Charge density wave order and electron-boson coupling in ternary superconductor Bi2Rh3Se2

The newly discovered ternary chalcogenide superconductor Bi2Rh3Se2 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 Bi2Rh3Se2 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 x 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 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 Bi2Rh3Se2.