Ab initiostudy of phonon-induced dephasing of plasmon excitations in silver quantum dots

Phonon-induced pure dephasing of electronic excitations in silver quantum dots (QDs) is investigated with ab initio molecular dynamics at ambient and low temperatures. Three types of electronic states are studied corresponding to bulk, surface, and plasmon excitations. The electron-phonon coupling is strongest for bulk states and decreases for surface and plasmon states. The plasmon states dephase within 30--40 fs, which is consistent with the recent experiments [M. Z. Liu, M. Pelton, and P. Guyot-Sionnest, Phys. Rev. B 79, 035418 (2009)]. The dephasing time shows weak dependence on the QD size but changes significantly with temperature. The bulk, surface, and plasmon states couple primarily to low-frequency acoustic phonons.