Creating superfluid vortex rings in artificial magnetic fields

Artificial gauge fields are versatile tools that allow to influence the dynamics of ultracold atoms in Bose-Einstein condensates. Here we discuss a method of artificial gauge field generation stemming from the evanescent fields of the curved surface of an optical nanofibre. The exponential decay of the evanescent fields leads to large gradients in the generalized Rabi frequency and therefore to the presence of geometric vector and scalar potentials. By solving the Gross-Pitaevskii equation in the presence of the artificial gauge fields originating from the fundamental HE$_{11}$ mode of the fibre, we show that vortex rings can be created in a controlled manner. We also calculate the magnetic fields resulting from the higher order HE$_{21}$, TE$_{01}$, and TM$_{01}$ modes and compare them to the fundamental HE$_{11}$ mode.Comment: 8 pages, 6 figure

Hydrodynamic theory of Rotating Ultracold Bose Einstein Condensates in Supersolid Phase

Within mean field Gross-Pitaevskii framework, ultra cold atomic condensates with long range interaction is predicted to have a supersolid like ground state beyond a critical interaction strength. Such mean field supersolid like ground state has periodically modulated superfluid density which implies the coexistence of superfluid and crystalline order. Ultra cold atomic system in such mean field ground state can be subjected to artificial gauge field created either through rotation or by introducing space dependent coupling among hyperfine states of the atoms using Raman lasers. Starting from this Gross-Pitaevskii energy functional that describes such systems at zero temperature, we construct hydrodynamic theory to describe the low energy long wavelength excitations of such rotating supersolid of weakly interacting ultra cold atoms in two spatial dimensions for generic type of long range interaction. We treat the supersolidity in such system within the framework of well known two fluid approximation. Considering such system in the fast rotation limit where a vortex lattice in superfluid coexists with the supersolid lattice, we analytically obtain the dispersion relations of collective excitations around this equilibrium state. The dispersion relation gives the modes of the rotating supersolid which can be experimentally measured within the current technology. We point out that this can clearly identify such a ultra cold atomic supersolid phase in an unambiguous way.Comment: Revised Latex file with .pdf figures, Accepted for publication in Journal of Physics B : At. Mol. Op

Shifting from Agriculture to Agribusiness: The Case of Aromatic Plants

This study has examined the agribusiness opportunities in medicinal and aromatic plants (MAPs), based on the field level information from the state of Uttarakhand. The financial feasibility of important aromatic plants has been studied. It has been found that the returns are substantially higher from these crops than the most profitable commercial crops like sugarcane. The study has identified the constraints that affect the spread of cultivation of MAPs; these include inadequate processing capacities, price risks and non-availability of planting material. It has been suggested that concerted efforts should be made to address these constraints and increase access to the world market.Agribusiness, Crop Production/Industries,

Cold atoms in rotating optical lattice with nearest neighbour interaction

Extended Bose Hubbard models with nearest neighbour interaction describe minimally the effect of long range interaction on ultra cold atoms in deep optical lattices. Rotation of such optical lattices subject such neutral cold atoms to the effect of an artificial magnetic field. The modification of the phase boundaries of the density wave and Mott Insulator phases due to this rotation are shown to be related to the edge spectrum of spinorial and scalar Harper equation. Corresponding profiles of the checkerboard vortex states with sublattice modulated superfluid order parameter near density wave phase boundary are calculated.Comment: Slightly revised, Accepted in Physical Review A for publicatio

Small and Medium Enterprises in the Agriculture Value Chain: Opportunities and Recommendations

Authored in collaboration with Oxfam, this report analyzes the effectiveness of development programs in addressing the effectiveness of SME agricultural value chains, and dissect whether these interventions would be Social Enterprises (SEs) in agriculture in Asia. The paper makes recommendations for donors and development agencies that seek to support SEs in agriculture

Sri Lanka Social Enterprise Needs Assessment and Advisory

Authored in collaboration with Oxfam, this research maps social enterprises within the agriculture sector, identifies the key challenges they face, and makes recommendations for donors and development agencies looking to support the space in Sri Lanka. Findings and recommendations developed based on secondary research and field survey of social enterprises in Sri Lanka

Extended Bose Hubbard model for two leg ladder systems in artificial magnetic fields

We investigate the ground state properties of ultracold atoms with long range interactions trapped in a two leg ladder configuration in the presence of an artificial magnetic field. Using a Gross-Pitaevskii approach and a mean field Gutzwiller variational method, we explore both the weakly interacting and strongly interacting regime, respectively. We calculate the boundaries between the density-wave/supersolid and the Mott-insulator/superfluid phases as a function of magnetic flux and uncover regions of supersolidity. The mean-field results are confirmed by numerical simulations using a cluster mean field approach.Comment: 11 pages, 11 figure

Twonniers: Interaction-induced effects on Bose-Hubbard parameters

We study the effects of the repulsive on-site interactions on the broadening of the localized Wannier functions used for calculating the parameters to describe ultracold atoms in optical lattices. For this, we replace the common single-particle Wannier functions, which do not contain any information about the interactions, by two-particle Wannier functions ("Twonniers") obtained from an exact solution which takes the interactions into account. We then use these interaction-dependent basis functions to calculate the Bose--Hubbard model parameters, showing that they are substantially different both at low and high lattice depths, from the ones calculated using single-particle Wannier functions. Our results suggest that density effects are not negligible for many parameter ranges and need to be taken into account in metrology experiments.Comment: 6 pages, 3 figure