Mailman 3 December 2013 - Kwant-discuss

1D Leads
by Thomas Schmidt Dec. 17, 2013

Dec. 17, 2013

Dear all, I'm trying out Kwant, and I've encountered a problem when investigating 1D leads. The simplest minimal example would be to take your file "quantum_wire_revisited.py", set W=1 there, and change the energy window to energies=[0.01 * i for i in xrange(1000)] The lattice is plotted correctly, but the conductance calculation yields a "ValueError: expected square matrix". Changing "kwant.lattice.square" to "kwant.lattice.chain" does not solve the problem. Can you reproduce the error, or could there be a problem with my Kwant installation? Thanks! Regards, Thomas -- ----------------------------------------------------------- Dr. Thomas Schmidt Department of Physics Klingelbergstrasse 82 Phone: +41 61 267 3751 CH-4056 Basel Email: Thomas.L.Schmidt(a)gmx.de Switzerland http://www.thoschmidt.de ----------------------------------------------------------- --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com

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Re: [Kwant] edge states in the quantum Hall regime
by Anton Akhmerov Dec. 4, 2013

Dec. 4, 2013

Hi Benoit, The object kwant.physics.PropagatingModes returned by the method modes() of a finalized infinite system has the wave functions of all the propagating modes. These wave functions are defined within a single unit cell of the lead, that's why I call them transverse. Best, Anton On Wed, Dec 4, 2013 at 10:16 PM, Benoit GAURY <benoitgaury(a)gmail.com> wrote: > Hi Anton, > > I'm not sure I understand what you mean when you write "the transverse > profile of the edge states". I was looking for a transverse wave function > this afternoon, with in mind the calculation of <x>, the average of the > position operator. I was not able to get the correct wave function though. > So, are you saying that my method is ok with the wave function you mention? > > Best, > > Benoit > > > 2013/12/4 Anton Akhmerov <anton.akhmerov(a)gmail.com> >> >> Hi Gaury, >> >> It's relatively simple: you can just make an infinite stripe with >> magnetic field, finalize it, and get access to the propagating states >> at the Fermi level using the modes() method. This will give you access >> to the transverse profile of every edge state (together with their >> momentum and velocities, see >> >> http://kwant-project.org/doc/1.0/reference/generated/kwant.physics.Propagat…). >> Note however that this is rather inaccurate, since to get the correct >> positions of the edge states one needs to take electrostatics into >> account, something that is not yet available in Kwant. >> >> Best, >> Anton >> >> On Wed, Dec 4, 2013 at 7:45 PM, GAURY Benoit 229701 <Benoit.GAURY(a)cea.fr> >> wrote: >> > Hello everyone, >> > >> > I am currently working on the quantum Hall regime. More precisely I want >> > to >> > know the position of the edge states from the edges my sample. Say I >> > have a >> > bar connected to two leads. Is the integration of the charge density >> > over >> > energy the best way to find the location of the edge states? >> > >> > I was wondering if the average of the position operator was something >> > accessible. >> > >> > Do you guys have any thoughts on that? >> > >> > Benoit >> > > >

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edge states in the quantum Hall regime
by GAURY Benoit 229701 Dec. 4, 2013

Dec. 4, 2013

Hello everyone, I am currently working on the quantum Hall regime. More precisely I want to know the position of the edge states from the edges my sample. Say I have a bar connected to two leads. Is the integration of the charge density over energy the best way to find the location of the edge states? I was wondering if the average of the position operator was something accessible. Do you guys have any thoughts on that? Benoit

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Site position in hamiltonian matrix
by Sebastien Guissart Dec. 2, 2013

Dec. 2, 2013

Hi, Kwant is very helpful for define a hamiltonian matrix (with .hamiltonian_submatrix()) and plot a wave function (with .plotter.map()). But how know where is a site in the matrix? for example for do a 1D plot of wave function in a special direction? Thanks in advance, Sebastien

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