Excitations in a superconducting Coulombic energy gap
arXiv:2101.10794 · doi:10.1038/s41467-022-29634-5
Abstract
Cooper pairing and Coulomb repulsion are antagonists, producing distinct energy gaps in superconductors and Mott insulators. When a superconductor exchanges unpaired electrons with a quantum dot, its gap is populated by a pair of electron-hole symmetric Yu-Shiba-Rusinov excitations between doublet and singlet many-body states. The fate of these excitations in the presence of a strong Coulomb repulsion in the superconductor is unknown, but of importance in applications such as topological superconducting qubits and multi-channel impurity models. Here we couple a quantum dot to a superconducting island with a tunable Coulomb repulsion. We show that a strong Coulomb repulsion changes the singlet many-body state into a two-body state. It also breaks the electron-hole energy symmetry of the excitations, which thereby lose their Yu-Shiba-Rusinov character.
Supplementary Information available as an ancillary file with this submission. Raw experimental data available at https://doi.org/10.17894/ucph.e17975c9-c12c-412b-b046-aca7526cb8ed
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- Reduced basis emulation of pairing in finite systems
- Impurity Knight shift in quantum dot Josephson junctions
- Exchange interaction between two quantum dots coupled through a superconducting island
- BCS surrogate models for floating superconductor-semiconductor hybrids
- Richardson model with complex level structure and spin-orbit coupling for hybrid superconducting islands: stepwise suppression of pairing and magnetic pinning
- Yu-Shiba-Rusinov states, the BCS-BEC crossover, and the exact solution in the flat-band limit
- Matrix product state simulations of quantum quenches and transport in Coulomb blockaded superconducting devices
- Effects of electron-electron interaction and spin-orbit coupling on Andreev pair qubits in quantum dot Josephson junctions
- Electronic transport in double-nanowire superconducting islands with multiple terminals