Dynamics of entanglement creation between two spins coupled to a chain

We study the dynamics of entanglement between two spins which is created by the coupling to a common thermal reservoir. The reservoir is a spin- 1/2 Ising transverse field chain thermally excited; the two defect spins couple to two spins of the chain which can be at a macroscopic distance. In the weak-coupling and low-temperature limit, the spin chain is mapped onto a bath of linearly interacting oscillators using the Holstein-Primakoff transformation. We analyze the time evolution of the density matrix of the two defect spins for transient times and deduce the entanglement which is generated by the common reservoir. We discuss several scenarios for different initial states of the two spins and for varying distances.