Tuning Bound States of Symmetry-Breaking Vortices via Unidirectional Charge Density Wave in a Transition-Metal Dichalcogenide Superconductor

Abstract

The interplay between charge density wave (CDW) and superconducting vortex bound states is crucial for the fundamental physics of superconductivity and advancing quantum nanotechnologies. However, the CDW-mediated modulation of vortex bound states, which opens up a new platform for vortex engineering, remains unexplored. Here, we report spatially anisotropic vortex states modulated by the unidirectional CDWs in a transition-metal dichalcogenide superconductor 1T″-NbTe₂ using ultralow-temperature scanning tunneling microscopy/spectroscopy. The stripe-like 3 × 1 × 3 CDW order exhibits a robust three-dimensional character across step edges and coexists with superconductivity below a critical temperature of 0.4 K. Under out-of-plane magnetic fields, we observe elliptical vortices whose elongation aligns with the CDW stripes, indicating strong coupling between vortex morphology and underlying electronic order. Remarkably, CDW domain boundaries induce abrupt changes in the vortex orientation and vortex bound states, enabling controllable vortex states across the CDW nanodomains. These findings establish a new pathway for manipulating superconducting vortex bound states via CDW coupling.