声学人工结构中声场与颗粒的相互作用及声场对颗粒的操控研究

The interaction between light and particles (including molecules and atoms) has remained the research frontier in physics, which had brought many important applications in practice such as laser cooling of atoms and optical tweezers etc.One of the current interests in this field lies in the interaction between the optical field in the optical metamaterials and particles.Similarly, the research on the interaction between sound and particles has also a long history, but in contrast, there is yet no study concerning the interaction of the acoustic field in acoustic materials with particles. Based on the new concepts of the acoustic metamaterials and the phononic crystals, this project aims to study the interaction between particles and the particular acoustic fields inside these new acoustic artificial structures, in order to discover new phenomena and establish new theory on the wave-particle interactions. We will study the radiation forces and torques of the acoustic fields exerting on particles, study how to turn the radiation force to a pulling force, and study the dynamics of the particles under the radiation force; We will also study how to trap the particles in the acoustic fields inside these artificial structures. Since these artificial structures may have abnormal properties, such as negative refraction, negative mass density and negative bulk modulus, the interaction between particles and acoustic fields may exhibit new features, and thus the investigations in the project are scientifically significant. Meanwhile, the project essentially studies the manipulation of particles by acoustic beams,and thus it is also of pratical importance.

光与颗粒（包括分子原子）相互作用一直是物理学研究的主流，已经产生了如原子激光冷却、光镊等许多新技术。该领域目前的热点之一是光学超常材料中光场与颗粒相互作用研究。声与颗粒相互作用的研究也具有悠久的历史，但声学超常材料中声场与颗粒相互作用问题目前尚无研究。本项目立足于声学超常材料和声子晶体等人工结构新概念，致力于这些新颖结构中独特的声场与颗粒相互作用的研究，以期发现声与颗粒相互作用的新现象和新规律。研究内容包括：研究人工结构中声场对颗粒作用的力学效应- - 声辐射力与力矩；研究声辐射力变为拽力的可能性及实现；研究颗粒在声辐射力作用下的自组织和动力学行为；研究人工结构声场囚禁颗粒的新思路。声学人工结构不同于通常的均匀介质，可具有如负折射率、负质量密度及负模量等反常性质，人工结构中声与颗粒相互作用可望展现新规律，从而为颗粒操控提供新方法。所以，本项目的研究不仅具有科学意义，同时还可能具有应用价值。

声波和物质会发生两种相互作用：物质对声波的散射、衍射、干涉等波动作用，反过来，声波对置于其中的物体有力学作用，称为声辐射力。在该项目的资助下，我们主要研究了：（a）声子晶体诱导的新型声场对细小颗粒的声辐射力作用；（b）声波诱导的人工结构板之间的新奇声辐射力现象；（c）声场诱导的颗粒之间的相互作用和自组织行为；（d）其它的一些人工结构声场的新效应。总体而言，我们出色地完成了项目的既定目标，基本弄清了利用声子晶体板设计声场的原理，利用这些新奇的声场成功地实现了对粒子的捕获、排列、以及输运效应；额外地，我们也研究了一些声子晶体中的其它效应，例如谷涡旋态、声谷态的拓扑输运等。在该面上基金的资助下，项目研究进展顺利，总共发表学术论文30篇，其中包括在顶级物理期刊上发表Nature Physics 2篇，Phys. Rev. Lett. 2篇（均为通讯作者）。