Angle-Resolved Photoemission Spectroscopy Study On Electronic Structure Of The Charge Density Wave Superconductor Bi₂Rh₃Se₂

The relationship between charge density waves and superconductivity has been drawing tremendous attention.Their respective electroacoustic couplers often exhibit competition.Meanwhile,they show coexistence in some high-temperature superconductors and TMDCs.Therefore,the microscopic physical effects here are worth studying.Moreover,the emergence of ternary charge density wave superconductor Bi₂Rh₃Se₂ provides an ideal research platform for this.In addition,there has been controversy over whether Bi₂Rh₃Se₂ had a CDW phase transition at 240K.Our work systematically studied the electronic structure of Bi₂Rh₃Se₂ using Angle-Resolved Photoemission Spectroscopy（ARPES）,mainly including the following results:（1）Bi₂Rh₃Se₂ single crystals were prepared by the self-flux method.The samples are characterized by structural and compositional analyses,such as X-ray diffraction and scanning electron microscopy.All the tests suggest the high crystalline quality of samples.The CDW phase transition was also characterized by Raman spectroscopy.（2）We studied the temperature-dependent electron structure of Bi₂Rh₃Se₂ single crystal using Angle-Resolved Photoemission Spectroscopy and obtained a clear Fermi surface and a band dispersion in the high symmetric direction of momentum.The results show:（a）The phase transition that occurs at 240 K is a second-order CDW transition.（b）a 2×2 CDW order in Bi₂Rh₃Se₂,accompanied by the reconstruction of electronic structure,such as band folding,band splitting,and opening of CDW gaps at and away from Fermi level;（c）the existence of electron-phonon coupling,which is manifested as an obvious kink and peak-dip-hump structure in dispersion;（d）the appearance of a flat band;and（e）band structure has multi-orbital properties and circular dichroism.Our observations thus enable us to shed light on the nature of the CDW order and its interplay with superconductivity in Bi₂Rh₃Se₂.