Charge density wave order and electron-boson coupling in ternary superconductor Bi 2 Rh 3 Se 2

The newly discovered ternary chalcogenide superconductor Bi 2 Rh 3 Se 2 has attracted growing attention, which provides an opportunity to explore the interplay between charge density wave (CDW) order and superconductivity. However, whether the phase transition around 240 K can be attributed to the formation of CDW remains controversial. To help resolve the debate, we study the electronic structure of Bi 2 Rh 3 Se 2 by angle-resolved photoemission spectroscopy, focusing on the nature of its high-temperature phase transition around 240 K. Our measurements demonstrate that the phase transition at 240 K is a second-order CDW phase transition. Our results reveal (i) a 2 × 2 CDW order in Bi 2 Rh 3 Se 2 , accompanied by the reconstruction of electronic structure, such as band folding, band splitting, and opening of CDW gaps at and away from the Fermi level; (ii) the existence of electron-boson coupling, which is manifested as an apparent kink and peak-dip-hump structure in dispersion. Our observations thus enable us to shed light on the nature of CDW order and superconductivity in Bi 2 Rh 3 Se 2 .