Mailman 3 October 2015 - Kwant-discuss

Energy eigenvalue of graphene edge states
by T.C. Wu Oct. 12, 2015

Oct. 12, 2015

Dear kwant developers, Concerning the graphene dot example shown in http://kwant-project.org/doc/1.0/tutorial/tutorial6, may I know the way to find the corresponding energy eigenvalue for the state shown (the edge state)? Moreover, is it possible to plot the energy band without attaching any leads? Thanks, T.C.

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Magnetic graphene
by Dedi Setiabudidaya Oct. 12, 2015

Oct. 12, 2015

Hi, I have already built a system of rectangular graphene with some vacancies.How do I calculate the total magnetic moment of my system ?Thank you. Regards, Dedi

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Computing current density
by Katja Nowack Oct. 10, 2015

Oct. 10, 2015

Dear Kwant community, I am interested in electron focusing and the Veselago lens in graphene. What I would like to simulate is how the current density in a device with a small bias voltage applied would look like. It seems straightforward to compute the local density of states, but I am not entirely sure how to go from there to obtain local current density within linear response. Any advice would be very much appreciated! Best wishes, Katja

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del sys[a(0,0)]
by Dedi Setiabudidaya Oct. 9, 2015

Oct. 9, 2015

Hi, I would like to modify the scattering region by deleting some atoms.For example, I would like to delete 10 atoms and I did it by inserting ten lines of del sys [(,)] in my codes.I was wandering if there is a concise way to do that.Thank you. Regards, Dedi

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kkghosh
by kamal ghosh Oct. 3, 2015

Oct. 3, 2015

Dear Roberts, Thanks for the guideline you provided me with in solving my problem related to quantum well through an earlier mail. Following your suggestions I now attempt to `see the potential profile of a structure of quantum well. Below is the code I tried but it could not though the quantum device structure was shown O.K. Please extend your help to solve. import kwant from matplotlib import pyplot lat=kwant.lattice.square(1) sys=kwant.Builder() def potential(site,pot): (x,y)=site.pos if 10 < x < 20: return pot else: return 0 def onsite(site,pot=0): return potential(site,pot) sys[(lat(x,y) for x in range(40) for y in range(10))]=onsite sys[lat.neighbors()]=-1 kwant.plot(sys) sys=sys.finalized() potential_profile=[] potential_profile.append(onsite) print potential_profile Thanks. K.K.Ghosh

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transport with strain
by Jonas Nascimento Oct. 2, 2015

Oct. 2, 2015

Hi, my friends. Recently, I studied, on Kwant, the transport properties of a graphene nanoribbon without dificulty. Now, I wanted to obtain the same thing, but applying a strain, as suggested by this reference: http://arxiv.org/abs/1409.6666 In the presence strain, the hopping is modified by the deformation of the lattice, which must now be t_ij=t_0*exp(d/a - 1), where d is the strain-modified distance between lattice sites and t_0 is hopping in absence of strain. Note that the network is no longer crystalline. That way, I can not define the vectors of a single cell and repeat it to obtain my lattice. In this case, I guess I'll have to build every atom of the network and add the hopping according with the relation above to the nearest neighbors. Obviously, this not is good idea. Someone help me with a simpler solution? Thank you so much. Jonas Nascimento

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