Ab initio nonadiabatic molecular dynamics study on spin–orbit coupling induced spin dynamics in ferromagnetic metals

Understanding the photoexcitation induced spin dynamics in ferromagnetic metals is important for the design of photo-controlled ultrafast spintronic device.In this work,by the ab initio nonadiabatic molecular dynamics simulation,we have studied the spin dynamics induced by spin–orbit coupling(SOC)in Co and Fe using both spin-diabatic and spin-adiabatic representations.In Co system,it is found that the Fermi surface(E_(F))is predominantly contributed by the spin-minority states.The SOC induced spin flip will occur for the photo-excited spin-majority electrons as they relax to the E_(F),and the spin-minority electrons tend to relax to the EFwith the same spin through the electron–phonon coupling(EPC).The reduction of spin-majority electrons and the increase of spin-minority electrons lead to demagnetization of Co within100 fs.By contrast,in Fe system,the E_(F) is dominated by the spin-majority states.In this case,the SOC induced spin flip occurs for the photo-excited spin-minority electrons,which leads to a magnetization enhancement.If we move the E_(F) of Fe to higher energy by 0.6eV,the E_(F) will be contributed by the spin-minority states and the demagnetization will be observed again.This work provides a new perspective for understanding the SOC induced spin dynamics mechanism in magnetic metal systems.

Exact solution of slow quench dynamics and nonadiabatic characterization of topological phases

Previous studies have shown that the bulk topology of single-particle systems can be captured by the band inversion surface or by the spin inversion surface emerging on the time-averaged spin polarization.Most of the studies,however,are based on the single-particle picture even though the systems are fermionic and multi-bands.Here,we study the slow quench dynamics of topological systems with all the valence bands fully occupied,and show that the concepts of band inversion surface and spin inversion surface are still valid.More importantly,the many-particle nonadiabatic quench dynamics is shown to be reduced to a new and nontrivial three-level Landau-Zener model.This nontrivial three-level Landau-Zener problem is then solved analytically by applying the integrability condition and symmetry considerations,and thus adds a new member to the few models that are exactly solvable.Based on the analytical results,the topological spin texture revealed by the time-averaged spin polarization can be applied to characterize the bulk topology and thus provides a direct comparison for future experiments.

On-the-Fly Nonadiabatic Dynamics of Caffeic Acid Sunscreen Compound

As a widely-used sunscreen com-pound,the caffeic acid(CA)shows the strong UV absorption,while the photoinduced reaction mecha-nisms behind its photoprotection ability are not fully understood.We try to investigate the photoin-duced internal conversion dynam-ics of CA in order to explore the photoprotection mechanism.The most stable CA isomer is selected to examine its nonadiabatic dy-namics using the on-the-fly surface hopping simulations at the semi-empirical level of electronic-struc-ture theory.The dynamics starting from different electronic states are simulated to explore the dependence of the photoinduced reaction channels on the excitation wavelengths.Several S1/S0 conical intersections,driven by the H-atom detachments and the ring deformations,have been found to be responsible for the nonadiabatic decay of the CA.The simulation re-sults show that the branching ratios towards these intersections are modified by the light with different excitation energies.This provides the valuable information for the understanding of the photoprotection mechanism of the CA compound.

The instability of electrostatic wave in a magnetized dusty plasma with nonadiabatic dust charge fluctuation

The effects of external magnetized field and nonadiabatic dust charge fluctuation on instability of wave incorporating the nonthermally distributed ions and the temperatures of ion and dust in dusty plasmas are investigated. A linear dispersion relation is obtained. The numerical results show that the external magnetized field, fast ions and nonadiabatic dust charge fluctuation have strong influence on the frequency and the damping of wave.

A Theoretical Study on Nonadiabatic Trapping Models of the Reaction NH+H←→N+H_2

The properties of nonadiabatic trapping models of the reaction NH+H -N+H, are investigated in a collinear model as \veil as a non-collinear thermal reaction on the basis of theintrinsic reaction coordinate (IRC) intbrmation obtained by ah initio calculations at QCISD/631 IG** ie\el. Using the unitied statistical theory fornonadiabatic trapping models. the thermal rateconstants over the temperature range of 2000-3000K are computed which are in excellent agreementwith the experiment results.

Nonadiabatic Effect on the Rescattering Trajectories of Electrons in Strong Laser Field Ionization Process

The important features of the rescattering trajectories in strong field ionization process such as the cutoff of the return energy at 3.17Up and that of the final energy at 10Up are obtained, based on the adiabatic approximation in which the initial momentum of the electron is assumed to be zero. We theoretically study the nonadiabatic effect by assuming a nonzero initial momentum on the rescattering trajectories based on the semiclassical simpleman model. We show that the nonzero initial momentum will modify both the maximal return energy at collision and the final energy after backward scattering, but in different ways for odd and even number of return trajectories. The energies are increased for even number of returns but are decreased for odd number of returns when the nonzero （positive or negative） initial momentum is applied.

Nonadiabatic Population Transfer in a Tangent-Pulse Driven Quantum Model

Fine control of the dynamics of a quantum system is the key element to perform quantum information processing and coherent manipulations for atomic and molecular systems. We propose a control protocol using a tangentpulse driven model and demonstrate that it indicates a desirable design, i.e., of being both fast and accurate for population transfer. As opposed to other existing strategies, a remarkable character of the present scheme is that high velocity of the nonadiabatic evolution itself not only will not lead to unwanted transitions but also can suppress the error caused by the truncation of the driving pulse.

AN IMPROVED NONADIABATIC COLLISION MODEL FOR ION-PIR FORMATION PROCESS:A+BC→A^++BC^- Zheng Ting CAI and Yu Guang MU

Hickman's fast nonadiabatic collision model for the ion-pair formation reaction A+BC→A^++BC^- was improved,where the classical trajectory has been represented by solution of motion equation UR=-dV(R)/dR, here V(R)is Morse potential.Employing this model to the CS+O_2→CS^++O_2^-reaction,a satisfactory agreement with experimental data has been obtained.

Linear and nonlinear excitations in complex plasmas with nonadiabatic dust charge fluctuation and dust size distribution

Both linear and nonlinear excitation in dusty plasmas have been investigated including the nonadiabatic dust charge fluctuation and Gaussian size distribution dust particles. A linear dispersion relation and a Korteweg-de Vries-Burgers equation governing the dust acoustic shock waves are obtained. The relevance of the instability of wave and the wave evolution to the dust size distribution and nonadiabatic dust charge fluctuation is illustrated both analytically and numerically. The numerical results show that the Gaussian size distribution of dust particles and the nonadiabatic dust charge fluctuation have strong common influence on the propagation of both linear and nonlinear excitations.

Nonadiabatic dynamics of electron injection into organic molecules

We numerically investigate the injection process of electrons from metal electrodes to one-dimensional organic molecules by combining the extended Su Schrieffer Heeger （SSH） model with a nonadiabatic dynamics method. It is found that a match between the Fermi level of electrodes and the highest occupied molecular orbital （HOMO） or the lowest unoccupied molecular orbital （LUMO） of organic molecules can be greatly affected by the length of the organic chains, which has a great impact on electron injection. The correlation between oligomers and electrodes is found to open more efficient channels for electron injection as compared with that in polymer/electrode structures. For oligomer/electrode structures, we show that the Schottky barrier essentially does not affect the electron injection as the electrode work function is smaller than a critical value work-function electrode. For polymer/electrode structures This means that the Schottky barrier is pinned for a small we find that it is possible for the Fermi level of electrodes to be pinned to the polaronic level. The condition under which the Fermi level of electrodes exceeds the polaronic level of polymers is shown to not always lead to spontneous electron transfer from electrodes to polymers.

进器官的分子的电子注射的 Nonadiabatic 动力学

We numerically investigate the injection process of electrons from metal electrodes to one-dimensional organic molecules by combining the extended Su–Schrieffer–Heeger (SSH) model with a nonadiabatic dynamics method. It is found that a match between the Fermi level of electrodes and the highest occupied molecular orbital (HOMO) or the lowest unoccupied molecular orbital (LUMO) of organic molecules can be greatly affected by the length of the organic chains, which has a great impact on electron injection. The correlation between oligomers and electrodes is found to open more efficient channels for electron injection as compared with that in polymer/electrode structures. For oligomer/electrode structures, we show that the Schottky barrier essentially does not affect the electron injection as the electrode work function is smaller than a critical value. This means that the Schottky barrier is pinned for a small work-function electrode. For polymer/electrode structures, we find that it is possible for the Fermi level of electrodes to be pinned to the polaronic level. The condition under which the Fermi level of electrodes exceeds the polaronic level of polymers is shown to not always lead to spontaneous electron transfer from electrodes to polymers.

Polaron-assisted nonadiabatic dynamics in protonated TiO_(2) with surface water molecule

We investigated the polaron-assisted nonadiabatic dynamics in protonated TiO_(2),as well as the polaron-H_(2)O coupling and its effects on the relaxation of photogenerated electrons.We observed that different polaron hopping regimes result in varied nonadiabatic couplings and relaxations of excited electrons from the conduction band minimum to the gap states of protonated TiO_(2),with a weak dependence on the actual trapping site of the polaron.Surface-adsorbed H_(2)O molecules can attract polarons toward the adsorbed Ti sites,with the coupling between H_(2)O and the polaron being inversely proportional to their distance.Our findings suggest that the lifetime of the photogenerated charge carriers can be extended by reducing the polaron-H_(2)O distances,with expected benefits to the efficiency of the reduced TiO 2 samples for photocatalytic applications.

Nonadiabatic geometric quantum computation with optimal control on superconducting circuits

Quantum gates,which are the essent ial building blocks of quantum computers,are very fragile.Thus,to realize robust quanturm gates with high fidelity is the ultimate goal of quantum manipulation.Here,we propose a nonadiabatic geometric quantum computation scheme on superconducting circuits to engineer arbitrary quantum gates,which share both the robust merit of geometric phases and the capacity to combine with optimal control technique to further enhance the gate robustness.Specif-ically,in our proposal,arbitrary geometric single-qubit gates can be realized on a transmon qubit,by a resonant microwave field driving,with both the amplitude and phase of the driving being time-dependent.Meanwhile,nontrivial two-qubit gometric gates can be implemented by two capacitively coupled transmon qubits,with one of the transmon qubits'frequency being modulated to obtain ef-fective resonant coupling between them.Therefore,our scheme provides a promising step towards fault-tolerant solid-state quantum computation.

Nonadiabatic dynamics and geometric phase of an ultrafast rotating electron spin

The spin in a rotating frame has attracted a lot of attentions recently,as it deeply relates to both fundamental physics such as pseudo-magnetic field and geometric phase,and applications such as gyroscopic sensors.However,previous studies only focused on adiabatic limit,where the rotating frequency is much smaller than the spin frequency.Here we propose to use a levitated nano-diamond with a built-in nitrogen-vacancy(NV)center to study the dynamics and the geometric phase of a rotating electron spin without adiabatic approximation.We find that the transition between the spin levels appears when the rotating frequency is comparable to the spin frequency at zero magnetic field.Then we use Floquet theory to numerically solve the spin energy spectrum,study the spin dynamics and calculate the geometric phase under a finite magnetic field,where the rotating frequency to induce resonant transition could be greatly reduced.

Optimized nonadiabatic holonomic quantum computation based on Förster resonance in Rydberg atoms

In this paper,we propose a scheme for implementing the nonadiabatic holonomic quantum computation(NHQC+)of two Rydberg atoms by using invariant-based reverse engineering(IBRE).The scheme is based on Förster resonance induced by strong dipole-dipole interaction between two Rydberg atoms,which provides a selective coupling mechanism to simply the dynamics of system.Moreover,for improving the fidelity of the scheme,the optimal control method is introduced to enhance the gate robustness against systematic errors.Numerical simulations show the scheme is robust against the random noise in control fields,the deviation of dipole-dipole interaction,the Förster defect,and the spontaneous emission of atoms.Therefore,the scheme may provide some useful perspectives for the realization of quantum computation with Rydberg atoms.

Intermolecular charge-transfer aggregates enable high-efficiency near-infrared emissions by nonadiabatic coupling suppression

Pursuing purely organic materials with high-efficiency near-infrared(NIR) emissions is fundamentally limited by the large nonradiative decay rates(k_(nr)) governed by the energy gap law. To date, reported endeavors to decelerate k_(nr) are mainly focused on reducing the electron-vibration coupling with the electronic nonadiabatic coupling assumed as a constant. Here, we demonstrated a feasible and innovative strategy by employing intermolecular charge-transfer(CT) aggregates(CTA) to realize high-efficiency NIR emissions via nonadiabatic coupling suppression. The formation of CTA engenders intermolecular CT in the excited states;thereby, not only reducing the electronic nonadiabatic coupling and contributing to small k_(nr) for high-efficiency NIR photoluminescence, but also stabilizing excited-state energies and achieving thermally activated delayed fluorescence for highefficiency NIR electroluminescence. This work provides new insights into aggregates and opens a new avenue for organic materials to overcome the energy gap law and achieve high-efficiency NIR emissions.

Role of rotational state-selected for nonadiabatic alignment： OCS molecules in femtosecond laser fields

Nonadiabatic alignment by intense nonresonant the spatial direction of molecules： By solving the the degree of alignment of the molecules initially laser fields is a versatile technique to manipulate time-dependent SchrSdinger equation numerically in different rotational state are calculated and the results show that the degree of alignment strongly depends on the initial rotational state. Thus, the present study indicates that, for obtaining a high degree of alignment for molecules, appropriate selection of molecular rotational states is necessary.

Experimental realization of nonadiabatic holonomic single‐qubit quantum gates with two dark paths in a trapped ion

For circuit-based quantum computation,experimental implementation of a universal set of quantum logic gates with high-fidelity and strong robustness is essential and central.Quantum gates induced by geometric phases,which depend only on global properties of the evolution paths,have built-in noise-resilience features.Here,we propose and experimentally demonstrate nonadiabatic holonomic single-qubit quantum gates on two dark paths in a trapped ^(171)γδ^(+)ion based on four-level systems with resonant drives.We confirm the implementation with measured gate fidelity through both quantum process tomography and randomized benchmarking methods.Meanwhile,we find that nontrivial holonomic two-qubit quantum gates can also be realized within current experimental technologies.Compared with previous implementations,our experiments share both the advantages of fast nonadiabatic evolution and robustness against systematic errors.Therefore,our experiments confirm a promising method for fast and robust holonomic quantum computation.

An Ab initio Theoretical Study on the Nonadiabatic Coupling for Na+I_2 Collision System

The ionic and neutral state potential energy surfaces (PESs) of Na+I 2 collision system have been calculated on QCISD(T) level by using ab initio method. The location and depth of the potential well, the collision radius and their fine structures have been analyzed at the equilibrium geometry of I 2 molecule. The electronic transfer probabilities are also calculated in terms of Landau Zener model. The lifetime of scattering resonance state is evaluated by the uncertainty principle. All the results have been compared with those obtained according to the Aten Lanting Los PES and Feng's PES.

Nonadiabatic collision model calculations of ion-pair formation cross sections of Cs+O2→Cs++O2-

This paper has improved Hickman's nonadiabatic collision model by substituting Hickman's constant velocity classical straight line trajectory approximation with the solution of motion equation mR=-dV(R)/dR, and has calculated the cross sections of ion-pair formation Cs+O2 -Cs++O2- with the improved nonadiabatic collision model (INCM). A comparison of our results with other theoretical and experimental results has been made.