Electron-phonon (e-ph) interactions are usually treated in the lowest order of perturbation theory. Here we derive next-to-leading order e-ph interactions, and compute from first principles the associated two-phonon e-ph scattering rates. The derivation involves Matsubara sums of the relevant two-loop Feynman diagrams, and the numerical calculations are challenging since they involve Brillouin zone integrals over two crystal momenta and depend critically on the intermediate state lifetimes. Using random grids and Monte Carlo integration, together with a self-consistent update of the intermediate state lifetimes, we compute and converge the two-phonon scattering rates, using GaAs as a case study. For the longitudinal optical phonon in GaAs, we find that the two-phonon scattering rates are as large as nearly half the value of the leading-order rates. The energy and temperature dependence of the two-phonon processes are analyzed. We show that including the two-phonon processes is important to accurately predicting the electron mobility in GaAs.
Ab initio phonon self-energies and fluctuation diagnostics of phonon anomalies: Lattice instabilities from Dirac pseudospin physics in transition metal dichalcogenides
Ab-initio calculation of all-optical time-resolved calorimetry of nanosized systems: Evidence of nanosecond-decoupling of electron and phonon temperatures
An unified theory of quantised electrons, phonons and photons out-of-equilibrium: a simplified {\em ab-initio} approach based on the Generalised Baym-Kadanoff ansatz
Abnormally low thermal conductivity of 2D selenene: An ab initio study
采用第一性原理计算研究了二维$α$ -硒烯的晶格热导率和热输运性质。在室温下，各向同性的面内热导率低至3.04 W m $^{-1}$ K $^{-1}$，甚至低于具有类似构型和较低德拜温度的$α$ -碲烯。我们发现这种反常现象合理地源于声学声子支较大的非谐性。此外，声子谱，弹性性能，以及相关的热性能也显示。声学声子主要贡献于总热导率。进一步研究了尺寸效应、边界效应、三声子过程的总相空间、声子群速度和弛豫时间，揭示了声子群速度是影响二维硒烯热输运的关键因素。
Electrons and phonons in single layers of hexagonal indium chalcogenides from ab initio calculations
我们用密度泛函理论计算了二维In $_2$ X $_2$（X为S、Se或Te）晶体的电子能带结构、结合能、声子色散和光吸收谱。我们确定了两个结晶相（α和β）的单层六方晶系的In $_2$ X $_2$，并表明，他们的特点是由不同的拉曼活性声子模式。我们发现，这些材料是间接带隙半导体与宽边帽形状的分散附近的价带边缘的孔。后一个特征导致Lifshitz转变（空穴掺杂的In $_2$ × $_2$的费米表面拓扑的变化），对于X=S、Se和Te，分别在空穴浓度$n_{\rm S}=6.86\times 10^{13}$ cm $^{-2}$、$n_{\rm Se}=6.20\times 10^{13}$ cm $^{-2}$和$n_{\rm Te}=2.86\times 10^{13}$ cm $^{-2}$下，对于α-In $_2$ × $_2$和$n_{\rm S}=8.32\times 10^{13}$ cm $^{-2}$、$n_{\rm Se}=6.00\times 10^{13}$ cm $^{-2}$、和β-In $_2$的$n_{\rm Te}=8.14\times 10^{13}$ cm $^{-2}$ × $_2$。
Thermoelectric transport properties of silicon: Towards an ab initio approach
我们将玻尔兹曼输运方程与{ \it ab initio}方法结合起来计算半导体的热电系数。电子声子，电离杂质，和电子等离子体散射率已被考虑。利用密度泛函理论计算了电子-声子耦合的能带结构和平均谷间形变势。线性化玻尔兹曼方程，然后解决了数值超过弛豫时间近似。我们的方法已被应用到晶体硅。我们目前的结果的迁移率，塞贝克系数，和电子的热导率的贡献，作为载流子浓度和温度的函数。计算的系数与实验结果吻合较好。
