2,970 research outputs found
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
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