pp-wave chiral superfluidity from an ss-wave interacting atomic Fermi gas

Chiral $p$-wave superfluids are fascinating topological quantum states of matter that have been found in the liquid $^3$He-A phase and arguably in the electronic Sr$_2$RuO$_4$ superconductor. They are shown fundamentally related to the fractional $5/2$ quantum Hall state which supports fractional exotic excitations. A common understanding is that such states require spin-triplet pairing of fermions due to $p$-wave interaction. Here we report by controlled theoretical approximation that a center-of-mass Wannier $p$-wave chiral superfluid state can arise from spin-singlet pairing for an $s$-wave interacting atomic Fermi gas in an optical lattice. Despite a conceptually different origin, it shows topological properties similar to the conventional chiral $p$-wave state. These include a non-zero Chern number and the appearance of chiral fermionic zero modes bounded to domain walls. Several signature quantities are calculated for the cold atom experimental condition.Comment: 16 pages and 7 figures including supplementary material

Stability of pp-orbital Bose-Einstein condensates in optical checkerboard and square lattices

We investigate $p$-orbital Bose-Einstein condensates in both the square and checkerboard lattice by numerically solving the Gross-Pitaevskii equation. The periodic potential for the latter lattice is taken exactly from the recent experiment [Nature Phys. 7, 147 (2011)]. It is confirmed that the staggered orbital-current state is the lowest-energy state in the $p$ band. Our numerical calculation further reveals that for both lattices the staggered $p$-orbital state suffers Landau instability but the situation is remarkably different for dynamical instability. A dynamically stable parameter region is found for the checkerboard lattice, but not for the square.Comment: 7 pages, 7 figure

Kinetic analysis of an efficient DNA-dependent TNA polymerase.

alpha-l-Threofuranosyl nucleoside triphosphates (tNTPs) are tetrafuranose nucleoside derivatives and potential progenitors of present-day beta-d-2'-deoxyribofuranosyl nucleoside triphosphates (dNTPs). Therminator DNA polymerase, a variant of the 9 degrees N DNA polymerase, is an efficient DNA-directed threosyl nucleic acid (TNA) polymerase. Here we report a detailed kinetic comparison of Therminator-catalyzed TNA and DNA syntheses. We examined the rate of single-nucleotide incorporation for all four tNTPs and dNTPs from a DNA primer-template complex and carried out parallel experiments with a chimeric DNA-TNA primer-DNA template containing five TNA residues at the primer 3'-terminus. Remarkably, no drop in the rate of TNA incorporation was observed in comparing the DNA-TNA primer to the all-DNA primer, suggesting that few primer-enzyme contacts are lost with a TNA primer. Moreover, comparison of the catalytic efficiency of TNA synthesis relative to DNA synthesis at the downstream positions reveals a difference of no greater than 5-fold in favor of the natural DNA substrate. This disparity becomes negligible when the TNA synthesis reaction mixture is supplemented with 1.25 mM MnCl(2). These results indicate that Therminator DNA polymerase can recognize both a TNA primer and tNTP substrates and is an effective catalyst of TNA polymerization despite changes in the geometry of the reactants

Ground states of hard-core bosons in one dimensional periodic potentials

With Girardeau's Fermi-Bose mapping, we find the exact ground states of hard-core bosons residing in a one dimensional periodic potential. The analysis of these ground states shows that when the number of bosons $N$ is commensurate with the number of wells $M$ in the periodic potential, the boson system is a Mott insulator whose energy gap, however, is given by the single-particle band gap of the periodic potential; when $N$ is not commensurate with $M$, the system is a metal (not a superfluid). In fact, we argue that there may be no superfluid phase for any one-dimensional boson system in terms of Landau's criterion of superfluidity. The Kronig-Penney potential is used to illustrate our results.Comment: 6 pages, 6 figure