doc/source/reference/kwant.system.rst

 :mod:`kwant.system` -- Low-level interface of systems
 *****************************************************
 
-.. currentmodule:: kwant.system
+.. automodule:: kwant.system
 
 This module is the binding link between constructing tight-binding systems and
 doing calculations with these systems.  It defines the interface which any
@@ -14,6 +14,11 @@ Any system which is provided to a solver should be derived from the appropriate
 class in this module, and every solver can assume that its input corresponds to
 the interface defined here.
 
+In practice, very often Kwant systems are finalized
+`builders <kwant.builder.Builder>` (i.e.
+`kwant.builder.FiniteSystem` or `kwant.builder.InfiniteSystem`) and offer some
+additional attributes.
+
 .. autosummary::
    :toctree: generated/
 

doc/source/reference/kwant.wraparound.rst

+:mod:`kwant.wraparound` -- Wrapping around translational symmetries
+===================================================================
+.. module:: kwant.wraparound
+.. autosummary::
+   :toctree: generated/
+
+   wraparound
+   plot_2d_bands

doc/source/tutorial/README

-Note for Kwant developers
--------------------------
-
-Say you have modified SCRIPT.py in this directory.  Make sure that the tutorial
-image generation patches still apply by deleting doc/source/images/SCRIPT.py
-and running ``make doc/source/images/SCRIPT.py`` in doc.  Now examine the newly
-created doc/source/images/SCRIPT.py.  If you do not like the result or the
-patch did not apply, edit doc/source/images/SCRIPT.py until you like it.  You
-can run `make html` during your edits to check things.  Finally, even if you
-did not edit the script, execute generate-diffs.sh in doc/source/images.  If
-the patches applied cleanly the diff files will usually stay unchanged.

doc/source/tutorial/ab_ring.py

-# Tutorial 2.3.3. Nontrivial shapes
-# =================================
-#
-# Physics background
-# ------------------
-#  Flux-dependent transmission through a quantum ring
-#
-# Kwant features highlighted
-# --------------------------
-#  - More complex shapes with lattices
-#  - Allows for discussion of subtleties of `attach_lead` (not in the
-#    example, but in the tutorial main text)
-#  - Modifcations of hoppings/sites after they have been added
-
-from cmath import exp
-from math import pi
-
-import kwant
-
-# For plotting
-from matplotlib import pyplot
-
-
-#HIDDEN_BEGIN_eusz
-def make_system(a=1, t=1.0, W=10, r1=10, r2=20):
-    # Start with an empty tight-binding system and a single square lattice.
-    # `a` is the lattice constant (by default set to 1 for simplicity).
-
-    lat = kwant.lattice.square(a)
-
-    sys = kwant.Builder()
-
-    #### Define the scattering region. ####
-    # Now, we aim for a more complex shape, namely a ring (or annulus)
-    def ring(pos):
-        (x, y) = pos
-        rsq = x ** 2 + y ** 2
-        return (r1 ** 2 < rsq < r2 ** 2)
-#HIDDEN_END_eusz
-
-    # and add the corresponding lattice points using the `shape`-function
-#HIDDEN_BEGIN_lcak
-    sys[lat.shape(ring, (0, r1 + 1))] = 4 * t
-    sys[lat.neighbors()] = -t
-#HIDDEN_END_lcak
-
-    # In order to introduce a flux through the ring, we introduce a phase on
-    # the hoppings on the line cut through one of the arms.  Since we want to
-    # change the flux without modifying the Builder instance repeatedly, we
-    # define the modified hoppings as a function that takes the flux as its
-    # parameter phi.
-#HIDDEN_BEGIN_lvkt
-    def fluxphase(site1, site2, phi):
-        return exp(1j * phi)
-
-    def crosses_branchcut(hop):
-        ix0, iy0 = hop[0].tag
-
-        # builder.HoppingKind with the argument (1, 0) below
-        # returns hoppings ordered as ((i+1, j), (i, j))
-        return iy0 < 0 and ix0 == 1  # ix1 == 0 then implied
-
-    # Modify only those hopings in x-direction that cross the branch cut
-    def hops_across_cut(sys):
-        for hop in kwant.builder.HoppingKind((1, 0), lat, lat)(sys):
-            if crosses_branchcut(hop):
-                yield hop
-    sys[hops_across_cut] = fluxphase
-#HIDDEN_END_lvkt
-
-    #### Define the leads. ####
-    # left lead
-#HIDDEN_BEGIN_qwgr
-    sym_lead = kwant.TranslationalSymmetry((-a, 0))
-    lead = kwant.Builder(sym_lead)
-
-    def lead_shape(pos):
-        (x, y) = pos
-        return (-W / 2 < y < W / 2)
-
-    lead[lat.shape(lead_shape, (0, 0))] = 4 * t
-    lead[lat.neighbors()] = -t
-#HIDDEN_END_qwgr
-
-    #### Attach the leads and return the system. ####
-#HIDDEN_BEGIN_skbz
-    sys.attach_lead(lead)
-    sys.attach_lead(lead.reversed())
-#HIDDEN_END_skbz
-
-    return sys
-
-
-def plot_conductance(sys, energy, fluxes):
-    # compute conductance
-
-    normalized_fluxes = [flux / (2 * pi) for flux in fluxes]
-    data = []
-    for flux in fluxes:
-        smatrix = kwant.smatrix(sys, energy, args=[flux])
-        data.append(smatrix.transmission(1, 0))
-
-    pyplot.figure()
-    pyplot.plot(normalized_fluxes, data)
-    pyplot.xlabel("flux [flux quantum]")
-    pyplot.ylabel("conductance [e^2/h]")
-    pyplot.show()
-
-
-def main():
-    sys = make_system()
-
-    # Check that the system looks as intended.
-    kwant.plot(sys)
-
-    # Finalize the system.
-    sys = sys.finalized()
-
-    # We should see a conductance that is periodic with the flux quantum
-    plot_conductance(sys, energy=0.15, fluxes=[0.01 * i * 3 * 2 * pi
-                                                for i in xrange(100)])
-
-
-# Call the main function if the script gets executed (as opposed to imported).
-# See <http://docs.python.org/library/__main__.html>.
-if __name__ == '__main__':
-    main()

doc/source/tutorial/band_structure.py

-# Tutorial 2.4.1. Band structure calculations
-# ===========================================
-#
-# Physics background
-# ------------------
-#  band structure of a simple quantum wire in tight-binding approximation
-#
-# Kwant features highlighted
-# --------------------------
-#  - Computing the band structure of a finalized lead.
-
-import kwant
-
-# For plotting.
-from matplotlib import pyplot
-
-#HIDDEN_BEGIN_zxip
-def make_lead(a=1, t=1.0, W=10):
-    # Start with an empty lead with a single square lattice
-    lat = kwant.lattice.square(a)
-
-    sym_lead = kwant.TranslationalSymmetry((-a, 0))
-    lead = kwant.Builder(sym_lead)
-
-    # build up one unit cell of the lead, and add the hoppings
-    # to the next unit cell
-    for j in xrange(W):
-        lead[lat(0, j)] = 4 * t
-
-        if j > 0:
-            lead[lat(0, j), lat(0, j - 1)] = -t
-
-        lead[lat(1, j), lat(0, j)] = -t
-
-    return lead
-#HIDDEN_END_zxip
-
-
-#HIDDEN_BEGIN_pejz
-def main():
-    lead = make_lead().finalized()
-    kwant.plotter.bands(lead, show=False)
-    pyplot.xlabel("momentum [(lattice constant)^-1]")
-    pyplot.ylabel("energy [t]")
-    pyplot.show()
-#HIDDEN_END_pejz
-
-
-# Call the main function if the script gets executed (as opposed to imported).
-# See <http://docs.python.org/library/__main__.html>.
-if __name__ == '__main__':
-    main()

doc/source/tutorial/boilerplate.py

+import matplotlib
+import matplotlib.pyplot
+from matplotlib_inline.backend_inline import set_matplotlib_formats
+
+matplotlib.rcParams['figure.figsize'] = matplotlib.pyplot.figaspect(1) * 2
+set_matplotlib_formats('svg')

doc/source/tutorial/index.rst

@@ -3,9 +3,14 @@ Tutorial: learning Kwant through examples
 
 .. toctree::
     introduction
-    tutorial1
-    tutorial2
-    tutorial3
-    tutorial4
-    tutorial5
-    tutorial6
+    first_steps
+    spin_potential_shape
+    spectrum
+    graphene
+    superconductors
+    operators
+    plotting
+    kpm
+    discretize
+    magnetic_field
+    faq