Effect of resonant coherent excitation on the electronic stopping of slow channeled ions

We calculated the nonlinear screening and the electronic stopping of energetic helium ions in a III-V compound semiconductor at low speeds below stopping maximum under channeling conditions. For the range of velocity considered, it is found the energy loss of the intruding ions show pronounced dependence on the electronic screening from the induced charge. Different with the prevalent scenario described by free-electron gas model that the induced charge distribution lags behind the projectile forming the so-called wake potential. We found through real-time time-dependent density functional theory that the induced charge by the channeling ion keeps oscillating back and front when channeling through the zinc-blende crystalline GaN, which is interpreted as a consequence of temporally oscillating Coulomb field arising from the periodical atomic arrangement along ion trajectory. When one of the frequencies coincides with the transition energy of the ionic charge, it would be resonantly excited by the oscillating field, which further gives rise to a depletion in electronic screening by bound electrons to the ion, resulting in odd enhanced stopping trend at narrow velocity windows.