Thermalization in simple metals: Role of electron-phonon and phonon-phonon scattering

Abstract

We study the electron and phonon thermalization in simple metals excited by a laser pulse. The thermalization is investigated numerically by solving the Boltzmann transport equation taking into account all the relevant scattering mechanism: the electron-electron, electron-phonon (e-ph), phonon-electron (ph-e), and phonon-phonon (ph-ph) scatterings. In the initial stage of the relaxation, most of the excitation energy is transferred from the electrons to phonons through the e-ph scattering. This creates hot high-frequency phonons due to the ph-e scatterings, followed by an energy redistribution between phonon subsystems through the ph-ph scatterings. This yields an overshoot of the total longitudinal-acoustic phonon energy at a time, across which a crossover occurs from a nonequilibrium state, where the e-ph and ph-e scatterings frequently occur, to a state, where the ph-ph scattering occurs to reach a thermal equilibrium. This picture is quite different from the scenario of the well-known two-temperature model (2TM). The behavior of the relaxation dynamics is compared with those calculated by several models, including the 2TM, the four-temperature model, and nonequilibrium electron or phonon models. The relationship between the relaxation time and the initial distribution function is also discussed.

Phonon softening in sodium with a stepwise electron distribution

“…Figure 4 shows the lowest E p at the N point as a function of E el for two cases: is not merely a function of E el but a functional of f (ε). A similar f (ε)-dependence has also been reported in the electron relaxation dynamics [20]. We next elucidate the origin of the imaginary frequency at the N point.…”

Fundamental limits of hot carrier injection from metal in nanoplasmonics

“…3b. As a result, as SPP is absorbed and a hot electron and [52]. But it is important to stress, that this is a quantum, not a classical process.…”

Generating Hot Carriers in Plasmonic Nanoparticles: When Quantization Does Matter?

“…Note that EL  is so long not because the electron-phonon scattering rate is weak (it is not! [57]) but because the energy transferred to lattice each time phonon scattering takes place is only a phonon energy. Therefore the fraction of nanoparticles that have elevated electron temperature at a given time t t    the nanoparticle "A" has cooled down to the lattice temperature T, as shown in Fig.…”