Carrier-envelope-phase effect on laser-driven bound-bound transitions in the high-frequency region

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Electron–electron correlation plays an important role in the underlying dynamics in physics and chemistry. Helium is the simplest and most fundamental two-electron system. The dynamic process of helium in a strong laser field is still a challenging issue because of the large calculation cost. In this study, a graphic processing unit (GPU) openACC based ab initio numerical simulations package HeTDSE is developed to solve the full-dimensional time-dependent Schrödinger equation of helium subjected to a strong laser pulse. HeTDSE uses B-spline basis sets expansion method to construct the radial part of the wavefunction, and the spherical harmonic functions is used to express for the angular part. Adams algorithm is employed for the time propagation. Our example shows that HeTDSE running on an NVIDIA Kepler K20 GPU can outperform the one on an Intel E5-2640 single CPU core by a factor of 147. HeTDSE code package can be obtained from the author or from the author’s personal website (doi: 10.13140/RG.2.2.15334.45128) directly under the GPL license, so HeTDSE can be downloaded, used and modified freely.

Section: B Excited States Dynamicsmentioning

confidence: 99%

HeTDSE: A GPU based program to solve the full-dimensional time-dependent Schrödinger equation for two-electron helium subjected to strong laser fields*

Xi-nan¹,

Zhang²,

Bai³

et al. 2021

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“…With the advent of attosecond pulse trains (APT) [1] and isolated attosecond pulses (IAP) [2][3][4] since 2001, attosecond pulses have been used to initiate photoionization of atoms, [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] molecules, [22][23][24][25][26] and condensed materials. [27][28][29][30][31][32] The goal is that the attosecond electron wave packets generated can then be probed by another attosecond pulse with different time delays, therefore electron dynamics can be probed at attosecond timescale.…”

Section: Introductionmentioning

confidence: 99%

Validity of extracting photoionization time delay from the first moment of streaking spectrogram

Wei

Xi-nan

2019

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Photoionization time delays have been studied in many streaking experiments in which an attosecond pulse is used to ionize the atomic or solid state target in the presence of a dressing infrared laser field. Among the methods of extracting the time delay from the streaking spectrogram, the simplest one is to calculate the first moment of the spectrogram and to measure its offset relative to the vector potential of the infrared field. The first moment method has been used in many theoretical simulations and analysis of experimental data, but the meaning of this offset needs to be investigated. We simulate the spectrograms and compare the extracted time delay from the first moment with the input Wigner delay. In this study, we show that the first moment method is valid only when the group delay dispersions corresponding to both the spectral phase of the attosecond pulse and the phase of the single-photon transition dipole matrix element of the target are small. Under such circumstance, the electron wave packet behaves like a classical particle and the extracted time delay can be related to a group delay in the photoionization process. To avoid ambiguity and confusion, we also suggest that the photoionization time delay be replaced by photoionization group delay and the Wigner time delay be replaced by Wigner group delay.

“…[10][11][12][13][14][15] The first experimental realization of the SOC in condensates was implemented in 2009 by dressing the cold atoms with two counter propagating polarized laser beams. [16,17] This technique opened a new perspective in the field of BEC, and more and more experimental [18][19][20][21] and theoretical [22][23][24] results have been reported. It was found that the total magnetization (or spin-polarizability, which measures the difference of the densities of the spin-components) varies with time.…”

Section: Introductionmentioning

confidence: 99%

“…[12,16,22] Besides, the collective-mode dynamics has been studied, the spatial motions along different directions could be correlated (say, a dipole mode might induce a breathing mode in its perpendicular plane). [24] The instability caused by the collective mode has also been studied. [23] On the other hand it is now possible to trap a condensate in ring geometry.…”

Section: Introductionmentioning

confidence: 99%

Oscillation of the spin-currents of cold atoms on a ring due to light-induced spin–orbit coupling

Xie¹,

He²,

Bao³

2015

The evolution of two-component cold atoms on a ring with spin-orbit coupling has been studied analytically for the case with N noninteracting particles. Then, the effect of interaction is evaluated numerically via a two-body system. Two cases are considered: (i) Starting from a ground state the evolution is induced by a sudden change of the laser field, and (ii) Starting from a superposition state. Oscillating persistent spin-currents have been found. A set of formulae have been derived to describe the period and amplitude of the oscillation. Based on these formulae the oscillation can be well controlled via adjusting the parameters of the laser beams. In particular, it is predicted that movable stripes might emerge on the ring.