Active control on topological immunity of elastic wave metamaterials

Abstract

The topology concept in the condensed physics and acoustics is introduced into the elastic wave metamaterial plate, which can show the topological property of the flexural wave. The elastic wave metamaterial plate consists of the hexagonal array which is connected by the piezoelectric shunting circuits. The Dirac point is found by adjusting the size of the unit cell and numerical simulations are illustrated to show the topological immunity. Then the closing and breaking of the Dirac point can be generated by the negative capacitance circuits. These investigations denote that the topological immunity can be achieved for flexural wave in mechanical metamaterial plate. The experiments with the active control action are finally carried out to support the numerical design.

Progress in Topological Mechanics

“…Although the bosons do not have half-integer spin as electrons, the QSHE is also demonstrated in photonics [35][36][37]81] and acoustics [47,48,51,82] by constructing pseudo spins. In addition, the QSHE has been verified in elastic materials theoretically and experimentally [58][59][60][61][62][63][64][65][66][67][68]. We note that there are three main methods used to construct mechanical structures via QSHE, which include designing coupled pendula mimicking spin-orbital coupling effects [58,59], using the elastic plates with distinct polarizations and coupled deformation mechanisms to produce accidental fourfold degeneracy [60,61], and a zone-folding method with honeycomb lattices [62][63][64][65][66][67][68].…”

Smart piezoelectric phononic crystals and metamaterials:State-of-the-art review and outlook

“…弹性波拓扑绝缘体是一类新型的超材料。 其最主要的特点是弹性波仅沿着拓扑绝缘体内的拓扑 界面传播。得益于外接分流电路的压电复合结构调节有效材料参数的便利性，可以通过打破空间对 称性从而获得拓扑绝缘体或界面态。例如 Li 等人 [132] 通过负电容电路控制狄拉克锥的打开与闭合， 从而获得了拓扑绝缘(免疫)态。Dorin 和 Wang [133] 打破了蜂窝晶格二维压电复合板的对称性，打 开了狄拉克锥，通过谷霍尔效应实现了弯曲波定向传播。类似的，Darabi 等人 [134] 亦通过谷霍尔效 应，利用分流电路打破蜂窝晶格的对称性，实现了拓扑绝缘体界面态。总的来讲，通过外界电路形 成的拓扑绝缘体，其界面态可由外接电路控制的开闭产生，界面态的方向和形状可由电路控制，无 须改变原始结构。利用类似的思路，同样可以通过主动控制实现基于复合压电声子晶体与超材料的 弹性波拓扑绝缘体。…”

Tuning of topological interface modes in an elastic beam array system with inerters

“…For example, Rosa et al [43] studied the topological pumping in the array of semi-infinite continuous elastic beams coupled through a distributed stiffness showing that adiabatic stiffness modulations along the beams' length causes the transition of localized states from one to the opposite boundary of an array. Moreover, some authors raise the question of using the active elastic metamaterials to achieve controllable elastic cloaking [44] or tunable topological states [45].…”