Enhanced Low-Temperature Thermoelectric Performance in (PbSe)(VSe) Heterostructures due to Highly Correlated Electrons in Charge Density Waves.

We explore the effect of charge density wave (CDW) on the in-plane thermoelectric transport properties of (PbSe)(VSe) and (PbSe)(VSe) heterostructures. In (PbSe)(VSe) we observe an abrupt 86% increase in the Seebeck coefficient, 245% increase in the power factor, and a slight decrease in resistivity over the CDW transition. This behavior is not observed in (PbSe)(VSe) and is rather unusual compared to the general trend observed in other materials. The abrupt transition causes a deviation from the Mott relationship through correlated electron states. Raman spectra of the (PbSe)(VSe) material show the emergence of additional peaks below the CDW transition temperature associated with VSe material. Temperature-dependent in-plane X-ray diffraction (XRD) spectra show a change in the in-plane thermal expansion of VSe in (PbSe)(VSe) due to lattice distortion. The increase in the power factor and decrease in the resistivity due to CDW suggest a potential mechanism for enhancing the thermoelectric performance at the low temperature region.