Emergence of Exotic Spin Texture in Supramolecular Metal Complexes on a 2D Superconductor

TL;DR

This study demonstrates how supramolecular metal complexes on a 2D superconductor induce exotic spin textures and magnetic reconstructions, revealing new pathways for designing tunable quantum materials with unconventional superconducting states.

Contribution

It introduces a heterostructure platform combining SMCs with NbSe₂, showing emergent magnetic textures and YSR bands through STM, XAS, and XMCD measurements, revealing antiferromagnetic coupling and a 3x3 magnetic reconstruction.

Findings

Emergence of Yu-Shiba-Rusinov bands from SMC-NbSe₂ interactions

Antiferromagnetic coupling between SMC units

Unconventional 3x3 magnetic reconstruction

Abstract

Designer heterostructures, where the desired physics emerges from the controlled interactions between different components, represent one of the most powerful strategies to realize unconventional electronic states. This approach has been particularly fruitful in combining magnetism and superconductivity to create exotic superconducting states. In this work, we use a heterostructure platform combining supramolecular metal complexes (SMCs) with a quasi-2D van der Waals (vdW) superconductor NbSe$_2$. Our scanning tunneling microscopy (STM) measurements demonstrate the emergence of Yu-Shiba-Rusinov (YSR) bands arising from the interaction between the SMC magnetism and the NbSe$_2$ superconductivity. Using X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements, we show the presence of antiferromagnetic coupling between the SMC units. These result in the emergence of an unconventional $3\times3$ reconstruction in the magnetic ground state that is directly reflected in real space modulation of the YSR bands. The combination of flexible molecular building blocks, frustrated magnetic textures, and superconductivity in heterostructures establishes a fertile starting point to fabricating tunable quantum materials, including unconventional superconductors and quantum spin liquids.