# Illumination effect by visible continuous-wave laser on bulk 40 K-superconductors

## TL;DR

This study investigates how continuous-wave visible laser heating affects the critical temperature and superconductivity of bulk CeFeAsO0.65F0.35 and MgB2, revealing laser-induced Tc reduction and slight enhancement in CeFeAsO0.65F0.35.

## Contribution

It demonstrates the impact of laser heating on bulk superconductors and models temperature effects, highlighting the role of temperature gradients in superconductivity suppression.

## Key findings

- Laser fluence reduces Tc in both superconductors.
- Temperature gradients trigger superconductivity destruction.
- CeFeAsO0.65F0.35 shows Tc enhancement under high fluence.

## Abstract

Visible CW (continuous wave) -laser heating effects on the bulk superconductors CeFeAsO0.65F0.35 and MgB2 with 1.5 mm thickness have been investigated by measuring the temperature dependence of electrical resistivity. Each compound shows a critical-temperature Tc reduction with increasing fluence rate. At the normal state, a parallel circuit model based on the Fourier's law can well reproduce the temperature dependence of electrical resistivity of illuminated sample. On the other hand, the predicted temperature-rise due to the laser heating in the superconducting state is much smaller than the observed Tc-reduction. A temperature gradient of a few K across the sample thickness easily triggers the destruction of bulk superconductivity. Furthermore we have found a slight Tc-enhancement in CeFeAsO0.65F0.35 after a rather high fluence-rate irradiation.