A new pathway to impact ionization in a photo-excited one-dimensional ionic Hubbard model

TL;DR

This study reveals a novel mechanism for impact ionization in a photo-excited one-dimensional ionic Hubbard model, where excess ionic potential energy, rather than kinetic energy, drives the process, offering new insights into strongly correlated systems.

Contribution

The paper uncovers a new pathway for impact ionization driven by ionic potential energy, distinct from conventional kinetic energy mechanisms, in a strongly correlated electron system.

Findings

Impact ionization occurs depending on staggered potential and laser frequency.

Excess ionic potential energy can be converted into double occupancy.

Interference between excited states influences impact ionization.

Abstract

Using the time-dependent Lanczos method, we study the non-equilibrium dynamics of the half-filled one-dimensional ionic Hubbard model, deep within the Mott insulating regime, under the influence of a transient laser pulse. In equilibrium, increasing the staggered potential in the Mott regime reduces the Mott gap and broadens the Hubbard bands, creating favorable conditions for impact ionization. After laser excitation, impact ionization is observed, with its occurrence depending on both the staggered potential and the laser pump frequency. By analyzing the time evolution of the kinetic, ionic, and Coulomb interaction energies, we identify a novel mechanism for impact ionization, in which excess ionic potential energy is converted into additional double occupancy-distinct from the conventional mechanism where excess kinetic energy drives this process. We further show that impact ionization arises from interference between excited states driven by photon excitation of the same order. These results present a new pathway for realizing impact ionization in strongly correlated electron systems.