Lattice-Vibration-Induced High-Frequency Phonons Enhance Spin Dynamics in Ruddlesden-Popper Cs2GeI2Cl2/InSe Heterostructure.

The phenomenon of intriguing Rashba spin splitting, which is driven by intrinsic structural symmetry breaking and spin-orbit coupling (SOC), has been observed in various perovskite materials. However, it remains unclear how phonon vibrational frequency affects spin carrier dynamics in two-dimensional perovskites exhibiting the Rashba effect. A thorough exploration of the electronic structures and the mechanism behind the strain-induced lattice vibration on spin dynamics in Ruddlesden-Popper (RP) Cs2GeI2Cl2/InSe heterostructure is presented herein, based on nonadiabatic molecular dynamics (NAMD) simulations with spin-orbit coupling (SOC) and density functional theory. Remarkably, the bandgap magnitudes and the extent of spin splitting within the Cs2GeI2Cl2/InSe heterostructure has been significantly increased under compressive strain (ε = -4%). This enhancement is attributed to the decrease of the in-plane Ge-Cl bond length, which results in stronger Coulomb interaction and increased distortion of the [GeI2Cl4]4- octahedral. When applying compressive strain on the heterostructure, more high frequency phonons (200-1000 cm-1) participate in carrier relaxation process, leading to ultrafast spin dynamics (310.01 fs). The frozen phonons NAMD results show that high-frequency phonons promote carrier transfer more than low-frequency phonons in the 2D perovskite-based heterostructure. Interestingly, the Rashba spin dynamics also can be manipulated by the temperature, revealing that the phonon vibrational frequency is temperature-dependent. These findings highlight the importance of high-frequency phonons on Rashba spin dynamics in perovskite-based photoelectronic devices.