High pressure growth and electron transport properties of superconducting SmFeAsO1-xHx single crystals

TL;DR

This study reports the successful growth of high-quality SmFeAsO1-xHx single crystals with a record Tc of 42 K, and investigates their structural, electronic, and transport properties, revealing electron doping via hydrogen substitution.

Contribution

It introduces a high-pressure synthesis method for SmFeAsO1-xHx single crystals and provides detailed insights into their electron transport and doping mechanisms.

Findings

Achieved single crystal growth with Tc of 42 K.

Confirmed electron doping through hydrogen substitution.

Observed metallic in-plane and semiconducting out-of-plane conduction.

Abstract

We report the single crystal growth and characterization of the highest Tc iron-based superconductor SmFeAsO1-xHx. Some sub-millimeter-sized crystals were grown using the mixture flux of Na3As + 3NaH + As at 3.0 GPa and 1473 K. The chemical composition analyses confirmed 10% substitution of hydrogen for the oxygen site (x = 0.10), however, the structural analyses suggested that the obtained crystal forms a multi-domain structure. By using the FIB technique we fabricated the single domain SmFeAsO0.9H0.10 crystal with the Tc of 42 K, and revealed the metallic conduction in in-plane (rhoab), while semiconducting in the out-of-plane (rhoc). From the in-plane Hall coefficient measurements, we confirmed that the dominant carrier of SmFeAsO0.9H0.10 crystal is an electron, and the hydride ion occupied at the site of the oxygen ion effectively supplies a carrier electron per iron following the equation: O2- = H- + e-.