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

TL;DR

This study uses angle-resolved photoemission spectroscopy to confirm a second-order charge density wave transition at 240 K in Bi$_2$Rh$_3$Se$_2$, revealing electronic structure reconstruction and electron-phonon coupling, shedding light on its interplay with superconductivity.

Contribution

The paper provides direct experimental evidence of a 2x2 CDW order and electron-phonon coupling in Bi$_2$Rh$_3$Se$_2$, clarifying the nature of its phase transition.

Findings

Confirmation of a second-order CDW transition at 240 K.

Observation of electronic structure reconstruction including band folding and gaps.

Detection of electron-phonon coupling features such as dispersion kinks.

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$_2$.