Multiband behavior and non-metallic low-temperature state of K$_{0.50}$Na$_{0.24}$Fe$_{1.52}$Se$_{2}$

Hyejin Ryu; F. Wolff-Fabris; J. B. Warren; M. Uhlarz; J. Wosnitza; C. Petrovic

doi:10.1103/physrevb.90.020502

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arXiv · 1604.06793

Multiband behavior and non-metallic low-temperature state of K$_{0.50}$Na$_{0.24}$Fe$_{1.52}$Se$_{2}$

Hyejin Ryu·F. Wolff-Fabris·J. B. Warren·M. Uhlarz·J. Wosnitza·C. Petrovic

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Abstract

We report evidence for multiband transport and an insulating low-temperature normal state in superconducting K$_{0.50}$Na$_{0.24}$Fe$_{1.52}$Se$_{2}$ with $T_{c}\approx 20$ K. The temperature-dependent upper critical field, $H_{c2}$, is well described by a two-band BCS model. The normal-state resistance, accessible at low temperatures only in pulsed magnetic fields, shows an insulating logarithmic temperature dependence as $T \rightarrow 0$ after superconductivity is suppressed. This is similar as for high-$T_{c}$ copper oxides and granular type-I superconductors, suggesting that the superconductor-insulator transition observed in high magnetic fields is related to intrinsic nanoscale phase separation.

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Hyejin Ryu, F. Wolff-Fabris, J. B. Warren, M. Uhlarz, J. Wosnitza, C. Petrovic. 2016-04-22. Multiband behavior and non-metallic low-temperature state of K$_{0.50}$Na$_{0.24}$Fe$_{1.52}$Se$_{2}$. https://doi.org/10.1103/physrevb.90.020502

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