Topological phases, quantum criticality, and bulk entanglement in spin-1/2 XX chain with anisotropic three-spin interactions

We investigate the one-dimensional spin-1/2 XX chain with anisotropic three-spin interactions, which hosts four distinct topological phases separated by critical lines. Using exact fermionization, we analyze the spin squeezing parameter, entanglement entropy, and bulk entanglement spectrum to characterize the ground state. Our results show that the system remains unsqueezed across the entire phase diagram, with maximal unsqueezing at criticality. The entanglement entropy exhibits cusp-like singularities at the critical lines, while the extracted central charges reveal distinct critical behaviors. Furthermore, the lowest level of the bulk entanglement spectrum is four-fold degenerate in two phases and two-fold in the others, reflecting the topological nature of each phase. These findings offer deeper insight into the interplay between topology, criticality, and quantum correlations in low-dimensional spin systems. • We identify four distinct topological phases in a spin-1/2 XX chain with anisotropic three-spin interactions, separated by quantum critical lines with central charges c = 0 . 5 , 1 . 0 , and 2 . 0 . • The ground state remains unsqueezed throughout the phase diagram, with maximal unsqueezing and sharp entanglement entropy peaks at critical points. • Bulk entanglement spectrum reveals phase-dependent degeneracies, four-fold for winding number ν = ± 2 , and two-fold for ν = ± 1 , highlighting topological distinctions. • The Jordan–Wigner transformation enables exact fermionization but introduces subtleties in interpreting topological features between spin and fermionic representations. • These findings deepen our understanding of quantum criticality and topology in low-dimensional systems, with implications for quantum computing and precision measurement technologies.