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arXiv · 2202.00166

Prominent electron-hole asymmetry in thermoelectric transport of LaCoO$_3$

Ryuji Okazaki·Keisuke Tomiyasu
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Abstract

We have measured the electrical resistivity and the thermopower of the electron-doped perovskite cobaltites LaCo$_{1-y}$Te$_y$O$_3$. In contrast to the hole-doped systems such as metallic ferromagnets La$_{1-x}M_x$CoO$_3$ ($M$ = Ca, Sr, Ba), the electron-doped samples show an insulating behavior even in a heavily doped range due to a spin-state blockade mechanism that an electron hopping from high-spin Co$^{2+}$ to low-spin Co$^{3+}$ site is energetically suppressed. We find that, despite the electron doping, the thermopower shows relatively large positive values above $y=0.05$, strikingly distinct from the hole-doped case where it comes close to zero with doping. This prominent electron-hole asymmetry seen in the thermopower originates from a bipolar conduction which consists of a slight amount of mobile holes and the main immobile electrons, demonstrating an impact of spin-state blockade on thermoelectric transport.

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Ryuji Okazaki, Keisuke Tomiyasu. 2022-02-01. Prominent electron-hole asymmetry in thermoelectric transport of LaCoO$_3$. https://doi.org/10.1103/physrevb.105.035154

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