Nature Communications 5: Article number: 4673 doi: 10.1038/ncomms5673 (2014); Published: 22 August 2014; Updated: 13 October 2014.

The original version of this Article contained a typographical error in the first sentence of the abstract, where the phrase 'transition metal dichalcogenides' was inadvertently duplicated. This has now been corrected in both the PDF and HTML versions of the Article.