科研之友
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摘要
Analytical expressions are presented for the motion of a point mass driven on a periodic potential by a lateral spring, approximating an atomically sharp tip rubbing over a crystal surface. The tip position before and after jumping between two consecutive minima, the kinetic friction force F-kin, and the energy barrier Delta E preventing the tip jumps are expressed in terms of a parameter., which is the ratio between the maximum curvature of the substrate potential and the elastic spring constant. In the two limiting cases of eta -%26gt; 1 (superlubric transition) and eta %26gt;%26gt; 1, we demonstrate that F-kin alpha (eta - 1)(2) and F-kin alpha eta, respectively. We also show that the relation Delta E alpha (F-c - F)(3/2), which is valid in the case of a strong interaction, is replaced by Delta E alpha (F - F-c)(3) close to the superlubric transition. The proportionality coefficients are determined in all cases. The case of multiple jumps is also studied, and numerical results reproducing the influence of the finite temperature and the viscous damping accompanying the tip slippage are shown.
- 出版日期2012-7-26
