Fig. 2: Addition energy spectrum and edge population of the SSHH model.
From: Topological phases of a dimerized Fermi–Hubbard model for semiconductor nano-lattices
The addition energy spectrum of the Su–Schrieffer–Heeger–Hubbard model as a function of interaction strengths in the a non-trivial phase and b trivial phase and c as a function of hopping amplitude difference in the strongly correlated limit. To keep track of the edge states, the energy levels are colored according to the population at the two ends of the chain (nedge); changes of color thus correspond to occupation of edge states. At strong interaction, there are three gaps formed, at half-filling and at quarter-/three-quarter-filling. The edge population shows that in the non-trivial phase the mid-gap edge states shift from half-filling at U = 0 to quarter-filling and three-quarter-fillings at large U [marked by the horizontal arrow in a]. The edge population as a function of filling in the strongly correlated limit is shown in d: In the trivial phase, the edge population increases gradually, while in the non-trivial phase the edge population increases sharply at quarter- and three-quarter-fillings, indicating the existence of an edge state for the charge excitation at these fillings.
