摘要
对二维声学超材料与常规材料界面处的负向Schoch位移进行了研究.研究表明,在界面处增加合适厚度的覆盖层,当声波在某一频率附近从常规材料向近零折射率材料传播时,反射声波相对于入射声波会在界面处发生负向Schoch位移,此时,超材料的有效体积模量倒数值趋近于零从而使它成为一种折射率近零的声学材料;同时,超材料有效阻抗的极大值和反射系数的极大值都在这一特殊频率处且反射系数虚部相位在对应频率处有πrad的相位突变;研究还发现,发生负向Schoch位移的频率位于MK方向第一带隙中且靠近上边界的通带频率.常规材料界面处的Schoch位移通常是正向的且大小可忽略不计的,本文利用近零折射率声学材料实现了负向的Schoch位移,为设计出基于界面声波的声学器件提供了一种新的理论参考.
In this paper,the Schoch displacement at the interface between different two-dimensional triangular phononic crystal metamaterial and natural material is studied by using finite element software.As is well known,the Schoch displacement is highly dependent on the surface wave and leakage wave excited at the interface between different materials.So,the negative Schoch displacement can be more easily obtained by adding a suitable thickness of covering layer at the interface between metamaterial material and natural material.The numerical results show that when the negative Schoch displacement happens,the effective parameters of metamaterials are close to zero.It means that the effective refraction index is near to zero and the reduced frequency of the incident acoustic wave is correlated with the reduced frequency of the band gap.It is also found from the results that the reduced frequency of the incident acoustic wave is located at the edge of the band gap when the negative Schoch displacement occurs.The maximum of the metamaterial effective impedance and the maximum of the reflection coefficient are almost at the same frequency.The phase of the imaginary part of the reflection coefficient has a phase mutation inπrad at the corresponding frequency.The frequency of negative Schoch displacement is located in the first band gap of MK direction and near the upper boundary.The Schoch displacement at the interface between conventional materials is usually positive and negligible in previous reports.In this paper,the negative Schoch displacement is obtained by using the nearzero refraction index metamaterials.This not only enriches the physics contents of Schoch effect but also provides a theoretical reference for designing the acoustic devices based on acoustic wave displacement at the interface.
作者
刘向东
吴福根
姚源卫
张欣
Liu Xiang-Dong;Wu Fu-Gen;Yao Yuan-Wei;Zhang Xin(School of Materials and Energy,Guangdong University of Technology,Guangzhou 510006,China;School of Physics and Optoelectronic Engineering,Guangdong University of Technology,Guangzhou 510006,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第12期123-129,共7页
Acta Physica Sinica
基金
国家自然科学基金(批准号:11374066,11374068)资助的课题。
关键词
近零折射率材料
有效参数
Schoch位移
near-zero refractive index material
effective parameter
Schoch displacement
