  We report the energy dependence of mid-rapidity (anti-)deuteron production in
Au+Au collisions at $\sqrt{s_\text{NN}} =\ $7.7, 11.5, 14.5, 19.6, 27, 39,
62.4, and 200 GeV, measured by the STAR experiment at RHIC. The yield of
deuterons is found to be well described by the thermal model. The collision
energy, centrality, and transverse momentum dependence of the coalescence
parameter $B_2$ are discussed. We find that the values of $B_2$ for
anti-deuterons are systematically lower than those for deuterons, indicating
that the correlation volume of anti-baryons is larger than that of baryons at
$\sqrt{s_\text{NN}}$ from 19.6 to 39 GeV. In addition, values of $B_2$ are
found to vary with collision energy and show a broad minimum around
$\sqrt{s_\text{NN}}=\ $20 to 40 GeV, which might imply a change of the equation
of state of the medium in these collisions.
