Excitons in solid state are bosons generated by electron-hole pairs as the Coulomb screening is sufficiently reduced.The exciton condensation can result in exotic physics such as super-fluidity and insulating state.In...Excitons in solid state are bosons generated by electron-hole pairs as the Coulomb screening is sufficiently reduced.The exciton condensation can result in exotic physics such as super-fluidity and insulating state.In charge density wave(CDW)state,1T-TiSe_(2) is one of the candidates that may host the exciton condensation.However,to envision its excitonic effect is still challenging,particularly at the two-dimensional limit,which is applicable to future devices.Here,we realize the epitaxial 1T-TiSe_(2) bilayer,the two-dimensional limit for its 2×2×2 CDW order,to explore the exciton-associated effect.By means of high-resolution scanning tunneling spectroscopy and quasiparticle interference,we discover an unexpected state residing below the conduction band and right within the CDW gap region.As corroborated by our theoretical analysis,this mysterious phenomenon is in good agreement with the electron-exciton coupling.Our study provides a material platform to explore exciton-based electronics and opto-electronics.展开更多
基金the National Key Research and Development Program of China(Grant Nos.2021YFA1400403,2018YFA0306800,2019YFA0210004,and 2016YFA0300401)the National Natural Science Foundation of China(Grant Nos.92165205,11774149,11790311,11774154,11674158,and 12074175)Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)。
文摘Excitons in solid state are bosons generated by electron-hole pairs as the Coulomb screening is sufficiently reduced.The exciton condensation can result in exotic physics such as super-fluidity and insulating state.In charge density wave(CDW)state,1T-TiSe_(2) is one of the candidates that may host the exciton condensation.However,to envision its excitonic effect is still challenging,particularly at the two-dimensional limit,which is applicable to future devices.Here,we realize the epitaxial 1T-TiSe_(2) bilayer,the two-dimensional limit for its 2×2×2 CDW order,to explore the exciton-associated effect.By means of high-resolution scanning tunneling spectroscopy and quasiparticle interference,we discover an unexpected state residing below the conduction band and right within the CDW gap region.As corroborated by our theoretical analysis,this mysterious phenomenon is in good agreement with the electron-exciton coupling.Our study provides a material platform to explore exciton-based electronics and opto-electronics.
