Revealing subterahertz atomic vibrations in quantum paraelectrics by surface-sensitive spintronic terahertz spectroscopy

• DOI: 10.1126/sciadv.ads8601
• Publication Date: 2024-11-29T18:58:27Z
• Authors: Zhaodong Chu; Junyi Yang; Yan Li; Kyle Hwangbo; Jianguo Wen; Ashley R. Bielinski; Qi Zhang; Alex B. F. Martinson; Stephan O. Hruszk...; Dillon D. Fong; Xiaodong Xu; Michael R. Norman; Anand Bhattacharya; Haidan Wen
• Keywords: Surface phonon

Understanding surface collective dynamics in quantum materials is crucial for advancing technologies. For example, phonon modes paraelectrics are thought to be essential facilitating interfacial superconductivity. However, detecting these modes, especially below 1 terahertz, challenging because of limited sampling volumes and the need high spectroscopic resolution. Here, we report soft transverse optical (TO1) KTaO 3 SrTiO by surface-sensitive spintronic terahertz spectroscopy that can sense only a few nanometers deep from surface. In , TO1 mode softens sharpens with decreasing temperature, leveling off at 0.7 terahertz. contrast, this broadens substantially paraelectric crossover coincides hardening sub–milli–electron volt related antiferrodistortive transition. These observations deviate their bulk properties may have implications superconductivity ferroelectricity. The developed technique opens opportunities sensing low-energy excitations.