Topological Anderson insulating phases in the long-range Su-Schrieffer-Heeger model

Abstract

In the long-range Su-Schriffer-Heeger (SSH) model, in which the next nearest-neighbor hopping is considered, there exhibits a rich topological phase diagram that contains winding numbers $w=0, 1$, and $2$. In the presence of disorder, the change in mean winding number with various disorder strengths is numerically calculated. We find that the disorder drives phase transitions: $w=0 \rightarrow 1, 0 \rightarrow 2 $, $1 \rightarrow 2$ and $2 \rightarrow 1$, in which the non-zero winding numbers driven by disorder are called the topological Anderson insulating (TAI) phases. The transition mechanisms in this long-range SSH model are investigated by means of localization length and self-energy. We find that the localization length has a drastic change at the transition point, and the corresponding critical disorder strength is obtained by further using Born approximation to the self-energy. The origin for the $w = 0$ to $w = 1, 2$ transitions is attributed to the energy gap renormalization (first Born approximation), while for the transitions from $w=1$ to $w=2$ and vice versa are the strong scattering (self-consistent Born approximation). The result of self-consistent Born approximation suggests that in the thermodynamic limit, the gap closing point is not at the Fermi level for the system with localized edge states. This agrees with the topological protection of edge states, such that the pre-existent edge states are protected from being scattered into bulk. Given the experimental feasibility of the long-range SSH model, the predicted TAI phases and transitions could be observed in experiments.