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Clarification of the relationship between electric current and the chemical binding force -- a possible guideline in the development of nano materials and devices


In cooperation with ABE Masayuki (Associate Professor, Graduate School of Engineering, Nagoya University), researchers of the Academy of Sciences of the Czech Republic Group, researchers of the Universidad Autónoma de Madrid Group, and a group of researchers led by SUGIMOTO Yoshiaki (Associate Professor, Graduate School of Engineering, Osaka University) and MORITA Seizo (Specially appointed professor, Institute of Scientific and Industrial Research, Osaka University) have demonstrated the presence of clear-cut mathematical relationships between the chemical force between two bodies and the conductance between them, clarifying its mechanism.
This group of researchers brought two bodies close to each other and precisely measured the chemical binding force and tunnelling conductance between the two atoms. They conducted experiments in silicon semiconductors with atom force microscopes. As a result, tunnelling conductance was found to increase as a square of the chemical binding force. This relationship is expected to serve as a guideline for designing a variety of nano materials and nano devices.


Quantum degeneracy is an important concept in quantum mechanics with large implications to many processes in condensed matter. Here, we show the consequences of electron energy level degeneracy on the conductance and the chemical force between two bodies at the atomic scale. We propose a novel way in which a scanning probe microscope can detect the presence of degenerate states in atomic-sized contacts even at room temperature. The tunneling conductance G and chemical binding force F between two bodies both tend to decay exponentially with distance in a certain distance range, usually maintaining direct proportionality G∝F. However, we show that a square relation G∝F2 arises as a consequence of quantum degeneracy between the interacting frontier states of the scanning tip and a surface atom. We demonstrate this phenomenon on the Si(111)-(7×7) surface reconstruction where the Si adatom possesses a strongly localized dangling-bond state at the Fermi level.

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To learn more about this research, please read the full research report entitled "Quantum Degeneracy in Atomic Point Contacts Revealed by Chemical Force and Conductance" at this page of the Physical Review Letters website.

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