NMR study of the AF-SC-SC-AF phased transition in a pnictide superconductor LaFeAsO$_{\mathrm{1-x}}$H$_{\mathrm{x}}$

We have performed $^{75}$As and $^{1}$H NMR measurements in LaFeAsO$_{\mathrm{1x}}$H$_{\mathrm{x}}$, an isomorphic compound of LaFeAsO$_{\mathrm{1x}}$F$_{\mathrm{x}}$. LaFeAsO$_{\mathrm{1x}}$H$_{\mathrm{x}}$ is an electron doped system, and O2- can be replaced with H$^{-}$ up to $x=$0.5. LaFeAsO$_{\mathrm{1x}}$H$_{\mathrm{x}}$ is known for having double superconducting (SC) domes on H doping. Recently, we discovered that a new antiferromagnetic (AF) phase follows the double SC domes on further H doping, forming a symmetric AF-SC-SC-AF phase alignment in the electronic phase diagram [1] Unlike the AF ordering in the lightly H-doped regime, the AF ordering in the highly H-doped regime is attributed to the nesting between electron pockets. In the conference, we will show the data of both NMR spectra and the relaxation rate 1/$T_{1}$ in the whole doping region. We will discuss the difference of electronic states between the lightly H-doped AF-SC phases and highly H-doped SC-AF phases.\\[4pt] [1] N. Fujiwara, et al., PRL \textbf{111} 097002 (2013)\\[0pt] [2] Y. Yamakawa, et al., PRB \textbf{88} 041106 (R) (2013)