Department of Physics, University of Basel, Klingelbergstraße 82, Basel 4056, Switzerland.
1] SISSA, Via Bonomea 265, Trieste 34136, Italy [2] CNR-IOM Democritos National Simulation Center, Via Bonomea 265, Trieste I-34136, Italy.
Nat Mater. 2014 Feb;13(2):173-7. doi: 10.1038/nmat3836. Epub 2013 Dec 15.
Understanding nanoscale friction and dissipation is central to nanotechnology. The recent detection of the electronic-friction drop caused by the onset of superconductivity in Nb by means of an ultrasensitive non-contact pendulum atomic force microscope (AFM) raised hopes that a wider variety of mechanical-dissipation mechanisms become accessible. Here, we report a multiplet of AFM dissipation peaks arising a few nanometres above the surface of NbSe2--a layered compound exhibiting an incommensurate charge-density wave (CDW). Each peak appears at a well-defined tip-surface interaction force of the order of a nanonewton, and persists up to 70 K, where the short-range order of CDWs is known to disappear. Comparison of the measurements with a theoretical model suggests that the peaks are associated with local, tip-induced 2π phase slips of the CDW, and that dissipation maxima arise from hysteretic behaviour of the CDW phase as the tip oscillates at specific distances where sharp local slips occur.
理解纳米级摩擦和耗散对于纳米技术至关重要。最近，通过超灵敏非接触摆式原子力显微镜（AFM）检测到 Nb 中超导引起的电子摩擦下降，这增加了人们的希望，即可以获得更多种类的机械耗散机制。在这里，我们报告了在 NbSe2 表面上方数纳米处出现的 AFM 耗散峰的多重峰，NbSe2 是一种表现出不相容电荷密度波（CDW）的层状化合物。每个峰出现在一个定义明确的约为纳牛顿的尖端-表面相互作用力下，并且一直持续到 70K，在该温度下，CDW 的短程有序性已知会消失。将测量结果与理论模型进行比较表明，这些峰与 CDW 的局部、由尖端诱导的 2π 位错有关，而耗散最大值则来自于 CDW 相位的滞后行为，因为尖端在发生急剧局部位错的特定距离处振荡。
