Topological properties lie at the heart of many fascinating phenomena in solid state systems such as quantum Hall systems or Chern insulators. The topology can be captured by the distribution of Berry curvature, which describes the geometry of the eigenstates across the Brillouin zone. Employing fermionic ultracold atoms in a hexagonal optical lattice, we generate topological bands using resonant driving and show a full momentumresolved measurement of the ensuing Berry curvature. Our results pave the way to explore intriguing phases of matter with interactions in topological band structures.Topology is a fundamental concept for our understanding of many fascinating systems that have recently attracted a lot of interest, such as topological superconductors or topological insulators, which conduct only at their edges [1]. The topology of the bulk band is quantified by the Berry curvature [2] and the integral over the full Brillouin zone is a topological invariant, called the Chern number. According to the bulk boundary correspondence principle, the Chern number determines the number of chiral conducting edge states [1]. While in a variety of lattice systems ranging from solid state systems to photonic waveguides and even coupled mechanical pendula, edge states have been directly observed [3][4][5][6][7], the underlying Berry curvature as the central measure of topology is not easily accessible. In recent years, ultracold atoms in optical lattices have emerged as a platform to study topological band structures [8,9] and these systems have seen considerable experimental and theoretical progress. Whereas in condensed matter systems, topological properties arise due to external magnetic fields or intrinsic spin-orbit coupling of the material, they can in cold atom systems be engineered by periodic driving analogous to illuminated graphene [10]. Interestingly, the resulting Floquet system can have totally new topological properties [11]. The driving can, for example, be realized by lattice shaking [12][13][14][15][16] or Raman coupling [17][18][19] with high precision control in a large parameter space. In particular, the driving can break time-reversal symmetry [13,14,16] and thus allows for engineering non-trivial topology [16,18]. In quantum gas experiments, topolog- ical properties have been probed via the Hall drift of accelerated wave packets [16,18], via an interferometer in momentum space [20,21]

Recently, the identification of non-equilibrium signatures of topology in the dynamics of such systems has attracted particular attention [3][4][5][6] . Here, we experimentally study the dynamical evolution of the wavefunction using time-and momentum-resolved full state tomography for spin-polarized fermionic atoms in driven optical lattices 7 . We observe the appearance, movement and annihilation of dynamical vortices in momentum space after sudden quenches close to the topological phase transition. These dynamical vortices can be interpreted as dynamical Fisher zeros of the Loschmidt amplitude 8 , which signal a so-called dynamical phase transition 9,10 . Our results pave the way to a deeper understanding of the connection between topological phases and non-equilibrium dynamics.The discovery of topological matter has revolutionized our understanding of band theory: not only are the dispersions of the energy bands important, but so is the geometry of the corresponding eigenstates 1 . The non-local nature of the topological invariants characterizing such phases goes beyond the Landau paradigm of local order parameters and leads to topological protection, for example, against disorder. Ultracold quantum gases in optical lattices allow for controlled studies of archetypal topological models [11][12][13][14] . In addition, compared with, for example condensed-matter systems, they also allow for detailed studies of the relation between dynamics and topology as the timescales are experimentally easier to access. Dynamical studies of driven systems have recently attracted attention in terms of their high T c superconductivity 15 . A particular challenge is to identify non-equilibrium signatures of topology in the dynamics of highly excited states 3,4,16 . Here, we observe the time evolution of the wavefunction after a sudden quench in a Haldanelike model and find dynamical vortices as a signature of the topological nature of the underlying ground state.In the experiments described here, the state tomography method allows mapping of the full quantum-mechanical wavefunction of non-interacting ultracold fermionic quantum gases in an optical lattice for any time after a sudden quench of the system close to or into a Chern insulating phase. As a key result, we identify in an intense series of measurements the appearance, movement and annihilation In the initial system, tunnelling J AB between the A and B sites is suppressed by a large energy offset. In the final Floquet system, tunnelling is re-established by means of near-resonant driving. b, At each momentum, the Hamiltonian describes the coupling between the states of the A and B sublattices, and can be visualized on a Bloch sphere. In the initial system, the Hamiltonian for all momenta points to the north pole, whereas in the Floquet system, the Hamiltonian covers a large surface of the Bloch sphere. c, Phase diagram for the Floquet Hamiltonian as a function of shaking amplitude and detuning with respect to the sublattice offset for the case of circular lattice shaking...

This article examines the use of performance information by public managers. It conceptualizes purposeful data use as a type of extra-role behaviour which requires additional effort on the part of the managers and which is not extrinsically rewarded. The article sheds light on one potential antecedent of performance information use -the motivation of the users. It argues that we can observe high levels of data use if managers driven by public service motivation (PSM) work under transformational leaders. Using a needs-supply perspective on supervisors and followers, we suggest that there is a PSM-leadership fit which fosters the performance of this extra-role behaviour. The article is based on data from German local government and its findings contribute to the literatures on PSM as well as on performance management. INTRODUCTIONPerformance measurement has affected the management of public organizations worldwide. Data on the efficiency, quality, and effectiveness of public services must be systematically collected and reported by public administrations ( Research on performance information use is on the rise. There are about two dozen articles which have studied variations of purposeful performance information use (Kroll 2012). These articles mainly used linear, additive models to uncover and compare the direct effects of different variables on the managers' use of performance data. This approach has been useful for structuring the research field and for distinguishing between crucial variables and unimportant factors. However, in order to improve our understanding of real life public management decision-making, we might need to further specify our models by using moderators ('interactions') and mediators ('indirect effects'). As Frazier et al. (2004, p. 116) concluded, 'the identification of important moderators [and mediators] of relations between predictors and outcomes indicates the maturity and sophistication of a field of inquiry'.This article focuses on one antecedent of performance information use that has not received much attention -a manager's motivation and values. We base our argument on the premise that the use of performance data demands extra effort from the managers and is a cognitive process which is not extrinsically rewarded (Moynihan et al. 2012a).

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Although there is debate about whether patients with UWS can perceive their own pain, our data indicate that many of them respond to the signals of pain in others. One can speculate that "affective consciousness" can remain even in patients with very severe brain damage who have no capacity for cognition.

Topological defects in Bloch bands, such as Dirac points in graphene, and their resulting Berry phases play an important role for the electronic dynamics in solid state crystals. Such defects can arise in systems with a two-atomic basis due to the momentum-dependent coupling of the two sublattice states, which gives rise to a pseudo-spin texture. The topological defects appear as vortices in the azimuthal phase of this pseudo-spin texture. Here, we demonstrate a complete measurement of the azimuthal phase in a hexagonal optical lattice employing a versatile method based on time-of-flight imaging after off-resonant lattice modulation. Furthermore we map out the merging transition of the two Dirac points induced by beam imbalance. Our work paves the way to accessing geometric properties in optical lattices also with spin-orbit coupling and interactions.

Previous research in health and disease has shown that exposure to pain changes the density of cortical grey matter (GM). Such structural changes of the brain might, however, depend crucially on how this pain experience is evaluated and processed in the brain. In the present study we aimed to detect pain-rating patterns and underlying GM changes after the application of repetitive painful stimulation using voxel-based morphometry (VBM). Healthy volunteers were investigated (n=27), receiving 8 noxious and 8 innocuous thermal stimuli on the right forearm for 11 consecutive working days. Data were compared with a control group without any intervention (n=18). Behavioural data demonstrated that a subgroup of volunteers (n=14) sensitised, whereas the others (n=13) habituated over the stimulation days. The VBM analysis revealed no increase but a significant reduction of GM density, eg, in the anterior cingulate cortex, the insular cortex and the frontal cortex, exclusively in the group of sensitisers. By contrast, pain habituaters did not show any density changes in the GM. Depending on the individual perception of pain during the time course of stimulation, the repetitive application of painful stimuli changed the GM density in pain-processing brain regions exclusively in those subjects who were characterised by the lack of habituation. Because VBM studies investigating patients experiencing chronic pain observed similar decreases in GM density and increasing pain ratings over time, the sensitisers in our study may have a higher vulnerability to developing chronic pain syndromes in later life.

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