Thermalization in simple metals: Role of electron-phonon and phonon-phonon scattering
Thermalization in simple metals: Role of electron-phonon and phonon-phonon scattering
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DOI：
10.1103/physrevb.97.054310
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发表时间：
2017-11
影响因子：
3.7
通讯作者：
S. Ono
中科院分区：
文献类型：
--
作者：
S. Ono
我们研究激光脉冲激发的简单金属中的电子和声子热化。通过求解玻尔兹曼输运方程，考虑所有相关的散射机制，对热化进行数值研究：电子-电子、电子-声子 (e-ph)、声子-电子 (ph-e) 和声子-声子 (ph-ph) 散射。在弛豫的初始阶段，大部分激发能通过 e-ph 散射从电子转移到声子。由于 ph-e 散射，这会产生热高频声子，然后通过 ph-ph 散射在声子子系统之间进行能量重新分配。这会产生一次总纵向声声子能量的超调，跨越该超调，从非平衡状态（频繁发生 e-ph 和 ph-e 散射）到发生 ph-ph 散射以达到热平衡的状态发生交叉。该图与著名的双温度模型（2TM）的场景有很大不同。将弛豫动力学的行为与几个模型计算的行为进行了比较，包括 2TM、四温度模型和非平衡电子或声子模型。还讨论了弛豫时间与初始分布函数之间的关系。
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.