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Quantum Dynamics and Fluctuations in Nonlinear Nanomechanical Systems

非线性纳米机械系统中的量子动力学和涨落

基本信息

批准号：
1806473
负责人：
Mark Dykman
金额：
$ 60万
依托单位：
Michigan State University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-08-01 至 2023-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1806473&HistoricalAwards=false
关键词：
Quantum Dynamics Fluctuations Nonlinear Nanomechanical

项目摘要

Nanomechanical systems are of significant fundamental interest and are also playing an increasingly important role in various applications - including biosensing, mass spectrometry, force detection at the atomic scale, and realization of stable frequency sources. The unique and advantageous feature of such systems is that they are sufficiently large that the vibrations can be studied in an individual system while, at the same time, they are sufficiently small as to provide that exceptional detection sensitivity enabling their novel applications. Because of the smallness of nanomechanical systems, a fundamentally important role in their dynamics is played by quantum fluctuations, which are unavoidable even for low temperatures. Also fundamental is that vibrations have a relatively large amplitude compared to the system size; as a consequence, they can become strongly nonlinear. Although substantial progress has been made over the last few years, major questions remain concerning the fluctuations of nanomechanical systems and their various consequences. Addressing these questions requires new characterization tools and new theoretical techniques. Poorly understood fluctuations and energy dissipation currently limit the performance of nanomechanical systems in applications. The proposed research is motivated by the largely untapped richness of this field. It has the dual aims of studying the underlying physics of nanoscale vibrational systems and using these systems to explore nonequilibrium phenomena in a uniquely well-controlled and highly-sensitive setting. The combined expertise of the principal investigators in theoretical and experimental physics should facilitate significant and rapid progress in these studies. The project should also provide an excellent platform for cross-disciplinary training of graduate and undergraduate students in theoretical and experimental physics.The major emphases of the proposed research are: (i) To develop new theoretical and experimental means and to study, using these means, both the spectra and the statistics of eigenfrequency fluctuations. This should reveal the physical mechanisms underlying these fluctuations. (ii) To explore Floquet dynamics of periodically-driven nonlinear quantum dissipative modes. Here, of particular interest is the spontaneous breaking of the discrete time-translation symmetry in the quantum-coherent regime. Also of interest are new types of quantum-coherent and dissipative states with a period, which is a multiple of the period of the driving, as well as the transitions between these states, and (iii) To explore interaction-induced symmetry-breaking for coupled, periodically-modulated nonlinear modes that is mediated by quantum and classical fluctuations. This symmetry breaking should sensitively depend on the connectivity of the nanomechanical modes - which the investigators can precisely engineer - and should encompass phenomena such as frustration and quantum phase transitions in the time domain, as well as the occurrence of microscopic currents in the stationary state of quantum systems far from thermal equilibrium.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

纳米机械系统具有重要的基础性意义，并在各种应用中发挥着越来越重要的作用--包括生物传感、质谱学、原子尺度的力检测以及实现稳定的频率源。这种系统的独特和有利的特征是，它们足够大，可以在单个系统中研究振动，同时，它们足够小，以提供特殊的检测灵敏度，使其能够实现新的应用。由于纳米机械系统的规模很小，量子涨落在其动力学中扮演着根本性的重要角色，即使在低温下，量子涨落也是不可避免的。另一个基本因素是，与系统大小相比，振动的幅度相对较大；因此，它们可能会变得强烈的非线性。尽管在过去的几年里已经取得了实质性的进展，但关于纳米机械系统的波动及其各种后果的主要问题仍然存在。解决这些问题需要新的表征工具和新的理论技术。目前对涨落和能量耗散知之甚少限制了纳米机械系统在应用中的性能。这项拟议的研究的动机是该领域在很大程度上尚未开发的丰富性。它具有双重目标，即研究纳米级振动系统的基本物理，并使用这些系统在独特的控制良好和高度敏感的环境中探索非平衡现象。主要研究人员在理论物理和实验物理方面的综合专门知识应有助于在这些研究中取得重大和迅速的进展。该项目还应为研究生和本科生在理论和实验物理方面的跨学科培训提供一个很好的平台。拟议研究的主要重点是：(I)发展新的理论和实验方法，并利用这些方法研究本征频率起伏的频谱和统计。这应该会揭示这些波动背后的物理机制。(Ii)探索周期驱动的非线性量子耗散模的Floquet动力学。这里，特别令人感兴趣的是量子相干体制中离散时间平移对称的自发破缺。同样有趣的还有新类型的量子相干态和耗散态，其周期是驱动周期的倍数，以及这些态之间的跃迁，以及(Iii)探索由量子和经典涨落介导的耦合的周期性调制的非线性模的相互作用诱导的对称破缺。这种对称性破缺应该敏感地依赖于纳米机械模式的连通性--研究人员可以精确地设计这种模式--并且应该包括时间域中的受挫和量子相变等现象，以及远离热平衡的量子系统静止状态中的微观电流的发生。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。