# Close correlation between superconducting transition temperatures and carrier densities in Te- and S-substituted FeSe thin films

## TL;DR

This study reveals a direct correlation between superconducting transition temperatures and carrier densities in FeSe thin films with S and Te substitutions, highlighting different effects of structural transitions on electronic properties.

## Contribution

It provides a comparative analysis showing how Te and S substitutions differently influence carrier densities and superconductivity in FeSe thin films.

## Key findings

- Carrier densities increase with Te content but not with S substitution.
- $T_c$ correlates with carrier densities, indicating structural transition impacts electronic structure.
- Different effects of structural transition on electronic properties between Fe(Se,S) and Fe(Se,Te).

## Abstract

We comparatively investigated the transport properties for S- and Te-substituted FeSe thin films under magnetic fields to clarify the origin of the contrasting behavior of the superconducting transition temperature in S and Te substitution. A classical two carrier analysis revealed that the carrier densities of the films increased with increasing Te content, while no significant change was observed for the S-substitution. This composition dependence of the carrier density well corresponds to the $T_{\mathrm c}$ behavior. The clear correlation between $T_{\mathrm c}$ and the carrier densities suggests that the structural transition affects the electronic structure in a different manner between Fe(Se,S) and Fe(Se,Te) and that this fact is the direct cause of the difference in the $T_{\mathrm c}$ behaviors at the end point of the structural transition.