Correction to: Nature Reviews Materials https://doi.org/10.1038/s41578-021-00289-w, published online 19 March 2021.

In Box 1, the image labels “Short-range electron–photon interaction” and “Long-range electron–photon interaction” should have read “Short-range electron–phonon interaction” and “Long-range electron–phonon interaction”, respectively. In the same Box, the sentence “shallow electronic state (≈ 10 eV below EF)” should have read “shallow electronic state (≈ 10 meV below EF)”. The information has been corrected both in the PDF and in the HTML versions of the article.