The "dark phase'' in Sr$_2$Ir$_{1-x}$Rh$_x$O$_4$ revealed by Seebeck and Hall measurements

TL;DR

This study uncovers a hidden electron contribution in Rh-doped Sr$_2$IrO$_4$, suggesting complex charge dynamics with potential electron localization in disordered clusters, revealed through thermoelectric and Hall measurements.

Contribution

It demonstrates the presence of an electron-like contribution in a system expected to be hole-doped, highlighting a novel aspect of charge transport in Sr$_2$Ir$_{1-x}$Rh$_x$O$_4$.

Findings

Detection of electron-like transport contribution.

Absence of electron band in ARPES measurements.

Possible electron delocalization in disordered clusters.

Abstract

It was found that, although isovalent, Rh substituted for Ir in Sr$_2$IrO$_4$ may trap one electron inducing effective hole doping of Ir sites. Transport and thermoelectric measurements on Sr$_2$Ir$_{1-x}$Rh$_x$O$_4$ single crystals presented here reveal the existence of an electron-like contribution to transport, in addition to the hole-doped one. As no electron band shows up in ARPES measurements, this points to the possibility that this hidden electron may delocalize in disordered clusters.