Effect of external electromagnetic radiation on the anomalous metallic behaviors in Ta thin films

TL;DR

This study shows that external electromagnetic radiation significantly influences the anomalous metallic behavior in Ta thin films, indicating that such metallic states are largely induced by unfiltered radiation rather than intrinsic properties.

Contribution

It demonstrates that electromagnetic radiation filters can suppress the anomalous metallic state in Ta films, suggesting the metallic behavior is primarily caused by external radiation effects.

Findings

Room-temperature filters shift the superconducting transition to higher temperatures.

Low-temperature filters weaken the resistance saturation, indicating radiation-induced metallic behavior.

Intrinsic metallic ground state, if it exists, is limited to a narrow magnetic field range near the critical point.

Abstract

We investigated transport characteristics of superconducting Ta thin films with three configurations in rf radiation filters; no filter, only room-temperature filters, and low-temperature filters in addition to room-temperature filters. The transport properties near the transition temperature are strongly dependent on whether the room-temperature filter is installed or not. The entire transition is shifted to higher temperature with loading layers of the room-temperature filters. Once the zero-resistance state is achieved at B=0, no strong radiation effect is observed even with low-temperature filters installed. When magnetic field is turned on, the nonzero-resistance saturation at low temperatures is revealed without low-temperature filters, which has been considered to be magnetic-field-induced quantum metallic phase. However, the insertion of the additional low-temperature filter weakens the saturation of the resistance, the signature of the metallic behavior. This observation suggests that the previously reported anomalous metallic state in Ta films is mainly induced by the unfiltered radiation and, thus, the intrinsic metallic ground state should be limited to the narrow range of magnetic fields near the critical point, if exists.