Relaxation dynamics in laser-excited metals under nonequilibrium conditions
Relaxation dynamics in laser-excited metals under nonequilibrium conditions
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DOI：
10.1103/physrevb.87.035139
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发表时间：
2013-01-30
影响因子：
3.7
通讯作者：
Rethfeld, B.
中科院分区：
文献类型：
--
作者：
Mueller, B. Y.;Rethfeld, B.
当超短激光脉冲照射金属时，能量被电子系统吸收，电子系统在飞秒时间尺度上被赶出热平衡。由于电子-电子碰撞，在一个特征时间，即所谓的热化时间内，建立了电子系统内新的热力学平衡态。吸收的电子能量将进一步转移到声子系统。热化时间和电子-声子耦合强度与材料性质和激发类型有很大关系。此外，非热化电子气体与声子系统的耦合方式与热化电子气体的耦合方式不同。为了在不需要假设热化电子的情况下跟踪相关的微观动力学，我们应用完全玻尔兹曼碰撞积分来描述由于激发，热化和弛豫引起的瞬态电子分布。我们在我们的方法中实现了真实材料的状态密度。通过模拟，我们得到了非平衡条件下的电子热化时间和电子-声子耦合。给出了铝、金和镍的例子。DOI: 10.1103 / PhysRevB.87.035139
When an ultrashort laser pulse irradiates a metal, energy is absorbed by the electron system which is driven out of thermal equilibrium on a femtosecond time scale. Due to electron-electron collisions, a new thermodynamical equilibrium state within the electron system is established in a characteristic time, the so-called thermalization time. The absorbed energy of the electrons will be further transferred to the phononic system. The thermalization time as well as the electron-phonon coupling strength both strongly depend on the material properties and the excitation type. Furthermore, a nonthermalized electron gas couples differently to the phononic system as a thermalized one. In order to follow the relevant microscopic dynamics without the need to assume thermalized electrons, we apply complete Boltzmann collision integrals to describe the transient electron distribution due to excitation, thermalization, and relaxation. We implement the density of states of real materials in our approach. As a result of our simulations, we extract the electron thermalization time and the electron-phonon coupling under nonequilibrium conditions. Examples are given for aluminum, gold, and nickel. DOI: 10.1103/PhysRevB.87.035139