Electron-Hole Asymmetry in GdBaCo_{2}O_{5+x}: Evidence for Spin Blockade of Electron Transport in a Correlated Electron System

TL;DR

This study reveals a significant electron-hole transport asymmetry in GdBaCo_{2}O_{5+x}, demonstrating that hole doping enhances conductivity while electron doping does not, due to a spin blockade effect in this correlated electron system.

Contribution

The paper provides experimental evidence for spin blockade causing electron transport suppression in GdBaCo_{2}O_{5+x}, highlighting a fundamental asymmetry in charge carrier behavior.

Findings

Hole doping significantly reduces resistivity and improves conductivity.

Electron doping results in persistent poor conductivity.

Spin blockade is identified as the mechanism behind electron transport suppression.

Abstract

In RBaCo_{2}O_{5+x} compounds (R is rare earth) variability of the oxygen content allows precise doping of CoO_2 planes with both types of charge carriers. We study transport properties of doped GdBaCo_{2}O_{5+x} single crystals and find a remarkable asymmetry in the behavior of holes and electrons doped into a parent insulator GdBaCo_{2}O_{5.5}. Doping dependences of resistivity, Hall response, and thermoelectric power reveal that the doped holes greatly improve the conductivity, while the electron-doped samples always remain poorly conducting. This doping asymmetry provides strong evidence for a spin blockade of the electron transport in RBaCo_{2}O_{5+x}.