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.

Weakened hydrogen bonds in water confined between lipid bilayers: the existence of a long-range attractive hydration force.

Abstract: Stronger or weaker H-bonds? H-bonds in interlamellar water in partially hydrated lipid multibilayers are stronger with respect to bulk water. In contrast, the authors show by ATR–FTIR spectroscopy that the H-bonds are weaker in multibilayers in excess water (see spectra). This finding is of biological relevance for water-mediated phenomena in membranes.

A Y2O3:Yb nanoscale magnet obtained by HEBM: C3i/C2 site occupancies, size/strain analysis and crystal field levels of Yb3+ ions

Abstract: A Y2O3:Yb nanoscale magnet that belongs to the cubic C-type or bixbyite structure family was synthesized by high energy ball milling (HEBM) An as-prepared sample (S1) was annealed at 650 °C (S2) and 950 °C (S3) Cation populations were determined by the refinement of site occupancies It was found that in S1 and S2 Yb3+ ions occupy exclusively the 8b (or C3i) position, whereas in S3 a small amount of Yb3+ is also located on Wyckoff-site 24d (or C2) X-ray powder diffraction line broadening analysis was done by using the Rietveld method using regular TCH-pV functions (isotropic effects) and symmetrized cubic harmonics (anisotropic effects) for the refinement The line broadening anisotropy decreases due to strain effects from S1 to S3, while the crystallite size anisotropy increases from S1 to S3 Transmission electron microscopy (TEM) and Raman spectroscopy were used to define the homogeneity, microstructure and to locally probe the structure of the samples S1–S3 Magnetic susceptibility results in the 2–300 K temperature regions were analysed by applying the first-order perturbation theory The mean energy gap between ground and excited crystal field levels (Ei), and their effective magnetic numbers Mieff, were determined The analysis of the paramagnetic temperature shows the absence of clusterization of the magnetic ions

Optical absorption of ZnGa 2 S 4 and ZnGa 2 S 4 : Co 2 + crystals

Abstract: Polycrystals of ${\mathrm{ZnGa}}_{2}$${\mathrm{S}}_{4}$ and ${\mathrm{ZnGa}}_{2}$${\mathrm{S}}_{4}$:${\mathrm{Co}}^{2+}$ were prepared from high-purity elements at 1270 \ifmmode^\circ\else\textdegree\fi{}C. The optical-absorption spectra of these polycrystalline powders were measured in the wavelength region 300--3000 nm with use of an integrating sphere and photoacoustic spectrophotometer at 298 K. The optical energy gap is found to be 3.18 eV for the ${\mathrm{ZnGa}}_{2}$${\mathrm{S}}_{4}$ crystal and 2.60 eV for the ${\mathrm{ZnGa}}_{2}$${\mathrm{S}}_{4}$:${\mathrm{Co}}^{2+}$ crystal. The optical-absorption peaks in the measurement of ${\mathrm{ZnGa}}_{2}$${\mathrm{S}}_{4}$:${\mathrm{Co}}^{2+}$ crystal absorption spectrum at 3790, 6049, 13 725, 20 704, and 22 779 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ are found to be the electron transition of the ${\mathrm{Co}}^{2+}$ ion with ${\mathit{T}}_{\mathit{d}}$ symmetry from the ground state $^{4}$${\mathit{A}}_{2}$${(}^{4}$F) to the excited states $^{4}$${\mathit{T}}_{2}$${(}^{4}$F), $^{4}$${\mathit{T}}_{1}$${(}^{4}$F), $^{4}$${\mathit{T}}_{1}$${(}^{4}$P), $^{2}$${\mathit{T}}_{2}$${(}^{2}$G), and $^{2}$E${(}^{2}$G). The crystal-field parameter and the Racah parameter, which were obtained from the optical-absorption peaks, are found to be Dq=379 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and B=560 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, respectively. The $^{4}$${\mathit{T}}_{1}$${(}^{4}$P) state of the ${\mathrm{Co}}^{2+}$ ion splits into three state of ${\mathrm{\ensuremath{\Gamma}}}_{6}$, ${\mathrm{\ensuremath{\Gamma}}}_{8}$, and ${\mathrm{\ensuremath{\Gamma}}}_{8}$+${\mathrm{\ensuremath{\Gamma}}}_{7}$ by first-order spin-orbit coupling effects at 298 K. The value of the spin-orbit coupling parameter was \ensuremath{\lambda}=-436 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$.

Band gap and broken chirality in single-layer and bilayer graphene

Abstract: Chirality is one of the key features governing the electronic properties of single- and bilayer graphene: the basics of this concept and its consequences on transport are presented in this review. By breaking the inversion symmetry, a band gap can be opened in the band structures of both systems at the K-point. This leads to interesting consequences for the pseu-dospin and, therefore, for the chirality. These consequences can be accessed by investigating the evolution of the Berry phase in such systems. Experimental observations of Fabry–Perot interference in a dual-gated bilayer graphene device are finally presented and are used to illustrate the role played by the band gap on the evolution of the pseudospin. The presented results can be attributed to the breaking of the chirality in the energy range close to the gap.