The Transport Characteristics Of Strain-induced Phononic Crystals

As a new field of condensed matter physics,phononic crystal has been highly concerned and discussed by experts and scholars all over the world due to its band structure similar to that of micro electrons in semiconductors.Phononic crystals are widely used in industrial production engineering and people’s daily life to control the vibration and noise because of their band gap characteristics which can completely suppress sound waves and elastic waves with specific frequency range.Furthermore,the concept of topology was introduced into the field of phononic crystals,which greatly promoted the research of phononic crystals and gave birth to the new field of topological phononic crystallography.By constructing phononic crystal structures with different topological properties,the researchers found that the combination of phononic crystal structures can achieve topological edge states with edge transmissions at their common interface.Later,inspired by the strain engineering of graphene,in the classical neutral boson quasiparticles researchers found the unique magnet-induced quantum phenomenon belonging to charged particles.In this paper,the theory of strain engineering of graphene is introduced into the solid-state phononic crystal system.Firstly,it is discussed that a certain form of vector potential can be induced by a suitable strain,and a uniform giant pseudomagnetic field can be generated.Furthermore,the energy band characteristics of the high field physical under the pseudomagnetic field,such as Landau energy level quantization,are discussed.Finally,the magnetic-induced quantum transmission phenomenon of the out-of-plane elastic wave under the pseudomagnetic field is studied.The main research contents are as follows:(1)The strain engineering theory is introduced into the solid-state phonon system,through solving the eigenvalue of Dirac particles Hamiltonian its energy band structure can be obtained.Furthermore,it is found that the displacement of the Dirac cone can represent the variation of the vector potential,and the pseudomagnetic field in the phononic crystal system can be obtained by solving the gradient of the vector potential.(2)Due to the tunability of the macrostructure of the phononic crystal,we have designed a strain phononic crystal with gradient snowflake arm angle.It is found that there is a linear relationship between the deviation of the arm angle and the displacement of the Dirac point,which makes it possible to induce a uniform high field pseudomagnetic field in our strained phononic crystal system.(3)By designing strain phononic crystal model with different arm angle gradients,wecompared the band characteristics of the phononic crystal under pseudomagnetic field with distinct strength.Under the pseudomagnetic field,the linear band near the Dirac cone region is found form a series of quantized Landau band energy levels.(4)Through the frequency-domain analysis of finite element method,we observed the sublattice polarized bulk state transport in rectangular phononic crystal sample and the magnetic-induce edge state transport in rectangular phononic crystal sample.Furthermore,the magnetic-like effects and magnetic-induced quantum phenomenon of elastic wave in phononic crystal are further proved by introducing IPR function.