ab_ring.py.diff

--- original
+++ modified
@@ -9,6 +9,7 @@
 #    example, but in the tutorial main text)
 #  - Modifcations of hoppings/sites after they have been added
 
+import _defs
 from cmath import exp
 from math import pi
 
@@ -37,12 +38,13 @@
     sys[lat.shape(ring, (0, r1 + 1))] = 4 * t
     sys[lat.neighbors()] = -t
 
-    # 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.
-    def fluxphase(site1, site2, phi):
+    # 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 Builder repeatedly,
+    # we define the modified hoppings as a function that takes the flux
+    # through the argument phi.
+    def fluxphase(site1, site2, phi=0):
         return exp(1j * phi)
 
     def crosses_branchcut(hop):
@@ -78,6 +80,50 @@
     return sys
 
 
+def make_system_note1(a=1, t=1.0, W=10, r1=10, r2=20):
+    lat = kwant.lattice.square(a)
+    sys = kwant.Builder()
+    def ring(pos):
+        (x, y) = pos
+        rsq = x**2 + y**2
+        return ( r1**2 < rsq < r2**2)
+    sys[lat.shape(ring, (0, 11))] = 4 * t
+    sys[lat.neighbors()] = -t
+    sym_lead0 = kwant.TranslationalSymmetry((-a, 0))
+    lead0 = kwant.Builder(sym_lead0)
+    def lead_shape(pos):
+        (x, y) = pos
+        return (-1 < x < 1) and ( 0.5 * W < y < 1.5 * W )
+    lead0[lat.shape(lead_shape, (0, W))] = 4 * t
+    lead0[lat.neighbors()] = -t
+    lead1 = lead0.reversed()
+    sys.attach_lead(lead0)
+    sys.attach_lead(lead1)
+    return sys
+
+
+def make_system_note2(a=1, t=1.0, W=10, r1=10, r2=20):
+    lat = kwant.lattice.square(a)
+    sys = kwant.Builder()
+    def ring(pos):
+        (x, y) = pos
+        rsq = x**2 + y**2
+        return ( r1**2 < rsq < r2**2)
+    sys[lat.shape(ring, (0, 11))] = 4 * t
+    sys[lat.neighbors()] = -t
+    sym_lead0 = kwant.TranslationalSymmetry((-a, 0))
+    lead0 = kwant.Builder(sym_lead0)
+    def lead_shape(pos):
+        (x, y) = pos
+        return (-1 < x < 1) and ( -W/2 < y < W/2  )
+    lead0[lat.shape(lead_shape, (0, 0))] = 4 * t
+    lead0[lat.neighbors()] = -t
+    lead1 = lead0.reversed()
+    sys.attach_lead(lead0)
+    sys.attach_lead(lead1, lat(0, 0))
+    return sys
+
+
 def plot_conductance(sys, energy, fluxes):
     # compute conductance
 
@@ -87,18 +133,31 @@
         smatrix = kwant.smatrix(sys, energy, args=[flux])
         data.append(smatrix.transmission(1, 0))
 
-    pyplot.figure()
+    fig = pyplot.figure()
     pyplot.plot(normalized_fluxes, data)
-    pyplot.xlabel("flux [flux quantum]")
-    pyplot.ylabel("conductance [e^2/h]")
-    pyplot.show()
+    pyplot.xlabel("flux [flux quantum]",
+                 fontsize=_defs.mpl_label_size)
+    pyplot.ylabel("conductance [e^2/h]",
+                 fontsize=_defs.mpl_label_size)
+    pyplot.setp(fig.get_axes()[0].get_xticklabels(),
+               fontsize=_defs.mpl_tick_size)
+    pyplot.setp(fig.get_axes()[0].get_yticklabels(),
+               fontsize=_defs.mpl_tick_size)
+    fig.set_size_inches(_defs.mpl_width_in, _defs.mpl_width_in * 3. / 4.)
+    fig.subplots_adjust(left=0.15, right=0.95, top=0.95, bottom=0.15)
+    fig.savefig("ab_ring_result.pdf")
+    fig.savefig("ab_ring_result.png", dpi=_defs.dpi)
 
 
 def main():
     sys = make_system()
 
     # Check that the system looks as intended.
-    kwant.plot(sys)
+    size = (_defs.figwidth_in, _defs.figwidth_in)
+    for extension in ('pdf', 'png'):
+        kwant.plot(sys, file="ab_ring_sys." + extension,
+                   fig_size=size, dpi=_defs.dpi)
+
 
     # Finalize the system.
     sys = sys.finalized()
@@ -108,6 +167,17 @@
                                                 for i in xrange(100)])
 
 
+    # Finally, some plots needed for the notes
+    sys = make_system_note1()
+    for extension in ('pdf', 'png'):
+        kwant.plot(sys, file="ab_ring_note1." + extension,
+                   fig_size=size, dpi=_defs.dpi)
+    sys = make_system_note2()
+    for extension in ('pdf', 'png'):
+        kwant.plot(sys, file="ab_ring_note2." + extension,
+                   fig_size=size, dpi=_defs.dpi)
+
+
 # Call the main function if the script gets executed (as opposed to imported).
 # See <http://docs.python.org/library/__main__.html>.
 if __name__ == '__main__':