Exploring structural and electronic responses of transition metal perovskite chalcogenides at high pressure*

Transition metal perovskite chalcogenides are emerging semiconductors with rich tunability and functionality for a wide range of optoelectronic and photonic applications. Applying an external pressure is a powerful way to finely tune the structural and electronic properties of materials and probe their mechanical stability. Here, we investigate the high-pressure behavior of a Strontium Titanium Sulfide perovskite with chemical formula Sr_9/8TiS₃. Its structure features quasi-1D chains of face-shared TiS₆ octahedra aligned along a 6-fold rotational axis, housing Sr cations in interstitial spaces. Exploiting complementary experimental techniques, we examine the resilience of the Sr_9/8TiS₃ structure and electronical properties, up to megabar pressure. Although Raman spectra reveal local distortions below 20 GPa, no amorphization is observed in X-ray diffraction data up to 100 GPa. Low-temperature resistivity experiments and infrared measurements show that the semiconductor behavior persists despite bandgap reduction. These results highlight how external pressure helps uncover the structure-properties relationship in this class of semiconductors.