# Correlation in transport coefficients of hole-doped CuRhO$_2$ single crystals

## TL;DR

This study systematically investigates the transport properties of single-crystalline CuRhO$_2$, revealing phonon-drag effects and correlations between resistivity and thermopower that clarify its thermoelectric behavior.

## Contribution

It provides the first detailed transport measurements on single-crystalline CuRhO$_2$, highlighting the relationship between resistivity and Seebeck coefficient in this material.

## Key findings

- Phonon-drag effect causes a peak in Seebeck coefficient.
- Resistivity and Seebeck coefficient decrease with Mg substitution.
- Low-temperature transport follows simple metallic relationships.

## Abstract

To clarify the origin of the nontrivial thermoelectric properties observed in the delafossite oxide CuRhO$_2$ polycrystals, we have performed the systematic transport measurements on the single-crystalline CuRhO$_2$ samples. In the parent compound, we find a pronounced peak structure due to a phonon-drag effect in the temperature dependence of the Seebeck coefficient, which is also confirmed by the size effect experiments. In the Mg-substituted crystals, in contrast to the results of the polycrystals, both the resistivity and the Seebeck coefficient decrease with increasing Mg content $y$. In particular, the coefficient $A$ for the $T^2$ term of the resistivity and the $T$-linear coefficient for the Seebeck coefficient at low temperatures are well described within a simple relationship expected for metals, which is also applicable to the correlated materials with low carrier densities.