Origin of multiple band gap values in single width nanoribbons

Deterministic band gap in quasi-one-dimensional nanoribbons is prerequisite for their integrated functionalities in high-performance molecular-electronics based devices. However, multiple band gap values commonly observed in the same width of graphene nanoribbons fabricated in same slot of the experiments remains unresolved, and raise a critical concern over scalable production of pristine and/or hetero-structure nanoribbons with deterministic properties and functionalities for plethora of applications. Here, we show that a modification in the depth of potential wells in the periodic direction of a supercell on relative shifting of passivating atoms at the edges is the origin of multiple band gap values for the same width of nanoribbons in a crystallographic orientation, although they carry practically the same ground state energy. The results are similar when calculations are extended from planar graphene to buckled silicene nanoribbons. Thus, the findings facilitate tuning of the electronic properties of quasi-one-dimensional materials such as bio-molecular chains, organic and inorganic nanoribbons by performing edge engineering.Comment: 11 pages, 6 figure

First principles investigation of topological phase in XMR material TmSb under hydrostatic pressure

In this article, we report emergence of topological phase in XMR material TmSb under hydrostatic pressure using first principles calculations. We find that TmSb, a topologically trivial semimetal, undergoes a topological phase transition with band inversion at X point without breaking any symmetry under a hydrostatic pressure of 12 GPa. At 15 GPa, it again becomes topologically trivial with band inversion at $\Gamma$ as well as X point. We find that the pressures corresponding to the topological phase transitions are far below the pressure corresponding to structural phase transition at 25.5 GPa. The reentrant behaviour of topological quantum phase with hydrostatic pressure would help in finding a correlation between topology and XMR effect through experiments.Comment: 12 pages, 4 figure

Analysis of TX-100 based microemulsion in the presence of TB drug isoniazid

The present study delineate the formulation of microemulsion composed of TX-100:AcOH(1:1), Chloroform, Water and to investigate its potential as drug delivery system for an antitubercular drug isoniazid. The pseudo-ternary phase diagram (Gibbs Triangle) were constructed for these systems with and without isoniazid. Microemulsion system showed the occurrence of structural changes from water-in-oil to oil-in-water microemulsion. It has been observed that the microemulsion remained stable after the incorporation of isoniazid. After dilution a controlled release of drug is expected from o/w emulsion droplet. Further to study the incorporation of drug in TX100 based microemulsion in presence of cetyl trimethyl ammonium dichromate (CTADC), a lipophylic oxidant, phase diagrams of systems containing TX-100:AcOH(1:1), Chloroform, CTADC, Water has been constructed in the presence and absence of isoniazid. The results suggested that isoniazid binds to the CTADC in o/w and w/o microemulsion. Thus drug release is possible where there is demand for the drug. The present TX 100 based microemulsion in presence of CTADC appears beneficial for the delivery of the isoniazid

Heat Kernels on the AdS(2) cone and Logarithmic Corrections to Extremal Black Hole Entropy

We develop new techniques to efficiently evaluate heat kernel coefficients for the Laplacian in the short-time expansion on spheres and hyperboloids with conical singularities. We then apply these techniques to explicitly compute the logarithmic contribution to black hole entropy from an N=4 vector multiplet about a Z(N) orbifold of the near-horizon geometry of quarter--BPS black holes in N=4 supergravity. We find that this vanishes, matching perfectly with the prediction from the microstate counting. We also discuss possible generalisations of our heat kernel results to higher-spin fields over Z(N) orbifolds of higher-dimensional spheres and hyperboloids.Comment: 41 page

Chip-integrated plasmonic cavity-enhanced single nitrogen-vacancy center emission

High temporal stability and spin dynamics of individual nitrogen-vacancy (NV) centers in diamond crystals make them one of the most promising quantum emitters operating at room temperature. We demonstrate a chip-integrated cavity-coupled emission into propagating surface plasmon polariton (SPP) modes narrowing NV center's broad emission bandwidth with enhanced coupling efficiency. The cavity resonator consists of two distributed Bragg mirrors that are built at opposite sides of the coupled NV emitter and are integrated with a dielectric-loaded SPP waveguide (DLSPPW), using electron-beam lithography of hydrogen silsesquioxane resist deposited on silver-coated silicon substrates. A quality factor of ~ 70 for the cavity (full width at half maximum ~ 10 nm) with full tunability of the resonance wavelength is demonstrated. An up to 42-fold decay rate enhancement of the spontaneous emission at the cavity resonance is achieved, indicating high DLSPPW mode confinement

Logarithmic Corrections to Extremal Black Hole Entropy in N = 2, 4 and 8 Supergravity

We compute the logarithmic correction to black hole entropy about exponentially suppressed saddle points of the Quantum Entropy Function corresponding to Z(N) orbifolds of the near horizon geometry of the extremal black hole under study. By carefully accounting for zero mode contributions we show that the logarithmic contributions for quarter--BPS black holes in N=4 supergravity and one--eighth BPS black holes in N=8 supergravity perfectly match with the prediction from the microstate counting. We also find that the logarithmic contribution for half--BPS black holes in N = 2 supergravity depends non-trivially on the Z(N) orbifold. Our analysis draws heavily on the results we had previously obtained for heat kernel coefficients on Z(N) orbifolds of spheres and hyperboloids in arXiv:1311.6286 and we also propose a generalization of the Plancherel formula to Z(N) orbifolds of hyperboloids to an expression involving the Harish-Chandra character of SL(2,R), a result which is of possible mathematical interest.Comment: 40 page