Unconventional superconductors are a class of materials where electronic interactions are believed to play a key role in establishing the electron pairing responsible for the superconducting state. Among them the iron-based superconductors (Fe SC) have a rich phase diagram where superconductivity lies nearby, or even coexists, with other electronic ordered phase like anti-ferromagnetism and electron nematicity. A defining feature of Fe SC is the nearby degeneracy of SC ground states which can be distinguished by the symmetry properties of the ground state wave function such as s-wave and d-wave pairing state. In particular, it has been predicted that the balance between SC ground states can be modified using anisotropic strain.The close proximity of symmetry distinct SC states is expected to lead to a novel SC collective mode, predicted more than 60 years ago by Bardasis and Schrieffer (BS). This mode can be probed by optical spectroscopies such as inelastic Raman light scattering. In this internship we propose to use uni-axial strain to induce a quantum phase transition between a s-wave and a d-wave SC ground state in the Fe SC BaKFe2As2. The quantum phase transition will be detected by tracking the evolution of the BS mode using low temperature Raman scattering combined with a piezo-based strain device.