Two Novel High-Pressure Probing Techniques: High-Pressure Ultrafast Spectroscopy and Quantum Sensing with Nitrogen-Vacancy Centers in Diamond

Pressure is a fundamental thermodynamic parameter for tuning the electronic structure and interactions in quantum materials. However, the enclosed geometry of diamond anvil cells has long constrained in-situ measurement capabilities under high pressure. In recent years, two emerging technologies—high-pressure ultrafast spectroscopy and quantum sensing with nitrogen-vacancy centers in diamond—have overcome this limitation in the temporal and spatial dimensions, respectively. The former utilizes femtosecond pump-probe measurements of quasiparticle relaxation and coherent collective excitations to identify structural phase transitions and electronic topological transitions under pressure, and to quantitatively extract density wave gaps, superconducting gaps, and electron-phonon coupling strengths. The latter integrates atomic-scale spin probes with diamond anvil cells to achieve micrometer-scale in-situ imaging of magnetic fields and stress, providing highly sensitive and spatially resolved detection means for magnetic phase transitions and superconducting transitions under high pressure. This article systematically introduces the experimental principles, analytical methods, and representative applications of both techniques, and discusses their synergistic prospects in the study of high-pressure quantum materials.