Large electric field effects on the resistance of La$_{0.67}$Ca$_{0.33}$MnO$_3$ microstructures

TL;DR

This study explores how large electric fields influence the resistance of La$_{0.7}$Ca$_{0.3}$MnO$_3$ microstructures near the metal-insulator transition, revealing phase-dependent resistance modulation and nonlinear transport behavior.

Contribution

It demonstrates the significant impact of electric fields on resistance in phase-separated manganite microstructures and links these effects to the state of polaron phases.

Findings

Unipolar electric field reduces resistance during metal-insulator transition.

Electric fields suppress nonlinear I-V features linked to phase separation.

Field effects vanish when the polaron glassy phase fully develops.

Abstract

We investigate electric field effects in thin film microbridges of La$_{0.7}$Ca$_{0.3}$MnO$_3$ with the focus on the regime of metal-insulator transition. A mechanically milled SrTiO$_3$ substrate is used as a backgate dielectric. Inside the metal-insulator transition we find a strong unipolar field-induced reduction in resistance, as well as a suppression of the nonlinear features in the I-V curves we observed earlier. We associate the observed effects with a phase separated state in which metallic regions coexist with short range correlated polaron regions. When the glassy polaron phase has fully developed, and closes off the microbridge, the field effects disappear leaving the strongly nonlinear behavior of the transport current unaltered.