Spontaneous spin-valley polarization in NbSe₂ at a van der Waals interface

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Electronics

Background:

• Van der Waals (vdW) heterostructures enable emergent quantum electronic ground states.
• Interfaces between different 2D materials can lead to novel physical phenomena.
• Superconducting and magnetic properties in 2D materials are of significant research interest.

Purpose of the Study:

• To investigate the electronic and magnetic properties of NbSe2/V5Se8 vdW heterostructures.
• To explore the anomalous Hall effect (AHE) in these magnetic vdW heterostructures.
• To understand the interplay between magnetism and spin-orbit interaction in 2D quantum materials.

Main Methods:

• Fabrication of NbSe2/V5Se8 vdW heterostructures with varying V5Se8 layer thickness.
• Experimental measurement of the anomalous Hall effect (AHE).
• Theoretical investigation using band structure calculations.

Main Results:

• A superconducting 2D NbSe2 forms a ferromagnetic ground state at the vdW interface with 2D V5Se8.
• The sign of the AHE in NbSe2/V5Se8 heterostructures reverses upon thinning V5Se8 to the monolayer limit.
• AHE signal enhancement with in-plane magnetic fields suggests contributions beyond simple magnetization.
• Band structure calculations reveal the role of Berry curvature along spin-degenerate nodal lines in 2D NbSe2.

Conclusions:

• The study demonstrates the creation of an emergent ferromagnetic ground state in 2D NbSe2 via proximity effect at a vdW interface.
• Unusual AHE behavior highlights a unique interplay between in-plane magnetization and Zeeman-type spin-orbit interaction in non-centrosymmetric 2D quantum materials.