  We investigate the exact entanglement dynamics of a two-qubit Heisenberg XXZ
chain with Dzyaloshinskii-Moriya (DM) interactions, interacting with an
anisotropic spin bath in thermal equi- librium at a temperature T, driven by an
external magnetic field B along the z-axis. We establish that, for an initially
entangled qubit pair, the DM interactions generate entanglement and enhance the
entanglement in the revival region. The effects of the DM interaction are also
seen to be very important at high temperatures and for weak coupling between
the two qubits where it is seen to preserve entanglement. These effects are
weakened when the magnetic field B and the Heisenberg coupling are switched on.
If the two-qubits are prepared in an initially separable state, the DM in-
teraction instead has a negative effect on their entanglement. On a whole
entanglement can better be preserve in the spin chain even at high temperatures
by increases the external magnetic field B and the Heisenberg couplings, and by
tuning the strength of the DM interaction.
