Superconductivity and magnetism generally do not coexist. Changing the relative number of up and down spin electrons disrupts the basic mechanism of superconductivity, where atoms of opposite momentum and spin form Cooper pairs. Nearly forty years ago Fulde and Ferrell and Larkin and Ovchinnikov (FFLO) proposed an exotic pairing mechanism in which magnetism is accommodated by the formation of pairs with finite momentum. Despite intense theoretical and experimental efforts, however, polarized superconductivity remains largely elusive. Unlike the three-dimensional (3D) case, theories predict that in one dimension (1D) a state with FFLO correlations occupies a major part of the phase diagram. Here we report experimental measurements of density profiles of a two-spin mixture of ultracold (6)Li atoms trapped in an array of 1D tubes (a system analogous to electrons in 1D wires). At finite spin imbalance, the system phase separates with an inverted phase profile, as compared to the 3D case. In 1D, we find a partially polarized core surrounded by wings which, depending on the degree of polarization, are composed of either a completely paired or a fully polarized Fermi gas. Our work paves the way to direct observation and characterization of FFLO pairing.

We calculate the zero-temperature (T=0) phase diagram of a polarized two-component Fermi gas in an array of weakly coupled parallel one-dimensional (1D) "tubes" produced by a two-dimensional optical lattice. Increasing the lattice strength drives a crossover from three-dimensional (3D) to 1D behavior, stabilizing the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulated superfluid phase. We argue that the most promising regime for observing the FFLO phase is in the quasi-1D regime, where the atomic motion is largely 1D but there is weak tunneling in the other directions that stabilizes long-range order. In the FFLO phase, we describe a phase transition where the quasiparticle spectrum changes from gapless near the 3D regime to gapped in quasi-1D.

Secreted aspartyl proteinases (Saps) contribute to the ability of Candida albicans to cause mucosal and disseminated infections. A model of vaginal candidiasis based on reconstituted human vaginal epithelium (RHVE) was used to study the expression and role of these C. albicans proteinases during infection and tissue damage of vaginal epithelium. Colonization of the RHVE by C. albicans SC5314 did not cause any visible epithelial damage 6 h after inoculation, although expression of SAP2, SAP9, and SAP10 was detected by reverse transcriptase PCR. However, significant epithelial damage was observed after 12 h, concomitant with the additional expression of SAP1, SAP4, and SAP5. Additional transcripts of SAP6 and SAP7 were detected at a later stage of the artificial infection (24 h). Similar SAP expression profiles were observed in three samples isolated from human patients with vaginal candidiasis. In experimental infection, secretion of antigens Sap1 to Sap6 by C. albicans was confirmed at the ultrastructural level by using polyclonal antisera raised against Sap1 to Sap6. Addition of the aspartyl proteinase inhibitors pepstatin A and the human immunodeficiency virus proteinase inhibitors ritonavir and amprenavir strongly reduced the tissue damage of the vaginal epithelia by C. albicans cells. Furthermore, SAP null mutants lacking either SAP1 or SAP2 had a drastically reduced potential to cause tissue damage even though SAP3, SAP4, and SAP7 were up-regulated in these mutants. In contrast the vaginopathic potential of mutants lacking SAP3 or SAP4 to SAP6 was not reduced compared to wild-type cells. These data provide further evidence for a crucial role of Sap1 and Sap2 in C. albicans vaginal infections.Although normally a commensal habitant of mucosal surfaces, Candida albicans frequently causes surface infections when certain host factors are imbalanced. Under certain circumstances these superficial infections may disseminate to cause serious systemic infections. Key virulence factors of C. albicans that appear to play major roles in the pathogenesis of this opportunistic fungus are the secreted aspartyl proteinases (Saps), which are encoded by 10 SAP genes. These genes are regulated differentially in vitro and in vivo during infection of three-dimensional models for oral and cutaneous candidiasis in infected tissue of mice and in patient samples (3, 10, 15). Therefore, it has been concluded that different SAP genes may have distinct roles at different times of the infection process and during different types of infection (15). For example, by use of SAP-deficient mutants, it has been shown that SAP1, SAP2, and SAP3 contribute significantly to tissue damage and invasion of oral epithelium and cutaneous epidermis (23, 25), while SAP4, SAP5, and SAP6 are important for systemic infections (12,22). Several studies dealing with proteinase secretion and proteinase activity have shown a clear correlation between the ability of C. albicans strains to secrete Saps and to cause disease (4,5,7,9). The expression and importance ...

Antiferromagnetism of ultracold fermions in an optical lattice can be detected by Bragg diffraction of light, in analogy to the diffraction of neutrons from solid-state materials. A finite sublattice magnetization will lead to a Bragg peak from the ( 1 2 1 2 1 2 ) crystal plane with an intensity depending on details of the atomic states, the frequency and polarization of the probe beam, the direction and magnitude of the sublattice magnetization, and the finite optical density of the sample. Accounting for these effects we make quantitative predictions about the scattering intensity and find that with experimentally feasible parameters the signal can be readily measured with a CCD camera or a photodiode and used to detect antiferromagnetic order.

We introduce an all-optical approach to producing high-flux synthetic magnetic fields for neutral atoms or molecules by designing intrinsically time-periodic optical superlattices. A single laser source, modulated to generate two frequencies, suffices to create dynamic interference patterns which have topological Floquet energy bands. We propose a simple laser setup that realizes a tightbinding model with uniform flux and well-separated Chern bands. Our method relies only on the particles' scalar polarizability and far detuned light.In the quest to establish ultracold atoms as versatile quantum simulators of condensed-matter physics [1], a key challenge is to develop minimally invasive methods of mimicking the orbital effects of a magnetic field [2]. In solid-state systems the interplay of strong magnetic fields with Coulomb interactions gives rise to strongly correlated phases, notably the fractional quantum Hall effect [3]. Atomic systems offer prospects for studying related phenomena of either bosons or fermions with tunable interactions, using new diagnostic tools.This goal has motivated intense theoretical and experimental effort at simulating, for neutral atoms, the Lorentz force experienced by a charged particle in a magnetic field [2]. Methods demonstrated to date have included subjecting quantum gases to rapid rotation [4,5] or imprinting geometric phases via spatially dependent couplings between internal states [6]. While the latter approach can in principle be extended to reach a high (net positive) flux density [7][8][9][10][11], only a select few atomic species offer a route to introducing the requisite optical couplings without significant spontaneous-emissioninduced heating or atom loss [9][10][11][12][13].A more broadly applicable means of producing highflux gauge fields is by modulating tight-binding optical lattices periodically in time [14][15][16][17][18][19][20][21][22]. This approach can be implemented with arbitrarily far-detuned light, in principle for any atomic or molecular species. Analogous methods [23][24][25] have even been applied in solidstate systems [26] and photonic crystals [27]. Common to all these systems is a breaking of time-reversal symmetry that endows the tunneling matrix elements with Peierls-like phases [14,15,18,28], mimicking the effect of a magnetic flux though each lattice plaquette.In optical lattices, Peierls phases have been engineered by large-amplitude off-resonant shaking [15,28]; or by direct modulation of on-site energies to produce a resonant photon-assisted hopping between orbitals of distinct lattice sites [29,30]. The latter method, requiring only small modulation amplitude, is less susceptible to (multiphoton) heating processes. To date, demonstrations of this method in periodic optical lattices lead to zero average flux. Recent success in producing large uniform flux by resonant photon-assisted hopping [30] is a technical feat, requiring not only multiple optical lattice lasers but also a strong magnetic field gradient [31].Here, we present an all-op...