Tunable vortex bound states in multiband CsV₃Sb₅-derived kagome superconductors.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Vortices and bound states are crucial for understanding superconductor electronic properties.
• Surface-dependent vortex core states were recently observed in kagome superconductors like CsV$_{3}$Sb$_{5}$.
• The origin of sharp zero-energy conductance peaks, potentially Majorana bound states, in these materials is not fully understood.

Purpose of the Study:

• To investigate tunable vortex bound states (VBSs) in chemically-doped kagome superconductors Cs(V$_{1-x}$Tr$_{x}$)$_{3}$Sb$_{5}$ (Tr = Ta, Ti).
• To explore the impact of doping on superconductivity and charge order in CsV$_{3}$Sb$_{5}$-derived materials.
• To elucidate the nature of zero-bias conductance peaks (ZBCPs) in these systems.

Main Methods:

• Low-temperature scanning tunneling microscopy/spectroscopy (STM/STS) was employed.
• Chemical doping with Tantalum (Ta) and Titanium (Ti) was performed on CsV$_{3}$Sb$_{5}$.
• Analysis of vortex lattice reorientation and spatial distribution of conductance peaks.

Main Results:

• Doped Cs(V$_{1-x}$Tr$_{x}$)$_{3}$Sb$_{5}$ superconductors exhibit full-gap-pairing and lack long-range charge order.
• Ta-doped samples show conventional Caroli-de Gennes-Matricon (CdGM) bound states with cross-shaped spatial evolution.
• Ti-doped samples display a robust, non-split zero-bias conductance peak (ZBCP) persisting across vortices, dependent on doping concentration.

Conclusions:

• Tunable VBSs were observed in the multiband chemically-doped CsV$_{3}$Sb$_{5}$ system.
• The study provides insights into the origin of ZBCPs in kagome superconductors, distinguishing them from surface effects.
• Findings contribute to understanding complex electronic states in novel superconducting materials.