Mailman 3 October 2018 - Kwant-discuss

Understanding current maps
by Marc Vila 19 Oct '18

19 Oct '18

Dear Kwant developers, I'm playing with the current maps and there is something I don't understand. I attatch a current plot of a 2 terminal-device of some edge states in a particular model of graphene (the current is the sum of all wavefunctions from the incoming lead which is positioned at the left). I understand thus that the arrows point from left to right, it's the current direction. But then, in one edge I have a stronger color meaning there is more current there, but on the other hand, in the other edge the arrow is thicker, which I assume it also represents more current. Does the arrow thickness and color represent the same thing and therefore both edges have the same current or do they represent different things and so I'm missing something? Could you please clarify this for me? In addition, when I plot the spin current projected on the Z axis (as in Kwant's documentation), I assume that the direction of the arrow is for example where the spin-up electrons move, while the spin-down electrons move to the other direction. Is this correct? Thank you in advance for your help. Bests?, Marc ------------------------ Marc Vila Tusell La Caixa - Severo Ochoa PhD in the Theoretical and Computational Nanoscience Group Catalan Institute of Nanoscience and Nanotechnology (ICN2) Barcelona Institute of Science and Technology (BIST) Additional information: http://icn2.cat/en/theoretical-and-computational-nanoscience-group https://www.researchgate.net/profile/Marc_Vila_Tusell https://www.becarioslacaixa.net/marc-vila-tusell-BI00042?nav=true https://orcid.org/0000-0001-9118-421X

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Merging two systems
by Shivang Agarwal 17 Oct '18

17 Oct '18

Hello All, I was wondering if there is a way in Kwant to combine two systems. For example, lets say I build two systems sys1 and sys2 (on the kwant.plot graph, the two systems do not overlap, i.e. they are separated by a finite distance). Then, would it be possible to plot the two systems on the same graph, and then calculate transmission of combined sys1+sys2? Any help would be much appreciated. Best Regards, Shivang Agarwal -- *Shivang Agarwal* Senior Undergraduate Coordinator - Academic Discussion Hours Discipline of Electrical Engineering IIT Gandhinagar Contact: +91-9869321451

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Using kwant for bosonic systems
by Thomas Sturges 15 Oct '18

15 Oct '18

Hi all, First time using a mailing list, sorry if I’ve done something annoying or stupid. Anyway, is it possible (and sensible) to use Kwant for bosonic systems? I’m talking about systems where you have a tight-binding Hamiltonian, but the creation operators are bosonic. For example, I would like to simulate the edge states in a chain of metallic nanoparticles (like in [1]), where I model each nanoparticle with a single dynamical degree of freedom describing the electric-dipole moment. Thanks very much for any input, Tom [1] https://arxiv.org/pdf/1611.03349.pdf

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Bilayer material tight-binding in Kwant
by Marc Vila 10 Oct '18

10 Oct '18

Dear Kwant developers, If I want to model a bilayer-type structure like bilayer graphene or phosphorene, do I need to work in three dimensions being the perpendicular lattice constant the interlayer spacing? Or can I still work in two-dimensions since these materials are two-dimensional when the material is periodic in the plane? Thanks in advance for the help! Kind regards, Marc?

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