Abstract
We have carried out a detailed study to investigate the existence of an insulating parent phase for FeSe superconductor. The insulating Fe4Se5 with √5 × √5 Fe-vacancy order shows a 3D-Mott variable range hopping behavior with a Verwey-like electronic correlation at around 45 K. The application of the RTA process at 450 °C results in the destruction of Fe-vacancy order and induces more electron carriers by increasing the Fe3+ valence state. Superconductivity emerges with Tc ~ 8K without changing the chemical stoichiometry of the sample after the RTA process by resulting in the addition of extra carriers in favor of superconductivity.
Highlights
The FeAs-based [1] and FeSe-based [2] superconductors are among the most investigated materials in condensed matter physics since their discovery in 2008
The nematic order coexists with superconductivity but not with longrange magnetic order which has led to arguments that the origin of the nematicity in FeSe is not magnetically but likely orbital-driven [14, 15]
After RTA treatment at 450°C, the superstructure peaks observed in X-ray diffraction (XRD) and TEM-SAED due to the √5 × √5 Fe-vacancy order disappear, as shown in Figure 1B and its inset
Summary
The FeAs-based [1] and FeSe-based [2] superconductors are among the most investigated materials in condensed matter physics since their discovery in 2008. The parent compounds of FeAs-based materials exhibit structural transitions from a hightemperature tetragonal phase to a low-temperature orthorhombic phase, which is accompanied by an antiferromagnetic (AF) order [9, 10].
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