Detecting Pairing Symmetry of Bilayer Nickelates Using Electronic Raman Scattering

The recent discovery of high-temperature superconductivity in both bulk and thin-film bilayer nickelates La_3Ni_2O_7 has garnered significant attention. However, the corresponding pairing symmetry remains debated in both experiments and theoretical studies due to conflicting experimental evidence from bulk and thin-film materials. In this work, we examine the electronic Raman response across different channels for various pairing symmetries within a two-orbital bilayer model. By comparing Raman susceptibilities obtained from multiorbital and band-additive approaches, we demonstrate that Raman response can distinguish between different pairing symmetries and identify pocket-dependent gap amplitudes for both fully gapped and nodal superconducting states. Specifically, the nodal d_x^2-y^2/d_xy-wave pairing exhibits robust low-energy power-law behavior, distinct from a fully gapped pairing. Additionally, for the s_\pm-wave pairing, the detailed gap anisotropy on the \beta pocket can be determined. Possible experimental implications are also discussed. Our results highlight the crucial role of multiorbital effects in shaping the Raman spectra and establish electronic Raman scattering as a powerful and symmetry-resolved probe for determining the superconducting gap in unconventional superconductors.