A possible implication of a sub-eV scalar dark matter (DM) field interacting with the Standard Model (SM) is oscillations of fundamental constants. Here, I will talk about how to establish the direct experimental bounds on the coupling of an oscillating DM to the SM using spectroscopy and/or various quantum sensors (DDM search). The equivalence principle (EP) violating tests can also be used to constrain the existence of a light scalar. Furthermore, I will discuss about the complementarity between the EP violating tests and DDM searches. We will further explore the challenges of a quadratically coupled light DM in the context of naturalness and how to probe such models.
With support from FCT through project UIDB/00777/2020