A Novel Approach to Discontinuous Bond Percolation Transition

We introduce a bond percolation procedure on a $D$-dimensional lattice where two neighbouring sites are connected by $N$ channels, each operated by valves at both ends. Out of a total of $N$, randomly chosen $n$ valves are open at every site. A bond is said to connect two sites if there is at least one channel between them, which has open valves at both ends. We show analytically that in all spatial dimensions, this system undergoes a discontinuous percolation transition in the $N\to \infty$ limit when $\gamma =\frac{\ln n}{\ln N}$ crosses a threshold. It must be emphasized that, in contrast to the ordinary percolation models, here the transition occurs even in one dimensional systems, albeit discontinuously. We also show that a special kind of discontinuous percolation occurs only in one dimension when $N$ depends on the system size.Comment: 6 pages, 6 eps figure

Quantum Phase Transitions in a Dimerized Bose-Hubbard Model: A DMRG Study

We investigate the phase diagram of a dimerized Bose-Hubbard model, using density matrix renormalization group technique. We find a new phase, which is the coexistence of superfluid and bond-wave phases, due to the effect of dimerization. Experimentally dimerization in optical lattice can be realized by using two counter propagating laser beams of different wavelengths. Apart from the conventional superfluid to Mott insulator transition, we find a new quantum phase transition: from superfluid-bond-wave to Mott insulator-bond wave phase. Our study suggests a rich phase diagram which can be easily probed.Comment: 5 pages, 4 figure

A Novel Approach to Discontinuous Bond Percolation Transition

We introduce a bond percolation procedure on a $D$-dimensional lattice where two neighbouring sites are connected by $N$ channels, each operated by valves at both ends. Out of a total of $N$, randomly chosen $n$ valves are open at every site. A bond is said to connect two sites if there is at least one channel between them, which has open valves at both ends. We show analytically that in all spatial dimensions, this system undergoes a discontinuous percolation transition in the $N\to \infty$ limit when $\gamma =\frac{\ln n}{\ln N}$ crosses a threshold. It must be emphasized that, in contrast to the ordinary percolation models, here the transition occurs even in one dimensional systems, albeit discontinuously. We also show that a special kind of discontinuous percolation occurs only in one dimension when $N$ depends on the system size.Comment: 6 pages, 6 eps figure

One-Dimensional Organometallic V-Anthracene Wire and Its B-N Analogue: Efficient Half-Metallic Spin Filters

Using density functional theory, we have investigated the structural, electronic and magnetic properties of infinitely periodic organometallic vanadium-anthracene ([V_2Ant]_\infinity) and [V_4(BNAnt)_2]_\infinity(where BNAnt is B-N analogue of anthracene) for their possible application in spintronics. From our calculations, we find that one-dimensional [V_2Ant]_\infinity and [V_4(BNAnt)_2]_\infinity wires exhibit robust ferromagnetic half-metallic and metallic behavior, respectively. The finite sized $V_6Ant_2$ and $V_6(BNAnt)_2$ clusters are also found to exhibit efficient spin filter properties when coupled to graphene electrodes on either side

The electronic and magnetic properties of a few transition-metal clusters

Using density functional theory we present a systematic study of the electronic and magnetic properties of various nickel clusters and two small bimetallic clusters, NinCo m and Nin Fem (n + m ≤ 6). A detail study of binding energy, magnetic moment and stability function of pure nickel clusters of nuclearity (N) 40-60 have been performed. We observe that the magic numbers occur at N = 43, 46, 49, 53, 55, and 58, which correspond to the most stable clusters. We find that, with increase in substitution of Co and Fe atoms in Ni cluster, while Ni nCo m becomes more stable, the NinFem clusters become less stable. The significant enhancement of average magnetic moment and suppression of local magnetic moment of nickel atoms are found in both clusters with increase in Co and Fe concentration

(85)Rb Bose-Einstein condensate with tunable interaction: A quantum many body approach

We present a quantum many body approach with van der Waal type of interaction to achieve (85)Rb Bose-Einstein condensate with tunable interaction which has been produced by magnetic field induced Feshbach resonance in the JILA experiment. (C) 2008 Elsevier B.V. All rights reserved.Department of Science and Technology (DST, India)Department of Science and Technology (DST, India)University Grants Commission (UGC, India)University Grants Commission (UGC, India)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq (Brazil)FAPESP (Brazil)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP