Nanogap-enhanced terahertz suppression of superconductivity

Superconductivity collapses when all Cooper pairs acquire energies exceeding the superconducting gap. Breaking these pairs requires photons with energy greater than the superconducting gap or strong terahertz (THz) electric fields, which has limited the practical use of superconducting devices at THz frequencies. Here, we show that GdBa₂Cu₃O_7-δ (GdBCO) film integrated with 15-nm metal nanogaps exhibit Cooper pair breaking at 20 K, which is lower than its critical temperature T _c, under incident THz fields as low as 60 V/cm. It should be noted that the extracted optical constants of the nanogap-integrated film exhibit a characteristic of a non-superconducting state, in contrast to the bare GdBCO film. This suppression of the superconductivity cannot be attributed to heating or fabrication damage but instead arises from the nanogap-enhanced THz fields delivering ponderomotive energy beyond the superconducting gap. Our results establish a non-thermal, low-field pathway for controlling superconductivity, opening opportunities for highly sensitive superconducting optoelectronic devices such as a THz single photon detector.