Charge Density Wave order and electron-phonon coupling in ternary superconductor Bi${}_2$Rh${}_3$Se${}_2$

Abstract

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 at 240 K can be attributed to CDW formation remains controversial. To help resolve the debate, we study the electronic structure study of Bi2Rh3Se2 by angle-resolved photoemission spectroscopy experiments, with emphasis on the nature of its high-temperature phase transition at 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 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 Fermi level; (ii) the existence of electron-phonon coupling, which is manifested as an obvious kink and peak-dip-hump structure in dispersion; and (iii) the appearance of a flat band. Our observations thus enable us to shed light on the nature of the CDW order and its interplay with superconductivity in Bi${}_2$Rh${}_3$Se${}_2$.

5 pages, 5 figures