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Gubbiotti G.,CNISM | Gubbiotti G.,CNR Institute of Materials | Tacchi S.,CNISM | Madami M.,CNISM | And 4 more authors.
Applied Physics Letters | Year: 2012

Spin waves propagating in a bicomponent magnonic crystal consisting of a two-dimensional array of alternated NiFe and Co nanodots have been investigated. The frequency dispersion of collective modes, measured by Brillouin light scattering, is compared with the band diagram obtained by numerically solving the eigenvalue problem derived from the linearized Landau-Lifshitz magnetic torque equation. It is shown that the modes which are active in Brillouin experiment are characterized by the simplest modal profiles within the NiFe dots. For such excitations, the Co dots act as mediators of dipole coupling between the NiFe dots. © 2012 American Institute of Physics.

Gubbiotti G.,CNISM | Tacchi S.,CNISM | Madami M.,CNISM | Carlotti G.,University of Perugia | And 3 more authors.
Journal of Physics D: Applied Physics | Year: 2010

The application of Brillouin light scattering to the study of the spin-wave spectrum of one-and two-dimensional planar magnonic crystals consisting of arrays of interacting stripes, dots and antidots is reviewed. It is shown that the discrete set of allowed frequencies of an isolated nanoelement becomes a finite-width frequency band for an array of identical interacting elements. It is possible to tune the permitted and forbidden frequency bands, modifying the geometrical or the material magnetic parameters, as well as the external magnetic field. From a technological point of view, the accurate fabrication of planar magnonic crystals and a proper understanding of their magnetic excitation spectrum in the gigahertz range is oriented to the design of filters and waveguides for microwave communication systems. © 2010 IOP Publishing Ltd.

Tacchi S.,CNISM | Madami M.,CNISM | Gubbiotti G.,CNISM | Gubbiotti G.,CNR Institute of Materials | And 6 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

The Brillouin light-scattering technique has been applied to study collective spin waves in a dense array of dipolarly coupled Ni80 Fe20 stripes of alternating widths, during the magnetization reversal process. Both the saturated "ferromagnetic" state, where the magnetizations of wide and narrow stripes are parallel, and the "antiferromagnetic" state, characterized by an antiparallel alignment of the static magnetization in adjacent stripes, have been analyzed. The experimental data provide strong evidence of sustained collective excitations in the form of Bloch waves with permitted and forbidden magnonic energy bands. The measured frequencies as a function of the exchanged wave vector have been satisfactorily reproduced by numerical simulations which enabled us to calculate the spatial profiles of the Bloch waves, showing that some of the modes are preferentially localized in either the wide or the narrow stripes. We estimated the expected light-scattering cross section for each mode at different magnetic ground states, achieving a good agreement with the measured intensities. The alternating-width stripes system studied here represents a one-dimensional artificial magnonic crystal with a complex base and can be considered as a model system for reprogrammable dynamical response, where the band structure of collective spin waves can be tailored by changing the applied magnetic field. © 2010 The American Physical Society.

Duerr G.,Technische University Mnchen | Madami M.,CNISM | Neusser S.,Technische University Mnchen | Tacchi S.,CNISM | And 4 more authors.
Applied Physics Letters | Year: 2011

Combined all-electrical spin-wave and micro-focused Brillouin light scattering spectroscopies have been used to study spin-wave eigenmodes in bicomponent lattices formed by periodic Co nanodisks introduced in nanotroughs etched into a thin Ni80Fe20 film. We find two characteristic spin-wave modes extending through the lattice perpendicular to the applied field. Their spatial positions depend crucially on the Co nanodisks as they reverse locally the polarity of the internal field. Embedded nanodisks are found to offer control of spin waves at nearly the same eigenfrequency in periodically patterned magnetic devices and magnonic crystals. © 2011 American Institute of Physics.

Tacchi S.,CNISM | Duerr G.,TU Munich | Klos J.W.,Adam Mickiewicz University | Madami M.,CNISM | And 7 more authors.
Physical Review Letters | Year: 2012

The spin-wave band structure of a two-dimensional bicomponent magnonic crystal, consisting of Co nanodisks partially embedded in a Permalloy thin film, is experimentally investigated along a high-symmetry direction by Brillouin light scattering. The eigenfrequencies and scattering cross sections are interpreted using plane wave method calculations and micromagnetic simulations. At the boundary of both the first and the second Brillouin zones, we measure a forbidden frequency gap whose width depends on the magnetic contrast between the constituent materials. The modes above and below the gap exhibit resonant spin-precession amplitudes in the complementary regions of periodically varying magnetic parameters. Our findings are key to advance both the physics and the technology of band gap engineering in magnonics. © 2012 American Physical Society.

Vasile R.,University of Turku | Maniscalco S.,Heriot - Watt University | Paris M.G.A.,University of Milan | Breuer H.-P.,CNISM | Piilo J.,Albert Ludwigs University of Freiburg
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We introduce a non-Markovianity measure for continuous-variable open quantum systems based on the idea put forward in H.-P. Breuer, that is, by quantifying the flow of information from the environment back to the open system. Instead of the trace distance we use here the fidelity to assess distinguishability of quantum states. We employ our measure to evaluate non-Markovianity of two paradigmatic Gaussian channels: the purely damping channel and the quantum Brownian motion channel with Ohmic environment. We consider different classes of Gaussian states and look for pairs of states maximizing the backflow of information. For coherent states we find simple analytical solutions, whereas for squeezed states we provide both exact numerical and approximate analytical solutions in the weak coupling limit. © 2011 American Physical Society.

Allevi A.,CNISM | Bondani M.,CNR Institute for Photonics and Nanotechnologies | Andreoni A.,University of Insubria
Optics Letters | Year: 2010

We demonstrate that by using pairs of photodetectors endowed with internal gain we are able to quantify the photon-number correlation coefficient between the two components of a pulsed bipartite state in the "mesoscopic" intensity regime (less than 100 mean photons). We compare the performances of hybrid photoemissive detectors to those of multipixel silicon photon counters and demonstrate that the absence of significant noise allows the evaluation of the variance of the distribution of the differences in photon numbers, and hence of the shot-noise level, without any correction. © 2010 Optical Society of America.

Tognetti M.V.,CNISM | Sali E.,University of Florence | Cavalieri S.,University of Florence | Buffa R.,CNISM | Buffa R.,University of Siena
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We present a theoretical analysis of a new scheme for temporal retardation combined with temporal compression of weak laser pulses, optically controlled by the presence of one additional light pulse. A realistic realization of this scheme in hot Rb is discussed, showing that a large range of values of the optically controllable delay-bandwidth product can be obtained with a limited pulse distortion. © 2010 The American Physical Society.

Alfinito E.,University of Salento | Reggiani L.,CNISM | Reggiani L.,University of Salento
Journal of Applied Physics | Year: 2014

The need of new diagnostic methods satisfying, as an early detection, a low invasive procedure and a cost-efficient value, is orienting the technological research toward the use of bio-integrated devices, in particular, bio-sensors. The set of know-why necessary to achieve this goal is wide, from biochemistry to electronics and is summarized in an emerging branch of electronics, called proteotronics. Proteotronics is here applied to state a comparative analysis of the electrical responses coming from type-1 and type-2 opsins. In particular, the procedure is used as an early investigation of a recently discovered family of opsins, the proteorhodopsins activated by blue light, BPRs. The results reveal some interesting and unexpected similarities between proteins of the two families, suggesting the global electrical response are not strictly linked to the class identity. © 2014 AIP Publishing LLC.

Journal of Physics Condensed Matter | Year: 2010

The Debye-Waller factor may be close to one, hence ineffective for decoherence, if it is caused by high-frequency vibrations. This appears as a manifestation of the Zeno effect,where the quantum properties of a system do not deteriorate (or do so very slowly) if the system is subjected to frequently repeated interactions. In the case of atom-surface scattering, the decoherence time is shown to be long for high frequencies, such that the oscillation period is short in comparison to the duration of a collision. For a periodic perturbation the restoration of coherence, in the case where many oscillation periods take place during a prescribed time, is shown. © 2010 IOP Publishing Ltd.

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