Erratum to: npj Quantum Materials (2017); doi:10.1038/s41535-017-0032-9; Published 13 June 2017
In the original version of this paper, the formula for ω 0 used in equation 10 incorrectly contained “k”, which should be “κ”. Equation 16c incorrectly contained the term 3(C2/3), which should be C2. 3(C2/3) has also been replaced by C2 on page 6 of the PDF in relation to LO mode frequency.
These corrections have been made to the HTML and PDF versions of this article.
The online version of the original article can be found at http://dx.doi.org/10.1038/s41535-017-0032-9.