Anomalous scaling law for thermoelectric transport of 2D-confined electrons in an organic molecular system

TL;DR

This study reveals an unusual enhancement of thermopower in a layered organic compound with strong 2D character, showing a larger slope in the Jonker plot than conventional semiconductors, indicating significant effects of 2D confinement on thermoelectric properties.

Contribution

The paper demonstrates a novel anomalous scaling law for thermoelectric transport in 2D-confined electrons within layered organic materials, highlighting the impact of 2D confinement on thermopower.

Findings

Enhanced thermopower observed in layered organic compound.

Large slope in Jonker plot exceeds that of conventional semiconductors.

Impact of 2D-confined carriers on thermoelectricity confirmed.

Abstract

Confined electrons in low dimensions host desirable material functions for downscaled electronics as well as advanced energy technologies. Thermoelectricity is a most fascinating example, since the dimensionality modifies the electron density of states dramatically, leading to enhanced thermopower as experimentally examined in artificial two-dimensional (2D) structures. However, it is still an open question whether such an enhanced thermopower in low dimensions is realized in layered materials with strong 2D characters such as cuprates. Here, we report unusual enhancement of the thermopower in the layered organic compound $\alpha$-(BEDT-TTF)$_2$I$_3$, where BEDT-TTF stands for bis(ethylenedithio)-tetrathiafulvalene. We find that the slope in the Jonker plot (thermopower $S$ vs. logarithm of electrical conductivity $\log\sigma$) for $\alpha$-(BEDT-TTF)$_2$I$_3$ is significantly larger than that of conventional semiconductors. Moreover, the large slope is also seen in the related layered salt, demonstrating the impact of the 2D-confined carriers in the layered organics on thermoelectricity.