I am trying to calculate the conductance through coupled quantum nanowires. I have basically considered a square lattice with hopping tx in x direction and modulating the coupling between the wires through ty i.e. the hopping in y direction. My system requires  periodic boundary condition along x direction and open boundary condition in y direction. Can you please help me in  how this can be done using kwant to meet the above boundary conditions. I have mentioned my code below. Since I am  new to Kwant, it would be of much help to me if you help me solving this.

Deepti Rana

def make_sys1(a=1,W=4,barrierpos=1):
    def onsite_normal(site,p):
        return( (2 * (p.tx+p.ty) - p.mu) * pauli.s0sz+p.Ez*pauli.szs0))

    def onsite_sc(site,p):
        return (2 * (p.tx+p.ty ) * pauli.s0sz+p.Ez*pauli.szs0)+p.delta*pauli.s0sx)

    def onsite_barrier(site,p):
        return((2*(p.tx+p.ty)+ p.Vbarrier-p.mu)*pauli.s0sz+p.Ez*pauli.szs0))

    def hopx(site1, site2, p):
        return -p.tx * pauli.s0sz +1j* p.alphax * pauli.sysz

    def hopy(site1, site2, p):
        return -p.ty * pauli.s0sz -1j * p.alphay * pauli.sxsz
    lat = kwant.lattice.square(a,norbs=4)
    syst = kwant.Builder()
    syst[(lat(x, y) for x in range(barrierpos)
         for y in range(W))]=onsite_barrier
    syst[kwant.builder.HoppingKind((1, 0), lat, lat)] = hopx
    syst[kwant.builder.HoppingKind((0, 1), lat, lat)] = hopy
    sym_left = kwant.TranslationalSymmetry((-a, 0))
    lead0 = kwant.Builder(sym_left, conservation_law=-pauli.s0sz)
    lead0[(lat(0, j) for j in range(W))]=onsite_normal
    lead0[kwant.builder.HoppingKind((1, 0), lat, lat)] = hopx
    lead0[kwant.builder.HoppingKind((0, 1), lat, lat)] = hopy
    sym_right = kwant.TranslationalSymmetry((a, 0))
    lead1 = kwant.Builder(sym_right)
    lead1[(lat(0, j) for j in range(W))]=onsite_sc
    lead1[kwant.builder.HoppingKind((1, 0), lat, lat)] = hopx
    lead1[kwant.builder.HoppingKind((0, 1), lat, lat)] = hopy

    syst = syst.finalized()
    return syst