Re: [Kwant] seeking help

31 Aug 2018


      Dear Shyam Lochan Bora,
Right now your question is rather poorly formulated, and not suitable
for this mailing list. Please read this instruction on how to ask good
questions: https://stackoverflow.com/help/how-to-ask
Additionally, it appears that your problem is due the lack of the
Python knowledge, I recommend you to follow a Python course, or
otherwise learn the language more systematically.
Best regards,
Anton Akhmerov
On Fri, Aug 31, 2018 at 5:08 PM shyam lochan bora
shyamlochan04@gmail.com wrote:
...
Dear sir,
Please help me with the following error in the program
from __future__ import print_function
from ipywidgets import interact, interactive, fixed, interact_manual
import ipywidgets as widgets
import kwant
from matplotlib import pyplot
import numpy as np
from holoviews.core.options import Cycle
from types import SimpleNamespace
def nanowire_chain():
    lat = kwant.lattice.chain()
    sys = kwant.Builder(kwant.TranslationalSymmetry(*lat.prim_vecs))
def onsite(onsite, p):
    return (2 * p.t - p.mu) * pauli.szs0 + p.B * (np.cos(p.phi)*pauli.s0sz+ np.sin(p.phi)*np.sin(p.theta)*pauli.s0sy+np.sin(p.phi)*np.sin(p.theta)*pauli.s0sx)+ p.delta * pauli.sxs0

sys[lat(0)] = onsite

def hop(site1, site2, p):
    return -p.t * pauli.szs0 - .5j * p.alpha * pauli.szsx

sys[kwant.HoppingKind((1,), lat)] = hop

return sys


def spinful_kitaev_chain():
    lat = kwant.lattice.chain()
    sys = kwant.Builder(kwant.TranslationalSymmetry(*lat.prim_vecs))
def onsite(site, p):
    return (2 * p.t - p.mu) * pauli.szs0 + p.B * pauli.szsz

sys[lat(0)] = onsite

def hop(site1, site2, p):
    return -p.t * pauli.szs0 - 1j * p.delta * pauli.sys0

sys[kwant.HoppingKind((1,), lat)] = hop

return sys


def find_gap(sys, p, resolution=1e-4):
    """Find gap in a system by doing a binary search in energy."""
# This tells us if there are modes at a certain energy.
if len(sys.modes(energy=0, args=[p])[0].momenta):
    return 0

gap = step = min(abs(kwant.physics.Bands(sys, args=[p])(k=0))) / 2
while step > resolution:
    step /= 2
    if len(sys.modes(gap, args=[p])[0].momenta):
        gap -= step
    else:
        gap += step

return gap


def spinorbit_band_gap(sys, mu, t, delta, Bs):
    sys = sys.finalized()
    alphas = [0.0, 0.1, 0.2, 0.3]
    p = SimpleNamespace(mu=mu, t=t, delta=delta,theta=theta,phi=phi)
def gap(sys, p, alpha, B):
    p.alpha = alpha
    p.B = B
    return find_gap(sys, p)

gaps = [gap(sys, p, alpha, B) for alpha in alphas for B in Bs]
gaps = np.reshape(gaps, (len(alphas), -1))
dims = {'kdims': [r'$B$'], 'vdims': ['Band gap']}
B_crit = holoviews.VLine(np.sqrt(p.delta**2 + p.mu**2))
plot = [holoviews.Curve((Bs, gaps[i]), label=r'$\alpha={}$'.format(
    alphas[i]), **dims) * B_crit for i, alpha in enumerate(alphas)]
title = r'$\Delta={delta}$, $\mu={mu}$'.format(delta=np.round(p.delta, 2), mu=np.round(p.mu, 2))
style = {'xticks': [0, 0.1, 0.2, 0.3], 'yticks': [0, 0.05, 0.1], 'fig_size': 150}
plot = holoviews.Overlay(plot)
return plot(plot=style)


def title(p):
    try:
        title = r"$\alpha={alpha}$, $\mu={mu}$, $B={B}$, $\Delta={delta}$"
        title = title.format(alpha=np.round(p.alpha, 2),
                             mu=np.round(p.mu, 2),
                             B=np.round(p.B, 2),
                             delta=np.round(p.delta, 2))
    except AttributeError:
        title = r"$\mu={mu}$, $B={B}$, $\Delta={delta}$"
        title = title.format(mu=np.round(p.mu, 2),
                             B=np.round(p.B, 2),
                             delta=np.round(p.delta, 2))
    return title
style = {'k_x': np.linspace(-1, 1, 101),
         'xdim': r'$k$',
         'ydim': r'$E/t$',
         'xticks': [-1, 0, 1],
         'yticks': [-1, 0, 1],
         'xlims': [-1, 1],
         'ylims': [-1.5, 1.5],
         'title': title}
sys = nanowire_chain()
p = SimpleNamespace(t=1, mu=0.1, delta=0.1, B=0.3,theta=np.pi/2,phi=np.pi/2)
alphas = np.linspace(0, 0.4, 10)
holoviews.HoloMap({alpha: spectrum(sys, p.update(alpha=alpha), **style) for alpha in alphas}, kdims=[r'$\alpha$'])
c:\python36\lib\site-packages\kwant\linalg\lll.py:103: FutureWarning: `rcond` parameter will change to the default of machine precision times ``max(M, N)`` where M and N are the input matrix dimensions.
To use the future default and silence this warning we advise to pass `rcond=None`, to keep using the old, explicitly pass `rcond=-1`.
  coefs = np.linalg.lstsq(vecs_orig.T, vecs.T)[0]
c:\python36\lib\site-packages\kwant\linalg\lll.py:144: FutureWarning: `rcond` parameter will change to the default of machine precision times ``max(M, N)`` where M and N are the input matrix dimensions.
To use the future default and silence this warning we advise to pass `rcond=None`, to keep using the old, explicitly pass `rcond=-1`.
  center_coords = np.array(np.round(np.linalg.lstsq(basis.T, vec)[0]), int)

NameError                                 Traceback (most recent call last)
<ipython-input-3-9ff9219a759e> in <module>()
      2 p = SimpleNamespace(t=1, mu=0.1, delta=0.1, B=0.3,theta=np.pi/2,phi=np.pi/2)
      3 alphas = np.linspace(0, 0.4, 10)
----> 4 holoviews.HoloMap({alpha: spectrum(sys, p.update(alpha=alpha), **style) for alpha in alphas}, kdims=[r'$\alpha$'])
NameError: name 'holoviews' is not defined