Figure 5
From: Topological incommensurate magnetization plateaus in quasi-periodic quantum spin chains
Butterfly-like spin-flip excitation spectrum for quasi-periodic Heisenberg models.
Spin-flip excitation spectrum versus α for (a) 
and (b) spin-1 chains with L = 50 and δ = 0 under PBC, where α is swept with step 0.02 in interval [0, 1]. The blue squares from left to right denote special cases with 
, 
and 
, respectively. Here we have taken λ = 0.8 for (a) and λ = 0.3 for (b).
