Raman spectroscopy study of pressure-induced phase transitions in single crystal CuInP2S6

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Chemistry

Background:

• Two-dimensional (2D) ferroic materials possess tunable functional properties influenced by external stimuli like temperature and pressure.
• Copper indium phosphorus disulfide (CuInP2S6) is a layered ferrielectric material at room temperature, with properties arising from ordered Cu+ and In3+ cations within a (P2S6)4- backbone.

Purpose of the Study:

• To investigate the structural and electronic responses of CuInP2S6 single crystals under hydrostatic pressure.
• To identify pressure-induced phase transitions and their impact on the material's properties.

Main Methods:

• Detailed Raman spectroscopy was employed to study the effects of hydrostatic pressure on CuInP2S6 single crystals.
• Analysis focused on changes in Raman peak frequencies, intensities, and widths across different pressure regimes.

Main Results:

• Four distinct high-pressure regimes were identified through Raman spectroscopy.
• A monoclinic-trigonal phase transition occurred at approximately 5 GPa.
• Raman peak sharpening (5-12 GPa) indicated electronic structure modifications, followed by an incommensurate phase (12-17 GPa), and bandgap reduction above 17 GPa.
• The material fully recovered its original state upon decompression, demonstrating the reversibility of pressure-induced changes.

Conclusions:

• Hydrostatic pressure is an effective tool for tuning the electronic and ferrielectric properties of CuInP2S6.
• The observed reversible phase transitions and electronic structure modifications highlight the potential for pressure-controlled applications of 2D ferroic materials.