[institut] Reminder: CSSPNM seminar: M. Houtput, Thursday Apr. 2, 12 h

[Darko Tanaskovic]

Dear colleagues,

You are cordially invited to the Center for Solid State Physics and New 
Materials seminar, which will be held on Thursday April 2 2026 at 12:00, 
in the library reading room "Dr. Dragan Popović" of the Institute of 
Physics Belgrade.

The talk, entitled "First principles theory of nonlinear long-range 
electron-phonon interaction" will be given by Dr. Matthew Houtput, 
University of Antwerp.

The abstract of the talk:

"When an electron moves through a solid, it can interact with the ions 
in the lattice of the solid. These so-called electron-phonon 
interactions are necessary to describe several important material 
properties, such as the electrical conductivity and conventional 
superconductivity. It is often sufficient to describe electron-phonon 
interactions using the approximation of linear interaction, where one 
only keeps the process where one electron interacts with one phonon. 
However, this is no longer true in anharmonic materials with significant 
electron-phonon interaction, such as quantum paraelectrics and halide 
perovskites. Currently, the only available models for nonlinear 
electron-phonon interaction are model Hamiltonians, written in terms of 
phenomenological parameters. Here, we provide a microscopic 
semi-analytical expression for the long-range dipole part of the 
1-electron-2-phonon matrix element, which can be interfaced with first 
principles techniques. We show that unlike for the long-range 
1-electron-1-phonon interaction, the continuum approximation is not 
sufficient and that the entire phonon dispersion must be considered. We 
calculate an expression for the quasiparticle energies and show that 
they can be written in terms of a 1-electron-2-phonon spectral function. 
To demonstrate the method in practice, we calculate the 
1-electron-2-phonon spectral function for LiF and CsPbI3 from first 
principles, and we show that the nonlinear interaction contributes 
significantly to the electron mobility of CsPbI3. The framework 
presented here bridges the gap between model Hamiltonians and 
first-principles calculations for the 1-electron-2-phonon interaction."

References:

[1] Matthew Houtput, Ingvar Zappacosta, Serghei Klimin, Samuel Poncé, 
Jacques Tempere, Cesare Franchini, arxiv.org/abs/2603.10954


Best regards,

Darko Tanaskovic