The structural, vibrational, and optical properties of ${\mathrm{Rb}}_2{\mathrm{TeBr}}_6$ have been investigated under high pressure using synchrotron x-ray diffraction, Raman spectroscopy, photoluminescence (PL), and optical absorption measurements. At ambient conditions, ${\mathrm{Rb}}_2{\mathrm{TeBr}}_6$ crystallizes in the cubic Fm-3m structure, which remains stable below 8.0 GPa. Our x-ray diffraction analyses reveal that in the parent cubic phase, subtle interoctahedral rotations develop, producing a localized deviation from the ideal cubic framework. This local asymmetry facilitates radiative recombination, leading to a pronounced enhancement of PL intensity up to 2.4 GPa. The gradual increase in phonon lifetime till about the same pressure as observed in Raman measurements corroborates an electronic transition. Above this pressure point, broadening in the widths of the Raman modes indicates an increase in the phonon scattering processes, leading to enhancement of nonradiative relaxation channels resulting in gradual PL quenching. Additionally, the PL intensity increases upon the application of a weak external magnetic field. A structural transition to the orthorhombic Pnnm phase occurs at around 8.0 GPa, followed by a monoclinic $\mathrm{P}{2}_1/m$ phase at around 10.7 GPa, and eventual amorphization at 25.5 GPa. Optical absorption spectra reveal continuous narrowing of the band gap upon compression. These findings demonstrate the strong coupling among lattice dynamics, electronic structure, and optical response in ${\mathrm{Rb}}_2{\mathrm{TeBr}}_6$, underscoring its potential as a pressure-tunable optoelectronic material.

Close

PrevNext

View figure in article

• High-pressure studies
• Structural phase transition
• Optical absorption spectroscopy
• Photoluminescence
• Raman spectroscopy