High-Pressure Ultrafast Dynamics in Sr2IrO4: Pressure-Induced Phonon Bottleneck Effect**Supported by the National Key Research and Development Program of China (Grant Nos. 2017YFA0303603, 2016YFA0300303, 2018YFA0305703), the National Natural Science Foundation of China (Grant Nos. 11774408, 11574383, 11874075, U1530402), the Strategic Priority Research Program of CAS (Grant No. XDB30000000), the International Partnership Program of Chinese Academy of Sciences (Grant Nos. GJHZ1826, GJHZ1403),

Abstract

By integrating pump-probe ultrafast spectroscopy with diamond anvil cell (DAC) technique, we demonstrate a time-resolved ultrafast dynamics study on non-equilibrium quasiparticle (QP) states in Sr2IrO4 under high pressure. On-site in situ condition is realized, where both the sample and DAC have fixed position during the experiment. The QP dynamics exhibits a salient pressure-induced phonon bottleneck feature at 20 GPa, which corresponds to a gap shrinkage in the electronic structure. A structural transition is also observed at 32 GPa. In addition, the slowest relaxation component reveals possible heat diffusion or pressure-controlled local spin fluctuation associated with the gap shrinkage. Our work enables precise pressure dependence investigations of ultrafast dynamics, paving the way for reliable studies of high-pressure excited state physics.