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

P. C. Cheng; W. Y. Tzeng; Y. J. Chu; C. W. Luo; A. A. Zhukov; J. Whittaker; J. -Y. Lin; K. H. Wu; J. Y. Juang; M. Liu; I. V. Morozov; A. I. Boltalin; A. N. Vasiliev

arXiv · 1903.05797

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

P. C. Cheng·W. Y. Tzeng·Y. J. Chu·C. W. Luo·A. A. Zhukov·J. Whittaker·J. -Y. Lin·K. H. Wu·J. Y. Juang·M. Liu·I. V. Morozov·A. I. Boltalin·A. N. Vasiliev

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Abstract

Phase separation of metallic and antiferromagnetic (AFM) insulating phases in alkaline iron selenides (AxFe2-ySe2) continues to attract intense interest because the relationship between two peculiar features probably is a key to clarifying the pairing mechanism of AxFe2-ySe2 superconductors. Here we report that the 3D visualizations of nano-scale phase separation in (Na0.32K0.68)0.95Fe1.75Se2 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 (Na0.32K0.68)0.95Fe1.75Se2 is studied by dual-color pump-probe spectroscopy. The anomalous changes in the electron and acoustic phonon components of transient reflectivity change ({\Delta}R/R) identify two characteristic temperatures T*~100 K (the onset temperature of coupling between nano-metallic and AFM phases) and TH~230 K (the onset temperature of metallic-interface-phase). An energy-transfer channel between the nano-metallic and AFM phases is inferred. This proposed channel provides a new insight into the pairing mechanism of alkaline iron selenide superconductors.

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P. C. Cheng, W. Y. Tzeng, Y. J. Chu, C. W. Luo, A. A. Zhukov, J. Whittaker, J. -Y. Lin, K. H. Wu, J. Y. Juang, M. Liu, I. V. Morozov, A. I. Boltalin, A. N. Vasiliev. 2019-03-14. 3D visualizations of nano-scale phase separation and ultrafast dynamic correlation between phases in (Na0.32K0.68)0.95Fe1.75Se2. https://arxiv.org/abs/1903.05797

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