Pseudogap Behavior of the Nuclear Spin-lattice Relaxation Rate in FeSe Probed by ${}^{77}$Se-NMR

Abstract

We conducted ${}^{77}$Se-nuclear magnetic resonance studies of the iron-based superconductor FeSe in magnetic fields of 0.6 to 19 T to investigate the superconducting and normal-state properties. The nuclear spin-lattice relaxation rate divided by the temperature $(T_{1}T{)}^{-1}$ increases below the structural transition temperature $T_{\mathrm{s}}$ but starts to be suppressed below $T^{\ast }$, well above the superconducting transition temperature $T_{\mathrm{c}}(H)$, resulting in a broad maximum of $(T_{1}T{)}^{-1}$ at $T_{\mathrm{p}}(H)$. This is similar to the pseudogap behavior in optimally doped cuprate superconductors. Because $T^{\ast }$ and $T_{\mathrm{p}}(H)$ decrease in the same manner as $T_{\mathrm{c}}(H)$ with increasing $H$, the pseudogap behavior in FeSe is ascribed to superconducting fluctuations, which presumably originate from the theoretically predicted preformed pair above $T_{\mathrm{c}}(H)$.

10 pages, 4 figures

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Cited by in corpus (2)

• Exotic Superconducting States in FeSe-based Materials
• Quantum vortex core and missing pseudogap in the multi-band BCS-BEC-crossover superconductor FeSe