Wang Neng, Feng Fanghu, Wang Guo Ping
China State Key Laboratory of Radio Frequency Heterogeneous Integration, College of Electronics and Information Engineering, Shenzhen University, Shenzhen 518060, People's Republic of China.
J Phys Condens Matter. 2023 Dec 4;36(10). doi: 10.1088/1361-648X/ad0dcc.
We have developed a nonlocal effective medium theory (EMT) for phononic temporal metamaterials using the multiscale technique. Our EMT yields closed-form expressions for effective constitutive parameters and reveals these materials as reciprocal media with symmetric band dispersion. Even without spatial symmetry breaking, nonzero Willis coupling coefficients emerge with time modulation and broken time-reversal symmetry, when the nonlocal effect is taken into account. Compared to the local EMT, our nonlocal version is more accurate for calculating the bulk band at high wavenumbers and essential for understanding nonlocal effects at temporal boundaries. This nonlocal EMT can be a valuable tool for studying and designing phononic temporal metamaterials beyond the long-wavelength limit.
我们使用多尺度技术为声子时间超材料开发了一种非局部有效介质理论（EMT）。我们的EMT给出了有效本构参数的闭式表达式，并揭示这些材料是具有对称带色散的互易介质。当考虑非局部效应时，即使没有空间对称性破缺，随着时间调制和时间反演对称性破缺，也会出现非零的威利斯耦合系数。与局部EMT相比，我们的非局部版本在计算高波数下的体带时更准确，并且对于理解时间边界处的非局部效应至关重要。这种非局部EMT可以成为研究和设计超越长波长极限的声子时间超材料的有价值工具。
