Chen Fangyuan, Kou Zepu, Jiang Zonghuiyi, Guo Wanlin, Liu Xiaofei
Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, China 210016.
J Phys Chem Lett. 2024 Feb 15;15(6):1719-1725. doi: 10.1021/acs.jpclett.3c03334. Epub 2024 Feb 6.
Quantum trap, a quantum and thermal fluctuations-induced nonmonotonous potential, offers a chance to build up microscopic mechanical systems completely dominated by fluctuations. Here, we explore the physical limit of the effective damping ratio of the nonlinear Brownian oscillator in a quantum trap, set by the finite separation for avoiding molecular-scale effects on the trap potential and the surface confinement effect-induced diverging damping and random forces. The quasiharmonic approximations and Langevin dynamics simulations show that the lowest effective damping ratios of the suspended Au plate and Au sphere upon a Teflon coating of 10 nm can be ∼210 and ∼145, respectively, at room temperature. Perforation is proposed as an effective route to reduce the damping ratio (down to 6.4) by attenuating the surface confinement effect. An unexpected result due to the temperature dependences of dielectric function and viscosity of ethanol is a further reduced damping ratio at 400 K (1.3). The nonlinear Brownian oscillator in the quantum trap shows promise of probing near-boundary hydrodynamics at nanoscale.
量子阱是一种由量子和热涨落诱导产生的非单调势，它为构建完全由涨落主导的微观机械系统提供了契机。在此，我们探究了量子阱中非线性布朗振子有效阻尼比的物理极限，该极限由避免分子尺度效应作用于阱势的有限间距以及表面限制效应诱导的发散阻尼和随机力所设定。准谐波近似和朗之万动力学模拟表明，在室温下，10纳米厚的聚四氟乙烯涂层的悬浮金板和金球的最低有效阻尼比分别约为210和约145。穿孔被认为是通过减弱表面限制效应来降低阻尼比（低至6.4）的有效途径。由于乙醇的介电函数和粘度与温度有关而产生的一个意外结果是，在400K时阻尼比进一步降低（至1.3）。量子阱中的非线性布朗振子有望用于探测纳米尺度下的近边界流体动力学。
