Ab initio study of temperature- and pressure dependence of energy and phonon-induced dephasing of electronic excitations in CdSe and PbSe quantum dots

The pressure and temperature dependence of the lowest excitation energy of PbSe (Pb68Se68, d = 2.0 nm) and CdSe (Cd33Se33, d = 1.6 nm) quantum dots (QDs) were investigated by ab initio density functional theory and molecular dynamics simulation. Additionally, pure-dephasing/decoherence induced by the electron-phonon interaction was studied using optical response theory for several pairs of electronic states, including ground, excitonic and biexcitonic states. Linear dependence on temperature was observed for all quantities under consideration. The results were consistent with other theoretical and experimental reports. The ab initio data was analyzed using the effective mass approximation and the hyperbolic band model. The analysis confirmed the temperature dependence of the effective mass in the PbSe QD, as suggested in a recent experimental report [Liptay, T. J.; Ram, R. J. Appl. Phys. Lett. 2006, 89, 223132].