Dear Antonio, I notice that you result is infinite: on the y-axis you have 1e206 ! I guess that you are dealing with a singularity. I see that you are using the bound [0,0.4]. In graphene, the energy 0 should be avoided in general since some singularities appear there (for example the S matrix is singular at E=0). Could you try with [.1,.4] for example?
Try to give a reproducible example (if not confidential) in order to check the problem. I hope this helps Adel On Mon, Jun 17, 2019 at 2:35 PM Antonio Lucas Rigotti Manesco < [email protected]> wrote: > Hi Adel, > > I'm doing some tests with graphene in the presence of a spatial-dependent > magnetic field. First, I calculated the DOS: > spectrum = kwant.kpm.SpectralDensity(fsyst) > and LDOS: > kwant_op = kwant.operator.Density(fsyst, where=sm_shape, sum=False) > local_dos = kwant.kpm.SpectralDensity(fsyst, operator=kwant_op, mean=False) > and both calculations lead to the results I expected. > > Next, I did the same calculation, with lower magnetic field (to reproduce > real-world conditions), and I noticed that the required memory needed was > way higher. So, I tried to fix a smaller window for KPM bounds: > spectrum = kwant.kpm.SpectralDensity(fsyst, bounds=(0.,0.4)) > and > local_dos = kwant.kpm.SpectralDensity(fsyst, operator=kwant_op, > mean=False, bounds=(0.,0.4)) > > The fact is: LDOS was similar in both calculations. On the other hand, the > resulting DOS looks like this: > [image: image.png] > which do not remind me about the Landau levels of the first calculation at > all. > > So, I'm not sure if I can rely on the LDOS result with limited energy > window, since DOS is different from the expected. Also, I wonder if it is > possible to get the correct DOS with limited energy window. > > Best, > Antonio > > Em dom, 16 de jun de 2019 às 05:11, Abbout Adel <[email protected]> > escreveu: > >> Dear Antonio, >> >> Without an example, your problem may be not very clear. Could you provide >> an example? >> >> I think that you are talking about the fact that the values that you get >> when you change the length of the interval are different which is quite >> normal. >> Put in mind that, the result is the number of appearance of some energies >> and that the density is not normalized. >> >> Regards, >> Adel >> >> On Thu, Jun 13, 2019 at 7:46 PM Antonio Lucas Rigotti Manesco < >> [email protected]> wrote: >> >>> Hello all, >>> >>> I'm trying to do some calculations using KPM method for graphene in a >>> somehow large quantum dot (300ax300a, where a is the lattice constant). >>> Since LDOS calculations uses lot of memory and I need good energy >>> resolution, I redefined my energy bounds to a smaller window, and the >>> behavior is similar to what I expected. However, if I do the same for DOS >>> calculations, I get something that looks very strange, compared with the >>> previous result using the automatically generated bounds. So, my question >>> is: are the LDOS results reliable even though the DOS does not looks right? >>> (I'm calculating the LDOS for energies about the middle of the new window, >>> in case that matters). >>> >>> Thanks >>> Antonio >>> >> >> >> -- >> Abbout Adel >> > > > -- > Antônio Lucas Rigotti Manesco > PhD fellow - University of São Paulo, Brazil > -- Abbout Adel
