Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany.
Phys Rev Lett. 2013 Nov 22;111(21):217401. doi: 10.1103/PhysRevLett.111.217401. Epub 2013 Nov 19.
We study the quasi-instantaneous change of electron density in the unit cells of LiH and NaBH4 in response to a nonresonant strong optical field. We determine for the first time the related transient electron density maps, applying femtosecond x-ray powder diffraction as a structure probe. The light-induced charge relocation in NaBH4 exhibits an electron transfer from the anion (BH(4)(-)) to the Na(+) cation. In contrast, LiH displays the opposite behavior, i.e., an increase of the ionicity of LiH in the presence of the strong electric field. This behavior originates from strong electron correlations in LiH, as is evident from a comparison with quasiparticle band structures calculated within the Coulomb-hole-plus-screened-exchange formalism.
我们研究了 LiH 和 NaBH4 单元晶格中电子密度对非共振强光场的准瞬时变化。我们首次应用飞秒 X 射线粉末衍射作为结构探针，确定了相关的瞬态电子密度图。光致电荷在 NaBH4 中的重新分布表现为阴离子 (BH(4)(-)) 向 Na(+) 阳离子的电子转移。相比之下，LiH 表现出相反的行为，即在强电场存在下 LiH 的离子性增加。这种行为源于 LiH 中的强电子相关，这可以从与库仑空穴加屏蔽交换形式计算的准粒子能带结构的比较中明显看出。
