Establishing non-thermal regimes in pump-probe electron-relaxation dynamics
MengXing Na, Fabio Boschini, Arthur K. Mills, Matteo Michiardi, Ryan P. Day, Berend Zwartsenberg, Giorgio Levy, Sergey Zhdanovich, Alexander F. Kemper, David J.… 展开作者
MengXing Na, Fabio Boschini, Arthur K. Mills, Matteo Michiardi, Ryan P. Day, Berend Zwartsenberg, Giorgio Levy, Sergey Zhdanovich, Alexander F. Kemper, David J. Jones, Andrea Damascelli
Time- and angle-resolved photoemission spectroscopy (TR-ARPES) accesses the electronic structure of solids under optical excitation, and is a powerful technique for studying the coupling between electrons and collective modes. One approach to infer electron-boson coupling is through the relaxation dynamics of optically-excited electrons, and the characteristic timescales of energy redistribution. A common description of electron relaxation dynamics is through the effective electronic temperature. Such a description requires that thermodynamic quantities are well-defined, an assumption that is generally violated at early delays. Additionally, precise estimation of the non-thermal window -- within which effective temperature models may not be applied -- is challenging. We perform TR-ARPES on graphite and show that Boltzmann rate equations can be used to calculate the time-dependent electronic occupation function, and reproduce experimental features given by non-thermal electron occupation. Using this model, we define a quantitative measure of non-thermal electron occupation and use it to define distinct phases of electron relaxation in the fluence-delay phase space. More generally, this approach can be used to inform the non-thermal-to-thermal crossover in pump-probe experiments.
Relaxation dynamics of the optically driven nonequilibrium states in the electron- and hole-doped topological-insulator materials $(Bi_{1-x}Sb_{x})_{2}Te_{3}$
Ultrafast electron dynamics in Au/Fe/MgO(001) analyzed by Au- and Fe-selective pumping in time-resolved two-photon photoemission spectroscopy: Separation of excitations in adjacent metallic layers
Electron spin dynamics of Ce$^{3+}$ ions in YAG crystals studied by pulse-EPR and pump-probe Faraday rotation
利用脉冲电子顺磁共振和时间分辨抽运探测法拉第旋转研究了重掺铈钇铝石榴石晶体中Ce $^{3+}$离子的自旋弛豫动力学。这两种技术都解决了4 $f$基态，而泵浦-探测法拉第旋转也提供了对激发的5 $d$态的访问。在低温下测量了Ce $^{3+}$基态的毫秒级自旋晶格弛豫时间$T_1$、微秒级自旋相干时间$T_2$和$\sim 10$ ns级非均匀自旋退相时间$T_2^*$. Ce $^{3+}$离子的自旋-晶格弛豫是由于涉及125 cm $^{-1}$处的光学声子模的修改的拉曼过程。在较高温度下的弛豫通过在约$\hbar ω\approx 228$ cm $^{-1}$处的$^{2}$ F $_{5/2}$项的第一激发能级。观察到Ce $^{3+}$与$^{27}$ Al核的超精细相互作用所提供的效应。
Barrier Softening near the onset of Non-Activated Transport in Supercooled Liquids: Implications for Establishing Detailed Connection between Thermodynamic and Kinetic Anomalies in Supercooled Liquids
