Negativity and quantum phase transition in a mixed spin-([formula omitted], [formula omitted], [formula omitted]) Ising–Heisenberg branched chain

Abstract

The thermal entanglement in a mixed spin-(1/2, 5/2, 1/2) Ising–Heisenberg branched chain is investigated by employing negativity as entanglement measurement. Using transfer-matrix approach, the negativity is calculated numerically both near and at a quantum phase transition point. We establish the relationship between negativity and quantum phase transition. It is found that whether negativity can be used to detect quantum phase transition point depends on the typical thermal energy, and we show the range of temperature at which negativity can be used to signal each ground-state transition. In addition, the thermal stability of negativity is closely related to energy gap in the system. It is worth noting that the negativity exhibits distinct behavior between quantum and classical phases. Negativity decreases with the increase of temperature in the quantum phase, while it exhibits a ”regrowth” behavior in the classical phases.