Probing Hidden Vortices and Geometrical Effect via Surface-Projected Quasiparticle States

Vortices host quasiparticle excitations, such as Caroli-de Gennes-Matricon or Majorana states. Understanding how these states are modulated by various geometrical structures is essential for both fundamental superconductivity research and quantum device design. However, this relationship remains challenging to elucidate. Here, using a scanning tunneling microscope equipped with a dilution refrigerator, we clearly resolve quasiparticle states from lateral vortices buried beneath the surface of 2H-NbSe₂ under in-plane magnetic fields. Our combined spectroscopic visualization and model calculation uncover a depth-dependent 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 Caroli-de Gennes-Matricon characteristics. Our findings establish a rescaling law of vortex-bound states under a geometrical effect and identify a critical length scale relevant for superconducting devices aimed to utilize intrinsic vortex quasiparticles.