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3D visualizations of nanoscale phase separation and ultrafast dynamic correlation between phases in (Na0.32K0.68)0.95Fe1.75Se2

Authors :
Kaung-Hsiung Wu
Jenh-Yih Juang
M. Liu
A. I. Boltalin
A. N. Vasiliev
Y. J. Chu
J. Whittaker
Igor Morozov
Jiunn-Yuan Lin
P. C. Cheng
Wen-Yen Tzeng
A. A. Zhukov
Chih-Wei Luo
Source :
Physical Review Materials. 3
Publication Year :
2019
Publisher :
American Physical Society (APS), 2019.

Abstract

Phase separation of metallic and antiferromagnetic (AFM) insulating phases in alkaline iron selenides $({\mathrm{A}}_{x}\mathrm{F}{\mathrm{e}}_{2\ensuremath{-}y}\mathrm{S}{\mathrm{e}}_{2})$ continues to attract intense interest because the relationship between two peculiar features probably is a key to clarifying the pairing mechanism of ${\mathrm{A}}_{x}\mathrm{F}{\mathrm{e}}_{2\ensuremath{-}y}\mathrm{S}{\mathrm{e}}_{2}$ superconductors. Here we report that the three-dimensional (3D) visualizations of nanoscale phase separation in ${(\mathrm{N}{\mathrm{a}}_{0.32}{\mathrm{K}}_{0.68})}_{0.95}\mathrm{F}{\mathrm{e}}_{1.75}\mathrm{S}{\mathrm{e}}_{2}$ single crystals are revealed by hybrid focused-ion-beam scanning electron microscopy and the superconducting paths are fully percolative in 3D. Moreover, the phase-related ultrafast dynamics in ${(\mathrm{N}{\mathrm{a}}_{0.32}{\mathrm{K}}_{0.68})}_{0.95}\mathrm{F}{\mathrm{e}}_{1.75}\mathrm{S}{\mathrm{e}}_{2}$ is studied by dual-color pump-probe spectroscopy. The anomalous changes in the electron and acoustic phonon components of transient reflectivity change $(\mathrm{\ensuremath{\Delta}}R/R)$ identify two characteristic temperatures ${T}^{*}\ensuremath{\sim}100\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ (the onset temperature of coupling between the nanometallic and AFM phases) and ${T}_{\mathrm{H}}\ensuremath{\sim}230\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ (the onset temperature of the metallic-interface phase). An energy-transfer channel between the nanometallic and AFM phases is inferred. This proposed channel provides insight into the pairing mechanism of alkaline iron selenide superconductors.

Details

ISSN :
24759953
Volume :
3
Database :
OpenAIRE
Journal :
Physical Review Materials
Accession number :
edsair.doi...........3a54e5780f0d5eb8f3f4132b075f97fc
Full Text :
https://doi.org/10.1103/physrevmaterials.3.034802