Correction to: Nature Materials https://doi.org/10.1038/s41563-019-0375-7, published online 6 May 2019.

In the version of this News & Views originally published, the numbers above –4ħω, –3ħω, –2ħω and –ħω in Fig. 3e incorrectly read 4, 3, 3 and 3, respectively; they should have read –4, –3, –2 and –1. This has been corrected in the online versions.