LateralDiscretization{ }

(Formerly LateralMotion)

Calling sequence

LateralDiscretization{ }

Functionality

Specifies the numerical discretization for the directions perpendicular to the growth axis (nextnano.NEGF considers a cylindrical structure along the growth axis).

Example
LateralDiscretization{
    MaterialForLateralMotion = "well"
    Value = 5
    DiagonalIncoherentScattering = no
    OptimizeSampling = no

    Dispersion{
        ...
    }
}

The following keywords are available within this group:

MaterialForLateralMotion

Calling sequence

LateralDiscretization{ MaterialForLateralMotion }

Properties

  • type: \(\mathrm{character\;string}\)

Functionality

Specifies the material for the in-plane dispersion using Material{ Alias }. This keyword is effective in 1,2,3-bands. The parameters are assumed to be homogeneous along the structure, and hence must be taken from a single material.

Value

Calling sequence

LateralDiscretization{ Value }

Properties

  • type: \(\mathrm{real\;number}\)

  • values: [0.0, ...)

  • unit: \(\mathrm{meV}\)

Functionality

Specifies the in-plane energy spacing between the ground and first excited Bessel modes (eigenstates in the in-plane direction), and determines the radius of the cylinder.

Note

What value should I choose?

It has to be smaller than the linewidth of the states (which you can see on the 2D DOS plots), but smaller value increases the calculation time. We recommend around 4-5 meV for THz QCL designs and around 10 meV for mid-infrared designs. It can be as large as 40 meV for typical mid-infrared QCLs (and the calculation is much faster than for 10 meV). Large values result in an overestimate of the broadening, which in turn helps the convergence with coarse energy grid. But this is not so accurate. This parameter should be reduced simultaneously with EnergyGridSpacing.

Attention

There is a further parameter for the in-plane motion, EnergyRangeLateral, which sets the cut-off energy (i.e. the energy range) for the subband dispersion.

OptimizeSampling

Calling sequence

LateralDiscretization{ OptimizeSampling }

Properties

  • type: \(\mathrm{choice}\)

  • choices: yes; no

  • default: no

Functionality

If yes, reduce the number of in-plane k points at which the Hamiltonian is considered. The scheme skips dense in-plane k points such that the resulting k mesh is nearly equidistant.

Dispersion{ }

Calling sequence

LateralDiscretization{ Dispersion{ } }

Properties

  • usage: \(\mathrm{\textcolor{ForestGreen}{optional\;within\;the\;group}}\)

Functionality

Setting for the in-plane dispersion in the 8-band model.

Example
LateralDiscretization{
    Dispersion{
        UnderRelaxationParameter = 0.7
        PrincipalInplaneK = 0
    }
}

Dispersion{ UnderRelaxationParameter }

Calling sequence

LateralDiscretization{ Dispersion{ UnderRelaxationParameter } }

Properties

  • type: \(\mathrm{real\;number}\)

  • values: [0.0, ...)

Functionality

Ratio of under-relaxation for the iterative method in the Hamiltonian folding.

Dispersion{ PrincipalInplaneK }

Calling sequence

LateralDiscretization{ Dispersion{ PrincipalInplaneK } }

Properties

  • type: \(\mathrm{integer}\)

  • values: {0, 1, 2, 3, ...}

Functionality

Index of in-plane k point at which the Hamiltonian is diagonalized exactly and the reduced real space basis is constructed. The zone-center is 0.