Dear Oscar, Ah, that's easy. You don't even need the second assignment, it is ensured by Kwant automatically. Compare with e.g. http://kwant-project.org/doc/1/tutorial/tutorial2#matrix-structure-of-on-sit... Best regards, Anton On Wed, Nov 18, 2015 at 9:09 PM, Oscar Erlandsson wrote:

Dear Anton,

Thank you for your reply. I have a follow-up question.

As far as I understand, a hopping is hermitian if the hopping from site A to site B is equal to the complex conjugate of the hopping from site B to site A. This is for instance fulfilled if both of the these hoppings are equal to -t (a real number). However, it should also be fulfilled if the two hoppings have equal real part and imaginary part of equal magnitude but opposite sign.

If I want to implement this (in e.g. a 2D system) in such a way that the hoppings in +x-direction (of my lattice 'lat') are equal to -t+1j and in -x-direction equal to -t-1j (where 1j is the imaginary unit), is the following code the correct way to do it:

sys[kwant.builder.HoppingKind((1, 0), lat, lat)] = -t+1j sys[kwant.builder.HoppingKind((-1, 0), lat, lat)] = -t-1j

Best regards,

Oscar Erlandsson

On 2015-11-17 08:52, Anton Akhmerov wrote:

...

Dear Oscar,

Unfortunately right now it is impossible to create a Hamiltonian where hoppings aren't hermitian.

Best regards, Anton

On Tue, Nov 17, 2015 at 2:09 AM, Oscar Erlandsson wrote:

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Hello all,

In Section 2.3 of the Kwant 1.0.3 documentation it says:

"(...) it is enough to specify one direction of the hopping (i.e. when specifying (1, 0) it is not necessary to specify (-1, 0)), Builder assures hermiticity."

However, if I want the hopping in the e.g. -x direction to be different from that in the +x direction, how do I implement this? Is it OK to write:

sys[kwant.builder.HoppingKind((0, 0, -1), lat, lat)] = value1 sys[kwant.builder.HoppingKind((0, 0, 1), lat, lat)] = value2

Will the above code produce the desired result?

Thanks,

Oscar Erlandsson