Plagiarism between a Physical Review Letters paper and a previous arXiv preprint I am a PhD student and today, a PRL paper has been published in which a part of its main section reports the same results as our arXiv preprint, that was submitted also to PRL (and to arXiv) at the end of 2019. They submitted their work after ours; however, our paper is still under review since the referees asked us for experiments to validate the theory and numerics. Furthermore, his work does not include experiments, is also mostly numerics and theory, and their analysis is not as exhaustive and detailed as ours. There are sentences in their work and even the plots that are pretty similar and some of them almost identical, and they even use the same name for a characteristic quantity that was used for the first time in our preprint. The thing is that they have only cited our preprint at the end of the paper as "Note added", not in the main section or even in the supplementary material where they also use almost identical sentences. I am 100% sure that they were aware of our preprint since day one since they read it in ResearchGate. It seems they wanted to include this result in their PRL at any cost, hoping that nothing happens since it is not a clear case of plagiarism and they succinctly added the note at the end of the Letter to cover their backs. Moreover, they did not publish any arXiv preprint of his work.

PRL is supposed to publish "new physics" and its standards are really high, so I cannot understand how PRL has permitted this publication.

I feel that this is a really bad practice, and I am strongly disappointed and sad, not just for my work, which in my eyes is a complete injustice, but for science. Indeed, the group that publishes this work used to be a big name in the field, so I feel that we cannot do much to solve this. My PhD advisor thinks that probably the only thing we can accomplish is an erratum from this group in PRL.

What do you think is the best way to proceed? Do you think it is possible that PRL retracts the work?
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I would contact the authors of the suspected plagiarism and demand an explanation in the politest possible way. Try not to imply that you're certain your paper was plagiarized, but ask instead if, by citing your paper, whether or not they are aware that your conclusions are so similar. I would also add that you have sent the paper to the same journal, which being a PRL should be rather obvious due to the length limitations.

If you are sure their submission date to PRL comes after you submitted your pre-print to ArXiv, and that they were also aware of it, then you have proof that you were the first to make those results public. I believe if the authors do not respond well to your email you have good chances of contacting the PRL editorial board and, using your pre-print as proof, claim that you were plagiarized.

The best case scenario is to be able to solve your problems with the authors of the other paper, but to be honest I'm not sure most human beings would respond well to this situation. Maybe you'll have to get in touch with the board. If I were you, I would definitely not leave things as be, and would insist until the matter was solved (even if legal measures are needed).