Time-dependent multiconfiguration methods for the numerical simulation of photoionization processes of many-electron atoms

Hochstuhl, David; Hinz, Christopher; Bönitz, M.

doi:10.1140/epjst/e2014-02092-3

Cited by 65 publications

(110 citation statements)

References 307 publications

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“…[46] for a thorough review, and it is mandatory to go beyond the level of time-dependent Hartree-Fock (TDHF) to allow for a description of electron-electron correlation effects.…”

Section: Theorymentioning

confidence: 99%

“…In the following, we will work out the formulas for the onedimensional (1D) case. Analogous expressions in 3D spherical coordinates [46] or prolate spheroidal coordinates [69] are straightforward and pose no conceptual difficulties. In short, the technique can be summarized by using localized HF-like orbitals for the description of the bound part of the spectrum and a grid-like representation for the continuum part.…”

Section: A Partially Rotated Basismentioning

confidence: 99%

“…Extending ideas from [46] we evaluate the transformations analytically by exploiting the δ-structure of the FE-DVR matrix elements and the transformation matrix b which results in fast transformations and offers a strategy for the efficient storage of the transformed integrals. Similar strategies can be applied for 3D spherical coordinates and prolate spheroidal coordinates.…”

Section: Appendix B: Transformation and Storage Of Electron Integralsmentioning

confidence: 99%

“…For numerical performance [46,96], at the cost of slightly increased memory consumption, it is favorable to split this transformation into two parts with a temporary matrix h 1 :…”

Section: A Transformation Of One-electron Integralsmentioning

confidence: 99%

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Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

2014

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We present a wave-function based method to solve the time-dependent many-electron Schrödinger equation (TDSE) with special emphasis on strong-field ionization phenomena. The theory builds on the configuration-interaction (CI) approach supplemented by the generalized-active-space (GAS) concept from quantum chemistry. The latter allows for a controllable reduction in the number of configurations in the CI expansion by imposing restrictions on the active orbital space. The method is similar to the recently formulated time-dependent restricted-active-space (TD-RAS) CI method [D. Hochstuhl, and M. Bonitz, Phys. Rev. A 86, 053424 (2012)]. We present details of our implementation and address convergence properties with respect to the active spaces and the associated account of electron correlation in both ground state and excitation scenarios. We apply the TD-GASCI theory to strong-field ionization of polar diatomic molecules and illustrate how the method allows us to uncover a strong correlation-induced shift of the preferred direction of emission of photoelectrons.

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“…[46] for a thorough review, and it is mandatory to go beyond the level of time-dependent Hartree-Fock (TDHF) to allow for a description of electron-electron correlation effects.…”

Section: Theorymentioning

confidence: 99%

Section: A Partially Rotated Basismentioning

confidence: 99%

Section: Appendix B: Transformation and Storage Of Electron Integralsmentioning

confidence: 99%

“…For numerical performance [46,96], at the cost of slightly increased memory consumption, it is favorable to split this transformation into two parts with a temporary matrix h 1 :…”

Section: A Transformation Of One-electron Integralsmentioning

confidence: 99%

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Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

2014

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“…Approaches which explicitly account for the exchange symmetry of the wave function are the MCTDH for fermions (MCTDHF) [40][41][42][43][44], which is based on a multiconfiguration expansion of the wave function in terms of Slater determinants built from time-dependent spin orbitals, and the bosonic version of the MCTDH, in which the many-body configurations are taken to be permanents [45][46][47].…”

Section: Mctdh In Second Quantization Representationmentioning

confidence: 99%

Multiconfiguration time-dependent Hartree impurity solver for nonequilibrium dynamical mean-field theory

et al. 2015

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Nonequilibrium dynamical mean-field theory (DMFT) solves correlated lattice models by obtaining their local correlation functions from an effective model consisting of a single impurity in a self-consistently determined bath. The recently developed mapping of this impurity problem from the Keldysh time contour onto a time-dependent single-impurity Anderson model (SIAM) [C. Gramsch et al., Phys. Rev. B 88, 235106 (2013)] allows one to use wave-function-based methods in the context of nonequilibrium DMFT. Within this mapping, long times in the DMFT simulation become accessible by an increasing number of bath orbitals, which requires efficient representations of the time-dependent SIAM wave function. These can be achieved by the multiconfiguration time-dependent Hartree (MCTDH) method and its multilayer extensions. We find that MCTDH outperforms exact diagonalization for large baths in which the latter approach is still within reach and allows for the calculation of SIAMs beyond the system size accessible by exact diagonalization. Moreover, we illustrate the computation of the self-consistent two-time impurity Green's function within the MCTDH second quantization representation.

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Quantum Breathing Mode of Trapped Particles: From Nanoplasmas to Ultracold Gases

Abraham

Bönitz

2014

Contrib. Plasma Phys.

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Particles spatially confined in trapping potentials have attracted increasing interest over the recent decade. Of particular importance are systems of charged particles, such as non-neutral plasmas, nanoplasmas, electrons in metal clusters, electrons in quantum-confined semiconductor structures ("artificial atoms"), electrons on the surface of liquid helium, ions in traps or highly charged particles (grains) in dusty plasmas. A second example of recent interest are systems with other kinds of pair interactions, including dipole interaction, which is important for excitons in quantum wells or ultracold Fermi and Bose gases in traps and optical lattices.Trapped systems are fundamentally different from macroscopic systems since they are dominated by strong spatial inhomogeneity and finite size effects (the properties depend on the exact particle number). Furthermore, by changing the strength of the confinement potential, the many-particle state of the system can be externally controlled-from weak coupling (gas-like) to strong coupling (crystal-like). While trapped classical particles are meanwhile well understood and accessible to first-principle computer simulations, their quantum counterparts still pose big challenges, both for experiment and theory. Therefore, collective properties that can be easily measured or computed and allow to diagnose the many-particle state of the system are of prime importance. It has been found that the quantum breathing mode (monopole oscillation) is one of the most important such properties. In recent years a number of theoretical studies has demonstrated that the quantum breathing mode is ideally suited to measure the coupling strength (the degree of nonideality) of a trapped system, its kinetic and interaction energy and other key observables. This give rise to a novel kind of "spectroscopy" of trapped systems.In this review these developments are summarized. The quantum breathing mode is studied for trapped fermions and bosons with Coulomb and dipole interaction, respectively. A systematic description of collective oscillations and especially the breathing mode is provided. Making use of time-dependent perturbation theory, it is shown how the corresponding breathing frequencies are connected to the properties of the initial equilibrium system. This gives rise to the application of the quantum mechanical sum rules. It is demonstrated how an improved version of the conventional sum rule formulas is suitable for an accurate description of the breathing mode in small systems. Finally, the dependence of the breathing mode on the particle number N is analyzed and the limit of large N is studied for one-dimensional and two-dimensional systems.

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Time-dependent multiconfiguration methods for the numerical simulation of photoionization processes of many-electron atoms

Cited by 65 publications

References 307 publications

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

Time-dependent generalized-active-space configuration-interaction approach to photoionization dynamics of atoms and molecules

Multiconfiguration time-dependent Hartree impurity solver for nonequilibrium dynamical mean-field theory

Quantum Breathing Mode of Trapped Particles: From Nanoplasmas to Ultracold Gases

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