Dynamical Superconducting Parity Effect in a Coulomb Pb Island

Single-electron tunneling in mesoscopic superconducting islands has demonstrated a parity-modulated Coulomb blockade periodicity for decades. Yet, the quasiparticle dynamics mediating the interplay between Cooper-pair condensate coherence and charging energy remains poorly understood. Here, we uncover a new type of superconducting parity effect in a Coulomb blockade system comprising nano-sized Pb islands, investigated via low-temperature scanning tunneling spectroscopy. Our spectroscopic measurements demonstrate parity-dependent Coulomb gaps near the Fermi energy, associated with equidistant Coulomb peaks at higher energies. The parity dependence is distinct from the conventional even-odd Coulomb peak alternations and is validated through a parity transition of a Coulomb charge ring. As corroborated by theoretical simulations, we dub such intriguing phenomenon as the "dynamical" superconducting parity effect, which originates from an emergent tunneling channel facilitated by electron-hole conversion processes, dynamically coupled to Cooper-pair condensation. Our observations underscore the essential role of quasiparticle-mediated Cooper-pair formation in Coulomb blockade transport.