Dear kwant community, I am new in Transport and kwant. I have two simple questions regarding the lead, I appreciate any reply. 1The lead's self energy is in principle a complex number. In kwant, If I want to add the self energy of a lead by hand, I can add the real part of it to the onsite energy of the site that lead is connected to. Where should I add the imaginary part of the self energy? 2 If I know the value of the level width function (\Gamma = 2πρt^2 = 1), and the lead is a 1D chain, can I calculate the value of the coupling parameter, t? Is there a way to obtain the DOS of the lead and then get t? Bests Chung
Hello Chung,
1The lead's self energy is in principle a complex number. In kwant, If I want to add the self energy of a lead by hand, I can add the real part of it to the onsite energy of the site that lead is connected to. Where should I add the imaginary part of the self energy? Kwant allows to to specify a lead by its self energy if you want. You need only construct a "SelfEnergyLead" and manually attach it to your Builder:
lat = kwant.lattice.chain(norbs=1) syst = kwant.Builder() syst[(lat(i) for i in range(4))] = 4 syst[lat.neighbors()] = 1 # not sure what this corresponds to, but whatever def self_energy(energy, args=(), *, params=None): return 1j # 'interface' is where we wish to "attach" the lead to the system left_lead = kwant.builder.SelfEnergyLead(self_energy, interface=[lat(0)]) right_lead = kwant.builder.SelfEnergyLead(self_energy, interface=[lat(3)]) syst.leads.append(left_lead) # tell the system about the lead syst.leads.append(right_lead) syst = syst.finalized() In the above I made the assumption that you have a 1D system. In the more general case 'self_energy' would need to return a matrix. Also the self energy chosen above does not really correspond to anything in particular (the self energy is energy dependent in general), it is just meant to be illustrative. You could also just put complex onsites on the interface sites in your system directly, but then you would not be able to calculate transport properties using Kwant (because you would not have told Kwant that there were any leads!)
2 If I know the value of the level width function (\Gamma = 2πρt^2 = 1), and the lead is a 1D chain, can I calculate the value of the coupling parameter, t? Is there a way to obtain the DOS of the lead and then get t? Sure, the DOS is just the reciprocal of dE/dk, the derivative of the dispersion relation in the lead (up to a bunch or prefactors etc.)
Happy Kwanting, Joe
participants (2)

Chung Tsai

Joseph Weston