Finite-frequency noise in a topological superconducting wire

In this paper we study the finite-frequency current cross-correlations for a topological superconducting nanowire attached to two terminals at one of its ends. Using an analytic 1D model we show that the presence of a Majorana bound state yields vanishing cross-correlations for frequencies larger than twice the applied transport voltage, in contrast to what is found for a zero-energy ordinary Andreev bound state. Zero cross-correlations at high frequency have been confirmed using a more realistic tight-binding model for finite-width topological superconducting nanowires. Finite-temperature effects have also been investigated.Comment: Contribution for the special issue of Physica E in memory of Markus B\"uttiker. 9 pages, 7 figure

Pumping through a quantum dot in the proximity of a superconductor

We study adiabatic pumping through a quantum dot tunnel-coupled to one normal and one superconducting lead. We generalize a formula which relates the pumped charge through a quantum dot with Coulomb interaction to the instantaneous local Green's function of the dot, to systems containing a superconducting lead. First, we apply this formula to the case of a non-interacting, single-level quantum dot in different temperature regimes and for different parameter choices, and we compare the results with the case of a system comprising only normal leads. Then we study the infinite-U Anderson model with a superconducting lead at zero temperature, and we discuss the effect of the proximity of the superconductor on the pumped charge.Comment: 10 pages, 8 figures, published version: typos corrected and some figures replace

Weak ergodicity breaking in Josephson-junctions arrays

We study the quantum dynamics of Josephson junction arrays. We find isolated groups of low-entanglement eigenstates, that persist even when the Josephson interaction is strong enough to destroy the organization of the spectrum in multiplets, and a perturbative description is no more possible. These eigenstates provide a weak ergodicity breaking, and are reminiscent of the quantum scars. Due to the presence of these eigenstates, initializing with a charge-density-wave state, the system does not thermalize and the charge-density-wave order persists for long times. Considering global ergodicity probes, we find that the system tends towards more ergodicity for increasing system size: The parameter range where the bulk of the eigenstates look nonergodic shrinks for increasing system size. We study two geometries, a one-dimensional chain and a two-leg ladder. In the latter case, adding a magnetic flux makes the system more ergodic.Comment: 16 pages, 13 figure

Chaos and subdiffusion in the infinite-range coupled quantum kicked rotors

We map the infinite-range coupled quantum kicked rotors over an infinite-range coupled interacting bosonic model. In this way we can apply exact diagonalization up to quite large system sizes and confirm that the system tends to ergodicity in the large-size limit. In the thermodynamic limit the system is described by a set of coupled Gross-Pitaevskij equations equivalent to an effective nonlinear single-rotor Hamiltonian. These equations give rise to a power-law increase in time of the energy with exponent $\gamma\sim 2/3$ in a wide range of parameters. We explain this finding by means of a master-equation approach based on the noisy behaviour of the effective nonlinear single-rotor Hamiltonian and on the Anderson localization of the single-rotor Floquet states. Furthermore, we study chaos by means of the largest Lyapunov exponent and find that it decreases towards zero for portions of the phase space with increasing momentum. Finally, we show that some stroboscopic Floquet integrals of motion of the noninteracting dynamics deviate from their initial values over a time scale related to the interaction strength according to the Nekhoroshev theorem.Comment: 17 pages, 11 figures, version published in PR

Many-body dynamical localization in the kicked Bose-Hubbard chain

We provide evidence that a clean kicked Bose-Hubbard model exhibits a many-body dynamically localized phase. This phase shows ergodicity breaking up to the largest sizes we were able to consider. We argue that this property persists in the limit of large size. The Floquet states violate eigenstate thermalization and then the asymptotic value of local observables depends on the initial state and is not thermal. This implies that the system does not generically heat up to infinite temperature, for almost all the initial states. Differently from many-body localization here the entanglement entropy linearly increases in time. This increase corresponds to space-delocalized Floquet states which are nevertheless localized across specific subsectors of the Hilbert space: In this way the system is prevented from randomly exploring all the Hilbert space and does not thermalize.Comment: 18 pages, 20 figures, revised version published in PR

CleAir monitoring system for particulate matter. A case in the Napoleonic Museum in Rome

Monitoring the air particulate concentration both outdoors and indoors is becoming a more relevant issue in the past few decades. An innovative, fully automatic, monitoring system called CleAir is presented. Such a system wants to go beyond the traditional technique (gravimetric analysis), allowing for a double monitoring approach: the traditional gravimetric analysis as well as the optical spectroscopic analysis of the scattering on the same filters in steady-state conditions. The experimental data are interpreted in terms of light percolation through highly scattering matter by means of the stretched exponential evolution. CleAir has been applied to investigate the daily distribution of particulate matter within the Napoleonic Museum in Rome as a test case

Communicating oesophageal duplication: a case report

ions of the oesophagus are rare congenital abnormalities and rarely comunicate with the oesophageal lumen. They are com - monly associated with other congenital malformations, such as spinal deformities, congenital heart disease, vertebral anomalies, malrota - tion of the bowel, Meckel’s diverticulum. During a percutaneous endoscopic gastrostomy, performed becau - se of a neurological dysphagia, the endoscopy revealed a very rare case of a 26-year old man affected by Klippel-Trenaunay syndrome, with an asymptomatic oesophageal duplication that communicated proxi - mally and distally

Honors Colleges as Levers of Educational Equity

While higher education is widely imagined as a tool for social mobility, the realities of enrollment, retention, and professional trajectories betray the conservative mechanisms through which higher education too often reproduces the status quo of inequality. Honors colleges can and should strive to act as levers of equity in this scenario of entrenchment, but the nature of this project varies depending on the institution’s own class position vis-à-vis its students. Elite, highly selective institutions may advocate for enrollment strategies that target student populations that do not typically attend those institutions, but other institutions likely already enroll such students in large numbers. These “lower tier” institutions, such as community colleges and regional universities, have a responsibility to act as “stewards of place” through “clear and ongoing commitments to the local K-12 school systems where they reside,” as well as to providing “access to regional students via bridge programs, admissions and financial aid,” especially including “access for local first generation and underrepresented students” (Saltmarsh et al.). Such institutions have the capacity to make a significant impact on students’ personal and professional trajectories, and honors colleges at these institutions are uniquely positioned to serve as levers of equity in higher education

Landau Cooling in Metal-Semiconductor Nanostructures

An electron-cooling principle based on Landau quantization is proposed for nanoscale conductor systems. Operation relies on energy-selective electron tunneling into a two-dimensional electron gas in quantizing magnetic fields. This quantum refrigerator provides significant cooling power (~1 nW at a few K for realistic parameters) and offers a unique flexibility thanks to its tunability via the magnetic-field intensity. The available performance is only marginally affected by nonidealities such as disorder or imperfections in the semiconductor. Methods for the implementation of this system and its characterization are discussed.Comment: 4 pages, 4 color figure