Normal-state conductivity in underdoped La_{2-x}Sr_xCuO_4 thin films: Search for nonlinear effects related to collective stripe motion

TL;DR

This study investigates whether high electric fields can induce collective stripe motion in underdoped La_{2-x}Sr_xCuO_4 thin films, finding no evidence of non-linear conductivity due to stripe depinning, likely because of strong pinning effects.

Contribution

It provides the first detailed electric-field dependence analysis of normal-state conductivity in underdoped La_{2-x}Sr_xCuO_4 films, testing for collective stripe motion.

Findings

No non-linear conductivity observed at high fields.

Joule heating explains observed non-linearities.

Strong pinning likely prevents stripe depinning.

Abstract

We report a detailed study of the electric-field dependence of the normal-state conductivity in La_{2-x}Sr_xCuO_4 thin films for two concentrations of doped holes, x=0.01 and 0.06, where formation of diagonal and vertical charged stripes was recently suggested. In order to elucidate whether high electric fields are capable of depinning the charged stripes and inducing their collective motion, we have measured current-voltage characteristics for various orientations of the electric field with respect to the crystallographic axes. However, even for the highest possible fields (~1000 V/cm for x=0.01 and \~300 V/cm for x=0.06) we observed no non-linear-conductivity features except for those related to the conventional Joule heating of the films. Our analysis indicates that Joule heating, rather than collective electron motion, may also be responsible for the non-linear conductivity observed in some other 2D transition-metal oxides as well. We discuss that a possible reason why moderate electric fields fail to induce a collective stripe motion in layered oxides is that fairly flexible and compressible charged stripes can adjust themselves to the crystal lattice and individual impurities, which makes their pinning much stronger than in the case of conventional rigid charge-density waves.