• DOI:10.1038/nphys4150
• Corpus ID: 216929081

Microwave spectroscopy of spinful Andreev bound states in ballistic semiconductor Josephson junctions

@article{Woerkom2017MicrowaveSO,
  title={Microwave spectroscopy of spinful Andreev bound states in ballistic semiconductor Josephson junctions},
  author={David J. van Woerkom and Alex Proutski and Bernard van Heck and Dani{\"e}l Bouman and Jukka I. Vayrynen and Leonid I. Glazman and Peter Krogstrup and Jesper Nygaard and Leo P Kouwenhoven and Attila Geresdi},
  journal={Nature Physics},
  year={2017},
  volume={13},
  pages={876-881}
}

• D. V. Woerkom, A. Proutski, +7 authors A. Geresdi
• Published 1 September 2016
• Physics
• Nature Physics

The superconducting proximity effect in semiconductor nanowires has recently enabled the study of new superconducting architectures, such as gate-tunable superconducting qubits and multiterminal Josephson junctions. As opposed to their metallic counterparts, the electron density in semiconductor nanosystems is tunable by external electrostatic gates, providing a highly scalable and in situ variation of the device properties. In addition, semiconductors with large g-factor and spin–orbit coupling have been shown to give rise to exotic phenomena in superconductivity, such as φ0 Josephson junctions and the emergence of Majorana bound states. Here, we report microwave spectroscopy measurements that directly reveal the presence of Andreev bound states (ABS) in ballistic semiconductor channels. We show that the measured ABS spectra are the result of transport channels with gate-tunable, high transmission probabilities up to 0.9, which is required for gate-tunable Andreev qubits and beneficial for braiding schemes of Majorana states. For the first time, we detect excitations of a spin-split pair of ABS and observe symmetry-broken ABS, a direct consequence of the spin–orbit coupling in the semiconductor. Andreev bound states in semiconductor–superconductor hybrid structures are studied using microwave spectroscopy — a tool that could be also used for investigating Majorana modes.