Electronic Excited States in Extreme Limits via Ensemble Density Functionals

Tim Gould, Derk P. Kooi, Paola Gori-Giorgi, Stefano Pittalis

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Abstract

Density functional theory (DFT) has greatly expanded our ability to affordably compute and understand electronic ground states, by replacing intractable ab initio calculations by models based on paradigmatic physics from high- and low-density limits. But, a comparable treatment of excited states lags behind. Here, we solve this outstanding problem by employing a generalization of density functional theory to ensemble states (EDFT). We thus address important paradigmatic cases of all electronic systems in strongly (low-density) and weakly (high-density) correlated regimes. We show that the high-density limit connects to recent, exactly solvable EDFT results. The low-density limit reveals an unnoticed and most unexpected result - density functionals for strictly correlated ground states can be reused directly for excited states. Nontrivial dependence on excitation structure only shows up at third leading order. Overall, our results provide foundations for effective models of excited states that interpolate between exact low- and high-density limits, which we illustrate on the cases of singlet-singlet excitations in H2 and a ring of quantum wells.

Original languageEnglish
Article number106401
Pages (from-to)1-7
Number of pages7
JournalPhysical review letters
Volume130
Issue number10
Early online date8 Mar 2023
DOIs
Publication statusPublished - 10 Mar 2023

Bibliographical note

Funding Information:
T. G. was supported by an Australian Research Council (ARC) Discovery Project (DP200100033) and Future Fellowship (FT210100663). D. P. K. and P. G.-G. were supported by the Netherlands Organisation for Scientific Research (NWO) under Vici Grant No. 724.017.001. S. P. was partially supported by the MIUR PRIN Grant No. 2017RKWTMY. We thank anonymous Referees B and C for suggesting extention to the (different) cases of finite temperatures and magnetic interactions, respectively.

Publisher Copyright:
© 2023 American Physical Society.

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