Reviving WIMP dark matter with temperature-dependent couplings (2509.07070v1)

Abstract: The persistent null results at dark matter (DM) direct detection experiments have pushed the popular weakly interacting massive particle (WIMP) DM to tight corners. Generic WIMP models with direct detection rate below the current upper limits often lead to thermally overproduced relic abundance after freeze-out. To resolve this conundrum, we propose a novel scenario where DM has temperature-dependent couplings with the standard model (SM) bath. A scalar field having a large vacuum expectation value (VEV) at high temperatures generates sizeable DM-SM interactions leading to efficient DM annihilations responsible for generating the desired thermal relic. At lower temperatures, the scalar field VEV settles down to a small value as a result of a first-order phase transition (FOPT), effectively leading to suppressed DM-SM interaction rate at low temperature, consistent with null results at direct detection experiments. Upper bound on thermal DM mass forces the FOPT to occur at scales such that the corresponding gravitational wave signal remains within reach of future experiments like LISA.