Raman Spectroscopic Study on Bi2Rh3Se2: Two-dimensional-Ising Charge Density Wave and Quantum Fluctuations

TL;DR

This study uses Raman spectroscopy to investigate the charge density wave state in Bi2Rh3Se2, revealing 2D Ising critical behavior, quantum fluctuations, and strong electron-phonon coupling, advancing understanding of CDW mechanisms.

Contribution

It provides the first systematic Raman analysis of Bi2Rh3Se2, demonstrating the role of 2D Ising criticality and quantum fluctuations in its CDW state.

Findings

Identification of a collective amplitude mode at 39 cm-1 associated with CDW.

Temperature dependence of Raman features consistent with 2D Ising critical behavior.

Evidence of strong electron-phonon coupling influencing CDW formation.

Abstract

The ternary chalcogenide Bi2Rh3Se2 was found to be a charge density wave (CDW) superconductor with a 2*2 periodicity. The key questions regarding the underlying mechanism of CDW state and its interplay with lattice and electronic properties remains to be explored. Here, based on the systematic Raman scattering investigations on single crystalline Bi2Rh3Se2, we observed the fingerprinting feature of CDW state, a collective amplitude mode at 39 cm-1. The temperature evolution of Raman shift and line width for this amplitude mode can be well described by the critical behavior of two-dimensional (2D) Ising model, suggesting the interlayer interactions of Bi2Rh3Se2 is negligible when CDW state is formed, as a consequence, the quantum fluctuations play an important role at low temperature. Moreover, temperature dependence of Raman shift for Ag9 mode deviates significantly from the expected anharmonic behavior when approaching the CDW transition temperature 240 K, demonstrated that strong electron-phonon coupling plays a key role in the formation of CDW. Our results reveal that Bi2Rh3Se2 is an intriguing quasi-2D system to explore electronic quantum phase transition and modulate the correlations between CDW and superconductivity.