Mailman 3 September 2020 - Kwant-discuss

parallel distribution
by Adel Belayadi 08 Sep '20

08 Sep '20

Dear user I hope you are doing well. I am having troubles when using parallel distribution to run my python script using kwant. I went through kwant discuss mailing list and tried to read about similar issues. I have red for instance the comment made by hristoph Groth Mon, 08 *Aug 2016 08:12:46 -0700.* *add "from mpi4py import MPI" in the preamble,• substitute kwant.smatrix(…) -> kwant.smatrix(…, comm=MPI.COMM_WORLD), • execute the script using "mpiexec", * I have got an error while using kwant.smatrix(comm=MPI.COMM_WORLD). kwant does not recognize comm TypeError: got an unexpected keyword argument 'comm' I have also tried without comm but with the following command OMP_NUM_THREADS=1 mpiexec -n 4 python file.py or mpirun.openmpi -n 4 -x OMP_NUM_THREADS=1 python file.py but I got the result 4 times Regards BELAYADI

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First release of TKwant
by Xavier Waintal 08 Sep '20

08 Sep '20

Dear colleagues, It is our pleasure to announce the first release of the free software TKwant for time-resolved quantum transport. An introduction to TKwant can be found in TKwant paper: https://arxiv.org/abs/2009.03132 <https://arxiv.org/abs/2009.03132> . The software itself and its tutorials can be found here: https://tkwant.kwant-project.org <https://tkwant.kwant-project.org/> . TKwant is an extension of Kwant (http://kwant-project.org <http://kwant-project.org/>) to time-dependent problems. A system is defined in TKwant in the same way as in Kwant except that some terms in the Hamiltonian may depend on the time parameter. Any system that can be studied in Kwant (e.g. graphene, metals, superconductors, topological insulators, magnetic systems, 2DEGs, any combination of the above and more) can be extended to TKwant. Typical problems where TKwant can be used include the propagation of voltage pulses, spectroscopy of interferometers, Floquet topological insulators, time resolved Andreev reflection and more. We had a lot of fun in making this package and we hope that many of you will have a lot of fun using it. Kind regards, Xavier and Thomas on behalf of TKwant authors. ___________________________________ Xavier Waintal Research Director University Grenoble Alpes CEA-IRIG, PHELIQS, 17 rue des Martyrs, 38054 Grenoble CEDEX 9, FRANCE Tel: 33 (0)4 38 78 03 27 email: xavier.waintal(a)cea.fr <mailto:xavier.waintal@cea.fr> http://www.pheliqs.fr/en/Pages/Portrait/Xavier-Waintal.aspx <http://www.pheliqs.fr/en/Pages/Portrait/Xavier-Waintal.aspx> http://kwant-project.org <http://kwant-project.org/> https://tkwant.kwant-project.org <https://tkwant.kwant-project.org/> ___________________________________

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Transmission for bulk graphene using wraparound
by Khani Hosein 07 Sep '20

07 Sep '20

Dear all, I want to calculate the transmission vs incident angle in graphene with a potential barrier. I use sys = kwant.wraparound.wraparound(sys) and lead = kwant.wraparound.wraparound(lead, keep=0) to construct the periodical system. I almost get the correct results, but I find that the definition of angle is different. Could you please help me to find out the reason. The results comparison is also attached. Regards, Khani Hosein my code is: import numpy as np import matplotlib.pyplot as plt from numpy import pi,sqrt import kwant import sys from numpy import pi from math import asin from matplotlib import pyplot a = 1. V0 = 0.0 W = 2. L = 448 t = 3 def Rectangle(pos): x,y=pos return 0<=x<=L and -0.5<=y<=W sin_30, cos_30 = (1 / 2, sqrt(3) / 2) lat = kwant.lattice.general([(1, 0), (sin_30, cos_30)], [(0, 0), (1/2, 1 / (2*sqrt(3)))]) a,b= lat.sublattices sys = kwant.Builder(kwant.TranslationalSymmetry(lat.vec((-1, 2)))) sys[lat.shape(Rectangle,(0,0.6))]= 0.2 sys[lat.neighbors(1)] = -t sys = kwant.wraparound.wraparound(sys) def lead_shape(pos): x,y=pos return -0.5<=y<=W lead = kwant.Builder(kwant.TranslationalSymmetry((1, 0), lat.vec((-1, 2)))) lead[lat.shape(lead_shape,(0,0.6))] = 0. lead[lat.neighbors(1)] = -t lead = kwant.wraparound.wraparound(lead, keep=0) kwant.plot(sys) sys.attach_lead(lead) sys.attach_lead(lead.reversed()) kwant.plot(sys) sys = sys.finalized() ky=0. momenta = [-2*pi + 0.002 * 2*pi * i for i in range(1001)] bands = kwant.physics.Bands(sys.leads[0],[ky]) energies = [bands(k) for k in momenta] pyplot.figure() pyplot.plot(momenta, energies) pyplot.xlabel("momentum [(lattice constant)^-1]") pyplot.ylabel("energy [t]") pyplot.show() kys = np.arange(-0.08, 0.08, 0.0002) kysp =np.arange(-90, 90, 0.225) energy=0.08 transmission = [] num_prop = [] thetap=[] for ky in kys: theta=180.*asin(ky/energy)/pi thetap.append(theta) smatrix = kwant.smatrix(sys, energy, [ky]) transmission.append(smatrix.transmission(1, 0)) num_prop.append(smatrix.num_propagating(0)) print (ky) plt.plot(thetap, transmission) plt.show()

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Mode wave function
by Prof. CHAN Kwok Sum 04 Sep '20

04 Sep '20

Dear Kwant developers, I would like to ask the following questions about mode wave functions. 1. The mode wave functions can be obtained in three ways: using the smatrix.lead_info, using finalised_lead.mode.wavefunction and using the physics.Progatingmodes. Are they the same? To find the modes used to obtain the s matrix, we should use the modes of matrix.lead_info. Am I correct? 2. I want to find the sites of the mode wave functions obtained from s matrix. Is it correct to use finalised_system.leads[n].sites as mentioned in one of the discussions. I print out finalised_system.leads[n].sites, which is a long list of Site(kwant.lattice.Monatomic([[1.7320508075688772, 0.0], [0.0, 1.0]], [0.2886751345948129, 0.0], '1', 1), array([0, 0])) Could you please help me to find out what the information represents? 3. Is it correct to use finalised_system.leads to find the sites information for the mode wave function obtained from the s matrix? I should be grateful, if you could help me in this regard. Thank you in advance. Your sincerely, KS Disclaimer: This email (including any attachments) is for the use of the intended recipient only and may contain confidential information and/or copyright material. If you are not the intended recipient, please notify the sender immediately and delete this email and all copies from your system. Any unauthorized use, disclosure, reproduction, copying, distribution, or other form of unauthorized dissemination of the contents is expressly prohibited.

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Spam messages on this mailing list
by Christoph Groth 02 Sep '20

02 Sep '20

Dear participants of the kwant-discuss list, This morning, a person or bot subscribed to this list and sent four unsolicited messages. We apologize for the disturbance that this has caused. As a consequence, we changed the moderation rules of this list. Up to now, new members who went through the subscription process could post to the list immediately. From now on, the first posting of new members will be put on hold for moderation, just like it is already the case for postings by non-members. Christoph on behalf of the Kwant team

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