kwant.physics.selfenergy

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

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 : numpy 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.