Ultracold atoms in optical lattices with random on-site interactions

We consider the physics of lattice bosons affected by disordered on-site interparticle interactions. Characteristic qualitative changes in the zero temperature phase diagram are observed when compared to the case of randomness in the chemical potential. The Mott-insulating regions shrink and eventually vanish for any finite disorder strength beyond a sufficiently large filling factor. Furthermore, at low values of the chemical potential both the superfluid and Mott insulator are stable towards formation of a Bose glass leading to a possibly non-trivial tricritical point. We discuss feasible experimental realizations of our scenario in the context of ultracold atoms on optical lattices.Comment: 4 pages, 3 eps figure

Manipulation of the dynamics of many-body systems via quantum control methods

We investigate how dynamical decoupling methods may be used to manipulate the time evolution of quantum many-body systems. These methods consist of sequences of external control operations designed to induce a desired dynamics. The systems considered for the analysis are one-dimensional spin-1/2 models, which, according to the parameters of the Hamiltonian, may be in the integrable or non-integrable limits, and in the gapped or gapless phases. We show that an appropriate control sequence may lead a chaotic chain to evolve as an integrable chain and a system in the gapless phase to behave as a system in the gapped phase. A key ingredient for the control schemes developed here is the possibility to use, in the same sequence, different time intervals between control operations.Comment: 10 pages, 3 figure

Interface States in Carbon Nanotube Junctions: Rolling up graphene

We study the origin of interface states in carbon nanotube intramolecular junctions between achiral tubes. By applying the Born-von Karman boundary condition to an interface between armchair- and zigzag-terminated graphene layers, we are able to explain their number and energies. We show that these interface states, costumarily attributed to the presence of topological defects, are actually related to zigzag edge states, as those of graphene zigzag nanoribbons. Spatial localization of interface states is seen to vary greatly, and may extend appreciably into either side of the junction. Our results give an alternative explanation to the unusual decay length measured for interface states of semiconductor nanotube junctions, and could be further tested by local probe spectroscopies

Atomic quantum gases in Kagom\'e lattices

We demonstrate the possibility of creating and controlling an ideal and \textit{trimerized} optical Kagom\'e lattice, and study the low temperature physics of various atomic gases in such lattices. In the trimerized Kagom\'e lattice, a Bose gas exhibits a Mott transition with fractional filling factors, whereas a spinless interacting Fermi gas at 2/3 filling behaves as a quantum magnet on a triangular lattice. Finally, a Fermi-Fermi mixture at half filling for both components represents a frustrated quantum antiferromagnet with a resonating-valence-bond ground state and quantum spin liquid behavior dominated by continuous spectrum of singlet and triplet excitations. We discuss the method of preparing and observing such quantum spin liquid employing molecular Bose condensates.Comment: 4 pages, 1 figure. Missing affiliations adde

Electronic transport through bilayer graphene flakes

We investigate the electronic transport properties of a bilayer graphene flake contacted by two monolayer nanoribbons. Such a finite-size bilayer flake can be built by overlapping two semiinfinite ribbons or by depositing a monolayer flake onto an infinite nanoribbon. These two structures have a complementary behavior, that we study and analyze by means of a tight-binding method and a continuum Dirac model. We have found that for certain energy ranges and geometries, the conductance of these systems oscillates markedly between zero and the maximum value of the conductance, allowing for the design of electromechanical switches. Our understanding of the electronic transmission through bilayer flakes may provide a way to measure the interlayer hopping in bilayer graphene.Comment: 11 pages, 8 figure

Sympathetic cooling of trapped fermions by bosons in the presence of particle losses

We study the sympathetic cooling of a trapped Fermi gas interacting with an ideal Bose gas below the critical temperature of the Bose-Einstein condensation. We derive the quantum master equation, which describes the dynamics of the fermionic component, and postulating the thermal distribution for both gases we calculate analytically the rate at which fermions are cooled by the bosonic atoms. The particle losses constitute an important source of heating of the degenerate Fermi gas. We evaluate the rate of loss-induced heating and derive analytical results for the final temperature of fermions, which is limited in the presence of particle losses.Comment: 7 pages, 2 figures, EPL style; final versio

Gender equality and modernity in Portugal. An analysis on the obstacles to gender equality in highly qualified professions

In this review article, we argue that the transformations related to the modernisation of Portuguese society triggered by the implementation of democracy did not fully accommodate gender equality. In particular, when we consider the areas where the most progress has been made in keeping with a broadly shared urge for modernisation, education and science; whereas women have contributed to boosting the Portuguese population’s level of education, thus inverting the worst legacy of the dictatorship and developing scientific research, gender inequalities are still visible in highly qualified professions. Reviewing the results of studies from different professions, science, medicine and engineering, our analysis illustrates several factors that hinder not only the recognition of women’s competences and merit at work but also their career opportunities. Some of these factors are rooted in the type of gender ideology that was central to the propaganda of the dictatorship, thereby establishing continuity with the previous regime that seems particularly difficult to break in the absence of women’s voices to raise awareness on gender equality.info:eu-repo/semantics/publishedVersio

Gender inequalities in highly qualified professions: a social psychological analysis

Research in social and political psychology contributes towards understanding the persistence of job market gender segregation prevailing in recent decades, the consequences for those involved and their reactions when having to cope with gender inequality. Within the framework of the literature on shared ideologies that justify and legitimize discrimination against women, this article focuses on Portugal and analyses the particular case of women in two highly qualified professions traditionally carried out by men – politics and medicine. Drawing on the results of quantitative and qualitative studies, our analytical approach demonstrates how while a majority of participants show awareness of the existence of gender inequality in these markedly masculine professions, meritocratic individualism and personal attributions to discrimination are the recurring explanations rather than any gender-based account. These results allow us to highlight the relevance of gender-based analysis as an ideology and furthermore to argue that ignoring this perspective not only diminishes individual responsibility for social change but also perpetuates gender asymmetries.info:eu-repo/semantics/publishedVersio