Dear Wilson, You said *I want to add random potentials on graphene. Within each unit cell, I want A site have the oppsite value to B site*. In fact you just need to set in the onsite function the sublattice dependence (I mean for instance *return +1 if site.family==a else -1.*) *SO in your case:* a, b =lat.sublattices def onsite(site,low, high): return *+1**np.random.uniform(low, high) if ifsite.family==*a* else -1*np.random.uniform(low, high) *or simply use the kwant.digest prebuilt function as* sites =list(syst.sites()) Random_sites = random.choices(sites, k = 10) def onsite(site): return *+*0.5 *kwant.digest.uniform(repr(Random_sites)) + 0.5 if if site.family==aelse* -* 0.5 * kwant.digest.uniform(repr(Random_sites)) + 0.5 I hope this will help. Best, Adel Le mer. 25 mai 2022 à 17:53, <wilson2048@outlook.com> a écrit :
Dear community,
I want to add random potentials on graphene. Within each unit cell, I want A site have the oppsite value to B site. That is, random across unit cells, but symmetric respect to zero within every unit cell. How to achieve this? I have tried to do so, but cannot find a way.
Below is my code:
``` import numpy as np import kwant
low = 0 high = 1 def make_syst(a=1): syst = kwant.Builder() lat = kwant.lattice.honeycomb(a, norbs=1, name=['a', 'b'])
r = 10
def circle(pos): x, y = pos return x ** 2 + y ** 2 < r ** 2
def onsite(site, low, high): return np.random.uniform(low, high)
# first attempt using function, not working, also cannot gurantee a, b are truly opposite in value # syst[lat.a.shape(circle, (0, 0))] = onsite # syst[lat.b.shape(circle, (0, 0))] = -1*onsite # wrong
# second attempt, still not right m = np.random.uniform(low, high) syst[lat.a.shape(circle, (0, 0))] = m syst[lat.b.shape(circle, (0, 0))] = -m
syst[lat.neighbors()] = 1 return syst.finalized()
fsyst = make_syst() # kwant.plot(fsyst) H = fsyst.hamiltonian_submatrix(params=dict(high=high, low=low)) Es = np.linalg.eigvalsh(H) plt.plot(Es, '.') plt.show() ```
Thanks for help!