Figure 3
From: Topological incommensurate magnetization plateaus in quasi-periodic quantum spin chains
Spin-flip excitation spectrum of quasi-periodic 
AFM Heisenberg chain.
(a) The spin-flip excitation spectrum 
with respect to the phase factor δ for 
AFM Heisenberg chain with 
, λ = 0.8 and L = 100 under OBC. The four large excitation gaps support the magnetization plateaus Pα, P2α, P−2α and P−α from bottom to top. (b) and (c) Distributions 
of in-gap spin-flip excitation modes for plateaus P2α and Pα, respectively. For each in-gap mode, Sz = mlL.
