Coexistence of Quasi-two-dimensional Superconductivity and Tunable Kondo Lattice in a van der Waals Superconductor

TL;DR

This study reveals the coexistence of quasi-two-dimensional superconductivity and a tunable Kondo lattice in the van der Waals superconductor 4Hb-TaS2, highlighting its potential for electronic property manipulation and understanding heavy fermion superconductivity.

Contribution

It demonstrates the simultaneous presence of superconductivity and Kondo resonance in 4Hb-TaS2, and shows how the Kondo effect can be tuned via surface modifications.

Findings

Quasi-two-dimensional superconductivity observed in 1H-TaS2 layers.

Kondo resonance detected in 1T-TaS2 layers due to electron screening.

Kondo resonance intensity can be enhanced by shifting it towards the Fermi level.

Abstract

Realization of Kondo lattice in superconducting van der Waals materials not only provides a unique opportunity for tuning the Kondo lattice behavior by electrical gating or intercalation, but also is helpful for further understanding the heavy fermion superconductivity. Here we report a low-temperature and vector-magnetic-field scanning tunneling microscopy and spectroscopy study on a superconducting compound (4Hb-TaS2) with alternate stacking of 1T-TaS2 and 1H-TaS2 layers. We observe the quasi-two-dimensional superconductivity in the 1H-TaS2 layer with anisotropic response to the in-plane and out-of-plane magnetic fields. In the 1T-TaS2 layer, we detect the Kondo resonance peak that results from the Kondo screening of the unpaired electrons in the Star-of-David clusters. We also find the intensity of the Kondo resonance peak is sensitive to its relative position with the Fermi level, and it can be significantly enhanced when it's further shifted towards the Fermi level by evaporating Pb atoms onto the 1T-TaS2 surface. Our results are not only important for fully understanding the electronic properties of 4Hb-TaS2, but also pave the way for creating tunable Kondo lattice in the superconducting van der Waals materials.