Flat-band energy filtering in interacting systems: conditions for improving thermoelectric performances
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arXiv
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2026
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| author | Cosco, F. Tuovinen, R. Plastina, F. Gullo, N. Lo |
| author_facet | Cosco, F. Tuovinen, R. Plastina, F. Gullo, N. Lo |
| contents | Motivated by recent theoretical and experimental studies on the role of flatbands in the thermoelectric properties of Ni$_3$In$_{1-x}$Sn$_x$ compounds, we investigate electron transport in two minimal one-dimensional flatband models, the sawtooth and diamond chains, which differ in a crucial aspect: the flatband is separated from the dispersive band by a finite gap in the former, while the two bands touch in the latter. Using a non-equilibrium Green function framework with interactions treated at the Hartree-Fock and GW levels, we compute the full set of thermoelectric coefficients and the figure of merit $zT$ as functions of gate voltage and temperature. We show that, contrary to naive expectation, a perfectly isolated flat-band is a physically ill-founded thermoelectric: the electrical conductivity vanishes as the chemical potential enters the flat-band, rendering the large Seebeck coefficient and the apparent violation of the Wiedemann-Franz law physically meaningless. Optimal thermoelectric performance is instead achieved just below the flat-band edge, where the transmission function varies most rapidly with energy, consistent with the Mahan-Sofo picture, and requires a finite broadening of the flat-band through hybridization with dispersive states. We further show that electron-electron interactions renormalize the flat-band structure itself, inducing an interaction-driven narrowing of the bandwidth and, in the diamond chain, a correlation-induced opening of a gap between the flat-band and the dispersive band near half-filling. Mean-field treatments are found to systematically overestimate \(zT\), highlighting the importance of beyond-mean-field correlations for quantitatively reliable predictions in flat-band thermoelectrics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_15684 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Flat-band energy filtering in interacting systems: conditions for improving thermoelectric performances Cosco, F. Tuovinen, R. Plastina, F. Gullo, N. Lo Materials Science Mesoscale and Nanoscale Physics Motivated by recent theoretical and experimental studies on the role of flatbands in the thermoelectric properties of Ni$_3$In$_{1-x}$Sn$_x$ compounds, we investigate electron transport in two minimal one-dimensional flatband models, the sawtooth and diamond chains, which differ in a crucial aspect: the flatband is separated from the dispersive band by a finite gap in the former, while the two bands touch in the latter. Using a non-equilibrium Green function framework with interactions treated at the Hartree-Fock and GW levels, we compute the full set of thermoelectric coefficients and the figure of merit $zT$ as functions of gate voltage and temperature. We show that, contrary to naive expectation, a perfectly isolated flat-band is a physically ill-founded thermoelectric: the electrical conductivity vanishes as the chemical potential enters the flat-band, rendering the large Seebeck coefficient and the apparent violation of the Wiedemann-Franz law physically meaningless. Optimal thermoelectric performance is instead achieved just below the flat-band edge, where the transmission function varies most rapidly with energy, consistent with the Mahan-Sofo picture, and requires a finite broadening of the flat-band through hybridization with dispersive states. We further show that electron-electron interactions renormalize the flat-band structure itself, inducing an interaction-driven narrowing of the bandwidth and, in the diamond chain, a correlation-induced opening of a gap between the flat-band and the dispersive band near half-filling. Mean-field treatments are found to systematically overestimate \(zT\), highlighting the importance of beyond-mean-field correlations for quantitatively reliable predictions in flat-band thermoelectrics. |
| title | Flat-band energy filtering in interacting systems: conditions for improving thermoelectric performances |
| topic | Materials Science Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2604.15684 |