Dirac nodal line semimetals represent a new state of quantum matters in which the electronic bands touch to form a closed loop with linear dispersion. Here, we report a combined study on ZrSiS by density functional theory calculation, scanning tunnelling microscope (STM) and magneto-transport measurements. Our STM measurements reveal the spectroscopic signatures of a diamond-shaped Dirac bulk band and a surface band on two types of cleaved surfaces as well as a spin-polarized surface band at G at E∼0.6 eV on S-surface, consistent with our band calculation. Furthermore, we find the surface termination does not affect the surface spectral weight from the Dirac bulk bands but greatly affect the surface bands due to the change in the surface orbital composition. From our magnetotransport measurements, the primary Shubnikov-de-Haas frequency is identified to stem from the hole-type quasi-two-dimensional Fermi surface between Γ and X. The extracted non-orbital magnetoresistance (MR) contribution D(θ, H) yields a nearly H-linear dependence, which is attributed to the intrinsic MR in ZrSiS. Our results demonstrate the unique Dirac line nodes phase and the dominating role of Zr-d orbital on the electronic structure in ZrSiS and the related compounds.

Polymer microlenses capable of using heat to control its focal length are presented. The microlenses are created by exposing droplets of the polymer SU-8 to UV light. By altering the temperature of the microlenses via on-chip heating, their curvature and focal length are actively controlled without mechanical movements. By directly and indirectly measuring temperature-dependent changes of the focal length, we test the ability of the microlenses as a tunable imaging component. The microlenses have potential use in applications such as laser systems, functional biomimetics, and endoscopy. (C) 2008 American Institute of Physics

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A monolayer of fullerene molecules on Si(111) surfaces is fabricated in an ultrahigh vacuum chamber through a controlled self-assembly process. The characteristics of self-assembled Si(111) surfaces, including supramolecular structures, electronic density of states, the quantum confinement effect, field emission features, and optoelectronical properties with embedded C 84 are determined by the use of an ultrahigh vacuum scanning probe microscope. The results revealed that such a silicon surface with embedded C 84 has a wide band gap of y3.4 eV, high emission efficiency and low turn-on voltage, all of which are crucial to nano-electronics, optoelectronics, and the fabrication of semiconductor carbide. The measured data derived from photoluminescence emission experiments further confirm the corresponding band gap value obtained from I-V curves. The theoretical results from first-principles calculations for the field enhancement factor are compared with experimental measurements.

The surface magneto-optical Kerr effect was used to study the magnetic properties of Co ultrathin films deposited on Pt͑111͒. The easy axis of the magnetization changes from the out-of-plane to the in-plane direction after the coverage of Co is larger than 3.5 ML. The spin can reorient to the normal of the surface when the proper thickness of Ag overlayers is deposited on Co/Pt͑111͒ with the in-plane magnetization. The out-of-plane magnetization and its coercivity as a function of Ag coverage were investigated during the spin-reorientation transition. The easy axis of the magnetization can shift back to the in-plane direction after the Ag overlayers are sputtered out. The chemical compositions of the interfaces were measured by Auger electron spectroscopy. The mechanism of the spin-reorientation transition induced by Ag is discussed.