Hot carrier decay dynamics of van der Waals room temperature ferroelectric α-In₂Se₃

In this study, we investigated the hot carrier decay dynamics of two-dimensional room temperature ferroelectric α-In₂Se₃via femtosecond transient optical spectroscopy. The photo-excited hot carriers in α-In₂Se₃ decay via electron-phonon coupling (τ₁) and inter-layer charge transfer (τ₂). We observe a change in the slope of the τ₁^-1-T curve near 145 K, which indicates the change in temperature-dependent phonon excitation of α-In₂Se₃. Below 145 K, the dephase rate τ₂^-1 shows an unusual temperature dependence, τ₂^-1 ∝ T^-1, while it exhibits a linear increase with temperature above 145 K. The temperature-dependent variation of hot-carrier decay in α-In₂Se₃ near 145 K may be related to a hidden phase transition. The dephase rate (τ₁^-1) exhibits a stronger temperature dependence below 145 K than above 145 K, which may arise from the more pronounced temperature dependence of optical phonon excitation at lower temperatures.