Leroy B J, Lemay S G, Kong J, Dekker C
Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands.
Nature. 2004 Nov 18;432(7015):371-4. doi: 10.1038/nature03046.
The interplay between discrete vibrational and electronic degrees of freedom directly influences the chemical and physical properties of molecular systems. This coupling is typically studied through optical methods such as fluorescence, absorption and Raman spectroscopy. Molecular electronic devices provide new opportunities for exploring vibration-electronic interactions at the single molecule level. For example, electrons injected from a scanning tunnelling microscope tip into a metal can excite vibrational excitations of a molecule situated in the gap between tip and metal. Here we show how current directly injected into a freely suspended individual single-wall carbon nanotube can be used to excite, detect and control a specific vibrational mode of the molecule. Electrons tunnelling inelastically into the nanotube cause a non-equilibrium occupation of the radial breathing mode, leading to both stimulated emission and absorption of phonons by successive electron tunnelling events. We exploit this effect to measure a phonon lifetime of the order of 10 ns, corresponding to a quality factor of well over 10,000 for this nanomechanical oscillator.
分立的振动自由度与电子自由度之间的相互作用直接影响分子系统的化学和物理性质。这种耦合通常通过诸如荧光、吸收和拉曼光谱等光学方法来研究。分子电子器件为在单分子水平上探索振动 - 电子相互作用提供了新的机会。例如，从扫描隧道显微镜尖端注入金属的电子可以激发位于尖端与金属之间间隙中的分子的振动激发。在此我们展示了如何将直接注入自由悬浮的单个单壁碳纳米管的电流用于激发、检测和控制分子的特定振动模式。非弹性隧穿进入纳米管的电子导致径向呼吸模式的非平衡占据，通过连续的电子隧穿事件导致声子的受激发射和吸收。我们利用这种效应测量到声子寿命约为10纳秒，对于这个纳米机械振荡器而言，其品质因数远超过10000。
