Electronic properties of the two-dimensional (Tl, Rb)/Si(1 1 1)[Formula: see text] compound having a honeycomb-like structure.

Heavy metal layers having a honeycomb structure on the Si(1 1 1) surface were theoretically predicted to show prospects for possessing properties of the quantum spin Hall (QSH) insulators. The (Tl, Rb)/Si(1 1 1)[Formula: see text] atomic-layer compound synthesized in the present work is the first real system of such type, where atoms of heavy metal Tl are arranged into the honeycomb structure stabilized by Rb atoms occupying the centers of the honeycomb units. Electronic properties of the (Tl, Rb)/Si(1 1 1)[Formula: see text] compound has been fully characterized experimentally and theoretically and compared with those of the hypothetical (Tl, H)/Si(1 1 1)[Formula: see text] prototype system. It is concluded that the QSH-insulator properties of the Tl-honeycomb layers on Si(1 1 1) surface are dictated by the stable adsorption sites occupied by Tl atoms which, in turn, are controlled by the atom species centering the Tl honeycombs. As a result, the real (Tl, Rb)/Si(1 1 1)[Formula: see text] compound where Tl atoms occupy the T4 sites does not possess QSH-insulator properties in contrast to the hypothetical (Tl, H)/Si(1 1 1)[Formula: see text] system where Tl atoms reside in the T1 (on-top) sites and it shows up as a QSH material.

[PLASTICITY OF THE THERMAL REACTION NORMS FOR DEVELOPMENT IN THE EUROPEAN PEACOCK BUTTERLY INACHIS IO (LEPIDOPTERA, NYMPHALIDAE)].

The goal of this study was to examine the plasticity of the thermal reaction norms for development in the European Peacock butterfly Inachis io under the effect of different photoperiodic conditions and group versus individual maintenance. The overwintered imagoes were collected in Old Peterhof (near Saint-Petersburg) in May, 2010 and 2012-2013. 12 experimental regimens were used: 4 temperatures (16, 18, 20 and 22 degrees C) and 3 photoperiods (12, 18 and 22 h of light a day). It was found that under short-day conditions (12 h) the caterpillars developed a little faster than under long-day ones (22 h). The developmental temperature thresholds in these two cases did not differ. A linear regression coefficient characterizing thermal sensitivity of development was significantly higher only in males with their development affected by short-day photoperiod stronger than in females. At 18-h day length, the caterpillar development was less temperature-sensitive and characterized by a lower threshold than in shorter and longer days. The influence of short-day photoperiod on the caterpillar development manifested itself most distinctly in the emerging pupae' weight changes: in all the temperature regimens the pupae were lighter at short than at long days. The pupal weight increased as the temperature rose. The found dependence does not agree with the "temperature-size rule". Individual rearing led to a longer duration and lower thermal sensitivity of caterpillar and pupal development as well as to a reduced weight of the pupae. Individual rearing had a stronger impact on the mineral of females than males.

Effect of Na adsorption on the structural and electronic properties of Si(111)√3 × âˆš3-Au surface.

Adsorption of ∼0.1 ML of Na onto the Si(111)√3 × âˆš3-Au surface held at 300 °C has been found to induce pronounced changes in its structural and electronic properties. Domain wall networks, characteristic of the pristine surface, are removed completely, leading to the formation of a highly ordered homogeneous surface. The original atomic arrangement of the Si(111)√3 × âˆš3-Au is preserved and Na atoms occupy T4 adsorption sites at the centers of surface Si trimers. Upon Na adsorption, a pronounced metallic S1 surface-state band develops. It is characterized by a large spin splitting (momentum splitting at the Fermi level Δk∥ = 0.027 Å(-1) and consequent energy splitting ΔEF = 110 meV), large electron filling (on the order of 0.5 electrons per √3 × âˆš3 unit cell) and small effective electron mass of (0.028 ± 0.006)me. The natural consequence of the latter properties is a high surface conductivity of the Si(111)√3 × âˆš3-(Au, Na) surface.