arXiv subjects

Haibo Ma

Publications and source records attributed to Haibo Ma.

17 recordsLinked to original sources

arXiv2026

An Ab initio Framework for Simulating Ultrafast Nonlinear Cavity Quantum Electrodynamics Spectra

In this letter we introduce a theoretical framework for the simulation of ultrafast transient absorption pump-probe spectra of molecular polaritons. We derive and implement the cavity quantum electrodynamics (QED) evolution equations of polaritonic states within the framework of the quasi-classical doorway-Window pproximation, hereto referred cQUEDA /sikeda/. This framework uses outputs from mixed quantum-classical dynamics simulations in the absence of the cavity. Then by including cavity parameters accounting for cavity rate loss, coupling strength, and frequency detuning, we simulate transient absorption pump-probe spectra. Consequently, we address one of the main standing problems of cavity QED, the simulation of polaritons ultrafast dynamics and nonlinear optical properties. We demonstrate the performance of our method by computing the ground-state bleach (GSB), stimulated emission (SE), and excited-state absorption (ESA) contributions of transient absorption pump-probe spectra of pyrazine strongly coupled to a cavity. The cQUEDA is an on-the-fly computationally efficient framework with low computer requirements: the pyrazine calculations, for example, took minutes on modern laptops. cQUEDA offers wide-ranging applicability and can be generalized to model diverse nonlinear spectroscopic signals and quantum optics responses.

physics.optics↗

arXiv2024

Efficient simulation of inhomogeneously correlated systems using block interaction product states

The strength of DMRG lies in its treatment of identical sites that are energetically degenerate and spatially similar. However, this becomes a drawback when applied to quantum chemistry calculations for large systems, as entangled orbitals often span broad ranges in energy and space, with notably inhomogeneous interactions. In this study, we propose addressing strong intra-fragment and weak inter-fragment correlations separately using a multi-configurational block interaction product state (BIPS) framework. The strong correlation is captured in electronic states on fragments, considering entanglement between fragments and their environments. This method has been tested in various chemical systems and shows high accuracy and efficiency in addressing inhomogeneous effects in quantum chemistry.

quant-ph↗

arXiv2021

Stochastic Adaptive Single-Site Time-Dependent Variational Principle

In recent years, the time-dependent variational principle (TDVP) method based on the matrix product state (MPS) wave function formulation has shown its great power in performing large-scale quantum dynamics simulations for realistic chemical systems with strong electron-vibration interactions. In this work, we propose a new stochastic adaptive single-site TDVP (SA-1TDVP) scheme to evolve the bond-dimension adaptively, which can integrate the tra-ditional advantages of both the high efficiency of single-site TDVP (1TDVP) variant and the high accuracy of the two-site TDVP (2TDVP) variant. Based on the assumption that the level statistics of entanglement Hamiltonians, which originate from the reduced density matrices of the MPS method, follows a Poisson or Wigner distribution, as generically predicted by random matrix theory, addi-tional random singular values are generated to expand the bond-dimension automatically. Tests on simulating the vibrationally-resolved quantum dynamics and absorption spectra in the pyrazine molecule and perylene bisimide (PBI) J-aggregate trimer as well as a spin-1/2 Heisenberg chain show that it can be automatic and as accurate as 2TDVP but reduce the computational time remarkably.

cond-mat.str-el↗

arXiv2021

Quantum dynamics simulation of intramolecular singlet fission in covalently linked tetracene dimer

In this work we study singlet fission in tetracene para-dimers, covalently linked by a phenyl group. In contrast to most previous works, we account for the full quantum dynamics of the combined excitonic and vibrational system. For our simulations we choose a numerically unbiased representation of the molecule's wave function enabling us to compare with experiments, exhibiting good agreement. Having access to the full wave function allows us to study in detail the post-quench dynamics of the excitons. Here, one of our main findings is the identification of a time scale $t_0 \approx 35 \text{fs}$ dominated by coherent dynamics. It is within this time scale that the larger fraction of the singlet fission yield is generated. We also report on a reduced number of phononic modes that play a crucial role for the energy transfer between excitonic and vibrational system. Notably, the oscillation frequency of these modes coincides with the observed electronic coherence time $t_0$. We extended our investigations by also studying the dependency of the dynamics on the excitonic energy levels that, for instance, can be experimentally tuned by means of the solvent polarity. Here, our findings indicate that the singlet fission yield can be doubled while the electronic coherence time $t_0$ is mainly unaffected.

cond-mat.mtrl-sci↗

arXiv2020

Charge transfer via deep hole in the J51/N2200 blend

In recently developed non-fullerene acceptor (NFA) based organic solar cells (OSCs), both the donor and acceptor parts can be excited by absorbing light photons. Therefore, both electron transfer and hole transfer channels could occur at the donor/acceptor interface for generating free charge carriers in NFA based OSCs. However, in many molecular and DNA systems, recent studies revealed the high charge transfer (CT) efficiency cannot be reasonably explained by a CT model with only highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of donor and acceptor molecules. In this work, taking an example of a full-polymer blend consisting of benzodithiophenealt-benzotriazole copolymers (J51) as donor and naphthalene diimide-bithiophene (N2200) as acceptor, in which the ultrafast hole transfer has been recently reported, we investigate its CT process and examine the different roles of various frontier molecular orbitals. Through a joint study of quantum mechanics electronic structure calculation and nonadiabatic dynamics simulation, we find the hole transfer between HOMOs of J51 and N2200 can hardly happen but the hole transfer from HOMO of N2200 to HOMO-1 of J51 is much more efficient. This points out the underlying importance of deep hole channel in CT process and indicates that including frontier molecular orbitals (FMOs) other than HOMOs and LUMOs is highly necessary to build a robust physical model for studying CT process in molecular optoelectronic materials.

physics.chem-ph↗

arXiv2020

Multi-Reference Epstein-Nesbet Perturbation Theory with Density Matrix Renormalization Group Reference Wavefunction

The accurate electronic structure calculation for strongly correlated chemical systems requires an adequate description for both static and dynamic electron correlation, and is a persistent challenge for quantum chemistry. In order to account for static and dynamic electron correlations accurately and efficiently, in this work we propose a new method by integrating the density matrix renormalization group (DMRG) method and multi-reference second-order Epstein-Nesbet perturbation theory (ENPT2) with a selected configuration interaction (SCI) approximation. Compared with previous DMRG-based dynamic correlation methods, the DMRG-ENPT2 method extends the range of applicability, allowing us to efficiently calculate systems with very large active space beyond 30 orbitals. We demonstrate this by performing calculations on H$_2$S with an active space of (16e, 15o), hexacene with an active space of (26e, 26o) and 2D H$_{64}$ square lattice with an active space of (42e, 42o).

cond-mat.str-el↗

arXiv2019

Time-dependent Density Matrix Renormalization Group Quantum Dynamics for Realistic Chemical Systems

Electronic and/or vibronic coherence has been found by recent ultrafast spectroscopy experiments in many chemical, biological and material systems. This indicates that there are strong and complicated interactions between electronic states and vibration modes in realistic chemical systems. Therefore, simulations of quantum dynamics with a large number of electronic and vibrational degrees of freedom are highly desirable. Due to the efficient compression and localized representation of quantum states in the matrix-product state (MPS) formulation, time-evolution methods based on the MPS framework, which we summarily refer to as tDMRG (time-dependent density-matrix renormalization group) methods, are considered to be promising candidates to study the quantum dynamics of realistic chemical systems. In this work, we benchmark the performances of four different tDMRG methods, including global Taylor, global Krylov, local one-site and two-site time-dependent variational principle (1TDVP and 2TDVP), with a comparison to multi-configuration time-dependent Hartree (MCTDH) and experimental results. Two typical chemical systems of internal conversion and singlet fission are investigated, one containing strong and high-order local and non-local electron-vibration couplings, the other exhibiting a continuous phonon bath. The comparison shows that the tDMRG methods (particularly, the 2TDVP method) can describe the full quantum dynamics in large chemical systems accurately and efficiently. Several key parameters in the tDMRG calculation including the truncation error threshold, time interval and ordering of local sites were also investigated to strike the balance between efficiency and accuracy of results.

cond-mat.str-el↗

arXiv2019

Integrating high-quality dielectrics with one-nanometer equivalent oxide thickness on two-dimensional electronic devices

Two-dimensional (2D) semiconductors are widely recognized as attractive channel materials for low-power electronics. However, an unresolved challenge is the integration of high-quality, ultrathin high-\k{appa} dielectrics that fully meet the roadmap requirements for low-power applications. With a dangling-bond free surface, the deposition of dielectrics by atomic layer deposition (ALD) on 2D materials is usually characterized with non-uniform nucleation and island formation, producing a highly porous dielectric layer with serious leakage particularly at the small equivalent oxide thickness (EOT) limit. Here, we report the robust ALD of highly uniform high-\k{appa} dielectric on 2D semiconductors by using ~0.3 nm-thick exclusively monolayer molecular crystal as seeding layer. Ultrathin dielectrics down to 1 nm EOT is realized on graphene, MoS2 and WSe2, with considerably reduced roughness, density of interface states, leakage current and improved breakdown field compared to prior methods. Taking advantage of the reduced EOT, we demonstrate graphene RF transistors operating at 60 GHz, as well as MoS2 and WSe2 complementary metal-oxide-semiconductor (CMOS) transistors with Vdd =0.8 V and ideal subthreshold swing (SS) of 60 mV/dec, 20 nm-channel-length MoS2 transistors with on/off ratio over 10^7. These studies highlight that our dielectric integration method is generally applicable for different 2D materials, and compatible with top-down fabrication process on large-area chemical vapor deposited films.

physics.app-ph↗

arXiv2018

Externally-Contracted Multi-Reference Configuration Interaction Method Using a DMRG Reference Wave Function

The recent development of the density matrix renormalization group (DMRG) method in multireference quantum chemistry makes it practical to evaluate static correlation in a large active space, while dynamic correlation provides a critical correction to the DMRG reference for strong-correlated systems and is usually obtained using multi-reference perturbation (MRPT) or configuration interaction (MRCI) methods with internal contraction (ic) approximation. These methods can use active space scalable to relatively larger size references than has previously been possible. However, they are still hardly applicable to systems with active space larger than 30 orbitals because of high computation and storage costs of high-order reduced density matrices (RDMs) and the number of virtual orbitals are normally limited to few hundreds. In this work, we propose a new effective implementation of DMRG-MRCI, in which we use re-constructed CASCI-type configurations from DMRG wave function via the entropy-driving genetic algorithm (EDGA), and integrate with MRCI by an external contraction (ec) scheme. This bypasses the bottleneck of computing high-order RDMs in traditional DMRG dynamic correlation methods with ic approximation and the number of MRCI configurations is not dependent on the number of virtual orbitals. Therefore, DMRG-ec-MRCI method is promising for dealing with larger active space than 30 orbitals and large basis sets. We demonstrate the capability of our DMRG-ec-MRCI method in several benchmark applications, including the evaluation of potential energy curve of Cr$_{2}$, single-triplet gaps of higher n-acene molecules and the energy of Eu-BTBP(NO$_3$)$_3$ complex.

cond-mat.str-el↗

arXiv2017

Efficient reconstruction of CASCI-type wave functions for a DMRG state using quantum information theory and genetic algorithm

We improve the methodology to construct a complete active space-configuration interaction (CAS-CI) expansion for density-matrix renormalization group (DMRG) wave function using matrix-product state representation, inspired by the sampling-reconstructed CAS [SR-CAS, Boguslawski et al, J. Chem. Phys. 2011, 134, 224101] algorithm. In our scheme, a genetic algorithm, in which the "crossover" and "mutation" process can be optimized based on quantum information theory, is employed when reconstructing the CASCI-type wave function in the Hilbert space. Test analysis results for the ground and excited state wave functions of conjugated molecules and transition metal compounds illustrate that our scheme is very efficient for searching the most important CI expansions in large active spaces.

cond-mat.str-el↗

arXiv2015

Density-Matrix Renormalization Group Algorithm with Multi-Level Active Space

The density-matrix renormalization group (DMRG) method, which can deal with a large active space composed of tens of orbitals, is nowadays widely used as an efficient addition to traditional complete active space (CAS)-based approaches. In this paper, we present the DMRG algorithm with a multi-level (ML) control of the active space based on chemical intuition-based hierarchical orbital ordering, which is called as ML-DMRG with its self-consistent field variant ML-DMRG-SCF. Ground and excited state calculations of H2O, N2, indole, and Cr2 with comparisons to DMRG references using fixed number of kept states (M) illustrate that MLtype DMRG calculations can obtain noticeable efficiency gains. It is also shown that the orbital re-ordering based on hierarchical multiple active subspaces may be beneficial for reducing computational time for not only ML-DMRG calculations but also DMRG ones with fixed M values.

cond-mat.str-el↗

arXiv2013

Assessment of various natural orbitals as the basis of large active space density matrix renormalization group calculations

It is well-known that not only the orbital ordering but also the choice of the orbitals themselves as the basis may significantly influence the computational efficiency of density-matrix renormalization group (DMRG) calculations. In this study, for assessing the efficiency of using various natural orbitals (NOs) as the DMRG basis, we performed benchmark DMRG calculations with different bases, which included the NOs obtained by various traditional electron correlation methods, as well as NOs acquired from preliminary moderate DMRG calculations (e.g., preserved states less than 500). The tested systems included N$_2$, transition metal Cr$_2$ systems, as well as 1-D hydrogen polyradical chain systems under equilibrium and dissociation conditions and 2-D hydrogen aggregates. The results indicate that a good compromise between the requirement for low computational costs of acquiring NOs and the demand for high efficiency of NOs as the basis of DMRG calculations may be very dependent on the studied systems' diverse electron correlation characteristics and the size of the active space. It is also shown that a DMRG-complete active space configuration interaction (DMRG-CASCI) calculation in a basis of carefully chosen NOs can provide a less expensive alternative to the standard DMRG-CASSCF calculation and avoid the convergence difficulties of orbital optimization for large active spaces. The effect of different NO ordering schemes on DMRG-CASCI calculations is also discussed.

cond-mat.str-el↗

arXiv2013

Calculating excited states of molecular aggregates by the renormalized excitonic method

In this paper, we apply the recently developed ab initio renormalized excitonic method (REM) to the excitation energy calculations of various molecular aggregates, through the extension of REM to the time-dependent density functional theory (TDDFT). Tested molecular aggregate systems include one-dimensional hydrogen-bonded water chains, ring crystals with $π$-$π$ stacking or van-der Waals interactions and the general aqueous systems with polar and non-polar solutes. The basis set factor as well as the effect of the exchange-correlation functionals are also investigated. The results indicate that the REM-TDDFT method with suitable basis set and exchange-correlation functionals can give good descriptions of excitation energies and excitation area for lowest electronic excitations in the molecular aggregate systems with economic computational costs. It's shown that the deviations of REM-TDDFT excitation energies from those by standard TDDFT are much less than 0.1 eV and the computational time can be reduced by one order.

physics.chem-ph↗

arXiv2010

Effect of Electron-Electron Interactions on the Charge Carrier Transitions in trans-Polyacetylene

By employing a newly developed dynamical simulation method, which is a combination of classical molecular dynamics (MD) and the adaptive time-dependent density matrix renormalization group (TDDMRG), we investigate the dynamics of charge carrier transitions in trans-polyacetylene (PA) with the inclusion of both electron-phonon and electron -electron interactions. The calculations are performed within a modified Su-Schrieffer-Heeger (SSH) model in which electron-electron interactions are taken into account via the combination with extended Hubbard model (EHM). We find that removing an electron from a trans-PA chain bearing a positively charged polaron leads to the formation of a pair of charged solitons. Furthermore, we study the effect of electron-electron interactions on such charge carrier transitions in trans-PA. Our results show that increasing the on-site Coulomb interaction U and the nearest-neighbor Coulomb repulsion V will not change the qualitative behavior of the transition from a polaron to a soliton pair in the evolution process but will quantitatively reduce the moving velocities of the both formed solitons significantly and change the conditions for the soliton collisions.

cond-mat.mtrl-sci↗

arXiv2008

Dynamical simulations of charged soliton transport in conjugated polymers with the inclusion of electron-electron interactions

We present numerical studies of the transport dynamics of a charged soliton in conjugated polymers under the influence of an external time-dependent electric field. All relevant electron-phonon and electron-electron interactions are nearly fully taken into account by simulating the monomer displacements with classical molecular dynamics (MD) and evolving the wavefunction for the $π$ electrons by virtue of the adaptive time-dependent density matrix renormalization group (TDDMRG) simultaneously and nonadiabatically. It is found that after a smooth turn-on of the external electric field the charged soliton is accelerated at first up to a stationary constant velocity as one entity consisting of both the charge and the lattice deformation. An ohmic region (6 mV/$\textÅ$ $\leq E_0\leq$ 12 mV/$\textÅ$) where the stationary velocity increases linearly with the electric field strength is observed. The relationship between electron-electron interactions and charged soliton transport is also investigated in detail. We find that the dependence of the stationary velocity of a charged soliton on the on-site Coulomb interactions $U$ and the nearest-neighbor interactions $V$ is due to the extent of delocalization of the charged soliton defect.

cond-mat.str-el↗

arXiv2008

Dynamical simulations of polaron transport in conjugated polymers with the inclusion of electron-electron interactions

Dynamical simulations of polaron transport in conjugated polymers in the presence of an external time-dependent electric field have been performed within a combined extended Hubbard model (EHM) and Su-Schrieffer-Heeger (SSH) model. Nearly all relevant electron-phonon and electron-electron interactions are fully taken into account by solving the time-dependent Schrödinger equation for the $π$-electrons and the Newton's equation of motion for the backbone monomer displacements by virtue of the combination of the adaptive time-dependent density matrix renormalization group (TDDMRG) and classical molecular dynamics (MD). We find that after a smooth turn-on of the external electric field the polaron is accelerated at first and then moves with a nearly constant velocity as one entity consisting of both the charge and the lattice deformation. An ohmic region (3 mV/$\textÅ$ $\leq E_0\leq$ 9 mV/$\textÅ$) where the stationary velocity increases linearly with the electric field strength is observed for the case of $U$=2.0 eV and $V$=1.0 eV. The maximal velocity is well above the speed of sound. Below 3 mV/$\textÅ$ the polaron velocity increases nonlinearly and in high electric fields with strength $E_0\geq$ 10.0 mV/$\textÅ$ the polaron will become unstable and dissociate. The relationship between electron-electron interaction strengths and polaron transport is also studied in detail. We find that the the on-site Coulomb interactions $U$ will suppress the polaron transport and small nearest-neighbor interactions $V$ values are also not beneficial to the polaronic motion while large $V$ values favor the polaron transport.

cond-mat.mtrl-sci↗

arXiv2008

Block Density Matrix Renormalization Group with Effective Interactions

Based on the contractor renormalization group (CORE) method and the density matrix renormalization group (DMRG) method, a new computational scheme, which is called the block density matrix renormalization group with effective interactions (BDMRG-EI), is proposed to deal with the numerical computation of quantum correlated systems. Different from the convential CORE method in the ways of calculating the blocks and the fragments, where the DMRG method instead of the exact diagonalization is employed in BDMRG-EI, DMRG-EI makes the calculations of larger blocks and fragments applicable. Integrating DMRG's advantage of high accuracy and CORE's advantage of low computational costs, BDMRG-EI can be widely used for the theoretical calculations of the ground state and low-lying excited states of large systems with simple or complicated connectivity. Test calculations on a 240 site one-dimensional chain and a double-layer polyacene oligomer containing 48 hexagons demonstrate the efficiency and potentiality of the method.

cond-mat.str-el↗