Design Of Metamaterials Based On Metal M(?)bius Knots And Their Electromagnetic Topological Properties

In natural materials,almost all materials are composed of periodic arrangement and combination of atoms,so atoms are usually considered to be the smallest unit of matter.It is impossible for humans to modify atoms to design new materials.Therefore,it is not feasible to introduce electromagnetic topological structures into natural material lattices.However,in the field of artificial electromagnetic metamaterials,it is very common to obtain materials with special properties by designing basic units,which undoubtedly provides a novel idea for the preparation of artificial lattice electromagnetic topological metamaterials(ALETM)by introducing electromagnetic topological structure into artificial crystal lattice.This paper proposes to introduce a topologically non-trivial chiral structure—the Mobius knot as the basic structural unit to design ALETM.According to the calculation of electrodynamic theory,electromagnetic waves will be scattered when propagating to the surface of the metal Mobius knot,and the surface electrons of the metal knot will move along this topological structure in the electromagnetic field.Due to the existence of the geometric phase factor in the structure,the electrons will have phase changes during the movement,and this change will produce a Berry phase difference after accumulating one cycle.This phase difference will make the excited electromagnetic waves interfere with the incident waves and cancel each other.As a result,a corresponding intrinsic transmission peak will be generated in the transmission coefficient spectrum.This intrinsic resonance peak produced by the interaction of electromagnetic waves and metal Mobius knots is completely different from the electric resonance peak produced by the interaction between metal structures and electromagnetic waves,It is similar to the spin splitting of the electron energy level,so it has strong robustness,and is insensitive to the polarization angle and polarization mode of incident electromagnetic waves,and it is not sensitive to the electrical size,lattice arrangement,lattice constants and cascade effects,etc.By designing the Mobius knot to carry out electromagnetic simulation calculations and preparing samples to test the transmission coefficient spectrum of electromagnetic waves in a microwave anechoic chamber,it is found that in addition to the electric resonance peak near 11 GHz,and a transmission peak appears at 5.95 GHz caused by the Berry phase,which is consistent with theoretical calculation of intrinsic resonance peak.Using a chiral Mobius knot with topology invariance as the basic unit,we have constructed a total of six kinds of two-dimensional ALETMs:tetragonal lattice,orthorhombic lattice,rectangular crystal,lattice,centered rectangular lattice,hexagonal lattice and honeycomb lattice.Electromagnetic simulation and experimental results show that two-dimensional ALETMs are very robust,and the intrinsic resonance peak position on the transmission coefficient spectrum does not vary with the lattice type,lattice spacing,electromagnetic wave polarization mode and a certain range of electromagnetic wave incidence angle,these are the advantages that electric resonant devices such as antennas,filters,and frequency selective surfaces do not have.In addition,we have also constructed a three-dimensional ALETMs,in which the intrinsic resonance peak also has strong topological stability,and the cascade effect of the multilayer two-dimensional material will not affect the intrinsic resonance frequency,and the electric resonance peak has a clear broadening effect.Using the robustness of ALETMs,we can design many new and more stable radar antennas,frequency selective surfaces,filters,wave absorbers and other commonly used devices in the defense,military,and electronic communications fields.The shortcomings of similar traditional devices designed based on electrical resonance can be overcome one by one,and even these new devices can have functions that were not available before,such as camouflage,codeability,flexibility and other new features.