Abstract
We report thermoelectric studies of () superconducting single crystals that feature high irreversibility fields and critical current density comparable to materials with much higher superconducting critical temperatures ('s). The ratio of to the Fermi temperature is very small, indicating weak electronic correlations. With a slight selenium substitution on sulfur site in FeS both and the effective mass rise considerably, implying increase in electronic correlation of the bulk conducting states. The first-principle calculations show rise of the density of states at the Fermi level in when compared to FeS, which is related not only to Fe but also to chalcogen-derived electronic states.
- Received 14 October 2021
- Revised 5 December 2021
- Accepted 10 January 2022
DOI:https://doi.org/10.1103/PhysRevB.105.045133
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