Hi Anton
I have another error with zigzag ribbons. When I run graphene lattice with
a complex next-nearest-neighbors (Kane-Mele model). I have the next error
for values "t2<0.0005j":
RuntimeError: Numbers of left- and right-propagating modes differ, possibly
due to a numerical instability.
If somebody know how fix it, please let me know.
Best Regards
César
2015-08-05 11:50 GMT-03:00 Anton Akhmerov
Hi Maximilian, César,
Thanks for reporting this, looks quite interesting. I don't have an immediate answer yet, but I'll check it out. Can you try and search for the simplest/smallest system that shows the instability?
Best, Anton
On Wed, Aug 5, 2015 at 4:45 PM, cesar nunez
wrote: Dear All
I have the same problem when used the Kane-Mele model. The problem disappears when the next-nearest-neighbor hopping is zero or lower than 0.0005j. Some ideas for fix it?
Best Regards César
2015-08-05 6:08 GMT-03:00 Maximilian Trescher
: Dear kwant users and developers,
this is my first post to this list, I'm a PhD student from Berlin. Currently I'm trying to implement a lattice model of a pyrochlore slab in kwant.
I found a (more or less straightforward) way to introduce periodic boundary conditions in the system in the maillinglist archive. This works very nicely as long as I keep the periodicity along a lattice vector.
But I run into problems when I choose different directions: Most of the time all solvers fail with a "LinAlgError: QZ iteration failed to converge in zgges".
I know about this post http://comments.gmane.org/gmane.comp.science.kwant.user/372 but in my case it occurs not only for a band bottom, but for a range of energies.
To give you all the details I prepared a Ipython notebook that you can view here: http://nbviewer.ipython.org/gist/faucon/729050da5e3f2eae1bb8#
(Note that the inclusion of complex next-nearest-neighbor hopping is crucial to produce the error, I tried to create the shortest example which reproduces my problem).
Do you have any idea how to circumvent this problem? Is it somehow related to http://netlib.org/lapack/Errata/vrac/lapack_known_issues.html#QZ this problem in Lapack?
I would be thankful for any hint, Best, Maximilian
-- César Núñez Ramírez Doctor(C) Física U.T.F.S.M.
-- César Núñez Ramírez Doctor(C) Física U.T.F.S.M.