Acoustic polarons generate quasiballistic photocurrent at room temperature

Semiconductor technologies fundamentally rely on efficient carrier transport from the source to the target. However, at room temperature, phonon and impurity scattering severely limit carrier scattering times (<1 ps) and mean free paths (<100 nm), motivating decades of efforts to discover materials with smaller effective masses and higher thermal velocities. In this talk, we introduce an opposite paradigm: employing acoustic polarons – energy carriers with over two orders of magnitude heavier effective mass and much slower thermal velocities than conventional semiconductors – as a means to achieve near-scatter-free transport. We show that acoustic exciton-polarons in the van der Waals superatomic semiconductor Re₆Se₈Cl₂ exhibit scattering times up to 370 ps and mean free paths exceeding 440 nm at room temperature, enabling direct photocurrent generation across 7 µm channel in functional devices. Through combined ultrafast optical imaging and Monte Carlo simulations, we further uncover their exceptional robustness against impurities, providing new design principles for next-generation, energy-efficient optoelectronic systems.