Physical Review A
Evolution of entanglement towards criticality in the XY model in a quantum phase transition induced by a quench
Banasri Basu, Pratul Bandyopadhyay, Priyadarshi Majumdar
Abstract
We have studied here the evolution of entanglement towards criticality in the $\mathit{XY}$ model when quantum phase transition (QPT) is induced by a quench. To this end, we have utilized the relation of the Berry phase acquired by a spin state when it traverses a closed path at criticality with the concurrence measuring the entanglement for a pair of nearest-neighbor spins. It has been argued that when the spin state is rotated towards the generation of the closed path, the segments of noncyclic paths with open ends can be mapped onto cyclic paths enclosing flux lines associated with $q$-deformed monopoles. This essentially gives rise to the sequence of Berry phases attained by the quasispin states belonging to the quantum group ${\mathrm{SU}}_{q}(2)$ when rotated in a closed path. As the standard Berry phase at criticality is obtained when the time-dependent deformation parameter $q$ attains the value 1, this formulation helps us to analyze the evolution of entanglement towards criticality when QPT is induced by a quench. From this analysis we also formulate a scaling law for the entanglement entropy for a block of $L$ spins with the rest at off-criticality. As in QPT off-critical points correspond to thermal fluctuations, this formulation represents the evolution of entanglement towards criticality with temperature as $T\ensuremath{\rightarrow}0$.