Lattice Dynamics and Electron-Phonon Coupling in Double Perovskite Cs₂NaFeCl₆

Area of Science:

• Materials Science
• Solid State Physics
• Spectroscopy

Background:

• Phonon-phonon and electron/exciton-phonon coupling are critical for the thermal, electronic, and optical properties of metal halide perovskites.
• Understanding these interactions is key to optimizing perovskite materials for various applications.

Purpose of the Study:

• To evaluate phonon anharmonicity and electron-phonon coupling in novel double perovskite Cs2NaFeCl6 single crystals.
• To elucidate the role of vibrational excitations in the electronic properties of this material.

Main Methods:

• Comprehensive Raman spectroscopy measurements.
• First-principles theoretical calculations.
• Analysis of temperature-dependent Raman modes and resonant multiphonon Raman scattering.

Main Results:

• Identified four Raman-active vibrational modes and confirmed Fm-3m lattice symmetry.
• Demonstrated high phonon anharmonicity through temperature-dependent Raman mode analysis.
• Revealed strong electron-phonon coupling via resonant multiphonon Raman scattering and Urbach tail analysis, evidenced by intense nA1 overtones and calculated Fröhlich coupling constant.

Conclusions:

• Phonon-phonon and electron-phonon interactions significantly influence the electronic properties of Cs2NaFeCl6.
• The findings highlight the importance of these coupling mechanisms for the potential applications of this novel double perovskite material.