Interplay between Force and Current in Atomic Junctions(Research)

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Other Title
  • 近接する2つの物体間の「力」と「電流」の関係(最近の研究から)
  • 近接する2つの物体間の｢力｣と｢電流｣の関係
  • キンセツ スル 2ツ ノ ブッタイ カン ノ 「 チカラ 」 ト 「 デンリュウ 」 ノ カンケイ

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Abstract

Atomic-scale junction is of importance in both fundamental physics and is also of practical importance for nanotechnology. As two objects are brought near to contact, an overlap of the wave-functions produces the chemical interaction force (F). If the bias voltage is applied between them, the tunneling current (I) is also generated in the atomic junction. It has been pointed out that there is equivalence between F and I as a corollary of quantum mechanics. The simple relation was theoretically predicted, i.e. the square relation (I∝F^2) and the linear relation (I∝F). Experimentally, the correlation has been investigated by atomic force microscopy (AFM). Recent AFM measurements produced I∝F relations on the metallic surfaces, which were supported by first principle calculations with nonperturbative treatment of the electron transport. According to the latest theoretical model, I∝F relation was reproduced for non-degenerate electronic states between tip and sample while I∝F^2 relation was also predicted for the quantum-degenerate situation for two energetically localized states. We combine site-specific force/current measurements and first-principles calculations on the Si (111)-(7×7) surface. We obtained I∝F^2 relation at the weak interaction regime. The quantum degeneracy of spatially and energetically localized electronic states between the tip and Si adatom can explain the relation.

Journal

  • Butsuri

    Butsuri 70 (8), 620-624, 2015-08-05

    The Physical Society of Japan

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