Lippmann-Schwinger Approach for Accurate Photoelectron Wave Functions and Angle-Resolved Photoemission Spectra from First Principles.

We present a conceptually simple and technically straightforward method for calculating photoelectron wave functions that is easily integrable with standard wave-function-based density-functional-theory packages. Our method is based on the Lippmann-Schwinger equation, naturally incorporating the boundary condition that the final photoelectron state must satisfy. The calculated results are in good agreement with the measured photon-energy and polarization dependence of the angle-resolved photoemission spectroscopy (ARPES) of graphene, the photon-energy-dependent evolution of the so-called dark corridor arising from the pseudospin, and WSe_{2}, the circular dichroism reflecting the hidden orbital polarization.

Plasmon-Phonon Hybridization in Doped Semiconductors from First Principles.

Although plasmons and phonons are the collective excitations that govern the low-energy physics of doped semiconductors, their nonadiabatic hybridization and mutual screening have not been studied from first principles. We achieve this goal by transforming the Dyson equation to the frequency-independent dynamical matrix of an equivalent damped oscillator. Calculations on doped GaAs and TiO_{2} agree well with available Raman data and await immediate experimental confirmation from infrared, neutron, electron-energy-loss, and angle-resolved photoemission spectroscopies.