def __init__(self, t, t2=0, U=0, mu=0., occ=True, nsite=6):
self.t, self.t2, self.U, self.mu = t, t2, U, mu
self.occ = occ
self.nsite = nsite
#occupation representation will use <SuperSpaceConfig>, otherwise <SpaceConfig>.
if self.occ:
spaceconfig = SuperSpaceConfig(chorder([nsite, 2, 1]))
else:
spaceconfig = SpaceConfig(chorder([1, 2, nsite, 1]), kspace=False)
if abs(U) > 0:
warnings.warn('U is ignored in non-occupation representation.')
hgen = RHGenerator(spaceconfig=spaceconfig)
#define the operator of the system
hgen.register_params({
't1': self.t,
't2': self.t2,
'U': self.U,
'-mu': -self.mu,
})
#define a structure and initialize bonds.
rlattice = Chain(N=nsite)
hgen.uselattice(rlattice)
b1s = rlattice.getbonds(1) #the nearest neighbor
b2s = rlattice.getbonds(2) #the nearest neighbor
#add the hopping term.
op_t1 = op_simple_hopping(label='hop1',
spaceconfig=spaceconfig,
bonds=b1s)
hgen.register_operator(op_t1, param='t1')
op_t2 = op_simple_hopping(label='hop2',
spaceconfig=spaceconfig,
bonds=b2s)
hgen.register_operator(op_t2, param='t2')
op_n = op_simple_onsite(label='n', spaceconfig=spaceconfig)
hgen.register_operator(op_n, param='-mu')
#add the hubbard interaction term if it is in the occupation number representation.
if self.occ:
op_ninj = op_U(label='ninj', spaceconfig=spaceconfig)
hgen.register_operator(op_ninj, param='U')
self.hgen = hgen
