Floquet topological transitions in a driven one-dimensional topological insulator

The Su-Schrieffer-Heeger model of polyacetylene is a paradigmatic Hamiltonian exhibiting non-trivial edge states. By using Floquet theory we study how the spectrum of this one-dimensional topological insulator is affected by a time-dependent potential. In particular, we evidence the competition among different photon-assisted processes and the native topology of the unperturbed Hamiltonian to settle the resulting topology at different driving frequencies. While some regions of the quasienergy spectrum develop new gaps hosting Floquet edge states, the native gap can be dramatically reduced and the original edge states may be destroyed or replaced by new Floquet edge states. Our study is complemented by an analysis of Zak phase applied to the Floquet bands. Besides serving as a simple example for understanding the physics of driven topological phases, our results could find a promising test-ground in cold matter experiments

Observation of the Meissner effect with ultracold atoms in bosonic ladders

We report on the observation of the Meissner effect in bosonic flux ladders of ultracold atoms. Using artificial gauge fields induced by laser-assisted tunneling, we realize arrays of decoupled ladder systems that are exposed to a uniform magnetic field. By suddenly decoupling the ladders and projecting into isolated double wells, we are able to measure the currents on each side of the ladder. For large coupling strengths along the rungs of the ladder, we find a saturated maximum chiral current corresponding to a full screening of the artificial magnetic field. For lower coupling strengths, the chiral current decreases in good agreement with expectations of a vortex lattice phase. Our work marks the first realization of a low-dimensional Meissner effect and, furthermore, it opens the path to exploring interacting particles in low dimensions exposed to a uniform magnetic field

Experimental realization of plaquette resonating valence bond states with ultracold atoms in optical superlattices

The concept of valence bond resonance plays a fundamental role in the theory of the chemical bond and is believed to lie at the heart of many-body quantum physical phenomena. Here we show direct experimental evidence of a time-resolved valence bond quantum resonance with ultracold bosonic atoms in an optical lattice. By means of a superlattice structure we create a three-dimensional array of independent four-site plaquettes, which we can fully control and manipulate in parallel. Moreover, we show how small-scale plaquette resonating valence bond states with s- and d-wave symmetry can be created and characterized. We anticipate our findings to open the path towards the creation and analysis of many-body RVB states in ultracold atomic gases.Comment: 7 page, 4 figures in main text, 3 figures in appendi

Measuring the Chern number of Hofstadter bands with ultracold bosonic atoms

Sixty years ago, Karplus and Luttinger pointed out that quantum particles moving on a lattice could acquire an anomalous transverse velocity in response to a force, providing an explanation for the unusual Hall effect in ferromagnetic metals. A striking manifestation of this transverse transport was then revealed in the quantum Hall effect, where the plateaus depicted by the Hall conductivity were attributed to a topological invariant characterizing Bloch bands: the Chern number. Until now, topological transport associated with non-zero Chern numbers has only been revealed in electronic systems. Here we use studies of an atomic cloud's transverse deflection in response to an optical gradient to measure the Chern number of artificially generated Hofstadter bands. These topological bands are very flat and thus constitute good candidates for the realization of fractional Chern insulators. Combining these deflection measurements with the determination of the band populations, we obtain an experimental value for the Chern number of the lowest band $\nu_{\mathrm{exp}} =0.99(5)$. This result, which constitutes the first Chern-number measurement in a non-electronic system, is facilitated by an all-optical artificial gauge field scheme, generating uniform flux in optical superlattices

Experimental Measurement of the Berry Curvature from Anomalous Transport

Geometrical properties of energy bands underlie fascinating phenomena in a wide-range of systems, including solid-state materials, ultracold gases and photonics. Most famously, local geometrical characteristics like the Berry curvature can be related to global topological invariants such as those classifying quantum Hall states or topological insulators. Regardless of the band topology, however, any non-zero Berry curvature can have important consequences, such as in the semi-classical evolution of a wave packet. Here, we experimentally demonstrate for the first time that wave packet dynamics can be used to directly map out the Berry curvature. To this end, we use optical pulses in two coupled fibre loops to study the discrete time-evolution of a wave packet in a 1D geometrical "charge" pump, where the Berry curvature leads to an anomalous displacement of the wave packet under pumping. This is both the first direct observation of Berry curvature effects in an optical system, and, more generally, the proof-of-principle demonstration that semi-classical dynamics can serve as a high-resolution tool for mapping out geometrical properties

Controle glicêmico em pacientes adultos com diabetes do tipo 1 em uma cidade brasileira: comparação entre abordagem multidisciplinar e endocrinológica de rotina

OBJECTIVE: To evaluate the metabolic control of a cohort of adult type 1 diabetes mellitus (T1DM) patients assisted in a public Diabetes Center (DC) that follows the rules of a national diabetes society. METHODS: We compared for one year the metabolic control and the characteristics of 175 T1DM patients attended by a multidisciplinary team in a DC (test group) with 30 patients assisted only by endocrinologists at a public endocrinology outpatient center (control group). RESULTS: The test group presented a larger proportion of well-controlled patients (p= 0.002). The proportions (test x control group) were as follows: 51.4% x 16.7% in the subgroup with A1C 8%. Patients assisted in the DC presented a likelihood 4.38 times higher of reaching levels of A1C up to 7%. CONCLUSIONS: This study shows the effectiveness of a DC and emphasizes the importance of education, adherence and multidisciplinarity as cornerstones for the treatment, showing that in developing countries it is possible to treat T1DM with satisfactory results.OBJETIVO: Avaliar o controle metabólico de uma coorte de pacientes adultos com diabetes do tipo 1 (DM1) atendidos em um Centro de Diabetes (CD) que segue as normas da Sociedade Brasileira de Diabetes. MÉTODOS: Foram comparados o controle glicêmico e as características de 175 pacientes com DM1 atendidos por uma equipe multidisciplinar em um CD (grupo teste) com 30 pacientes assistidos em um ambulatório de endocrinologia geral (grupo controle) durante um ano. RESULTADOS: O grupo teste apresentou uma maior proporção de pacientes bem controlados (p= 0,002). As proporções (grupo teste x grupo controle) foram: 51,4% x 16,7% no subgrupo com A1C 8%. Os pacientes atendidos no CD apresentaram probabilidade 4,38 vezes maior de atingir níveis de A1C até 7%. CONCLUSÃO: O estudo mostra a efetividade do CD e enfatiza a importância da educação, aderência e da multidisciplinaridade como pedras angulares do tratamento, mostrando ser possível tratar o DM1 nos países em desenvolvimento com resultados satisfatórios.Universidade Federal de São Paulo (UNIFESP)Universidade Federal de Juiz de Fora Departamento de FisiologiaUNIFESPSciEL

Observation of Bose-Einstein Condensation in a Strong Synthetic Magnetic Field

Extensions of Berry's phase and the quantum Hall effect have led to the discovery of new states of matter with topological properties. Traditionally, this has been achieved using gauge fields created by magnetic fields or spin orbit interactions which couple only to charged particles. For neutral ultracold atoms, synthetic magnetic fields have been created which are strong enough to realize the Harper-Hofstadter model. Despite many proposals and major experimental efforts, so far it has not been possible to prepare the ground state of this system. Here we report the observation of Bose-Einstein condensation for the Harper-Hofstadter Hamiltonian with one-half flux quantum per lattice unit cell. The diffraction pattern of the superfluid state directly shows the momentum distribution on the wavefuction, which is gauge-dependent. It reveals both the reduced symmetry of the vector potential and the twofold degeneracy of the ground state. We explore an adiabatic many-body state preparation protocol via the Mott insulating phase and observe the superfluid ground state in a three-dimensional lattice with strong interactions.Comment: 6 pages, 5 figures. Supplement: 6 pages, 4 figure

The impact of the merger of Income Tax Department with Sales Tax Department with their associated accounting and legal policies in the reduction of tax evasion

The current study aimed at identifying the impact of the integration of the merger of Income Tax Department with Sales Tax Department with their associated accounting and legal policies in the reduction of tax evasion. In order to achieve the objectives of the current study, the researcher has applied the Descriptive approach for data view, while he has applied the analytical approach for the analysis of the results of the current study. The study population consisted of the auditors of Income & Sales Tax Department in medium taxpayers directorates working in auditing  whose number was (150) auditors. A questionnaire was distributed on the study sample consisting of (150) respondents.(128) questionnaires were retrieved ,(22) were excluded because they were not valid for analysis. The actual percentage of the study sample was (85,3%). The researcher, having analyzed the responses of the study sample using SPSS, he has concluded a set of results, the most important are: There is a statistically significant difference of the merger of Income Tax Department with Sales Tax Department in the reduction of tax evasion in Jordan. There is a statistically significant difference for the merger of information systems in Income & Sales Tax Departments in the reduction of tax evasion in Jordan. There is a statistically significant difference for Anti Tax Evasion Directorate in the reduction of tax evasion in Jordan. There is a statistically significant difference for the accounting and legal policies of Income Tax Law no. 28 of 2009 in the reduction of tax evasion in Jordan. In light of the results of the current study, the researcher recommends the following: The activation of the role of Directorate of Information in the Department and supplying it with experienced staff and necessary equipment.The activation of the role of Anti Tax Evasion Directorate in the Department and supplying it with experienced staff and necessary equipment.The activation of procedures applications with regard to the in advance deduction that shall be imposed on business activities.Rehabilitation and training of Income & Sales Tax Departments staff and increase their competencies through the necessary training programs.Raising the taxpayers ‘awareness regarding the importance of tax and its role in the national economy

Quantum transport in ultracold atoms

Ultracold atoms confined by engineered magnetic or optical potentials are ideal systems for studying phenomena otherwise difficult to realize or probe in the solid state because their atomic interaction strength, number of species, density, and geometry can be independently controlled. This review focuses on quantum transport phenomena in atomic gases that mirror and oftentimes either better elucidate or show fundamental differences with those observed in mesoscopic and nanoscopic systems. We discuss significant progress in performing transport experiments in atomic gases, contrast similarities and differences between transport in cold atoms and in condensed matter systems, and survey inspiring theoretical predictions that are difficult to verify in conventional setups. These results further demonstrate the versatility offered by atomic systems in the study of nonequilibrium phenomena and their promise for novel applications.Comment: 24 pages, 7 figures. A revie