Very weak bonds to artificial atoms formed by quantum corrals

Area of Science:

• Surface science
• Quantum corrals
• Artificial atoms

Background:

• Quantum corrals, structures of atoms on surfaces, confine electrons to discrete energy states.
• Previous work by Crommie et al. (1993) established quantum corrals as a platform for studying electron confinement.
• Artificial atoms offer tunable electronic properties for fundamental research.

Purpose of the Study:

• To investigate the bonding properties of quantum corrals acting as artificial atoms.
• To measure the interaction forces between confined electrons and atomic force microscope (AFM) tips.
• To explore the nature of electron confinement and its interaction with different tip terminations.

Main Methods:

• Utilized an atomic force microscope (AFM) to probe quantum corrals.
• Studied a 48-atom iron quantum corral on a copper surface and its variants.
• Analyzed electron confinement in 28 discrete energy states within the corral.

Main Results:

• Confined electrons in the quantum corral formed a bond with the AFM tip atom, exhibiting an energy of approximately 5 millielectron volts.
• Measured interaction forces were exceptionally small, about 1/1000 of typical forces in atomically resolved AFM.
• Observed covalent attraction to metal tips and Pauli repulsion to CO-terminated tips, confirmed by experiments with internal atoms and scaled corrals.

Conclusions:

• Quantum corrals can function as artificial atoms with measurable bonding interactions.
• The weak forces involved allow for sensitive probing of electron states and tip-surface interactions.
• Electron behavior within quantum corrals demonstrates distinct responses to different chemical environments at the AFM tip.