Engineering Spin Splitting in Antiferromagnets by Superatoms with Internal Degrees of Freedom

Superatoms, stable atomic clusters acting as building blocks for new materials, offer unique opportunities due to their rich properties and potential for 2D material assembly. While their similarities to atoms have been extensively studied, their internal degrees of freedom (IDOFs) remain underexplored. Concurrently, compensated antiferromagnets (AFMs) with spin-split band structures have emerged as a promising class of materials for spintronics, yet their experimental realization, particularly in two dimensions, is limited. We propose a novel strategy to engineer spin-split AFMs by using superatoms with IDOFs. We demonstrate how superatom IDOFs can manipulate the system symmetry to induce spin splitting in AFM states. First-principles calculations on Mo-decorated carborophene, built from closo-carborane superatoms, show that distinct IDOFs (electric-dipole-like and nematic) dictate the 2D crystal's symmetry and spin-splitting patterns. This highlights the unique role of superatom IDOFs, absent in ordinary atoms, and establishes a new paradigm for designing advanced spintronic and quantum materials.