Switching in Driven Microscopic Systems

驱动微观系统中的切换

• 批准号: 0305746
• 负责人: Brage Golding
• 金额: --
• 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: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0305746&HistoricalAwards=false
• 关键词: Switching; Driven; Microscopic; Systems

This combined experiment and theory project will explore thermally activated switching in model physical systems that are driven by time-dependent fields. The underlying theoretical idea is that a field interferes with switching dynamics and can therefore strongly affect switching probabilities. Since experimental understanding of this process requires a well-characterized physical system, the use of a mesoscopic particle trapped in an optically-induced double well potential is adopted. This system exhibits behavior analogous to the hysteretic response of a single-domain nanomagnet in a magnetic field or a current-biased resistively-shunted Josephson junction. However, the 3-dimensional confining potential can be readily tuned and modulated by controlling the laser beams comprising the trap. The damping rate can be varied by changing the particle properties or by controlling the environmental coupling. Theoretical studies can provide deeper understanding of fluctuation processes in systems driven far from thermal equilibrium. Results can be directly transferred to areas of current technological importance, for example, controlled switching in nanomagnetic random access memory devices. Graduate and postdoctoral students involved with this research will acquire understanding of lasers, optical methods, real-time computing, theory of transport phenomena and non-linear dynamical systems, preparing them for careers in teaching and/or research in science and engineering.%%%Switching events play a pivotal role in many physical and biological processes. On computer hard disks, information is written into billions of tiny regions with 1's and 0's expressed as the orientations of nanomagnets. Switching between these two states should be easy to do when information is stored but it should not happen spontaneously, which would lead to a loss of memory. In this investigation, a model of a two-state switch is created by two laser beams. A single beam can confine a transparent sub-micron particle to a small region in space. With two parallel beams separated by less than the particle diameter, the particle can switch between the two beams if it acquires enough energy. By modulating the energy of the particle, the transition rates can be controlled and the conditions under which switching occurs studied quantitatively, even in a noisy environment. The experiments are analyzed by statistical theories that will be developed to predict the particle's behavior under extreme conditions, i.e., when the particle is moved rapidly and with large amplitude. These studies should lead to optimal methods for controlling random switching processes with applications not only to magnetism but also to chemistry and biology. Students will receive training in optics, real-time computing, condensed matter and statistical physics.

这个组合的实验和理论项目将探索由时间相关场驱动的模型物理系统中的热激活切换。 基本的理论思想是一个场会干扰切换动力学，因此可以强烈影响切换概率。 由于对此过程的实验理解需要一个良好的物理系统，因此采用了被困在光学引起的双井潜力中的介观粒子的使用。 该系统表现出类似于磁场中单域纳米磁体或电流偏置的电阻旋转的约瑟夫森连接的行为。 但是，可以通过控制包含陷阱的激光束来轻松调整和调节3维限制电势。 阻尼率可以通过更改粒子特性或控制环境耦合来改变。 理论研究可以更深入地了解远离热平衡的系统的波动过程。 结果可以直接转移到当前技术重要性的领域，例如，在纳米磁随机访问存储器设备中受控的切换。参与这项研究的研究生和博士后生将了解激光，光学方法，实时计算，运输现象理论和非线性动力学系统，为他们在科学和工程学领域的教学和/或研究中做好准备。%%％转换事件在许多物理和生物学过程中起着关键作用。 在计算机硬盘上，信息写入数十亿个小区域，其中1和0表示为纳米磁体的方向。 在存储信息时，在这两个状态之间的切换应该很容易执行，但不应自发地发生，这将导致记忆力损失。 在这项研究中，两个激光束创建了一个两态开关的模型。 单光束可以将透明的亚微米粒子限制在空间中的小区域。如果两个平行梁被小于颗粒直径隔开，则粒子可以在两个梁中获得足够的能量在两个梁之间进行切换。 通过调节粒子的能量，可以控制过渡速率，即使在嘈杂的环境中，也可以定量研究开关的条件。 通过统计理论对实验进行分析，这些理论将在极端条件下（即，当粒子迅速移动并且具有较大的幅度移动时，可以预测粒子的行为。 这些研究应导致最佳方法控制随机切换过程，不仅应用于磁性，而且还针对化学和生物学。 学生将接受光学，实时计算，冷凝物和统计物理学的培训。