We observe the emergence of a disorder-induced insulating state in a strongly interacting atomic Fermi gas trapped in an optical lattice. This closed quantum system free of a thermal reservoir realizes the disordered Fermi-Hubbard model, which is a minimal model for strongly correlated electronic solids. In measurements of disorder-induced localization obtained via mass transport, we detect interaction-driven delocalization and localization that persists as the temperature of the gas is raised. These behaviors are consistent with many-body localization, which is a novel paradigm for understanding localization in interacting quantum systems at non-zero temperature.PACS numbers: 37.10.Jk,71.23.AnThe impact of inter-particle interactions on localization of disordered quantum systems has been the subject of intense scrutiny for decades (see [1][2][3][4][5] and references therein). Obtaining new insights into the interplay of interactions and disorder is critical to improving our understanding of quantum electronic solids such as the high-temperature superconducting cuprates and materials that exhibit colossal magnetoresistance, such as the manganites [4,6,7]. Despite the application of a wide variety of sophisticated theoretical and numerical approaches, consensus regarding the nature of metalinsulator transitions and localization in strongly correlated systems has not been achieved. A recent theoretical approach to these questions is many-body localization (MBL) [8][9][10][11], which overturns the conventional view holding that materials above zero temperature have nonzero conductivity in the presence of interactions. In a many-body localized state, a quantum system can remain an Anderson-localized insulator at non-zero temperature because the inter-particle interactions fail to generate thermally activated conductivity.We investigate localization using an ultracold atomic gas trapped in a disordered optical lattice. This precisely controllable system, which realizes the disordered FermiHubbard model (DFHM) [12]-the minimal model for strongly correlated, disordered electronic solids-is free of a heat bath, such as phonons, that can lead to finite conductivity at nonzero temperature and foils direct tests of theories such as MBL in the solid state. The seminal theoretical work by Basko et al. on MBL [8] explored the weakly interacting regime of a spinless DFHM; we investigate the strongly correlated limit which is challenging for theory and numerical approaches. We probe disorder-induced metal-insulator transitions using mass transport measurements. The disorder ∆ c required to localize the gas and produce an insulating state is determined for different ratios of the Hubbard interaction to tunneling energies. We find that increased interactions stabilize the metal against localization and lead to an insulator-metal transition. We also show that localization occurs across a range of thermal energy densities at fixed disorder strength by varying the temperature of the gas.In our experiment, fermionic 40 K atoms cooled...

Block copolymers with their rich phase behavior and ordering transitions have become a paradigm for the study of structured soft materials. A major challenge in the study of the phase behavior of block copolymers is to obtain different stable and metastable phases of the system. A strategy to discover complex ordered phases of block copolymers within the self-consistent field theory framework is developed by a combination of fast algorithms and novel initialization procedures. This strategy allows the generation of a large number of candidate structures, which can then be used to construct phase diagrams. Application of the strategy is illustrated using ABC star triblock copolymers as an example. A large number of candidate structures, including many three-dimensionally ordered phases, of the system are obtained and categorized. A phase diagram is constructed for symmetrically interacting ABC star triblock copolymers.

A new series of dinuclear ruthenium(II) polypyridyl complexes, which possess larger π-conjugated systems, good water solubility and pH resistance, and high photostability, were developed to act as single and two-photon luminescence cellular imaging probes.

A new dinuclear Ru(II) polypyridyl complex, [(bpy)2 Ru(H2 bpip)Ru(bpy)2 ](4+) (RuH2 bpip, bpy=2,2-bipyridine, H2 bpip=2,6-pyridyl(imidazo[4,5-f][1,10]phenanthroline), was developed to act as a one- and two-photon luminescent probe for biological Cu(2+) detection. This Ru(II) complex shows a significant two-photon absorption cross section (400 GM) and displays a remarkable one- and two-photon luminescence switch in the presence of Cu(2+) ions. Importantly, RuH2 bpip can selectively recognise Cu(2+) in aqueous media in the presence of other abundant cellular cations (such as Na(+) , K(+) , Mg(2+) , and Ca(2+) ), trace metal ions in organisms (such as Zn(2+) , Ag(+) , Fe(3+) , Fe(2+) , Ni(2+) , Mn(2+) , and Co(2+) ), prevalent toxic metal ions in the environment (such as Cd(2+) , Hg(2+) , and Cr(3+) ), and amino acids, with high sensitivity (detection limit≤3.33×10(-8)  M) and a rapid response time (≤15 s). The biological applications of RuH2 bpip were also evaluated and it was found to exhibit low cytotoxicity, good water solubility, and membrane permeability; RuH2 bpip was, therefore, employed as a sensing probe for the detection of Cu(2+) in living cells and zebrafish.

The development of non‐covalent synthetic strategy to fabricate efficient photocatalysts is of great importance in theranostic and organic materials. Herein, a fluorochrome N,N′‐dimethyl 2,5‐bis(4‐pyridinium)thiazolo[5,4‐d]thiazolediiodide (MPT) was transformed into an efficient photocatalyst through supramolecular dimerization in the cavity of cucurbit[8]uril (CB[8]). The host‐enhanced charge transfer interaction within the supramolecular dimer 2MPT‐CB[8] dramatically promoted intersystem crossing to produce triplet. In addition, the staggered conformation of 2MPT‐CB[8] facilitated the energy transfer and electron transfer of the triplet. As a result, 2MPT‐CB[8] could serve as a high‐efficiency photocatalyst for the oxidative hydroxylation of arylboronic acids. This supramolecular dimerization strategy enriches the supramolecular engineering of functional π‐systems. It is anticipated that this strategy can be extended to fabricate various π‐systems with tailor‐made functions.