Multipartite entanglement in the XY spin-1/2 chain

Multipartite entanglement (ME) in the XY spin-1/2 chain is investigated by using negativity as a quantitative measure. The results show that ME persists over longer distances than bipartite entanglement, with its range and strength dependent on the anisotropy parameter γ, external magnetic field h, and the size of spin blocks. Notably, ME could serve as a sensitive probe for quantum phase transitions, due to the divergent behavior in its first derivative at the critical point h = 1. In essence, ME may primarily derive from collective effects rather than pairwise spin-spin entanglement, particularly in disjoint spin configurations. At finite temperatures and γ= 1, the thermal suppression of ME follows a hierarchical pattern, and such suppression is further modulated by ℎ and the specific block geometries. This behavior challenges the conventional conjecture of a simplistic monotonic decay.