Proximitized Ge quantum wells have emerged as a novel platform for studying Andreev bound states (ABSs), due to their expected strong spin-orbit interaction and high mobility. Here, we used microwave spectroscopy techniques to investigate ABSs in Josephson junctions (JJs) realized in proximitized Ge quantum wells. Spectroscopic signatures observed in a 350 nm junction indicated the presence of multiple ABSs, and were reproduced with a model including finite-length effects. The ABS spectra measured for a 1.2μm junction were explained by a model including three ABSs in two conduction channels and finite Coulomb interaction. Our work highlights the importance of interactions in JJs and serves as a basis for understanding and manipulating ABSs in Ge-based hybrid devices.
@article{arxiv.2508.06180,
title = {Finite Length Effects and Coulomb Interaction in Ge Quantum Well-Based Josephson Junctions Probed with Microwave Spectroscopy},
author = {S. C. ten Kate and D. C. Ohnmacht and M. Coraiola and T. Antonelli and S. Paredes and F. J. Schupp and M. Hinderling and S. W. Bedell and W. Belzig and J. C. Cuevas and A. E. Svetogorov and F. Nichele and D. Sabonis},
journal= {arXiv preprint arXiv:2508.06180},
year = {2025}
}