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Hybrid organic–inorganic perovskites (HOIPs) have emerged as a promising class of materials for optoelectronic and spintronic applications. Layered two-dimensional (2D) HOIP variants have received considerable attention, primarily due to their unique properties that can be modulated through the tailored selection of both organic and inorganic components. The spin splitting in the band structure due to the strong spin–orbit coupling is one of the most intriguing properties of such 2D HOIPs materials for their potential utility in spintronics. In addition to observing the spin splitting in equilibrium due to the non-centrosymmetric structure, the possibility of having dynamic spin splitting at room temperature of the otherwise centrosymmetric systems has become a topic of great debate. While modern first-principles molecular dynamics (FPMD) simulation is able to address such a question in principle by taking into account the lattice anharmonicity in electronic structure calculation, the finite-size error poses a great challenge in practice. In this work, we employ a machine learning (ML) model to overcome this practical limitation to investigate the dynamic spin splitting in phenylethyl ammonium lead iodide 2D HOIP. Specifically, we use the deep potential molecular dynamics approach [Zeng et al., J. Chem. Phys. 159(5), 054801 (2023)] for ML FPMD simulation, and we also develop a surrogate model for predicting the spin splitting based on the recent finding that relates the spin splitting to structural descriptors in 2D HOIPs. Our work shows that even in globally centrosymmetric structures, the inclusion of lattice anharmonicity can induce dynamic spin splitting at room temperature. 

Nonadiabatic Thouless pumping of electrons is studied within the framework of topological Floquet engineering, focused on how atomic lattice dynamics affect the emergent Floquet topological phase in polyacetylene under the driving electric field. 

Abstract Plasmon decay is believed to play an essential role in inducing hot carrier transfer at the interfaces between plasmonic nanoparticles and semiconductor surfaces. In this work, we employ real-time time-dependent density functional theory (RT-TDDFT) simulation in the Wannier gauge to gain quantum-mechanical insights into the nonlinear dynamics of the plasmon decay in the Ag₂₀nanoparticle at a semiconductor surface. The first-principles simulations show that the plasmon decay is more than two times faster when the Ag₂₀nanoparticle is adsorbed on a hydrogen-terminated Si(111) surface, taking place within 100 femtoseconds of the plasmon excitation. Hot carrier transfer across the interface is observed as the plasmon decay takes place, and nearly 30% of holes are generated deep in the valence band of the semiconductor surface. The use of Wannier gauge in RT-TDDFT simulation is particularly convenient for gaining quantum-mechanical insights into non-equilibrium electron dynamics in complex heterogeneous systems. 

The plane-wave pseudopotential (PW-PP) formalism is widely used for the first-principles electronic structure calculation of extended periodic systems. The PW-PP approach has also been adapted for real-time time-dependent density functional theory (RT-TDDFT) to investigate time-dependent electronic dynamical phenomena. In this work, we detail recent advances in the PW-PP formalism for RT-TDDFT, particularly how maximally localized Wannier functions (MLWFs) are used to accelerate simulations using the exact exchange. We also discuss several related developments, including an anti-Hermitian correction for the time-dependent MLWFs (TD-MLWFs) when a time-dependent electric field is applied, the refinement procedure for TD-MLWFs, comparison of the velocity and length gauge approaches for applying an electric field, and elimination of long-range electrostatic interaction, as well as usage of a complex absorbing potential for modeling isolated systems when using the PW-PP formalism. 

We present a novel theoretical formulation for performing quantum dynamics in terms of moments within the single-particle description. By expressing the quantum dynamics in terms of increasing orders of moments, instead of single-particle wave functions as generally done in time-dependent density functional theory, we describe an approach for reducing the high computational cost of simulating the quantum dynamics. The equation of motion is given for the moments by deriving analytical expressions for the first-order and second-order time derivatives of the moments, and a numerical scheme is developed for performing quantum dynamics by expanding the moments in the Taylor series as done in classical molecular dynamics simulations. We propose a few numerical approaches using this theoretical formalism on a simple one-dimensional model system, for which an analytically exact solution can be derived. The application of the approaches to an anharmonic system is also discussed to illustrate their generality. We also discuss the use of an artificial neural network model to circumvent the numerical evaluation of the second-order time derivatives of the moments, as analogously done in the context of classical molecular dynamics simulations.