The integration of high-pressure physics with ultrafast spectroscopy has recently opened a new academic cutting-edge frontier—high-pressure ultrafast dynamics—that explores the non-equilibrium ultrafast condensed matter physics under high-pressure extreme conditions. Ultrafast pump-probe spectroscopy, with its unique ultrafast temporal resolution, has been widely applied to investigate intrinsic non-equilibrium properties above the Fermi surface, such as ultrafast quasiparticle dynamics, electron-phonon coupling, coherent bosonic excitations, and laser-induced novel quantum states. Meanwhile, the intrinsic properties of correlated quantum materials often manifest only at low temperatures (e.g., liquid helium or nitrogen temperature regimes), such as superconducting phase transitions and multi-degree-of-freedom coupling phenomena, demanding the incorporation of low-temperature experimental conditions. Achieving high-pressure ultrafast dynamics studies spanning from liquid helium to room temperatures would significantly advance this field, holding profound scientific implications.

Recently, the research team led by Prof. Zhao Jimin from the Surface Physics Laboratory (SF10i Group) at the Institute of Physics, Chinese Academy of Sciences (CAS)/Beijing National Laboratory for Condensed Matter Physics, in collaboration with partners, designed and developed a low-temperature on-site in situ high-pressure ultrafast spectroscopy instrument that functions under liquid helium cryogenic conditions, successfully realizing this vision. This instrument integrates diamond anvil cell (DAC) high-pressure technology, liquid helium-to-room temperature control, and femtosecond time-resolved spectroscopy, enabling critical studies of non-equilibrium excited-state behaviors in condensed matter. The emerge of high-pressure ultrafast dynamics as a new science is ground-breaking. It plays a pivotal role in understanding the high-pressure-induced non-equilibrium ultrafast dynamics, phase transitions, and the advancement of high-pressure ultrafast science.

On-site in situ means the sample remains stationary during the pressure and temperature variations, ensuring data reliability and precision. A double-gas-membrane technology overcomes pressure drift caused by temperature variations, enabling precise independent control of pressure and temperature. Key innovations include: (1) Double-membrane gas-tuning high-pressure (DMGT) technology, (2) A DAC-compatible home-designed double-windowed cryostat (DAC-cryostat), (3) A relay lens confocal mapping system (CFM) for extended focal-length monitoring. To validate the instrument’s performance and reliability, ultrafast dynamics data were collected for multiple quantum material samples, with partial results already published.

This research was recently published in Review of Scientific Instruments [Rev. Sci. Instrum. 96, 013004 (2025)] with the title “Low-temperature on-site in situ high-pressure ultrafast pump-probe spectroscopy instrument” and featured as the cover story of Physics (Issue 1, 2025, Chinese). Ph.D. student Jiazila Hasain is the first author, with her Advisor Prof. Zhao Jimin being the corresponding author. Contributions include co-author Dr. Zhou Faran and high-pressure sample loading technique support from Shan Pengfei (supervised by Prof. Cheng Jinguang (EX6 Group), now a postdoc at the Beijing High Pressure Science Research Center). Funding was provided by the National Key R&D Program of China (MOST), CAS Youth Innovation Promotion Association, and Beijing Natural Science Foundation.

Article link: https://doi.org/10.1063/5.0233958. 《Physics》Cover Story: www.wuli.ac.cn.