Nonequilibrium electron and lattice dynamics of Sb2Te3 under pressure

Abstract

Combined measurements including Raman scattering and optical pump-probe spectroscopy (OPPS) are carried out to investigate the lattice and electron dynamics of ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ under hydrostatic pressures. The pressure evolutions of nonequilibrium photocarrier dynamics, containing the hot electron relaxations and coherent acoustic phonons, have been accessed up to 30 GPa. With increasing pressure, the Raman vibrations and electron relaxations manifest anomalies around 3 GPa and 5 GPa, indicating the sudden changes of electron-phonon couplings across the electronic topological transition (ETT) and semiconductor-semimetal transition (SST). Especially, the OPPS reveals that the hot phonon bottleneck is effectively suppressed along with the onset of ETT, which is likely due to the abrupt increase in the density of state and the number of energy valley in conduction band, basing on the calculated electronic and lattice structures. Furthermore, a comprehensive phase diagram of ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ composed with ETT, SST, as well as the additional three high-pressure structures and a mixture phase has been distinguished according to the pressure behavior of OPPS. Our paper not only develop understandings for the interactions between electron and lattice in ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$, but also may provide a strategy to probe the electronic topological changes under pressure.