Ribeiro, SofiaTerças, Hugo2026-01-052026-01-052026-01-09Ribeiro, S. & Terças, H. (2026). Quantum theory of plasmon-phonon scattering in multisubband systems. Journal of Physics: Condensed Matter, 38(1), 1-14. https://doi.org/10.1088/1361-648X/ae2b1b0953-8984http://hdl.handle.net/10400.21/22425We present a first-principles quantum theory of a critical yet unexplored energy-loss pathway in low-dimensional semiconductors: resonant second-order scattering between multisubband (MSB) plasmons mediated by longitudinal optical phonons. Specifically, we demonstrate how a high-energy MSB plasmon decays into a lower-energy plasmon state via phonon emission-a fundamental process governing energy relaxation and decoherence in quantum wells. Through exact diagonalization of the coupled plasmon-phonon system and derivation of an effective Hamiltonian, we identify density-tunable resonance conditions that maximize scattering efficiency. Our numerical simulations for GaInAs quantum wells reveal scattering rates ( similar to 10ns-1) competitive with radiative losses, with carrier density acting as a control knob. These results resolve the interplay of collective electronic and vibrational modes in confined systems, providing design principles to mitigate losses in infrared photodetectors, quantum cascade lasers, and plasmon-based quantum devices.engMultisubband plasmonsPhononsScattering processesresearch article10.1088/1361-648X/ae2b1b1361-648X