Newer
Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
import kwant
import numpy as np
def diamond_chain_system(N_c, system_params):
'''
Create a diamond chain of trimer unit cells. Each atom of the trimer has two orbital angular momentum states, + and -
_______
... | C_i_+ |
| C_i_- | ...
/ ------- \ ______ /
... | A_i_+ | ...
| A_i_- |
\ ______ / ------- \
... | B_i_+ | ...
| B_i_- |
-------
:param int N_c: number of unit cells to include in the cell
:param dict system_params: parameters
:rtype kwant.system.FiniteSystem:
'''
# make lattices and sublattices
lat = kwant.lattice.Polyatomic(prim_vecs = [[1,0],[0,1]], basis = [[1,0],[1,0], [0,-1],[0,-1], [0,1],[0,1]])
a_lat_pos, a_lat_neg, b_lat_pos, b_lat_neg, c_lat_pos, c_lat_neg = lat.sublattices
#make builder and populate with onsite and hoppings
syst = kwant.Builder()
for i in range(N_c):
#staggered point
sp = 2*i
syst[a_lat_pos(sp,0)] = 0
syst[a_lat_neg(sp,0)] = 0
syst[b_lat_pos(sp,0)] = 0
syst[b_lat_neg(sp,0)] = 0
syst[c_lat_pos(sp,0)] = 0
syst[c_lat_neg(sp,0)] = 0
if i < N_c - 1:
syst[c_lat_pos(sp+2,0)] = 0
syst[b_lat_pos(sp+2,0)] = 0
syst[c_lat_neg(sp+2,0)] = 0
syst[b_lat_neg(sp+2,0)] = 0
# + <--> +
syst[a_lat_pos(sp,0), c_lat_pos(sp+2,0)] = 1
syst[a_lat_pos(sp,0), b_lat_pos(sp+2,0)] = 1
# - <--> -
syst[a_lat_neg(sp,0), c_lat_neg(sp+2,0)] = 1
syst[a_lat_neg(sp,0), b_lat_neg(sp+2,0)] = 1
# + <--> -
syst[a_lat_pos(sp,0), b_lat_neg(sp+2,0)] = 1
syst[a_lat_neg(sp,0), b_lat_pos(sp+2,0)] = 1
# + <--> - hopping with phase
syst[a_lat_pos(sp,0), c_lat_neg(sp+2,0)] = 1
syst[a_lat_neg(sp,0), c_lat_pos(sp+2,0)] = 1
# + <--> +
syst[a_lat_pos(2*i,0), c_lat_pos(sp,0)] = 1
syst[a_lat_pos(2*i,0), b_lat_pos(sp,0)] = 1
# - <--> -
syst[a_lat_neg(2*i,0), c_lat_neg(sp,0)] = 1
syst[a_lat_neg(2*i,0), b_lat_neg(sp,0)] = 1
# + <--> -
syst[a_lat_pos(2*i,0), c_lat_neg(sp,0)] = 1
syst[a_lat_neg(2*i,0), c_lat_pos(sp,0)] = 1
# + <--> - hopping with phase
syst[a_lat_pos(2*i,0), b_lat_neg(sp,0)] = 1
syst[a_lat_neg(2*i,0), b_lat_pos(sp,0)] = 1
return syst
m = diamond_chain_system(10,None)
kwant.plot(m)