History and perspective of phonon–drag effect advancing thermoelectrics

Phonon–drag effect, arising from the momentum transfer between heat-carrying phonons and charge carriers, is known to produce exceptionally high Seebeck coefficients at low temperatures. Recent advances have uncovered materials with extraordinary thermoelectric performance, driven by pronounced phonon–drag contributions, including enhanced Seebeck coefficients and power factors. Notably, phonon–drag effects have been observed to improve thermoelectric conversion efficiencies even at room temperature, positioning this mechanism as a compelling strategy for advancing thermoelectric technologies. This review explores the historical evolution of phonon–drag research, spanning both theoretical and experimental milestones, and highlights recent progress in narrow-gap semiconductors, interfaces, and thin films, where phonon–drag phenomena are increasingly revealing their potential to enhance thermoelectric performance.