# kwant.physics.selfenergy¶

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

Compute the self-energy generated by the lead.

Parameters
• h_cell (numpy array, real or complex, shape (N,N) The unit cell Hamiltonian) – of the lead unit cell.

• h_hop (numpy 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).

• tol (float) – Numbers are considered zero when they are smaller than tol times the machine precision.

Returns

Sigma – 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.)

Return type

numpy array, real or complex, shape (M,M)

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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