Bethe-Salpeter

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In this tutorial

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BSE Tutorials at present:

• SiH_4

• Fantastic dimension

• LiF

• you Hydrogen

• GaSb (SOC)

• hexagonal BN (on slides only)

The material

Bulk hexagonal BN [1] hexagonal lattice Two atoms per cell (16 electrons) Lattice constant a = 4.72 [a.u.] c/a= 2.58 Plane waves cutoff 40 Rydberg

Calculate screening

A key ingredient in the construction of the BS kernel in the screeened exchange approximation (sex) is the screened electron-electron interaction W which is commonly evaluated in the static approximation.

Runlevel to be used is yambo -b

Calculate the BS kernel in the SEX (Screened Exchange approximation) in the transitions space

Here we learn how to create the BS kernel in the screened exchange (SEX) approximation which includes both exchange (V) and correlation (-W) terms Runlevel to be used yambo -o b -k sex

Solve the BSE by haydock solver

Runlevel to be used yambo -y h

Solve the BSE by diagonalizing the excitonic matrix

Runlevel to be used yambo -y d

Steps:

-Calculate screening

-Calculate the BS Kernel

-Diagonalize the BS Matrix and calculate spectrum

-Visualize/Analyze excitons (with ypp)

-How to Converge

-How to work with SOC