Electronic and Magnetic Characterization of Epitaxial VSe$_2$ Monolayers on Superconducting NbSe$_2$

TL;DR

This study synthesizes and characterizes a novel superconductor-magnet heterostructure using monolayer VSe₂ on NbSe₂, revealing magnetic properties and superconducting gap modifications at the interface.

Contribution

It introduces a method for creating clean, atomically sharp superconductor-magnet heterostructures and investigates their electronic and magnetic properties using combined experimental and theoretical approaches.

Findings

Reduction of superconducting gap on VSe₂ layer

Absence of charge density wave signatures

Indication of sheet magnetization without conventional ferromagnetism

Abstract

Vertical integration of two-dimensional (2D) van der Waals (vdW) materials with different quantum ground states is predicted to lead to novel electronic properties that are not found in the constituent layers. Here, we present the direct synthesis of superconductor-magnet hybrid heterostructures by combining superconducting niobium diselenide (NbSe$_2$) with the monolayer (ML) vanadium diselenide (VSe$_2$). More significantly, the in-situ growth in ultra-high vacuum (UHV) allows to produce a clean and an atomically sharp interfaces. Combining different characterization techniques and density-functional theory (DFT) calculations, we investigate the electronic and magnetic properties of VSe$_2$ on NbSe$_2$. Low temperature scanning tunneling microscopy (STM) measurements demonstrate a reduction of the superconducting gap on VSe$_2$ layer. This together with the lack of charge density wave signatures indicates magnetization of the sheet, but not of a conventional itinerant ferromagnet.