Correction to: Nature Photonics https://doi.org/10.1038/s41566-020-0588-y, published online 17 February 2020.

In the version of this Letter originally published online, in the Acknowledgements, the following sentence was missing “We also gratefully acknowledge the critical support and infrastructure provided for this work by The Kavli Nanoscience Institute at Caltech.” It has now been added.