Monolayer Control of Spin-Charge Conversion in van der Waals Heterostructures.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Two-dimensional (2D) materials and van der Waals (vdW) stacking offer pathways to engineer novel materials and quantum states.
• Tailoring electronic properties of vdW heterostructures is possible by inserting single 2D material layers.
• Atomic-scale engineering of vdW materials for spin-charge interconversion remains underexplored.

Purpose of the Study:

• To investigate and control spin-charge interconversion phenomena at the monolayer level in vdW heterostructures.
• To demonstrate the impact of inserting a single 2D material layer on terahertz (THz) spintronic emission.
• To elucidate the underlying mechanisms responsible for enhanced spin-charge conversion.

Main Methods:

• Fabrication of fully epitaxial, large-area stacked structures using graphene, PtSe2, and a single MoSe2 layer.
• Utilizing spin and angle-resolved photoemission spectroscopy (SARPES) to probe electronic and spin structures.
• Employing density functional theory (DFT) calculations to understand charge transfer and electronic hybridization effects.

Main Results:

• A drastic increase in intensity and a sign change of THz spintronic emission were observed upon inserting a monolayer of MoSe2.
• Two distinct mechanisms, charge transfer and electronic hybridization, were identified as crucial for forming Rashba states.
• These Rashba states were confirmed to be responsible for the observed spin-charge conversion and THz emission.

Conclusions:

• Atomic-scale engineering of 2D vdW heterostructures enables precise control over spin-charge interconversion.
• The insertion of a single MoSe2 layer effectively enhances THz spintronic emission through Rashba state formation.
• This work opens avenues for designing efficient THz spintronic emitters and other spintronic devices based on 2D materials.