Organometallic halide perovskites have drawn substantial interest due to their outstanding performance in solar energy conversion and optoelectronic applications. The presence of ferroelectric domain walls these materials has shown a profound effect on electronic structure. Here, we use density-functional-based tight-binding model, coupled nonequilibrium Green's function method, investigate the effects transport properties charge carrier recombination methylammonium lead–iodide perovskite,...

Basing on our hierarchical equations of motion for time-dependent quantum transport [X. Zheng, G. H. Chen, Y. Mo, S. K. Koo, Tian, C. Yam, and J. Yan, Chem. Phys. 133, 114101 (2010)10.1063/1.3475566], we develop an efficient accurate numerical algorithm to solve the Liouville-von-Neumann equation. We real-time evolution reduced single-electron density matrix at tight-binding level. Calculations are carried out simulate transient current through a linear chain atoms, with each represented by...

We establish the dependence of permittivity oxidized ultra-thin silicon films on film thickness by means atomistic simulations within density-functional-based tight-binding (DFTB) theory. This is utmost importance for modeling and extremely thin silicon-on-insulator MOSFETs, evaluating their scaling potential. demonstrate that electronic contribution to dielectric response naturally emerges from DFTB Hamiltonian when coupled Poisson equation solved in vacuum, without phenomenological...

Based on the complex absorbing potential (CAP) method, a Lorentzian expansion scheme is developed to express self-energy. The CAP-based of self-energy employed solve efficiently Liouville-von Neumann equation one-electron density matrix. resulting method applicable for both tight-binding and first-principles models used simulate transient currents through graphene nanoribbons benzene molecule sandwiched between two carbon-atom chains.

Basing on the earlier works hierarchical equations of motion for quantum transport, we present in this paper a first principles scheme time-dependent transport by combining density functional theory (TDDFT) and Keldysh's non-equilibrium Green's function formalism. This is beyond wide band limit approximation directly applicable to case non-orthogonal basis without need transformation. The overlap between lead device region treated properly including it self-energy can be shown that approach...

Time-dependent quantum transport parameters for graphene nanoribbons (GNR) are calculated by the hierarchical equation of motion (HEOM) method based on nonequilibrium Green's function (NEGF) theory [Xie et al., J. Chem. Phys. 137, 044113 (2012)]. In this paper, a new initial-state calculation technique is introduced and accelerated contour integration large systems. Some Lorentzian fitting schemes self-energy matrices developed to effectively reduce number Lorentzians maintain good results....

How far can the miniaturization of metal-oxide-semiconductor field-effect transistors (MOSFETs) continue is a recurring question, essential to all aspects digital technology. Recent claims well-performing MOSFETs with gate lengths below 4 nm apparently defy fundamental limit source-to-drain direct tunneling (SDDT). Here, we investigate that by simulating gate-all-around Si nanowire FETs between 8 and 3 using state-of-the-art atomistic quantum transport modeling. We find at 3-nm length,...

ConspectusPhotovoltaic devices, electrochemical cells, catalysis processes, light emitting diodes, scanning tunneling microscopes, molecular electronics, and related devices have one thing in common: open quantum systems where energy matter are not conserved. Traditionally chemistry is confined to isolated closed systems, while dissipation theory studies systems. The key quantity the reduced system density matrix. As matrix an O(M! × M!) matrix, M number of particles interest, can only be...

Using a simulation protocol that mimics ultrafast scanning tunneling microscopy (STM) experiments, we demonstrate how pump–probe STM may be used to image electron migration in molecules. Two pulses are applied model system, and the time-integrated current through tip is calculated versus delay time position generate images. With suitable pump probe parameters, images can track charge with atomistic spatial femtosecond temporal resolutions.

Quantum interference in cross-conjugated molecules can be utilized to construct molecular quantum effect transistors. However, whether its application achieved depends on the survivability of under real conditions such as nuclear vibration. We use two simulation methods investigate effects vibration a meta-linked benzene system. The results suggest that is robust against not only steady state but also transient dynamics, and thus transistors realized.

Understanding electronic dynamics on material surfaces is fundamentally important for applications including nanoelectronics, inhomogeneous catalysis, and photovoltaics. Practical approaches based time-dependent density functional theory open systems have been developed to characterize the dissipative of electrons in bulk materials. The accuracy reliability such depend critically how structure memory effects surrounding environment are accounted for. In this work, we develop a novel...

Carrier-envelope-phase (CEP) stable optical pulses combined with state-of-the-art scanning tunneling microscopy (STM) can track and control ultrafast electronic currents. On the basis of nonequilibrium Green's function formalism, we present a time frequency domain theoretical study CEP-stable pulse-induced currents between an STM tip metal substrate. It is revealed that experimentally observed phase shift maximum current electric field caused by third-order response to field. The also found...

Recent development of theoretical method for dissipative quantum transport have achieved notable progresses in the weak or strong electron-phonon coupling regime. However, a generalized theory at arbitrary parameter regime is not figured out until now. In this work, variational developed by employing polaron theory. The optimal transformation determined optimization Feynman-Bogoliubov upper bound free energy. % which nature. energy minimization ends up with an mean-field Hamiltonian and...

A new time-domain simulation protocol of two-dimensional electronic spectra with photocurrent detection is presented. Time-dependent density functional theory for open systems at finite temperature applied to evaluate the response four laser pulses, and a non-perturbative phase-matching approach implemented extract fourth-order signal desired condition. Simulations an three-level model indicates that transition dipoles interact resonantly incident pulses different sample-electrode couplings...

We use density-functional-based tight binding theory, coupled to a Poisson solver investigate the dielectric response in oxidized ultra-thin Si films with thickness range of 0.8 10.0 nm. Building on our recent work electronic structure such using same formalism, we demonstrate that contribution permittivity and SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is modeled good accuracy. The simulations agree well available experimental...

Time-dependent quantum transport for graphene nanoribbons (GNR) are calculated by the hierarchical equation of motion (HEOM) method based on nonequilibrium Green's function (NEGF) theory (Xie et.al, J. Chem. Phys. 137, 044113, 2012). In this paper, a new steady state calculation technique is introduced and accelerated contour integration, which suitable large systems. Three Lorentzian fitting schemes self-energy matrices developed nonlinear least square method. Within these schemes, number...