# kwant.physics.selfenergy¶

kwant.physics.selfenergy(h_cell, h_hop, tol=1000000.0)[source]

Compute the self-energy generated by the lead.

Parameters
h_cellnumpy array, real or complex, shape (N,N) The unit cell Hamiltonian

h_hopnumpy array, real or complex, shape (N,M)

The hopping matrix from a lead cell to the one on which self-energy has to be calculated (and any other hopping in the same direction).

tolfloat

Numbers are considered zero when they are smaller than tol times the machine precision.

Returns
Sigmanumpy array, real or complex, shape (M,M)

The computed self-energy. Note that even if h_cell and h_hop are both real, Sigma will typically be complex. (More precisely, if there is a propagating mode, Sigma will definitely be complex.)

Notes

For simplicity this function internally calculates the modes first. This may cause a small slowdown, and can be improved if necessary.

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