Ultrafast dynamics in photo-excited Mott insulator Sr3Ir2O7 at high pressure

High-pressure ultrafast dynamics, as a new crossed research direction, are sensitive to subtle non-equilibrium state changes that might be unresolved by equilibrium states measurements, providing crucial information for studying delicate phase transitions caused by complex interactions in Mott insulators. With time-resolved transient reflectivity measurements, we identified the new phases in the spin-orbit Mott insulator Sr3Ir2O7 at 300 K that was previously unidentified using conventional approaches such as x-ray diffraction. Significant pressure-dependent variation of the amplitude and lifetime obtained by fitting the reflectivity Delta R/R reveal the changes of electronic structure caused by lattice distortions, and reflect the critical phenomena of phase transitions. Our findings demonstrate the importance of ultrafast nonequilibrium dynamics under extreme conditions for understanding the phase transition of Mott insulators.