Strain-Tunable RKKY Exchange Between Fe Adatoms on Monolayer TaS<sub><sup>2</sup></sub>: A First-Principles Study
POSTER
Abstract
Long-range, controllable magnetic exchange is a key ingredient for 2D spintronics. RKKY, a natural candidate, remains largely unexplored in metallic monolayer TMDs, especially with multi-pocket Fermi surfaces, for which no widely accepted analytical form exists.
Through a first-principles study, we discover a long-range magnetic exchange between Fe adatoms on monolayer 2H-TaS₂ and identify it as RKKY. The coupling is tunable under biaxial strain from −3% to +3%, with the origin traced to strain-induced changes in the bands near the Fermi level.
Using DFT, we evaluate the pairwise exchange J(R,ε) between Fe adatoms as a function of separation R and biaxial strain ε∈[−3%,+3%]. At ε = 0, J(R) exhibits the hallmarks of 2D RKKY—oscillatory decay with sign reversals. Biaxial strain systematically shifts the oscillation wave vector and amplitude, demonstrating strain-tunable indirect exchange. DFT band and Fermi-surface analyses trace the origin to strain-induced changes of states near the Fermi level. To identify the microscopic origin and provide a predictive handle, we build a minimal tight-binding model fitted to the DFT bands, augment it with a local s − d exchange term, and treat it at a mean-field level; it reproduces the strain trends in J(R,ε), supporting an electronic-structure-mediated RKKY origin.
These results outline a pathway to engineer 2D magnetic lattices via strain and artificial Kondo-lattice design, enabling tunable spintronic platforms and magnetic textures.
Through a first-principles study, we discover a long-range magnetic exchange between Fe adatoms on monolayer 2H-TaS₂ and identify it as RKKY. The coupling is tunable under biaxial strain from −3% to +3%, with the origin traced to strain-induced changes in the bands near the Fermi level.
Using DFT, we evaluate the pairwise exchange J(R,ε) between Fe adatoms as a function of separation R and biaxial strain ε∈[−3%,+3%]. At ε = 0, J(R) exhibits the hallmarks of 2D RKKY—oscillatory decay with sign reversals. Biaxial strain systematically shifts the oscillation wave vector and amplitude, demonstrating strain-tunable indirect exchange. DFT band and Fermi-surface analyses trace the origin to strain-induced changes of states near the Fermi level. To identify the microscopic origin and provide a predictive handle, we build a minimal tight-binding model fitted to the DFT bands, augment it with a local s − d exchange term, and treat it at a mean-field level; it reproduces the strain trends in J(R,ε), supporting an electronic-structure-mediated RKKY origin.
These results outline a pathway to engineer 2D magnetic lattices via strain and artificial Kondo-lattice design, enabling tunable spintronic platforms and magnetic textures.
Presenters
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Xiaohang Jia
- Brown University