Thermoelectric Properties of YBa2Cu3O7-(La,Ca)MnO3 Superlattices

TL;DR

This study investigates the thermoelectric properties of YBCO/LCMO superlattices, revealing a sign reversal in the Seebeck coefficient due to interface-induced electronic reconstruction, differing from bulk behavior.

Contribution

It demonstrates that interface effects in superlattices can alter thermoelectric properties, specifically causing a sign change in the Seebeck coefficient not seen in bulk materials.

Findings

Superlattices show positive Seebeck coefficients unlike negative in bulk.

Sign reversal attributed to electronic reconstruction at interfaces.

Lattice strain and oxygenation ruled out as causes.

Abstract

We report measurements of the thermoelectric power and electrical resistivity of superlattices composed of the high-temperature superconductor YBa2Cu3O(7-delta) (YBCO) and the metallic ferromagnet La(2/3)Ca(1/3)MnO3 (LCMO) with individual layer thicknesses between 5 and 50 nm. Whereas YBCO and LCMO reference films prepared under the same conditions exhibit negative Seebeck coefficients, in excellent agreement with data on bulk compounds of identical composition, those of all superlattices are positive, regardless of the individual layer thickness. Having ruled out lattice strain and incomplete oxygenation, we attribute the observed sign reversal of the Seebeck coefficient to a long-range electronic reconstruction nucleated at the YBCO-LCMO interfaces.