The Mechanism Of Tunability Of The Interface States In One Dimensional Granular Chain

In the past decades,phononic crystal which is an artificial periodic structure made up o f repetitive elastic composites has caught more and more attention.Phononic crystal has since been proved to support some novel properties including bandgap structures,negative refraction phenomena,defect state,which can be used to design newfangled devices to tailor and tune the propagation o f the acoustic wave or elastic wave and energy flow.In this study,we focus our attention on a type o f nonlinear phononic crystal— granular crystal,which contains not only bandgap structures but also numerical special nonlinear phenomena.It' s thus made a big sense and highly desirable to tune the band gap and other properties without reconfigure the elastic composites and the geometry o f the tunable granular crystal.Here,we firstly deduce the dispersion relationship o f one dimensional(1D)dimer granular crystal,sort out the factors which influencing its energy band,and find a way to tune the band gap without reconfigure the elastic composites or the geometry o f this granular crystal.Then,we introduce the prevalent topology conceptions into this system,and apply this concept to study the topological phase transition o f the granular crystals under the applied axial force.The research findings show that it is possible to tune the topological phase o f the energy band,the topological property and the sign o f surface impedance o f the band gap o f dimer granular system by changing the applied axial force.Based on the Su-Schrieffer-Heeger(SSH)model,we construct a heterostructure which is consist of a nonlinear granular crystal that can be switched from topological nontrivial state to topological nontrivial state by altering the applied force,and a linear granular crystal which keep topological trivial state from the beginning to the end while the applied force changing.W e take advantage o f this heterostructure to achieve the goal o f the switch-on/off o f the interface state on the interface by varying the applied axial force.Our study combines the topology notion with nonlinearity,which pave a broad way to develop the new acoustic functional devices,such as acoustic filter,single frequency acoustic switch,acoustic logic unit,and so on.