The Unruh effect establishes a fundamental equivalence between acceleration and thermality by demonstrating that a uniformly accelerated ground-state detector undergoes excitation as if immersed in a thermal bath. In this paper, we investigate how acceleration influences the interaction between two ground-state atoms that are synchronously and uniformly accelerated in vacuum with proper acceleration $a$ and coupled to a fluctuating electromagnetic field. We find that the resulting interaction potential comprises both diagonal components $(\delta E{)}^{jk}$ with $j=k$, which are present in both inertial and acceleration cases, and off-diagonal components $(\delta E{)}^{jk}$ with $j\ne k$, which arise exclusively due to acceleration and vanish in the inertial case. The dependence of each component on acceleration and interatomic separation $L$ generally differs. For small accelerations, the leading-order diagonal components of the van der Waals (vdW) and Casimir-Polder ($CP$) interaction potentials remain unchanged from their inertial counterparts, exhibiting the standard scaling behaviors $\sim L^{-6}$ and $\sim L^{-7}$, respectively. In contrast, the off-diagonal components scale as $\sim a^2{L}^{-4}$ in the vdW subregions and $\sim a^2{L}^{-5}$ in the $CP$ subregion. However, when the acceleration becomes sufficiently large, both diagonal and off-diagonal components of the vdW and $CP$ interaction potentials are significantly modified, giving rise to entirely new interaction behaviors that deviate from those observed in the inertial case, whether in vacuum or thermal environments, indicating a breakdown of the acceleration-thermality equivalence established by the Unruh effect for single detectors.

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• Light-matter interaction
• Unruh effect