Polaron with quadratic electron-phonon interaction Universiteit Antwerpen
We present a numerically exact study of a polaron with quadratic coupling to the oscillator displacement, or X2 polaron, using two alternative methodological developments. Our results cover both antiadiabatic and adiabatic regimes and the entire range of electron-phonon coupling g2, from the system's stability threshold at attractive g2 = -1 to arbitrary strong repulsion at g2 >> 1. The key properties of X2 polarons prove dramatically ...