Qiqi Su, Ying Chen, Bingqian Shi, Di Mai, Rucheng Dai, Sergey Ivanov, Matthias Weil, Zengming Zhang, Huayun Geng*, Peter Lazor*, Lei Liu*

Cite this article: https://doi.org/10.1016/j.cjsc.2026.101057

Publication date:

Keywords: Pressure engineering; Bandgap reduction; Structural phase transition; Jahn-Teller effect; Tellurate oxides

ABSTRACT

The growing demand for sustainable energy has intensified the search for efficient photovoltaic materials with suitable bandgaps. Multiferroic oxides (M3TeO6) have emerged as promising candidates for solar-energy harvesting due to their structural flexibility and strong electron-lattice coupling. However, a unified physical understanding of their pressure-dependent bandgap evolution-particularly the role of Jahn-Teller effects (JTE) remains elusive. In this work, we investigate the structural and electronic evolution of Cu3TeO6 as a function of pressure using synchrotron-based X-ray diffraction, Raman spectroscopy, and UV-vis absorption techniques. We discovered a complicated bandgap response of Cu3TeO6, characterized by an initial widening followed by a sharp collapse, corresponding to the sequential phase transitions Ia $$ → Ibca → P2/m. The low-bandgap state of Cu3TeO6 (∼2.28 eV) is quenchable to ambient pressure. This bandgap behavior of Cu3TeO6 can be rationalized by the competition between octahedral distortion and bond-length compression. At low pressures, octahedral tilting may reduce effective orbital overlap, widening the bandgap, whereas at high pressures, Cu–O shortening is expected to enhance Cu 3d–O 2p wave-function overlap, triggering the bandgap collapse. By comparing M3TeO6 systems (M = Mn, Co, Cu) with varying Jahn-Teller strengths, we suggest that compression energy is partitioned differently across these materials. In strong-JTE compounds, a significant portion of the applied pressure is consumed in suppressing Jahn-Teller distortions, thereby delaying structural transitions and moderating the rate of bandgap collapse. These findings provide a useful working framework for understanding pressure-dependent bandgap evolution in representative M3TeO6 tellurates and underscore the utility of high pressure as a controllable tool for rational bandgap tuning in multifunctional and correlated oxide materials.