Rashba quantum wire: exact solution and ballistic transport

The effect of Rashba spin-orbit interaction in quantum wires with hard-wall boundaries is discussed. The exact wave function and eigenvalue equation are worked out pointing out the mixing between the spin and spatial parts. The spectral properties are also studied within the perturbation theory with respect to the strength of the spin-orbit interaction and diagonalization procedure. A comparison is done with the results of a simple model, the two-band model, that takes account only of the first two sub-bands of the wire. Finally, the transport properties within the ballistic regime are analytically calculated for the two-band model and through a tight-binding Green function for the entire system. Single and double interfaces separating regions with different strengths of spin-orbit interaction are analyzed injecting carriers into the first and the second sub-band. It is shown that in the case of a single interface the spin polarization in the Rashba region is different from zero, and in the case of two interfaces the spin polarization shows oscillations due to spin selective bound states

Behavior of quantum entropies in polaronic systems

Quantum entropies and state distances are analyzed in polaronic systems with short range (Holstein model) and long range (Fr$\ddot{o}$hlich model) electron-phonon coupling. These quantities are extracted by a variational wave function which describes very accurately polaron systems with arbitrary size in all the relevant parameter regimes. With the use of quantum information tools, the crossover region from weak to strong coupling regime can be characterized with high precision. Then, the linear entropy is found to be very sensitive to the range of the electron-phonon coupling and the adiabatic ratio. Finally, the entanglement entropy is studied as a function of the system size pointing out that it not bounded, but scales as the logarithm of the size either for weak electron-phonon coupling or for short range interaction. This behavior is ascribed to the peculiar coupling induced by the single electron itinerant dynamics on the phonon subsystem.Comment: 4 figures, to be published in Phys. Rev.

Odontogenic keratocyst and uterus bicornis in nevoid basal cell carcinoma syndrome: Case report and literature review

Nevoid basal cell carcinoma syndrome (NBCCS), an autosomal dominant disorder with a high degree of penetrance and variable expressivity, is characterized by basal cell carcinomas, odontogenic keratocysts, palmar and/or plantar pits and ectopic calcifications of the falx cerebri. More than 100 minor criteria have been described but two major and one minor criteria or one major and three minor criteria are necessary for the diagnosis. In this report we present a 8 year old girl affected by NBCCS showing an uterus bicornis, an hitherto unreported association. However further researches are needed to confirm the association between NBCCS and mullerian fusion defects and to assess the hypothesis that focuses on chromosome 9 the mutant gene for NBCCS and fusion defects of female genital tract

Rashba effect induced localization in quantum networks

We study a quantum network extending in one-dimension (chain of square loops connected at one vertex) made up of quantum wires with Rashba spin-orbit coupling. We show that the Rashba effect may give rise to an electron localization phenomenon similar to the one induced by magnetic field. This localization effect can be attributed to the spin precession due to the Rashba effect. We present results both for the spectral properties of the infinite chain, and for linear transport through a finite-size chain connected to leads. Furthermore, we study the effect of disorder on the transport properties of this network.Comment: To appear in Phys. Rev. Let

Rashba effect in quantum networks

We present a formalism to study quantum networks made up by single-channel quantum wires in the presence of Rashba spin-orbit coupling and magnetic field. In particular, linear transport through one-dimensional and two-dimensional finite-size networks is studied by means of the scattering formalism. In some particular quantum networks, the action of the magnetic field or of the Rashba spin-orbit coupling induces localization of the electron wave function. This phenomenon, which relies on both the quantum-mechanical interference and the geometry of the network, is manifested through the suppression of the conductance for specific values of the spin-orbit-coupling strength or of the magnetic field. Furthermore, the interplay of the Aharonov-Bohm phases and of the non-Abelian phases introduced by spin-orbit coupling, is discussed in a number of cases.Comment: 8 pages and 6 figure

Multiple double-exchange mechanism by Mn2+^{2+}-doping in manganite compounds

Double-exchange mechanisms in RE$_{1-x}$AE$_{x}$MnO$_{3}$ manganites (where RE is a trivalent rare-earth ion and AE is a divalent alkali-earth ion) relies on the strong exchange interaction between two Mn$^{3+}$ and Mn$^{4+}$ ions through interfiling oxygen 2p states. Nevertheless, the role of RE and AE ions has ever been considered "silent" with respect to the DE conducting mechanisms. Here we show that a new path for DE-mechanism is indeed possible by partially replacing the RE-AE elements by Mn$^{2+}$-ions, in La-deficient La$_{x}$MnO$_{3-\delta}$ thin films. X-ray absorption spectroscopy demonstrated the relevant presence of Mn$^{2+}$ ions, which is unambiguously proved to be substituted at La-site by Resonant Inelastic X-ray Scattering. Mn$^{2+}$ is proved to be directly correlated to the enhanced magneto-transport properties because of an additional hopping mechanism trough interfiling Mn$^{2+}$-ions, theoretically confirmed by calculations within the effective single band model. The very idea to use Mn$^{2+}$ both as a doping element and an ions electronically involved in the conduction mechanism, has never been foreseen, revealing a new phenomena in transport properties of manganites. More important, such a strategy might be also pursed in other strongly correlated materials.Comment: 6 pages, 5 figure

Interference of Fano-Rashba conductance dips

We study the interference of two tunable Rashba regions in a quantum wire with one propagating mode. The transmission dips (Fano-Rashba dips) of the two regions either cross or anti cross depending on the distance between the two regions. For large separations we find Fabry-P\'erot oscillations due to the interference of forwards and backwards propagating modes. At small separations overlapping evanescent modes play a prominent role, leading to an enhanced transmission and destroying the conductance dip. Analytical expressions in scattering-matrix theory are given and the relevance of the interference effect in a device is discussed.Comment: 10 pages, 4 embedded figure

Physical capacity and match running performance in very young soccer players

Aim. The aim of this study was to analyze match running performance in relation to age and individual physical capacity in youth soccer players aged 8-10 years. Methods. Physical capacity of 12 under-10 (U10) and 15 under-8 (U8) male players was assessed by counter movement jump (CMJ), 20 meter shuttle run (20m-SR) and 10, 20 and 30 meters (10m, 20m and 30m) sprint tests. Shuttle dribble test (SHD) and slalom dribble test (SLD) were also performed to evaluate technical ability. Time motion analyses by global positioning system (K-Gps 10Hz, K-Sport) were performed during 30 (200 observations) official matches (lasting three equal periods of 15-min). Results. U10 vs U8 showed a better shuttle-running performance (1215\ub177 vs 872\ub178m, p<0.005), a lower sprint time on 20m (4.15\ub10.05 vs 4.38\ub10.07s, p<0.05) and 30m (5.72\ub10.06 vs 6.31\ub10.08s, p<0.0001) and a better technical ability (SDL: 10.7\ub10.2 vs 11.8\ub10.2, p<0.001; SHD: 22.3\ub10.3 vs 29.4\ub10.7s, p<0.0001). No differences were observed in CMJ and 10m. U10 covered higher total (3437\ub1137 vs 2348\ub1124m, p<0.0001) and high-intensity distance (1455\ub1104m vs 992\ub1116m, p<0.005) than U8. Distance covered at high-intensity in the third time was not significantly different from first and second time both for U10 and U8. A linear relationship (r2=0.74, p<0.0001) was observed between high-intensity distance and 20m-SR. Conclusions. This is the first study characterizing the match running activity of very young soccer players. If confirmed in a larger population, these data could be used by coaches and support staff as starting point in the design of training programs

Conductance oscillations of a spin-orbit stripe with polarized contacts

We investigate the linear conductance of a stripe of spin-orbit interaction in a 2D electron gas; that is, a 2D region of length $\ell$ along the transport direction and infinite in the transverse one in which a spin-orbit interaction of Rashba type is present. Polarization in the contacts is described by means of Zeeman fields. Our model predicts two types of conductance oscillations: Ramsauer oscillations in the minority spin transmission, when both spins can propagate, and Fano oscillations when only one spin propagates. The latter are due to the spin-orbit coupling with quasibound states of the non propagating spin. In the case of polarized contacts in antiparallel configuration Fano-like oscillations of the conductance are still made possible by the spin orbit coupling, even though no spin component is bound by the contacts. To describe these behaviors we propose a simplified model based on an ansatz wave function. In general, we find that the contribution for vanishing transverse momentum dominates and defines the conductance oscillations. Regarding the oscillations with Rashba coupling intensity, our model confirms the spin transistor behavior, but only for high degrees of polarization. Including a position dependent effective mass yields additional oscillations due to the mass jumps at the interfaces.Comment: 8.5 pages, 9 figure