Light-Induced Switching between Singlet and Triplet Superconducting States

While the search for triplet superconductors has garnered much attention as a fertile ground for topological superconductivity, most known superconducting compounds prefer spin-singlet pairing. Here, we devise a theory of competing superconducting orders that permits ultrafast optical switching to an opposite-parity metastable superconducting state in centrosymmetric crystals with strong spin-orbit coupling. Remarkably, since inversion and spin-exchange symmetries are linked for a Cooper pair, dynamical inversion symmetry breaking due to a tailored light pulse can induce odd-parity (spin triplet) order in a conventional even-parity (spin singlet) superconductor, trapping the system in a long-lived metastable state after the pulse. We analyze this effect both with a microscopic description of quasiparticle dynamics under irradiation with a laser, and with a phenomenological time-dependent Ginzburg-Landau theory of multiple competing order parameters, revealing a protocol to efficiently switch to an odd-parity instability. Our results suggest a new avenue for manipulating metastable electronic states of matter, which among other applications may allow an out-of-equilibrium realization of topological superconductivity.