Solid State Physics Laboratory

About: Solid State Physics Laboratory is a facility organization based out in Delhi, India. It is known for research contribution in the topics: Quantum dot & Dielectric. The organization has 1754 authors who have published 2597 publications receiving 50601 citations.

Measurement Back-Action in Stacked Graphene Quantum Dots

Abstract: We present an electronic transport experiment in graphene where both classical and quantum mechanical charge detector back-action on a quantum dot are investigated. The device consists of two stacked graphene quantum dots separated by a thin layer of boron nitride. This device is fabricated by van der Waals stacking and is equipped with separate source and drain contacts to both dots. By applying a finite bias to one quantum dot, a current is induced in the other unbiased dot. We present an explanation of the observed measurement-induced current based on strong capacitive coupling and energy dependent tunneling barriers, breaking the spatial symmetry in the unbiased system. This is a special feature of graphene-based quantum devices. The experimental observation of transport in classically forbidden regimes is understood by considering higher-order quantum mechanical back-action mechanisms.

Structure and dynamics of alkali borate glasses: a molecular dynamics study

Abstract: Structural and dynamical properties of lithium, cesium and mixed alkali (i.e., lithium and cesium) borate glasses have been studied by the molecular dynamics method. The calculations yield glass structures consisting of planar BO3 triangles and BO4 tetrahedrons with no sixfold ring structures at all. Alkali ions show a strong preference to reside in the vicinity of nan-bridging oxygen atoms, a tendency which is stronger for lithium ions than for cesium ions. The experimental Raman peaks at 805 and 770 cm(-1) are reproduced by symmetric breathing modes of BO3 and BO4 units, respectively. Simulated infrared absorption spectra reproduce the experimental spectra quite well. It appears that the velocities of different cesium ions show much more correlation than those of the lithium ions and that the frequency spectra of Li+ and Cs+ ions are in good agreement with far-infrared measurements.

Anisotropic optical conductivity and two colors of MgB 2

Abstract: We present the anisotropic optical conductivity of ${\mathrm{MgB}}_{2}$ between 0.1 and $3.7\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ at room temperature obtained on single crystals of different purity by spectroscopic ellipsometry and reflectance measurements. The bare (unscreened) plasma frequency ${\ensuremath{\omega}}_{p}$ is almost isotropic and equal to $6.3\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, which contrasts some earlier reports of a very small value of ${\ensuremath{\omega}}_{p}$. The data suggests that the $\ensuremath{\sigma}$ bands are characterized by a stronger electron-phonon coupling ${\ensuremath{\lambda}}_{tr}$ but smaller impurity scattering ${\ensuremath{\gamma}}_{\mathrm{imp}}$, compared to the $\ensuremath{\pi}$ bands. The optical response along the boron planes is marked by an intense interband transition at $2.6\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, due to which the reflectivity plasma edges along the $a$ and $c$ axes are shifted with respect to each other. As a result, the sample spectacularly changes color from a blueish-silver to the yellow as the polarization is rotated from the in-plane direction toward the $c$ axis. The optical spectra are in good agreement with the published ab initio calculations. The remaining discrepancies can be explained by the relative shift of $\ensuremath{\sigma}$ bands and $\ensuremath{\pi}$ bands by about $0.2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ compared to the theoretical band structure, in agreement with the de Haas-van Alphen experiments. The widths of the Drude and the interband peaks are both very sensitive to the sample purity.

Thermal evolution of morphological, structural, optical and photocatalytic properties of CuO thin films

Abstract: Nanostructured CuO thin films were synthesized by thermal evaporation and annealing. Structural, optical and morphological changes in the CuO film upon annealing and their overall impact on its photocatalytic activity were investigated employing X-ray diffraction, UV–Vis absorption spectroscopy, atomic force microscopy and field emission scanning electron microscopy. Significant modifications in the morphological, optical, structural and photocatalytic behavior of nanostructured CuO thin film were observed upon thermal annealing. Thermal annealing led to the growth of CuO nanoparticles and the average size of CuO nanoparticles increased from 23 nm to 293 nm as the annealing temperature was increased to 600 o C. CuO thin film sample annealed at 400 °C exhibited superior photocatalytic activities over other samples for the degradation of malachite green and methylene blue dyes in 120 and 160 min, respectively. The improved photocatalytic behavior of CuO thin film annealed at 400 °C is attributed to its narrower band gap, improved utilization of sunlight and enhanced adsorption of dye due to increased surface area arising from formation of CuO nanoparticles and their aggregates at the surface.