Charge density waves in pyrochlore crystallite encapsulated by an amorphized matrix

Charge-density waves (CDWs) are symmetry-broken quantum states characterized by periodic modulations of electron density. While the Peierls’ distortion model has effectively described CDW dynamics in low-dimensional systems and cryogenic temperatures, robust evidence for CDW in three-dimensional (3D) systems and under ambient conditions are thin, and the mechanisms driving such condensate are still under debate. Here, we observe pressure-induced CDWs in Lu ₂ Ti ₂ O ₇ crystallite encapsuled by an amorphous matrix, representing a class of 3D systems featuring both ordered and disordered structures. Raman spectroscopy revealed a stable low-energy excitation mode emerging above 31.2 GPa, coinciding with a cubic-to-monoclinic symmetry-breaking transition identified by synchrotron X-ray diffraction. This mode persisted upon decompression to ambient pressure and strengthened at low-temperature, yet remained insensitive to external magnetic fields. High-resolution transmission electron microscopy uncovers a unique microstructure comprising nanometer-sized Lu ₂ Ti ₂ O ₇ crystallites coexisted with the amorphized matrix, and confirmed a (2×2) commensurate CDW-modulated superstructure via selected area electron diffractions. These findings highlight a pressure-induced CDW dynamics in a 3D pyrochlore that survives decompression, and demonstrate the potential of partially amorphized structures for hosting unconventional quantum critical behaviors.