Nonmetallic Low-Temperature Normal State of K0.70Fe1.46Se1.85Te0.15

TL;DR

This study investigates the low-temperature normal state of a phase-separated superconductor, revealing a logarithmic increase in resistivity and suggesting a superconductor-insulator transition induced by high magnetic fields.

Contribution

It provides new insights into the normal-state behavior and phase separation effects in K-doped iron selenide superconductors under high magnetic fields.

Findings

Resistivity increases logarithmically as temperature decreases.

Evidence of a superconductor-insulator transition in high magnetic fields.

Normal-state behavior linked to intrinsic phase separation.

Abstract

The normal-state in-plane resistivity below the zero-field superconducting transition temperature $T_c$ and the upper critical field Hc2 were measured by suppressing superconductivity in pulsed magnetic fields for K0.70Fe1.46Se1.85Te0.15. The normal-state resistivity $\rho_{ab}$ is found to increase logarithmically with decrasing temperature as $\frac{T}{T_c}\rightarrow 0$. Similar to granular metals, our results suggest that a superconductor - insulator transition below zero-field T$_{c}$ may be induced in high magnetic fields. This is related to the intrinsic real-space phase-separated states common to all inhomogeneous superconductors.