Persistent X-Ray Photoconductivity and Percolation of Metallic Clusters in Charge-Ordered Manganites

TL;DR

This study investigates how x-ray exposure induces persistent photoconductivity in charge-ordered manganites by enhancing electron mobility through phase separation and barrier modification, rather than increasing conduction electrons.

Contribution

It reveals that x-ray illumination causes a phase-separated state that improves electron mobility by modifying barriers, offering a new understanding of persistent photoconductivity in manganites.

Findings

X-ray exposure leads to phase separation in manganites.

Enhanced electron mobility occurs without increasing conduction electrons.

Barrier modification underpins persistent photoconductivity.

Abstract

Charge-ordered manganites of composition $\rm Pr_{1-x}(Ca_{1-y}Sr_{y})_{x}MnO_3$ exhibit persistent photoconductivity upon exposure to x-rays. This is not always accompanied by a significant increase in the {\it number} of conduction electrons as predicted by conventional models of persistent photoconductivity. An analysis of the x-ray diffraction patterns and current-voltage characteristics shows that x-ray illumination results in a microscopically phase separated state in which charge-ordered insulating regions provide barriers against charge transport between metallic clusters. The dominant effect of x-ray illumination is to enhance the electron {\it mobility} by lowering or removing these barriers. A mechanism based on magnetic degrees of freedom is proposed.