Electronic stopping power for slow ions in the low-hardness semimetal HgTe using first-principles calculations

Abstract

The electronic stopping power for low-velocity ions (including protons, -particles, and ) is investigated in a novel semimetal HgTe system, where the data are obtained with the aid of Ehrenfest dynamics combined with time-dependent density functional theory. For the light projectile ions (protons and -particles), the linear and nonlinear behaviors of electronic stopping power in three different channel directions are analyzed in detail. In the case where the projectile ion is a proton, the linear results for the threshold velocity are correlated with an indirect band gap; the direction of the electronic stopping power depends on the radial drag force, the channeling electronic density and the trapped charge. More notably, we report an interesting channel-geometry fact, i.e. that the electronic stopping power of HgTe is powerfully modulated by the impact parameters. The parallel off-center tracks increase the electronic stopping power, making it more consistent with the SRIM data. In the case of an -particle as the projectile ion, nonlinear behavior that varies with velocity can be ascribed to the charge transfer, which is another mode of energy dissipation. In addition, when the slightly heavier projectile travels through the medium HgTe, the projectile can capture more free charges than the protons and -particles under the same circumstances. Especially, for the projectile in the off-channel, the electronic stopping power is close to the SRIM data with the decrease of the impact parameter. These results extend the study of radiation damage to a new field of materials.