Higher-Order Topological Rainbow Effect in Non-Hermitian Acoustic Kagome Structures

【摘要】 <正>A significant paradigm shift in condensed matter physics has been precipitated by the emergence of higher-order topological insulators.We design a higher-order Kagome acoustic crystal incorporating balanced gain and loss factors,thereby emulating non-Hermitian characteristics.This system exhibits the coexistence of two distinct corner states localized at the same angular positions within a supercell composed of two triangular domains with different topological phases,and the radius of one cylinder can control the frequency of the corner state.By constructing a polygonal structure formed by the expanded and shrunk lattices with distinct topological phases,we theoretically demonstrate that acoustic waves of various frequencies can be selectively trapped at a series of specific angles of this polygon.Moreover,these corner states are locked to the corner order,corresponding to the clockwise or anticlockwise orientation of the polygon,which leads to the higher-order topological rainbow.This work opens a new avenue for guiding and trapping multi-frequency acoustic energy,with potential applications in advanced acoustic devices.更多还原