Signals of strong electronic correlation in ion scattering processes.

F. BONETTO; C. GONZALEZ; E. C. GOLDBERG

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 2016 vol. 93 p. 1954391 - 1954399

1098-0121

Previous measurements of neutral atom fractions for Sr+ scattered by gold polycrystalline surfaces show asingular dependence with the target temperature. There is still not a theoretical model that can properly describethe magnitude and the temperature dependence of the neutralization probabilities found. Here, we applied afirst-principles quantum-mechanical theoretical formalism to describe the time-dependent scattering process.Three different electronic correlation approaches consistent with the system analyzed are used: (i) the spinlessapproach, where two charge channels are considered (Sr0 and Sr+) and the spin degeneration is neglected; (ii)the infinite-U approach, with the same charge channels (Sr0 and Sr+) but considering the spin degeneration; and(iii) the finite-U approach, where the first ionization and second ionization energy levels are considered very, butfinitely, separated. Neutral fraction magnitudes and temperature dependence are better described by the finite-Uapproach, indicating that e-correlation plays a significant role in charge-transfer processes. However, none ofthem is able to explain the nonmonotonous temperature dependence experimentally obtained. Here, we suggestthat small changes in the surface work function introduced by the target heating, and possibly not detected byexperimental standard methods, could be responsible for that singular behavior. Additionally, we apply the sametheoretical model using the infinite-U approximation for the Mg-Au system, obtaining an excellent descriptionof the experimental neutral fractions measured.