7 research outputs found
Large spin splitting of metallic surface state bands at adsorbate modified gold silicon surfaces
Finding appropriate systems with a large spin splitting of metallic surface-state band which can be fabricated on silicon using routine technique is an essential step in combining Rashba-effect based spintronics with silicon technology. We have found that originally poor structural and electronic properties of the [Image: see text] surface can be substantially improved by adsorbing small amounts of suitable species (e.g., Tl, In, Na, Cs). The resultant surfaces exhibit a highly-ordered atomic structure and spin-split metallic surface-state band with a momentum splitting of up to 0.052 Å(−1) and an energy splitting of up to 190 meV at the Fermi level. The family of adsorbate-modified [Image: see text] surfaces, on the one hand, is thought to be a fascinating playground for exploring spin-splitting effects in the metal monolayers on a semiconductor and, on the other hand, expands greatly the list of material systems prospective for spintronics applications
Cooperative Jahn-Teller effect in a 2D mesoscopic C
Fullerene molecules adsorbed on surfaces often show macroscopic average distortions. As
charged ions C60n- are known to be Jahn-Teller (JT)
active, it is suggested that these distortions could be a manifestation of cooperative JT
effects (CJTE) due to interactions between neighbouring fullerene ions. In order to
understand the distortion properties it is necessary to take correlations between
different distortions into account. However, this can’t easily be done in the mean field
approximation usually used to describe the CJTE. We therefore propose an alternative
procedure to describe 2D mesoscopic islands of C60 ions in which a pseudo
vector spin \hbox{} is evoked to represent degenerate JT-distorted states when the quadratic
JT coupling is considered. This approach is analogous to methods used for 2D magnetic
systems. We then use the differential operator technique in effective field theory within
the Ising approach. We include the effects of weak surface interactions and dynamic motion
between equivalent distortions via terms equivalent to anisotropy and a transverse field
in magnetism respectively. For distortions to
D5d symmetry, we determine single site
correlations as a function of temperature, the macroscopic average distortion describing a
structural phase transition, and the isothermal response function. Phase diagrams are
presented for relevant cases of the system parameters