No abstract

We report the calculations of dielectric functions and quasiparticle lifetimes for noble metals Cu, Ag, and Au performed within the LMTO-GW approach. We show that by changing the value of continuous principal quantum number of d states it is possible to improve the calculated local density approximation ͑LDA͒ band structures and dielectric functions. In particular, the plasmon absorption in Ag, which is absent in the selfconsistent LDA approach, is obtained with the corrected band structure. We also show that the drawbacks of the LDA band structures do not lead to qualitative changes of the quasiparticle lifetimes. The lifetimes of electron excitations calculated by the LMTO-GW method agree well with the results of the LDA plane-wave GW approach. By adjusting the value of the density parameter r s good agreement with the results of the many-body free-electron gas calculations is also achieved for the electrons and holes in s,p-bands. For the holes in the top d bands we report the lifetime band structures.

Spin-polarized two-dimensional electron states (2DESs) at surfaces and interfaces of magnetically active materials attract immense interest because of the idea of exploiting fermion spins rather than charge in next generation electronics. Applying angle-resolved photoelectron spectroscopy, we show that the silicon surface of GdRh2Si2 bears two distinct 2DESs, one being a Shockley surface state, and the other a Dirac surface resonance. Both are subject to strong exchange interaction with the ordered 4f-moments lying underneath the Si-Rh-Si trilayer. The spin degeneracy of the Shockley state breaks down below ~90 K, and the splitting of the resulting subbands saturates upon cooling at values as high as ~185 meV. The spin splitting of the Dirac state becomes clearly visible around ~60 K, reaching a maximum of ~70 meV. An abrupt increase of surface magnetization at around the same temperature suggests that the Dirac state contributes significantly to the magnetic properties at the Si surface. We also show the possibility to tune the properties of 2DESs by depositing alkali metal atoms. The unique temperature-dependent ferromagnetic properties of the Si-terminated surface in GdRh2Si2 could be exploited when combined with functional adlayers deposited on top for which novel phenomena related to magnetism can be anticipated.