Electron–vibration coupling induced renormalization in the photoemission spectrum of diamondoids

Abstract

The development of theories and methods devoted to the accurate calculation of the electronic quasi-particle states and levels of molecules, clusters and solids is of prime importance to interpret the experimental data. These quantum systems are often modelled by using the Born–Oppenheimer approximation where the coupling between the electrons and vibrational modes is not fully taken into account, and the electrons are treated as pure quasi-particles. Here, we show that in small diamond cages, called diamondoids, the electron–vibration coupling leads to the breakdown of the electron quasi-particle picture. More importantly, we demonstrate that the strong electron–vibration coupling is essential to properly describe the overall lineshape of the experimental photoemission spectrum. This cannot be obtained by methods within Born–Oppenheimer approximation. Moreover, we deduce a link between the vibronic states found by our many-body perturbation theory approach and the well-known Jahn–Teller effect.

Band gap renormalization of diamondoids: vibrational coupling and excitonic effects

“…Another approach [6] based on the Franck-Condon idea and a Monte Carlo sampling technique was used to calculate the optical absorption spectra of small diamondoids. Both of these very recent contributions [6,26] highlight the importance of the vibrational coupling in these structures.…”

“…Recently, theories based on the AHC approach have been implemented in a fully ab initio framework [10][11][12][18][19][20][21], path-integral molecular dynamics simulation [22], and first principles frozen-phonon calculations [12,21,[23][24][25]. A dynamical extension of the AHC approach [11] had been applied to small diamondoids [26] to calculate the spectral function and compare the results to photoemission experiments. Another approach [6] based on the Franck-Condon idea and a Monte Carlo sampling technique was used to calculate the optical absorption spectra of small diamondoids.…”

Many-body perturbation theory calculations using the yambo code

“…If the QP approximation holds, the spectral function A nk (ω, T ) = [G nk (ω, T )] is a single-peak Lorentzian function centered at [E nk ] with width Γ nk = [E nk ]. In case of strong EP interaction it has been proven that the spectral function spans a wide energy range [110,111] and the QP approximation is no longer valid. Figure 11 shows the spectral functions (SFs) of transpolyethylene and trans-polyacetylene, calculated at 0K.…”

Optical Properties of Vanadium in 4 H Silicon Carbide for Quantum Technology

“…The excited state is calculated by ∆SCF method [26], in order to determine the zero-phonon-line (ZPL) energy. In order to calculate the phonon sideband, the Huang-Rhys (HR) approximation was employed as implemented by Gali et al [27]. The strength of the coupling is represented by the total HR factor (S( ω)).…”