Thermally induced suppression of friction at the atomic scale

Atomic-scale friction, as accessed in tip-based experiments, is investigated theoretically in the full range of surface corrugations, temperatures, and velocities. Emphasis is given to the regime of thermal drift, when the regular stick-slip behavior is completely ruined by thermal effects. The possibility of nearly vanishing friction (“thermolubricity”) is predicted even for strong (overcritical) surface corrugations, when traditional models would predict significant friction. The manifestation of this effect in recently published experimental data is demonstrated.

Figure 1

Characteristic lateral-force loops at two different relative surface corrugations, measured in the FFM experiment reported in [2]: (a) $\gamma =4.96$, (b) $\gamma =2.46$.

Figure 2

Total potential $U$ vs tip position $x$, for $\gamma =10$ and for two support positions, $X=1.5a$ (solid) and $X^{\left(c\right)}=1.82a$ (dashed). Arrows (a, b, c) show different types of slips.

Figure 3

Friction force as a function of relative surface corrugation $\gamma$ for $V=30\mathrm{nm}∕\mathrm{s}$, $a=0.25\mathrm{nm}$, and $K=1.8\mathrm{N}∕\mathrm{m}$. Solid curves: present theory for (from left to right) $V∕a{r}_0=7.5\times {10}^{-n}$ with $n=1,2,3,4$. Dashed curve: Tomlinson model. Experimental points retrieved from Ref. 2. Inset: experimental points retrieved from Ref. 3 $(V=3\mathrm{nm}∕\mathrm{s},K=1.3\mathrm{N}∕\mathrm{m},a=0.5\mathrm{nm})$.