EPJ E Celebrates 20th Anniversary

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Published on 24 September 2020

In 2020 The European Physical Journal E - Soft Matter and Biological Physics marks twenty years since the publication of its first papers. To commemorate this milestone, the Editors-in-Chief have made a selection of articles published over these two decades, representing the breadth of coverage of the journal. These articles are now freely accessible until 15 October via this Q&A with Prof Holger Stark, Editor-in-Chief of EPJ E.

EPJ H Highlight - A question of reality

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Published on 24 September 2020

John Stewart Bell’s eponymous theorem and inequalities set out, mathematically, the contrast between quantum mechanical theories and local realism. They are used in quantum information, which has evolving applications in security, cryptography and quantum computing.

The distinguished quantum physicist John Stewart Bell (1928-1990) is best known for the eponymous theorem that proved current understanding of quantum mechanics to be incompatible with local hidden variable theories. Thirty years after his death, his long-standing collaborator Reinhold Bertlmann of the University of Vienna, Austria, has reviewed his thinking in a paper for EPJ H, ‘Real or Not Real: That is the question’. In this historical and personal account, Bertlmann aims to introduce his readers to Bell’s concepts of reality and contrast them with some of his own ideas of virtuality.

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EPJ B Highlight - Impurities enhance polymer LED efficiencies

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Published on 23 September 2020

Molecular dynamics simulations have shown that the mysteriously high efficiency of polymer LEDs arises from interactions between triplet excitons in their polymer chains, and unpaired electrons in their molecular impurities.

Polymer LEDs (PLEDs) are devices containing single layers of luminescent polymers, sandwiched between two metal electrodes. They produce light as the metal layers inject electrons and holes into the polymer, creating distortions which can combine to form two different types of electron-hole pair: either light-emitting ‘singlets,’ or a non-emitting ‘triplets.’ Previous theories have suggested that the ratio between these two types should be around 1:3, which would produce a light emission efficiency of 25%. However, subsequent experiments showed that the real value can be as high as 83%. In new research published in EPJ B, physicists in China, led by Yadong Wang at Hebei North University, found that this higher-than-expected efficiency can be reached through interactions between triplet excitons, and impurities embedded in the polymer.

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