Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 14: Superconductivity: Properties and Electronic Structure

TT 14.11: Vortrag

Montag, 9. März 2026, 17:45–18:00, HSZ/0103

Probing hidden vortices and geometrical effect via surface-projected quasiparticle states — •Ruijun Xi and Hao Zheng — Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China

Vortices host quasiparticle excitations such as Caroli-de Gennes-Matricon (CdGM) or Majorana states. Understanding how these states are modulated by various geometrical structures is essential for both fundamental superconductivity research and quantum device design. Yet, this relationship remains challenging to elucidate. Here, using a scanning tunneling microscope equipped with a dilution refrigerator, we clearly resolve coherent quasiparticle states from lateral vortices buried beneath the surface of NbSe₂ under in-plane magnetic fields. Our combined spectroscopic visualization and model calculation uncover a depth-dependent quantum coupling behavior between vortices and the superconductor surface: shallow vortices (depth of ∼ 1.5 coherence lengths) exhibit anomalous split quasiparticle states accompanied by a pseudogap, while deeper vortices (> 4 coherence lengths) restore the conventional CdGM characteristics. Our findings establish a rescaling law of vortex bound states under geometrical effect and identify a critical length scale relevant for superconducting devices aimed to utilize intrinsic vortex quasiparticles.

Keywords: vortex bound states; Caroli-de Gennes-Matricon states; in-plane vortices; Scanning Tunneling Microscope