Presentation Information
[10p-E308-10]Critical-Tunneling Stabilization of Single Fe Atoms on MgO/Fe(001)
〇Toyokazu Yamada1, Kohei Tada2 (1.Chiba Univ., 2.Osaka Univ.)
Keywords:
qubit,magnetic atom,organic molecule
Atomically flat insulating films are crucial for electrically decoupling adsorbates from metallic substrates and preserving the intrinsic quantum states of single atoms. Here, we demonstrate that the widely used MgO/Fe(001) system provides a robust platform for single-atom spin qubits. Using low-temperature scanning tunneling microscopy (STM) at 4.6 K under ultrahigh vacuum, we investigated ~1 nm-thick MgO films exhibiting high crystallinity, a well-defined band gap, and low defect density. Single Fe atoms deposited on the MgO surface form a double-barrier tunneling junction with the Fe(001) substrate and STM tip serving as electrodes. Owing to the relatively large MgO thickness, STM imaging is considerably more challenging than for conventional bilayer MgO films on noble metals, and tunneling near the band gap readily causes adatom displacement. We identified a narrow critical tunneling regime that enables stable imaging and revealed strong stabilization of isolated Fe atoms on the MgO surface. Density functional theory calculations indicate that crystal-field and ligand-field effects lift the orbital degeneracy of Fe, yielding cationic Fe atoms with an effective spin of S ≈ 3/2 that are strongly bound to surface oxygen atoms. These results establish MgO/Fe(001) as a promising platform for atomically engineered quantum spin devices.