# Strong electron-phonon coupling and its influence on the transport and optical properties of hole-doped single-layer InSe

## TL;DR

This study reveals strong electron-phonon interactions in hole-doped single-layer InSe, significantly affecting its transport and optical properties, with potential observable effects at realistic doping levels and temperatures.

## Contribution

It demonstrates the impact of electron-phonon coupling on mobility and optical excitations in single-layer InSe, highlighting effects of Fermi surface warping and many-body renormalization.

## Key findings

- Charge carrier mobility is suppressed to ~1 cm^2V^{-1}s^{-1} at 100 K.
- Sharp low-energy resonances in the spectral function lead to satellite quasiparticle states.
- Unusual temperature-dependent optical excitations are predicted in the midinfrared region.

## Abstract

We show that hole states in recently discovered single-layer InSe are strongly renormalized by the coupling with acoustic phonons. The coupling is enhanced significantly at moderate hole doping ($\sim$10$^{13}$ cm$^{-2}$) due to hexagonal warping of the Fermi surface. While the system remains dynamically stable, its electron-phonon spectral function exhibits sharp low-energy resonances, leading to the formation of satellite quasiparticle states near the Fermi energy. Such many-body renormalization is predicted to have two important consequences. First, it significantly suppresses charge carrier mobility reaching $\sim$1 cm$^2$V$^{-1}$s$^{-1}$ at $100$ K in a freestanding sample. Second, it gives rise to unusual temperature-dependent optical excitations in the midinfrared region. Relatively small charge carrier concentrations and realistic temperatures suggest that these excitations may be observed experimentally.