235 research outputs found
Self-organized synchronization of mechanically coupled resonators based on optomechanics gain-loss balance
We investigate collective nonlinear dynamics in a blue-detuned optomechanical
cavity that is mechanically coupled to an undriven mechanical resonator. By
controlling the strength of the driving field, we engineer a mechanical gain
that balances the losses of the undriven resonator. This gain-loss balance
corresponds to the threshold where both coupled mechanical resonators enter
simultaneously into self-sustained limit cycle oscillations regime. Rich sets
of collective dynamics such as in-phase and out-of-phase synchronizations
therefore emerge, depending on the mechanical coupling rate, the optically
induced mechanical gain and spring effect, and the frequency mismatch between
the resonators. Moreover, we introduce the quadratic coupling that induces
enhancement of the in-phase synchronization. This work shows how phonon
transport can remotely induce synchronization in coupled mechanical resonator
array and opens up new avenues for metrology, communication, phonon-processing,
and novel memories concepts.Comment: Comments are welcome
Cleaving-temperature dependence of layered-oxide surfaces
The surfaces generated by cleaving non-polar, two-dimensional oxides are
often considered to be perfect or ideal. However, single particle
spectroscopies on Sr2RuO4, an archetypal non-polar two dimensional oxide, show
significant cleavage temperature dependence. We demonstrate that this is not a
consequence of the intrinsic characteristics of the surface: lattice parameters
and symmetries, step heights, atom positions, or density of states. Instead, we
find a marked increase in the density of defects at the mesoscopic scale with
increased cleave temperature. The potential generality of these defects to
oxide surfaces may have broad consequences to interfacial control and the
interpretation of surface sensitive measurements
Scanning tunneling spectroscopy of superconducting LiFeAs single crystals: Evidence for two nodeless energy gaps and coupling to a bosonic mode
The superconducting compound, LiFeAs, is studied by scanning tunneling
microscopy and spectroscopy. A gap map of the unreconstructed surface indicates
a high degree of homogeneity in this system. Spectra at 2 K show two nodeless
superconducting gaps with meV and
meV. The gaps close as the temperature is increased to the bulk
indicating that the surface accurately represents the bulk. A dip-hump
structure is observed below with an energy scale consistent with a
magnetic resonance recently reported by inelastic neutron scattering
Stochastic Development Regression on Non-Linear Manifolds
We introduce a regression model for data on non-linear manifolds. The model
describes the relation between a set of manifold valued observations, such as
shapes of anatomical objects, and Euclidean explanatory variables. The approach
is based on stochastic development of Euclidean diffusion processes to the
manifold. Defining the data distribution as the transition distribution of the
mapped stochastic process, parameters of the model, the non-linear analogue of
design matrix and intercept, are found via maximum likelihood. The model is
intrinsically related to the geometry encoded in the connection of the
manifold. We propose an estimation procedure which applies the Laplace
approximation of the likelihood function. A simulation study of the performance
of the model is performed and the model is applied to a real dataset of Corpus
Callosum shapes
Magnetic relaxation of exchange biased (Pt/Co) multilayers studied by time-resolved Kerr microscopy
Magnetization relaxation of exchange biased (Pt/Co)5/Pt/IrMn multilayers with
perpendicular anisotropy was investigated by time-resolved Kerr microscopy.
Magnetization reversal occurs by nucleation and domain wall propagation for
both descending and ascending applied fields, but a much larger nucleation
density is observed for the descending branch, where the field is applied
antiparallel to the exchange bias field direction. These results can be
explained by taking into account the presence of local inhomogeneities of the
exchange bias field.Comment: To appear in Physical Review B (October 2005
Nonlinear dynamics and chaos in an optomechanical beam
[EN] Optical nonlinearities, such as thermo-optic mechanisms and free-carrier dispersion, are often considered unwelcome effects in silicon-based resonators and, more specifically, optomechanical cavities, since they affect, for instance, the relative detuning between an optical resonance and the excitation laser. Here, we exploit these nonlinearities and their intercoupling with the mechanical degrees of freedom of a silicon optomechanical nanobeam to unveil a rich set of fundamentally different complex dynamics. By smoothly changing the parameters of the excitation laser we demonstrate accurate control to activate two-and four-dimensional limit cycles, a period-doubling route and a six-dimensional chaos. In addition, by scanning the laser parameters in opposite senses we demonstrate bistability and hysteresis between two-and four-dimensional limit cycles, between different coherent mechanical states and between four-dimensional limit cycles and chaos. Our findings open new routes towards exploiting silicon-based optomechanical photonic crystals as a versatile building block to be used in neurocomputational networks and for chaos-based applications.This work was supported by the European Comission project PHENOMEN (H2020-EU-713450), the Spanish Severo Ochoa Excellence program and the MINECO project PHENTOM (FIS2015-70862-P). DNU, PDG and MFC gratefully acknowledge the support of a Ramon y Cajal postdoctoral fellowship (RYC-2014-15392), a Beatriu de Pinos postdoctoral fellowship (BP-DGR 2015 (B) and a Severo Ochoa studentship, respectively. We would like to acknowledge Jose C. Sabina de Lis, J.M. Plata Suarez, A. Trifonova and C. Masoller for fruitful discussions.Navarro-Urrios, D.; Capuj, NE.; Colombano, MF.; GarcÃa, PD.; Sledzinska, M.; Alzina, F.; Griol Barres, A.... (2017). Nonlinear dynamics and chaos in an optomechanical beam. Nature Communications. 8. https://doi.org/10.1038/ncomms14965S8Strogatz, S. H. Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry, and Engineering Westview Press (2014).Lorenz, E. N. Deterministic nonperiodic ow. J. Atmos. Sci. 20, 130–141 (1963).Sparrow, C. The Lorenz Attractor: Bifurcations, Chaos and Strange Attractors Springer (1982).Aspelmeyer, M., Kippenberg, T. & Marquardt, F. Cavity optomechanics. Rev. Mod. Phys. 86, 1391 (2014).Kippenberg, T., Rokhsari, H., Carmon, T., Scherer, A. & Vahala, K. Analysis of radiation-pressure induced mechanical oscillation of an optical microcavity. Phys. Rev. Lett. 95, 033901 (2005).Marquardt, F., Harris, J. G. E. & Girvin, S. M. Dynamical multistability induced by radiation pressure in high-finesse micromechanical optical cavities. Phys. Rev. Lett. 96, 103901 (2006).Krause, A. G. et al. Nonlinear radiation pressure dynamics in an optomechanical crystal. Phys. Rev. Lett. 115, 233601 (2015).Metzger, C. et al. Self-induced oscillations in an optomechanical system driven by bolometric backaction. Phys. Rev. Lett. 101, 133903 (2008).Bakemeier, L., Alvermann, A. & Fehske, H. Route to chaos in optomechanics. Phys. Rev. Lett. 114, 013601 (2015).Sciamanna, M. & Shore, K. A. Physics and applications of laser diode chaos. Nat. Photon. 9, 151–162 (2015).Williams, C. R. et al. Experimental observations of group synchrony in a system of chaotic optoelectronic oscillators. Phys. Rev. Lett. 110, 064104 (2013).Sciamanna, M. Optomechanics: vibrations copying optical chaos. Nat. Photon. 10, 366–368 (2016).Carmon, T., Cross, M. C. & Vahala, K. J. Chaotic quivering of micron-scaled on-chip resonators excited by centrifugal optical pressure. Phys. Rev. Lett. 98, 167203 (2007).Carmon, T., Rokhsari, H., Yang, L., Kippenberg, T. J. & Vahala, K. J. Temporal behavior of radiation-pressure-induced vibrations of an optical microcavity phonon mode. Phys. Rev. Lett. 94, 223902 (2005).Monifi, F. et al. Optomechanically induced stochastic resonance and chaos transfer between optical fields. Nat. Photon. 10, 399–405 (2016).Wu, J. et al. Dynamical chaos in chip-scale optomechanical oscillators. Preprint at https://arxiv.org/abs/1608.05071 (2016).Navarro-Urrios, D., Tredicucci, A. & Sotomayor-Torres, C. M. Coherent phonon generation in optomechanical crystals. SPIE Newsroom, doi:10.1117/2.1201507.006036 (2015).Navarro-Urrios, D. et al. A self-stabilized coherent phonon source driven by optical forces. Sci. Rep. 5, 15733 (2015).Johnson, T. J., Borselli, M. & Painter, O. Self-induced optical modulation of the transmission through a high-Q silicon microdisk resonator. Opt. Express 14, 817–831 (2006).Navarro-Urrios, D. et al. Self-sustained coherent phonon generation in optomechanical cavities. J. Opt. 18, 094006 (2016).Kemiktarak, U., Durand, M., Metcalfe, M. & Lawall, J. Mode competition and anomalous cooling in a multimode phonon laser. Phys. Rev. Lett. 113, 030802 (2014).Rosenstein, M. T., Collins, J. J. & De Luca, C. J. A practical method for calculating largest Lyapunov exponents from small data sets. Physica D 65, 117–134 (1993).Sprott, J. C. Chaos and Time-Series Analysis Vol. 69, Citeseer (2003).Grassberger, P. & Procaccia, I. Characterization of strange attractors. Phys. Rev. Lett. 50, 346–349 (1983).Hoppensteadt, F. C. & Izhikevich, E. M. Synchronization of MEMS resonators and mechanical neurocomputing. IEEE Trans. Circuits Syst. I, Reg. Papers 48, 133–138 (2001).Pennec, Y. et al. Band gaps and cavity modes in dual phononic and photonic strip waveguides. AIP Adv. 1, 041901 (2011).Gomis-Bresco, J. et al. A one-dimensional optomechanical crystal with a complete phononic band gap. Nat. Commun. 5, 4452 (2014).Johnson, S. G. et al. Perturbation theory for Maxwells equations with shifting material boundaries. Phys. Rev. E 65, 066611 (2002).Chan, J., Safavi-Naeini, A. H., Hill, J. T., Meenehan, S. & Painter, O. Optimized optomechanical crystal cavity with acoustic radiation shield. Appl. Phys. Lett. 101, 081115 (2012).Pennec, Y. et al. Modeling light-sound interaction in nanoscale cavities and waveguides. Nanophotonics 3, 413–440 (2014)
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