[Paper Review] Anisotropic proximity-induced superconductivity and edge supercurrent in Kagome metal, K1-xV3Sb5

Yaojia Wang, S. Y. Yang+12 more|arXiv (Cornell University)|Dec 10, 2020

Advanced Condensed Matter Physics51 references45 citations

TL;DR

The paper demonstrates anisotropic proximity-induced superconductivity in K1-xV3Sb5 Josephson junctions, revealing direction-dependent magnetoresistance and evidence for edge-state–driven currents. It also suggests an anisotropic internal magnetic field that may favor spin-triplet pairing.

ABSTRACT

Materials with transition metals in triangular lattices are of great interest for their potential combination of strong correlation, exotic magnetism and electronic topology. Kagome nets are of particular importance since the discovery of geometrically frustrated magnetism and topological band structures in crystals like Herbertsmithite and Fe3Sn2, respectively. KV3Sb5 was discovered to be a layered topological metal with a Kagome net of vanadium. Here, we fabricated Josephson Junctions (JJ) of K1-xV3Sb5 and induced superconductivity over long junction lengths. Through magnetoresistance and current vs. phase measurements, we observed magnetic field sweeping direction dependent magnetoresistance, and an anisotropic interference pattern with a Fraunhofer pattern for in-plane magnetic field, but a suppression of critical current for out-of-plane magnetic field. These results indicate an anisotropic internal magnetic field in K1-xV3Sb5 which influences the superconducting coupling in the junction, possibly giving rise to spin-triplet superconductivity. In addition, the observation of long-lived fast oscillations shows evidence of spatially localized conducting channels arising from edge states. These observations pave the way for studying unconventional superconductivity and Josephson device based on Kagome metals with electron correlation and topology.

Motivation & Objective

• Motivate exploration of superconductivity in Kagome metals with strong correlations and topology.
• Investigate proximity-induced superconductivity in K1-xV3Sb5-based Josephson junctions over long lengths.
• Identify magnetic-field–dependent transport signatures indicative of unconventional pairing or edge states.

Proposed method

• Fabricate Josephson junctions using K1-xV3Sb5 to induce superconductivity across long junction lengths.
• Perform magnetoresistance measurements under varying in-plane and out-of-plane magnetic fields.
• Conduct current-versus-phase (I–φ) measurements to map interference patterns.
• Analyze field-direction dependence to infer internal magnetic field anisotropy affecting superconducting coupling.
• Look for fast oscillations and edge-channel–related transport signatures.

Experimental results

Research questions

• RQ1 Does K1-xV3Sb5 exhibit anisotropic magnetic-field–dependent superconducting coupling in Josephson junctions?
• RQ2 Can edge states in K1-xV3Sb5 support spatially localized, long-lived edge currents under proximity-induced superconductivity?
• RQ3 Is there evidence for unconventional (potentially spin-triplet) pairing arising from the material's internal magnetic field and topology?

Key findings

• Magnetic-field direction controls magnetoresistance, showing anisotropic transport in the junctions.
• An in-plane field yields a Fraunhofer-like interference pattern, while out-of-plane fields suppress the critical current.
• Evidence suggests an anisotropic internal magnetic field that modulates superconducting coupling in the junction.
• Observation of long-lived fast oscillations indicates spatially localized conducting channels likely associated with edge states.
• Results point toward potential unconventional superconductivity in Kagome metal with correlated and topological aspects.