Berlin 2024 – scientific programme

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O: Fachverband Oberflächenphysik

O 11: Focus Session: Spins on Surfaces studied by Atomic Scale Spectroscopies II

O 11.3: Talk

Monday, March 18, 2024, 15:45–16:00, MA 004

Microwave excitation of atomic scale superconducting bound states — Janis Siebrecht¹, Haonan Huang¹, Piotr Kot¹, Robert Drost¹, Ciprian Padurariu², Björn Kubala², Jochim Ankerhold², Juan Carlos Cuevas³, and •Christian R. Ast¹ — ¹MPI für Festkörperforschung, Stuttgart — ²Institut für Komplexe Quantensysteme, Universität Ulm, Ulm — ³Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, Spain

Magnetic impurities on superconductors lead to bound states within the superconducting gap, so called Yu-Shiba-Rusinov (YSR) states. They are parity protected, which enhances their lifetime, but makes it more difficult to excite them. Here, we realize the excitation of YSR states by microwaves facilitated by the tunnel coupling to another superconducting electrode in a scanning tunneling microscope (STM). We identify the excitation process through a family of anomalous microwave-assisted tunneling peaks originating from a second order resonant Andreev process, in which the microwave excites the YSR state triggering a tunneling event transferring a total of two charges. We vary the amplitude and the frequency of the microwave to identify the energy threshold and the evolution of this excitation process. Our work sets an experimental basis and proof-of-principle for the manipulation of YSR states using microwaves with an outlook towards YSR qubits.

Keywords: superconductivity; magnetism; bound states; Yu-Shiba-Rusinov States; scanning tunneling microscopy