Topological properties of the bond-modulated honeycomb lattice

We study the combined effects of lattice deformation, e-e interaction and spin-orbit coupling in a two-dimensional (2D) honeycomb lattice. We adopt different kinds of hopping modulation--generalized dimerization and a Kekule distortion--and calculate topological invariants for the non-interacting system and for the interacting system. We identify the parameter range (Hubbard U, hopping modulation, spin-orbit coupling) where the 2D system behaves as a trivial insulator or Quantum Spin Hall Insulator.Comment: 8 pages, 4 figures: discussion improved, typos corrected, references updated. Matches version published in PR

Phonon-induced electron relaxation in weakly-confined single and coupled quantum dots

We investigate charge relaxation rates due to acoustic phonons in weakly-confined quantum dot systems, including both deformation potential and piezoelectric field interactions. Single-electron excited states lifetimes are calculated for single and coupled quantum dot structures, both in homonuclear and heteronuclear devices. Piezoelectric field scattering is shown to be the dominant relaxation mechanism in many experimentally relevant situations. On the other hand, we show that appropriate structure design allows to minimize separately deformation potential and piezolectric field interactions, and may bring electron lifetimes in the range of microseconds.Comment: 20 pages (preprint format), 7 figures, submitted to Physical Review

Topological invariants in interacting Quantum Spin Hall: a Cluster Perturbation Theory approach

Using Cluster Perturbation Theory we calculate Green's functions, quasi-particle energies and topological invariants for interacting electrons on a 2-D honeycomb lattice, with intrinsic spin-orbit coupling and on-site e-e interaction. This allows to define the parameter range (Hubbard U vs spin-orbit coupling) where the 2D system behaves as a trivial insulator or Quantum Spin Hall insulator. This behavior is confirmed by the existence of gapless quasi-particle states in honeycomb ribbons. We have discussed the importance of the cluster symmetry and the effects of the lack of full translation symmetry typical of CPT and of most Quantum Cluster approaches. Comments on the limits of applicability of the method are also provided.Comment: 7 pages, 7 figures: discussion improved, one figure added, references updated. Matches version published in New J. Phy

Adiabatic Invariants and Scalar Fields in a de Sitter Space-Time

The method of adiabatic invariants for time dependent Hamiltonians is applied to a massive scalar field in a de Sitter space-time. The scalar field ground state, its Fock space and coherent states are constructed and related to the particle states. Diverse quantities of physical interest are illustrated, such as particle creation and the way a classical probability distribution emerges for the system at late times.Comment: 9 pages, Latex, no figure

Entanglement dynamics of electron-electron scattering in low-dimensional semiconductor systems

We perform the quantitative evaluation of the entanglement dynamics in scattering events between two insistinguishable electrons interacting via Coulomb potential in 1D and 2D semiconductor nanostructures. We apply a criterion based on the von Neumann entropy and the Schmidt decomposition of the global state vector suitable for systems of identical particles. From the timedependent numerical solution of the two-particle wavefunction of the scattering carriers we compute their entanglement evolution for different spin configurations: two electrons with the same spin, with different spin, singlet, and triplet spin state. The procedure allows to evaluate the mechanisms that govern entanglement creation and their connection with the characteristic physical parameters and initial conditions of the system. The cases in which the evolution of entanglement is similar to the one obtained for distinguishable particles are discussed.Comment: 22 pages, 7 figures, submitted to Physical Review

On demand entanglement in double quantum dots via coherent carrier scattering

We show how two qubits encoded in the orbital states of two quantum dots can be entangled or disentangled in a controlled way through their interaction with a weak electron current. The transmission/reflection spectrum of each scattered electron, acting as an entanglement mediator between the dots, shows a signature of the dot-dot entangled state. Strikingly, while few scattered carriers produce decoherence of the whole two-dots system, a larger number of electrons injected from one lead with proper energy is able to recover its quantum coherence. Our numerical simulations are based on a real-space solution of the three-particle Schroedinger equation with open boundaries. The computed transmission amplitudes are inserted in the analytical expression of the system density matrix in order to evaluate the entanglement.Comment: 20 pages, 5 figure

Grice subtalar arthrodesis of bilateral adult flatfoot in a professional dancer: A case report

Background and aim: Adult acquired flatfoot deformity (AAFD) is a common pathology and an important cause of pain and disability. This deformity causes a progressive flattening of the foot arch which has traditionally been associated with posterior tibialis tendon (PTT) dysfunction. Operative treatment is indicated after the failure of conservative management aiming to achieve proper alignment of the hindfoot and to maintain as much flexibility as possible. If subtalar osteoarthritis is present, subtalar arthrodesis is usually the best therapeutic option. Grice-Green subtalar arthrodesis is a widely used procedure. Methods: This report describes a case of bilateral painful AAFD in a 39-years old female professional dancer treated with Grice-Green subtalar arthrodesis with an autologous corticocancellous graft harvested from the ipsilateral proximal tibia. Surgeries were performed 3 years apart from each other. Results: The patient had good clinical and radiological outcomes. She returned to dance 4 months after surgery with no referred pain or limitations. Conclusions: Due to its versatility and capability to restore the shape and thickness of the hindfoot Grice-Green procedure is a simple and effective technique for the treatment of AAFD with subtalar osteoarthritis and a valid option to solve professional disabilities as it happened in this case with a professional dancer. (www.actabiomedica.it)

Conversation avec Guido Mazzoni sur son livre "Teoria del romanzo"

Conversazione-intervista a Guido Mazzoni, autore di "Teoria del romanzo", il Mulino, Bologna 2011, una delle pubblicazioni pi\uf9 significative nell'ambito della teoria letteraria apparsa negli ultimi tempi. Gli argomenti principali affrontati nella conversazione riguardano l'impianto metodologico del libro, la teoria e la storia del romanzo, la storiografia letteraria, il realismo, il ruolo della letteratura nel sistema delle arti e dei saperi