Pressure-induced quantum critical point in a heavily hydrogen-doped iron-based superconductor LaFeAsO

2019/05/16 by Takeuchi, Masayoshi, Fujiwara, Naoki, Kuwayama, Takanori +6
#FOS: Physical sciences #Superconductivity (cond-mat.supr-con)

paper · doi:10.48550/arxiv.1905.06606

Abstract

An iron-based superconductor LaFeAsO_1-xH_x (0 ≤ x ≤ 0.6) undergoes two antiferromagnetic (AF) phases upon H doping. We investigated the second AF phase (x=0.6) using NMR techniques under pressure. At pressures up to 2 GPa, the ground state is a spin-density-wave state with a large gap; however, the gap closes at 4.0 GPa, suggesting a pressure-induced quantum critical point. Interestingly, the gapped excitation coexists with gapless magnetic fluctuations at pressures between 2 and 4 GPa. This coexistence is attributable to the lift up of the d_xy orbital to the Fermi level, a Lifshitz transition under pressure.

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