The topological valley transport,realized in phononic crystals,has aroused tremendous interest in these years.Many previous researches have further promoted the development of this transport phenomenon.Crucially,the b...The topological valley transport,realized in phononic crystals,has aroused tremendous interest in these years.Many previous researches have further promoted the development of this transport phenomenon.Crucially,the bandwidth of the valley-projected edge mode has been an essential research topic.As is well known,the broadband will improve the adaptability of the acoustic edge-states,which will be more conducive to the transmission of information.Therefore,in this paper,we present a composite structure,composed of the atoms with different shapes forming a hexagonal lattice,which can achieve larger bandwidth than a single structure.Meanwhile,the results demonstrate that the topological protected edge states are also observed in our structure.Furthermore,the backscattering suppressions from associated valley-protected edge states under certain perturbations have also been investigated and demonstrated.Our work can provide a new idea for designing acoustic devices based on valley degree of freedom.展开更多
The existence of a single topologically protected edge state in the first bulk bandgap for acoustic/elastic valley Hall insulators(VHIs)with zigzag interface configurations(ZICs)is well known.However,in this work,we s...The existence of a single topologically protected edge state in the first bulk bandgap for acoustic/elastic valley Hall insulators(VHIs)with zigzag interface configurations(ZICs)is well known.However,in this work,we show that an ultra-broadband edgestate pair in this bandgap can be created using the inverse design by topology optimization.The valley Hall insulator design increases the operational bandwidth 121%compared with an existing valley Hall insulator from recent literature and exhibits extreme field confinement,where more than 99%of the field intensity is concentrated within three unit-cells from the interface.One-way propagation and topological robustness towards small cavity defects are confirmed for the full bandwidth.The exploitation of such edge-state pairs of valley Hall insulators opens an avenue for realizing broadband confined edge modes.In tests for disorder and bend defects,we show that the additional ZIC,with a different operational frequency interval,encountered at the defects,degrades the transmission for bend and disorder defects which may prove significant for the application of VHIs.Through an alternative topology optimization method based on two ZICs,we further increase their common operational bandwidth.展开更多
The conductance spectra of a graphene ribbon and graphene-superconductor （G-S） junctions are investi- gated, using the tight-binding model and non-equilibrium Green＇s function formalism. It is found that the quanti...The conductance spectra of a graphene ribbon and graphene-superconductor （G-S） junctions are investi- gated, using the tight-binding model and non-equilibrium Green＇s function formalism. It is found that the quantized conductance related to graphene＇s edge-states is robust against perturbations in the model parameters for a graphene monolayer ribbon with the zigzag boundary. With appropriate a new bound state with odd-frequency symmetry is found in conductance amplitude is followed model parameter of the spin-orbit interaction strength, the G-S junction. An enhancement in the zero-energy展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61775050)the Fundamental Research Funds for the Central Universities,China(Grant No.PA2019GDZC0098).
文摘The topological valley transport,realized in phononic crystals,has aroused tremendous interest in these years.Many previous researches have further promoted the development of this transport phenomenon.Crucially,the bandwidth of the valley-projected edge mode has been an essential research topic.As is well known,the broadband will improve the adaptability of the acoustic edge-states,which will be more conducive to the transmission of information.Therefore,in this paper,we present a composite structure,composed of the atoms with different shapes forming a hexagonal lattice,which can achieve larger bandwidth than a single structure.Meanwhile,the results demonstrate that the topological protected edge states are also observed in our structure.Furthermore,the backscattering suppressions from associated valley-protected edge states under certain perturbations have also been investigated and demonstrated.Our work can provide a new idea for designing acoustic devices based on valley degree of freedom.
基金supported by the China Scholarship Council(CSC)the Danmarks Grundforskningsfond(Grant No.DNRF147)。
文摘The existence of a single topologically protected edge state in the first bulk bandgap for acoustic/elastic valley Hall insulators(VHIs)with zigzag interface configurations(ZICs)is well known.However,in this work,we show that an ultra-broadband edgestate pair in this bandgap can be created using the inverse design by topology optimization.The valley Hall insulator design increases the operational bandwidth 121%compared with an existing valley Hall insulator from recent literature and exhibits extreme field confinement,where more than 99%of the field intensity is concentrated within three unit-cells from the interface.One-way propagation and topological robustness towards small cavity defects are confirmed for the full bandwidth.The exploitation of such edge-state pairs of valley Hall insulators opens an avenue for realizing broadband confined edge modes.In tests for disorder and bend defects,we show that the additional ZIC,with a different operational frequency interval,encountered at the defects,degrades the transmission for bend and disorder defects which may prove significant for the application of VHIs.Through an alternative topology optimization method based on two ZICs,we further increase their common operational bandwidth.
基金Supported by the National Natural Science Foundation of China under Grant No.61271163
文摘The conductance spectra of a graphene ribbon and graphene-superconductor （G-S） junctions are investi- gated, using the tight-binding model and non-equilibrium Green＇s function formalism. It is found that the quantized conductance related to graphene＇s edge-states is robust against perturbations in the model parameters for a graphene monolayer ribbon with the zigzag boundary. With appropriate a new bound state with odd-frequency symmetry is found in conductance amplitude is followed model parameter of the spin-orbit interaction strength, the G-S junction. An enhancement in the zero-energy
