was applied to calculate electron and hole quasibound states in a periodic array of vertically stacked pyramidal self-assembled InAs/GaAs quantum dots for different values of the distance between the dots and external axial magnetic field. As the distance between the dots in an array is varied, an interesting effect of simultaneous change of ground hole state symmetry, type and the sign of miniband effective mass is predicted. This effect is explained in terms of the change of biaxial strain. It is also found that the magnetic field splitting of Kramer's double degenerate states is most prominent for the first and second excited state in the conduction band and that the magnetic field can both separate otherwise overlapping minibands and concatenate otherwise nonoverlapping minibands.

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Broken symmetry and quantum entanglement of an exciton inInxGa1−xAs∕GaAs

Cited by 146 publications

References 33 publications

Supercoupling between heavy-hole and light-hole states in nanostructures

Supercoupling between heavy-hole and light-hole states in nanostructures

Optical properties and optimization of electromagnetically induced transparency in strained InAs/GaAs quantum dot structures

Symmetry ofk∙pHamiltonian in pyramidalInAs∕GaAsquantum dots: Application to the

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