Mailman 3 August 2014 - Kwant-discuss

How the spin is positioned in the Smatrix?
by Qingtian Zhang 06 Mar '22

06 Mar '22

Dear all, I am trying square lattice with spin-orbit coupling and Zeeman splititng just like the example of Tutorial 2.3.1. Now I want to get the spin-dependent conductance：Guu,Gud,Gdu,and Gdd, where "u" indicates up spin, d indicates down spin. We can have the scattering matrix through Smatrix=kwant.smatrix(sys, energy), but how the spin is positioned in the scattering matrix? I have checked some simple cases, it seems the Smatrix is organized like this: | r t | S= | t' r' | but how the spin is included? Thanks in advance. Qingtiian Zhang The code is: import kwant from matplotlib import pyplot from numpy import matrix import tinyarray sigma_0 = tinyarray.array([[1, 0], [0, 1]]) sigma_x = tinyarray.array([[0, 1], [1, 0]]) sigma_y = tinyarray.array([[0, -1j], [1j, 0]]) sigma_z = tinyarray.array([[1, 0], [0, -1]]) sys=kwant.Builder() lat=kwant.lattice.square() a=1 t=1.0 alpha=0.5 e_z=0.08 W=2 L=2 sys[(lat(x, y) for x in range(L) for y in range(W))] = \ 4 * t * sigma_0 + e_z * sigma_z # hoppings in x-direction sys[kwant.builder.HoppingKind((1, 0), lat, lat)] = \ -t * sigma_0 - 1j * alpha * sigma_y # hoppings in y-directions sys[kwant.builder.HoppingKind((0, 1), lat, lat)] = \ -t * sigma_0 + 1j * alpha * sigma_x #### Define the left lead. #### lead = kwant.Builder(kwant.TranslationalSymmetry((-a, 0))) lead[(lat(0, j) for j in xrange(W))] = 4 * t * sigma_0 + e_z * sigma_z # hoppings in x-direction lead[kwant.builder.HoppingKind((1, 0), lat, lat)] = \ -t * sigma_0 - 1j * alpha * sigma_y # hoppings in y-directions lead[kwant.builder.HoppingKind((0, 1), lat, lat)] = \ -t * sigma_0 + 1j * alpha * sigma_x #### Attach the leads and return the finalized system. #### sys.attach_lead(lead) sys.attach_lead(lead.reversed()) kwant.plot(sys) sys=sys.finalized() print "Hamiltonian=" print sys.hamiltonian_submatrix() Smatrix=kwant.smatrix(sys, energy=3.) print "The scattering matrix=" print matrix.round((Smatrix.data),2) print "T=",(Smatrix.transmission(1, 0))

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How to caculate hall resistance
by ZHANG Bing 12 Sep '21

12 Sep '21

Dear Sir, I am a PhD student of Hong Kong University of Science and Technology. I want to use KWANT to caculate Hall resistance of a Hall bar structure.We can get the conductance between 6 electrodes, but how to get hall resistance? Can you give me some help? Thank you very much. Best Regards, Zhang Bing

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question on parallelization
by Luis Foa Torres 23 Aug '14

23 Aug '14

Hi, First, thanks to the authors for opening kwant to the community. In the kwant paper it is mentioned that "a few additional lines of code allow us to parallelize the script for a multi-core workstation or cluster". I was wondering if you could share any tip in this direction. Best regards. Luis.

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Help on a basic issue
by Ian R George 12 Aug '14

12 Aug '14

Hello, I messaged a coupled months back on a basic question. I have another one. KWANT has been very useful to me so far, and I like to think I've made some progress with it, however, I still occasionally am tripping up on basic things. I'm sorry if the answer to this is obvious. I am trying to create an SNS junction to study helical ABSs in a magnetic field, but I'm having some basic problems implementing the magnetic field in the code along with the Bogliubov de-Gennes equation. Using the tutorials and paper as my guide, I'm defining a global method for the hopping and have tried to use it in the system, without success. How would I implement it with the hoppings with the superconductor formalism, with separate leads for electrons and holes? Is there something I'm missing on how to do it-you can't just use the magentic field as the hopping, as in the examples. Would I just subtract it as a gauge from the Hamiltonian diagonal entries, as you do analytically? Is there an example out there for that? At the moment, as a side question, when I try to simply to multiply the magnetic field with 4t-mu, I'm getting a ValueError: that the hoppings then do not match the dimensions of the onsite Hamiltonian. So I'm guessing that's not the way of going about it. Thank you.

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Please help: Kwant installation on Mac OSX 10.9
by Chagaan Baatar 12 Aug '14

12 Aug '14

I’m doing the MacPorts installation and got stuck at the following error message: sudo port install py27-kwant Password: ---> Computing dependencies for libgcc ---> Fetching archive for libgcc ---> Attempting to fetch libgcc-4.9.1_0.darwin_13.x86_64.tbz2 from http://packages.macports.org/libgcc ---> Attempting to fetch libgcc-4.9.1_0.darwin_13.x86_64.tbz2.rmd160 from http://packages.macports.org/libgcc ---> Installing libgcc @4.9.1_0 ---> Cleaning libgcc ---> Computing dependencies for libgcc ---> Deactivating libgcc @4.8.2_2 ---> Cleaning libgcc ---> Activating libgcc @4.9.1_0 ---> Cleaning libgcc ---> Computing dependencies for gcc48 ---> Fetching archive for gcc48 ---> Attempting to fetch gcc48-4.8.3_0.darwin_13.x86_64.tbz2 from http://packages.macports.org/gcc48 ---> Attempting to fetch gcc48-4.8.3_0.darwin_13.x86_64.tbz2.rmd160 from http://packages.macports.org/gcc48 ---> Installing gcc48 @4.8.3_0 ---> Cleaning gcc48 ---> Computing dependencies for gcc48 ---> Deactivating gcc48 @4.8.2_2 ---> Cleaning gcc48 ---> Activating gcc48 @4.8.3_0 ---> Cleaning gcc48 ---> Computing dependencies for py27-kwant ---> Dependencies to be installed: mumps_seq scotch5 py27-matplotlib freetype bzip2 libpng py27-cairo cairo expat fontconfig glib2 gettext ncurses perl5 perl5.16 gdbm libpixman xorg-libXext xorg-libX11 xorg-kbproto xorg-libXau xorg-xproto xorg-libXdmcp xorg-libxcb python27 db46 db_select libedit openssl python_select sqlite3 xorg-libpthread-stubs xorg-xcb-proto libxml2 xz xorg-xextproto xorg-xcb-util xrender xorg-renderproto py27-dateutil py27-tz py27-numpy fftw-3 py27-nose nosetests_select py27-setuptools py27-parsing py27-pyobjc-cocoa py27-pyobjc py27-py2app py27-macholib py27-modulegraph py27-altgraph py27-six py27-tkinter tk tcl py27-tornado py27-backports-ssl_match_hostname py27-backports py27-certifi py27-scipy SuiteSparse swig-python swig pcre py27-tinyarray ---> Building scotch5 Error: org.macports.build for port scotch5 returned: error copying "/opt/local/var/macports/build/_opt_local_var_macports_sources_downloads.kwant-project.org_macports_ports_science_scotch5/scotch5/work/scotch5_5.1.12_esmumps/src/Make.inc/Makefile.inc.i686_mac_darwin8": no such file or directory Error: Failed to install scotch5 Please see the log file for port scotch5 for details: /opt/local/var/macports/logs/_opt_local_var_macports_sources_downloads.kwant-project.org_macports_ports_science_scotch5/scotch5/main.log Error: The following dependencies were not installed: mumps_seq scotch5 py27-matplotlib freetype bzip2 libpng py27-cairo cairo expat fontconfig glib2 gettext ncurses perl5 perl5.16 gdbm libpixman xorg-libXext xorg-libX11 xorg-kbproto xorg-libXau xorg-xproto xorg-libXdmcp xorg-libxcb python27 db46 db_select libedit openssl python_select sqlite3 xorg-libpthread-stubs xorg-xcb-proto libxml2 xz xorg-xextproto xorg-xcb-util xrender xorg-renderproto py27-dateutil py27-tz py27-numpy fftw-3 py27-nose nosetests_select py27-setuptools py27-parsing py27-pyobjc-cocoa py27-pyobjc py27-py2app py27-macholib py27-modulegraph py27-altgraph py27-six py27-tkinter tk tcl py27-tornado py27-backports-ssl_match_hostname py27-backports py27-certifi py27-scipy SuiteSparse swig-python swig pcre py27-tinyarray To report a bug, follow the instructions in the guide: http://guide.macports.org/#project.tickets Error: Processing of port py27-kwant failed

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Please help: Kwant installation on Mac OSX 10.9
by C.B. 08 Aug '14

08 Aug '14

Please help me! I’m doing the MacPorts installation and got stuck at the following error message: sudo port install py27-kwant Password: ---> Computing dependencies for libgcc ---> Fetching archive for libgcc ---> Attempting to fetch libgcc-4.9.1_0.darwin_13.x86_64.tbz2 from http://packages.macports.org/libgcc ---> Attempting to fetch libgcc-4.9.1_0.darwin_13.x86_64.tbz2.rmd160 from http://packages.macports.org/libgcc ---> Installing libgcc @4.9.1_0 ---> Cleaning libgcc ---> Computing dependencies for libgcc ---> Deactivating libgcc @4.8.2_2 ---> Cleaning libgcc ---> Activating libgcc @4.9.1_0 ---> Cleaning libgcc ---> Computing dependencies for gcc48 ---> Fetching archive for gcc48 ---> Attempting to fetch gcc48-4.8.3_0.darwin_13.x86_64.tbz2 from http://packages.macports.org/gcc48 ---> Attempting to fetch gcc48-4.8.3_0.darwin_13.x86_64.tbz2.rmd160 from http://packages.macports.org/gcc48 ---> Installing gcc48 @4.8.3_0 ---> Cleaning gcc48 ---> Computing dependencies for gcc48 ---> Deactivating gcc48 @4.8.2_2 ---> Cleaning gcc48 ---> Activating gcc48 @4.8.3_0 ---> Cleaning gcc48 ---> Computing dependencies for py27-kwant ---> Dependencies to be installed: mumps_seq scotch5 py27-matplotlib freetype bzip2 libpng py27-cairo cairo expat fontconfig glib2 gettext ncurses perl5 perl5.16 gdbm libpixman xorg-libXext xorg-libX11 xorg-kbproto xorg-libXau xorg-xproto xorg-libXdmcp xorg-libxcb python27 db46 db_select libedit openssl python_select sqlite3 xorg-libpthread-stubs xorg-xcb-proto libxml2 xz xorg-xextproto xorg-xcb-util xrender xorg-renderproto py27-dateutil py27-tz py27-numpy fftw-3 py27-nose nosetests_select py27-setuptools py27-parsing py27-pyobjc-cocoa py27-pyobjc py27-py2app py27-macholib py27-modulegraph py27-altgraph py27-six py27-tkinter tk tcl py27-tornado py27-backports-ssl_match_hostname py27-backports py27-certifi py27-scipy SuiteSparse swig-python swig pcre py27-tinyarray ---> Building scotch5 Error: org.macports.build for port scotch5 returned: error copying "/opt/local/var/macports/build/_opt_local_var_macports_sources_downloads.kwant-project.org_macports_ports_science_scotch5/scotch5/work/scotch5_5.1.12_esmumps/src/Make.inc/Makefile.inc.i686_mac_darwin8": no such file or directory Error: Failed to install scotch5 Please see the log file for port scotch5 for details: /opt/local/var/macports/logs/_opt_local_var_macports_sources_downloads.kwant-project.org_macports_ports_science_scotch5/scotch5/main.log Error: The following dependencies were not installed: mumps_seq scotch5 py27-matplotlib freetype bzip2 libpng py27-cairo cairo expat fontconfig glib2 gettext ncurses perl5 perl5.16 gdbm libpixman xorg-libXext xorg-libX11 xorg-kbproto xorg-libXau xorg-xproto xorg-libXdmcp xorg-libxcb python27 db46 db_select libedit openssl python_select sqlite3 xorg-libpthread-stubs xorg-xcb-proto libxml2 xz xorg-xextproto xorg-xcb-util xrender xorg-renderproto py27-dateutil py27-tz py27-numpy fftw-3 py27-nose nosetests_select py27-setuptools py27-parsing py27-pyobjc-cocoa py27-pyobjc py27-py2app py27-macholib py27-modulegraph py27-altgraph py27-six py27-tkinter tk tcl py27-tornado py27-backports-ssl_match_hostname py27-backports py27-certifi py27-scipy SuiteSparse swig-python swig pcre py27-tinyarray To report a bug, follow the instructions in the guide: http://guide.macports.org/#project.tickets Error: Processing of port py27-kwant failed

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Kwant-discuss August 2014