from matplotlib import pyplot
import kwant
import math
def make_system(a=1,W=10,t=1.4):
    lat=kwant.lattice.square(a)
    sys=kwant.Builder()
    def bias(site,volt):
       (x,y)=site.pos
       if 0 <=x <10:
          return (volt/10)*x
       elif x==10:
            return volt
       else:
          return 0
    def onsite(site,volt=0):
        print(volt)
        return 4*t- bias(site,volt)
    
    sys[(lat(x,y) for x in range(0,10) for y in range(W))]=onsite
    sys[lat.neighbors()]=1.4
    sym=kwant.TranslationalSymmetry((-a,0))
    lead=kwant.Builder(sym)
    lead[(lat(0,y) for y in range(10))]=4*t
    lead[lat.neighbors()]=1
    sys.attach_lead(lead)
    sys.attach_lead(lead.reversed())
    return sys              
    
def main():
    sys=make_system()
    sys=sys.finalized()     
    kwant.plot(sys)
    pyplot.show()

if __name__=='__main__':
    main()