Author Correction: Influence of microstructure on superconductivity in KxFe2−ySe2 and evidence for a new parent phase K2Fe7Se8

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Specifically, the fourth sentence in the original legend of Fig. 4 currently reads 'The yellow arrowed line highlights the trace along which the spatial distribution of compositions of K and Fe are measured and presented in (b).' In the corrected version of the legend, this sentence reads 'The yellow arrowed line highlights the trace along which the line scan profile of the compositions was taken, as shown in (b).' The seventh and eighth sentences of the original legend read '(c) The SEM image of the sample SFC in another region. The red spots and blue spots mark the positions where the local compositions are analysed.' This is incorrect: these 25 red spots and 25 blue spots do not represent the precise locations from which EDS data were collected. In the corrected version of the legend, these two sentences state '(c) Representative SEM image (taken with an accelerating voltage of 10 kV) of the typical domain (marked by blue arrows) and background (marked by red arrows) regions. From these two different regions the EDS spectra were collected for point-wise composition analysis.' The 10th and 11th sentences of the original legend read '(d) The compositions of K and Fe measured on the rectangular domains (blue diamond) and the background (red circles). One can clearly see that the data fall into two groups: the formula K 0.68 Fe 1.78 Se 2 on the domain, and K 0.81 Fe 1.6 Se 2 on the background.' In the original version of Fig. 4d, we presented the composition obtained from 50 different EDS data (25 from domains and 25 from background regions) that were selected from a total of 79 pointwise EDS measurements (40 on the background and 39 on the domains) collected from three samples cleaved from a single bulk SFC sample, instead of one sample indicated in the original paper. We want to clarify that there is no positionwise correlation between these data and those points marked in Fig. 4c of the original paper. We apologize for not presenting the full set of data points in the paper, which is a clear deviation of standard practice. The corrected version of the legend replaces these two sentences with '(d) The compositions of K and Fe were measured from the total 79 spots on the domain and on the background regions of three SFC samples cleaved from a single bulk. One can clearly see that the EDS data fall into two groups. By analyzing the total EDS dataset (39 points on the domains and 40 points in the background region), we get the average compositions with the formula K 0.69 Fe 1.78 Se 2 on the domain, and K 0.80 Fe 1.65 Se 2 on the background, respectively.' In addition to these errors in Fig. 4 and the related discussion, the fourth sentence in the third paragraph of the 'Scanning electron microscope measurements' section of the Results currently reads: 'Similar behaviour of the composition distribution is observed in the sample S350, which presents better global appearance of superconductivity, although now the domains become much smaller.' This is incorrect. This sentence should be replaced with: 'Similar grey-scale fraction is observed in samples SFC and S350, which may suggest similar compositions of the superconducting areas of SFC and S350, the latter presents better global appearance of superconductivity, although now the domains become much smaller.' The first sentence of the Discussion reads 'In our local analysis presented above, it is found that the composition of the superconducting domains are converged at about K 0.68 Fe 1.78 Se 2 .' It should say 'K 0.69 Fe 1.78 Se 2 ' instead of 'K 0.68 Fe 1.78 Se 2 '.
The fourth and fifth sentences of the Discussion read 'Concerning the uncertainties in these totally distinct techniques, the consistency between the two techniques are remarkable, which also validates the argument that the domains are superconducting and have a composition of about K 0.68 Fe 1.78 Se 2 . In the background phase, the analysis shows a composition of K 0.8 Fe 1.63 Se 2 , which is naturally attributed to the well-known 245 phase.' These should say 'K 0.69 Fe 1.78 Se 2 ' instead of 'K 0.68 Fe 1.78 Se 2 ' and 'K 0.8 Fe 1.65 Se 2 ' in place of 'K 0.8 Fe 1.63 Se 2 '.
The 17th sentence of the same paragraph reads 'A glance at our formula K 0.68 Fe 1.78 Se 2 of the superconducting domains would suggest that a possible phase with the formula of K 0.5 Fe 1.75 Se 2 (or called as 278 phase) is next to the K 0.8 Fe 1.6 Se 2 (or the 245) phase and may act as the parent phase for superconductivity.' It should say 'K 0.69 Fe 1.78 Se 2 ' instead of 'K 0.68 Fe 1.78 Se 2 '.
The 12th sentence of the second paragraph in the Discussion reads 'Although our STM data here cannot give a direct evidence for the 1/8 Fe-vacancy ffiffi ffi 8 p ffiffiffiffiffi 10 p state, the expectation of the composition of this state is very consistent with the chemical composition obtained from the superconducting domains, that is, K 0.68 Fe 1.78 Se 2 .' It should say 'K 0.69 Fe 1.78 Se 2 ' instead of 'K 0.68 Fe 1.78 Se 2 '.
The fifth sentence of the 'Structure characterization' section of the Methods currently reads 'In the spot mode, 50 spots were randomly selected on and off the domains of each sample to obtain high resolution spectra with a measurement time of 1 min for one point, with the voltage of 20 kV.' This should state '79 spots were selected' instead of '50 spots were randomly selected', 'of three SFC samples' instead of 'of each sample' and '25 kV' instead of '20 kV'. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.