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.

Selective Chemical Modification of Graphene Surfaces: Distinction Between Single‐ and Bilayer Graphene

Abstract: Graphene modifications with oxygen or hydrogen are well known in contrast to carbon attachment to the graphene lattice. The chemical modification of graphene sheets with aromatic diazonium ions (carbon attachment) is analyzed by confocal Raman spectroscopy. The temporal and spatial evolution of surface-adsorbed species allows accurate tracking of the chemical reaction and identification of intermediates. The controlled transformation of sp2 to sp3 carbon proceeds in two separate steps. The presented derivatization is faster for single-layer graphene and allows controlled transformation of adsorbed diazonium reagents into covalently bound surface derivatives with enhanced reactivity at the edge of single-layer graphene. On bilayer graphene the derivatization proceeds to an adsorbed intermediate, which reacts slower to a covalently attached species on the carbon surface.

Spin and charge ordering in self-doped Mott insulators

Abstract: We have investigated possible spin and charge ordered states in $3d$ transition-metal oxides with small or negative charge-transfer energy, which can be regarded as self-doped Mott insulators, using Hartree-Fock calculations on $d\ensuremath{-}p$-type lattice models. It was found that an antiferromagnetic state with charge ordering in oxygen $2p$ orbitals is favored for relatively large charge-transfer energy and may be relevant for ${\mathrm{PrNiO}}_{3}$ and ${\mathrm{NdNiO}}_{3}.$ On the other hand, an antiferromagnetic state with charge ordering in transition-metal $3d$ orbitals tends to be stable for highly negative charge-transfer energy and can be stabilized by the breathing-type lattice distortion; this is probably realized in ${\mathrm{YNiO}}_{3}.$

Transport gap in side-gated graphene constrictions

Abstract: We present measurements on side-gated graphene constrictions of different geometries. We characterize the transport gap by its width in back-gate voltage and compare this to an analysis based on Coulomb blockade measurements of localized states. We study the effect of an applied side-gate voltage on the transport gap and show that high side-gate voltages lift the suppression of the conductance. Finally we study the effect of an applied magnetic field and demonstrate the presence of edge states in the constriction.

Spin and orbital occupation and phase transitions in V2O3

Abstract: Polarization dependent x-ray-absorption measurements were performed on pure and Cr-doped ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ single crystals in the antiferromagnetic insulating, paramagnetic insulating, and metallic phases. The orbital occupation of the V ${3d}^{2}$ ion is found to depend appreciably on the phase, but always with the $S=1$ character, requiring an explanation which is beyond the elegant simplicity of the pure one-band Hubbard model or of models in which the ${a}_{1g}$ orbital is projected out by means of a simple dimerization. The results reveal the critical role of the spin and orbital dependence of the on-site $3d\ensuremath{-}3d$ Coulomb energy, and a mechanism is proposed to explain the closing or opening of the band gaps which are of much higher energy scale than the transition temperatures.