CIC nanoGUNE-BRTA, 20018 Donostia-San Sebastián, Spain.
School of Physics, Sun Yat-sen University, Guangzhou 510275, China.
Phys Rev Lett. 2023 Mar 31;130(13):136004. doi: 10.1103/PhysRevLett.130.136004.
Breaking a correlated pair in a superconductor requires an even number of fermions providing at least twice the pairing energy Δ. Here, we show that a single tunneling electron can also excite a pair breaking excitation in a proximitized gold film in the presence of magnetic impurities. Combining scanning tunneling spectroscopy with theoretical modeling, we map the excitation spectrum of an Fe-porphyrin molecule on the Au/V(100) proximitized surface into a manifold of entangled Yu-Shiba-Rusinov and spin excitations. Pair excitations emerge in the tunneling spectra as peaks outside the spectral gap only in the strong coupling regime, where the presence of a bound quasiparticle in the ground state ensures the even fermion parity of the excitation. Our results unravel the quantum nature of magnetic impurities on superconductors and demonstrate that pair excitations unequivocally reveal the parity of the ground state.
在超导体内打破相关联的电子对需要偶数个费米子提供至少两倍的配对能 Δ。在这里，我们表明，在存在磁杂质的情况下，单个隧穿电子也可以在近邻化的金膜中激发对破坏激发。通过将扫描隧道光谱学与理论模型相结合，我们将 Fe-卟啉分子在 Au/V(100)近邻化表面上的激发谱映射到纠缠的 Yu-Shiba-Rusinov 和自旋激发的多重态中。在隧穿谱中，对激发的出现仅在强耦合 regime 中在能隙之外的峰中出现，其中在基态中存在束缚准粒子确保了激发的偶数费米子奇偶性。我们的结果揭示了超导体内磁杂质的量子性质，并证明了对激发明确揭示了基态的奇偶性。
