Dear all,
I am trying a graphene bulk with magnetic field, and I use
spectrum = kwant.kpm.SpectralDensity(fsyst, num_vectors=None,
vector_factory=s_factory,
rng=0)
energies, densities = spectrum()
to calculate the dos and compare with some previous studies. My definition
of the hopping is:
def Hop_magnetic(site1,site2):
B_magneic=200. # units Tesla
a0=0.142 # nm
x1,y1=site1.pos
x2,y2=site2.pos
xy=0.5*(x1+x2)*sqrt(3)*a0*(y1-y2)*sqrt(3)*a0 # the units is nm**2
phb=1j*2.*pi*B_magneic/4.135667 # phi0=h/e=4.135667*e-15 V*s
return t*exp(xy*phb*0.001)
I found that the effect of the magnetic field is too small and I can not
obtain the correct results.
Could you give me some suggestions?
Best regards
Khani
My code is pasted:
import kwant
from matplotlib import pyplot
from numpy import sqrt,pi,exp
import numpy as np
def make_system(r=8, t=1, tp=-0.1):
lat = kwant.lattice.honeycomb(norbs=1)
a, b = lat.sublattices
def circle(pos):
x, y = pos
return x**2 + y**2 < 100**2 #-100<x<100 and -100<y<100
def Hop_magnetic(site1,site2):
B_magneic=200. # the unit of B_magneic is Tesla=V*s/m**2
a0=0.142 # nm
x1,y1=site1.pos
x2,y2=site2.pos
xy=0.5*(x1+x2)*sqrt(3)*a0*(y1-y2)*sqrt(3)*a0 # the units change
it to nm**2
phb=1j*2.*pi*B_magneic/4.135667 # phi0=h/e=4.135667*e-15 V*s,
the unit of B_magneic is Tesla=V*s/m**2
return t*exp(xy*phb*0.001)
def Nearest_Hop(site1,site2):
return Hop_magnetic(site1,site2)
syst = kwant.Builder()
syst[lat.shape(circle, (0, 0))] = 0
syst[lat.neighbors()] = Nearest_Hop
syst.eradicate_dangling()
return lat, syst.finalized()
lat, fsyst = make_system()
#kwant.plot(fsyst)
where = lambda s: np.linalg.norm(s.pos) < 1
s_factory = kwant.kpm.LocalVectors(fsyst, where)
spectrum = kwant.kpm.SpectralDensity(fsyst, num_vectors=None,
vector_factory=s_factory,
rng=0)
energies, densities = spectrum()
pyplot.figure()
pyplot.plot(energies, densities)
pyplot.xlabel("energy [t]")
pyplot.ylabel("DOS")
pyplot.show()
