Optical probes of two-component pairing states in transition metal dichalcogenides

Signatures of unconventional superconductivity have been recently observed in certain transition metal dichalcogenides (TMDs), including 4 H b − TaS 2 and monolayer 2H- NbSe 2 . While the pairing channel remains unknown, it has been argued that spin fluctuations can stabilize pairing in the two-component E ′ channel, a p -wave spin-triplet state which could be consistent with some of the reported signatures. Exploiting the particular multiorbital character of the Fermi surface and the presence of Ising spin-orbit coupling, which enable finite optical conductivity in the clean limit, in this work we predict clear-cut optical signatures to detect and distinguish the chiral and nematic ground states of the E ′ pairing. We quantify how nematic E ′ states produce a diagonal anisotropy σ x x ≠ σ y y due to the broken threefold symmetry ( C 3 ), while chiral E ′ states yield a finite optical Hall conductivity σ x y H due to broken time-reversal symmetry, and find both signals could be detected in current experiments. For instance, for realistic gaps in the meV range, we predict a relative anisotropy Δ σ / σ ∼ 10 − 5 in the nematic states, and a polar Kerr rotation of θ K ∼ 10 − 5 rad in the chiral states. These symmetry fingerprints provide a practical route to distinguish nematic and chiral superconducting order in TMD superconductors.