Tailored pump-probe transient spectroscopy with time-dependent density-functional theory: controlling absorption spectra

European Physical Journal B 89, 128 (2016)

Tailored pump-probe transient spectroscopy with time-dependent density-functional theory: controlling absorption spectra

J. Walkenhorst, U.De Giovannini, A.Castro, A. Rubio

Recent advances in laser technology allow us to follow electronic motion at its natural time-scale with ultra-fast time resolution, leading the way towards attosecond physics experiments of extreme precision. In this work, we assess the use of tailored pumps in order to enhance (or reduce) some given features of the probe absorption (for example, absorption in the visible range of otherwise transparent samples). This type of manipulation of the system response could be helpful for its full characterization, since it would allow us to visualize transitions that are dark when using unshaped pulses. In order to investigate these possibilities, we perform first a theoretical analysis of the non-equilibrium response function in this context, aided by one simple numerical model of the hydrogen atom. Then, we proceed to investigate the feasibility of using time-dependent density-functional theory as a means to implement, theoretically, this absorption-optimization idea, for more complex atoms or molecules. We conclude that the proposed idea could in principle be brought to the laboratory: tailored pump pulses can excite systems into light-absorbing states. However, we also highlight the severe numerical and theoretical difficulties posed by the problem: large-scale non-equilibrium quantum dynamics are cumbersome, even with TDDFT, and the shortcomings of state-of-the-art TDDFT functionals may still be serious for these out-of-equilibrium situations.

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Doi
http://dx.doi.org/10.1140/epjb/e2016-70064-0
arxiv
http://arxiv.org/abs/1601.04544
Notes
We acknowledge fi nancial support from the European Research Council (ERC-2010-AdG-267374), Spanish grant (FIS2013-46159-C3-1-P), Grupos Consolidados (IT578-13), and AFOSR Grant No. FA2386- 15-1-0006 AOARD 144088, H2020-NMP-2014 project MOSTOPHOS, GA no. SEP-210187476 and COST Action MP1306 (EUSpec). Computational time was granted by BSC Red Espanola de Supercomputacion.

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