Iacopo Carusotto

Università degli Studi di Trento, Trient, Trentino-Alto Adige, Italy

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Publications (150)562.5 Total impact

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    ABSTRACT: The Berry curvature is a geometrical property of an energy band which can act as a momentum space magnetic field in the effective Hamiltonian of a wide-range of systems. We apply the effective Hamiltonian to a spin-1/2 particle in two dimensions with spin-orbit coupling, a Zeeman field and an additional harmonic trap. Depending on the parameter regime, we show how this system can be described in momentum space as either a Fock-Darwin Hamiltonian or a 1D ring pierced by a magnetic flux. With this perspective, we interpret important single-particle properties, and identify analogue magnetic phenomena in momentum space. Finally we discuss the extension of this work to higher spin systems, as well as experimental applications in ultracold atomic gases and photonic systems.
    12/2014;
  • Hannah M Price, Tomoki Ozawa, Iacopo Carusotto
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    ABSTRACT: The Berry curvature is a geometrical property of an energy band which acts as a momentum space magnetic field in the effective Hamiltonian describing single-particle quantum dynamics. We show how this perspective may be exploited to study systems directly relevant to ultracold gases and photonics. Given the exchanged roles of momentum and position, we demonstrate that the global topology of momentum space is crucially important. We propose an experiment to study the Harper-Hofstadter Hamiltonian with a harmonic trap that will illustrate the advantages of this approach and that will also constitute the first realization of magnetism on a torus.
    Physical Review Letters 11/2014; 113(19):190403. · 7.73 Impact Factor
  • Tomoki Ozawa, Hannah M. Price, Iacopo Carusotto
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    ABSTRACT: We show how the weakly trapped Harper-Hofstadter model can be mapped onto a Harper-Hofstadter model in momentum space: the Berry curvature plays the role of an effective magnetic field, the trap position sets the boundary conditions around the toroidal magnetic Brillouin zone, and spatially local interactions translate into non-local interactions in momentum space. Within a mean-field approximation, we show that increasing inter-particle interactions are responsible for a phase transition from a single rotationally-symmetric ground state to degenerate ground states that spontaneously break rotational symmetry.
    11/2014;
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    ABSTRACT: We report on a joint theoretical and experimental study of an integrated photonic device consisting of a single mode waveguide vertically coupled to a disk-shaped microresonator. Starting from the general theory of open systems, we show how the presence of a neighboring waveguide induces reactive inter-mode coupling in the resonator, analogous to an off-diagonal Lamb shift from atomic physics. Observable consequences of this coupling manifest as peculiar Fano lineshapes in the waveguide transmission spectra. The theoretical predictions are validated by full vectorial 3D finite element numerical simulations and are confirmed by the experiments.
    Physical Review A 11/2014; 90(5):053811. · 3.04 Impact Factor
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    ABSTRACT: We report an experimental study of superfluid hydrodynamic effects in a one-dimensional polariton fluid flowing along a laterally patterned semiconductor microcavity and hitting a micron-sized engineered defect. At high excitation power, superfluid propagation effects are observed in the polariton dynamics, in particular, a sharp acoustic horizon is formed at the defect position, separating regions of sub- and super-sonic flow. Our experimental findings are quantitatively reproduced by theoretical calculations based on a generalized Gross-Pitaevskii equation. Promising perspectives to observe Hawking radiation via photon correlation measurements are illustrated.
    10/2014;
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    Iacopo Carusotto
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    ABSTRACT: We review how the paraxial approximation naturally leads to a hydrodynamic description of light propagation in a bulk Kerr nonlinear medium in terms of a wave equation analogous to the Gross-Pitaevskii equation for the order parameter of a superfluid. The main features of the many-body collective dynamics of the fluid of light in this propagating geometry are discussed: generation and observation of Bogoliubov sound waves in the fluid of light is first described. Experimentally accessible manifestations of superfluidity are then highlighted. Perspectives in view of realizing analogue models of gravity are finally given.
    Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences 09/2014; 470(2169):20140320. · 2.38 Impact Factor
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    ABSTRACT: One of the most fundamental properties of electromagnetism and special relativity is the coupling between the spin of an electron and its orbital motion. This is at the origin of the fine structure in atoms, the spin Hall effect in semiconductors, and underlies many intriguing properties of topological insulators, in particular their chiral edge states. Configurations where neutral particles experience an effective spin-orbit coupling have been recently proposed and realized using ultracold atoms and photons. Here we use coupled micropillars etched out of a semiconductor microcavity to engineer a spin-orbit Hamiltonian for photons and polaritons in a microstructure. The coupling between the spin and orbital momentum arises from the polarisation dependent confinement and tunnelling of photons between micropillars arranged in the form of a hexagonal photonic molecule. Dramatic consequences of the spin-orbit coupling are experimentally observed in these structures in the wavefunction of polariton condensates, whose helical shape is directly visible in the spatially resolved polarisation patterns of the emitted light. The strong optical nonlinearity of polariton systems suggests exciting perspectives for using quantum fluids of polaritons11 for quantum simulation of the interplay between interactions and spin-orbit coupling.
    06/2014;
  • P. -É. Larré, I. Carusotto
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    ABSTRACT: We propose an experimental setup that makes it possible to reveal the frictionless flow of a superfluid of light from the suppression of the drag force that it exerts onto a material defect. In the paraxial-propagation geometry considered here, the photon-fluid dynamics is described by a wave equation analogous to the Gross-Pitaevskii equation of dilute Bose-Einstein condensates and the obstacle consists in a solid dielectric plate immersed into a nonlinear optical liquid. By means of ab initio calculations of the electromagnetic force experienced by the obstacle, we anticipate that superfluidity is detectable in state-of-the-art experiments from the disappearance of the optomechanical deformation of the obstacle.
    05/2014;
  • P. -É. Larré, I. Carusotto
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    ABSTRACT: We propose an experimental setup that makes it possible to reveal the frictionless flow of a superfluid of light from the suppression of the drag force that it exerts onto a material defect. In the paraxial-propagation geometry considered here, the photon-fluid dynamics is described by a wave equation analogous to the Gross-Pitaevskii equation of dilute Bose-Einstein condensates and the obstacle consists in a solid dielectric plate immersed into a nonlinear optical liquid. By means of ab initio calculations of the electromagnetic force experienced by the obstacle, we anticipate that superfluidity is detectable in state-of-the-art experiments from the disappearance of the optomechanical deformation of the obstacle.
    04/2014;
  • Tomoki Ozawa, Iacopo Carusotto
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    ABSTRACT: We theoretically discuss analogues of the anomalous and the integer quantum Hall effect in driven-dissipative two-dimensional photonic lattices in the presence of a synthetic gauge field. Photons are coherently injected by a spatially localized pump, and the transverse shift of the in-plane light distribution under the effect of an additional uniform force is considered. Depending on pumping parameters, the transverse shift turns out to be proportional either to the global Chern number (integer quantum Hall effect) or to the local Berry curvature (anomalous Hall effect). This suggests a viable route to experimentally measure these quantities in photonic lattices.
    Physical Review Letters 04/2014; 112(13):133902. · 7.73 Impact Factor
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    Hannah M. Price, Tomoki Ozawa, Iacopo Carusotto
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    ABSTRACT: Artificial magnetism in momentum space can be engineered from the geometrical properties of energy bands. We show that the Berry curvature acts as a magnetic field in momentum space in the effective quantum Hamiltonian of a wide-range of systems. The effective Hamiltonian is equivalent to the textbook magnetic Hamiltonian, with the roles of momentum and position reversed. This duality has important implications for research into solid-state materials, spin-orbit coupling, ultracold gases and photonic systems. We propose a simple experiment that will demonstrate the advantages of this approach and that will also constitute the first realisation of magnetism on a torus.
    03/2014;
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    ABSTRACT: Two-dimensional lattices of coupled micropillars etched in a planar semiconductor microcavity offer a workbench to engineer the band structure of polaritons. We report experimental studies of honeycomb lattices where the polariton low energy dispersion is analogous to that of electrons in graphene. Using energy resolved photoluminescence we directly observe Dirac cones, around which the dynamics of polaritons is described by the Dirac equation for massless particles. At higher energies, we observe p orbital bands, one of them with the non-dispersive character of a flat band. The realization of this structure which holds massless, massive and infinitely-massive particles opens the route towards studies of the interplay of dispersion, interactions and frustration in a novel and controlled environment.
    Physical Review Letters 03/2014; 112(11):116402. · 7.73 Impact Factor
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    ABSTRACT: In a recent preprint (arXiv:1401.1128v1) Cilibrizzi and co-workers report experiments and simulations showing the scattering of polaritons against a localised obstacle in a semiconductor microcavity. The authors observe in the linear excitation regime the formation of density and phase patterns reminiscent of those expected in the non-linear regime from the nucleation of dark solitons. Based on this observation, they conclude that previous theoretical and experimental reports on dark solitons in a polariton system should be revised. Here we comment why the results from Cilibrizzi et al. take place in a very different regime than previous investigations on dark soliton nucleation and do not reproduce all the signatures of its rich nonlinear phenomenology. First of all, Cilibrizzi et al. consider a particular type of radial excitation that strongly determines the observed patterns, while in previous reports the excitation has a plane-wave profile. Most importantly, the nonlinear relation between phase jump, soliton width and fluid velocity, and the existence of a critical velocity with the time-dependent formation of vortex-antivortex pairs are absent in the linear regime. In previous reports about dark soliton and half-dark soliton nucleation in a polariton fluid, the distinctive dark soliton physics is supported both by theory (analytical and numerical) and experiments (both continuous wave and pulsed excitation).
    01/2014;
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    R. O. Umucalilar, M. Wouters, I. Carusotto
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    ABSTRACT: We propose methods to create and observe Laughlin-like states of photons in a strongly nonlinear optical cavity. Such states of strongly interacting photons can be prepared by pumping the cavity with a Laguerre-Gauss beam, which has a well-defined orbital angular momentum per photon. The Laughlin-like states appear as sharp resonances in the particle-number-resolved transmission spectrum. Power spectrum and second-order correlation function measurements yield unambiguous signatures of these few-particle strongly-correlated states.
    11/2013; 89(2).
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    Xavier Busch, Iacopo Carusotto, Renaud Parentani
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    ABSTRACT: We study the quantum state of phonons propagating on top of a fluid of light coherently generated in a planar microcavity device by a quasi-resonant incident laser beam. In the steady-state under a monochromatic pump, because of the finite radiative lifetime of photons, a sizable incoherent population of low frequency phonons is predicted to appear. Their mean occupation number differs from a Planck distribution and is independent on the photon lifetime. When the photon fluid is subjected to a sudden change of its parameters, additional phonon pairs are created in the fluid with remarkable two-mode squeezing and entanglement properties. Schemes to assess non-separability of the phonon state from measurements of the correlation functions of the emitted light are discussed.
    11/2013; 89(4).
  • Stefano Finazzi, Iacopo Carusotto
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    ABSTRACT: We theoretically study the entanglement between phonons spontaneously generated in atomic Bose-Einstein condensates by analog Hawking and dynamical Casimir processes. The quantum evolution of the system is numerically modeled by a truncated Wigner method based on a full microscopic description of the condensate and state non-separability is assessed by applying a generalized Peres-Horodecki criterion. The peculiar distribution of entanglement is described in both real and momentum spaces and its robustness against increasing initial temperature is investigated. Viable strategies to experimentally detect the predicted phonon entanglement are briefly discussed.
    Physical Review A 09/2013; 90(3). · 3.04 Impact Factor
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    Tomoki Ozawa, Iacopo Carusotto
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    ABSTRACT: We propose a method to experimentally measure the Berry curvature and the Chern number of the photonic bands of lossy two-dimensional photonic lattices in the presence of a synthetic gauge field. Photons are coherently injected by a spatially localized pump and the transverse shift of the in-plane light distribution under the effect of an additional uniform force is considered. Depending on the pumping parameters, this offers quantitative information on either the local Berry curvature or the global Chern number. We finally give an extension of the method to the case of photonic honeycomb lattices.
    07/2013;
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    ABSTRACT: Exciton-polaritons are composite bosons (exciton-photon mixtures) in semiconductor microcavities. Relying on their strong interactions, we have demonstrated quantum optical effects in the microcavity emission, as well as quantum fluid properties in the polariton propagation.
    Conference on Coherence and Quantum Optics; 06/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Exciton-polaritons are composite bosons (exciton-photon mixtures) in semiconductor microcavities. Relying on their strong interactions, we have demonstrated quantum optical effects in the microcavity emission, as well as quantum fluid properties in the polariton propagation.
    Quantum Information and Measurement; 06/2013

Publication Stats

3k Citations
562.50 Total Impact Points

Institutions

  • 2004–2014
    • Università degli Studi di Trento
      • Department of Physics
      Trient, Trentino-Alto Adige, Italy
  • 2013
    • Fondazione Bruno Kessler
      • Microtechnologies Laboratory (MTLab)
      Trient, Trentino-Alto Adige, Italy
  • 2012
    • Ludwig-Maximilians-University of Munich
      München, Bavaria, Germany
  • 2011
    • Pierre and Marie Curie University - Paris 6
      • Laboratoire Kastler-Brossel (LKB)
      Paris, Ile-de-France, France
  • 2010
    • ETH Zurich
      • Institute of Quantum Electronics
      Zürich, ZH, Switzerland
    • École Polytechnique Fédérale de Lausanne
      • Institut de théorie des phénomènes physiques
      Lausanne, VD, Switzerland
    • University of Bologna
      Bolonia, Emilia-Romagna, Italy
  • 2007
    • University of Antwerp
      Antwerpen, Flanders, Belgium
  • 2000–2007
    • Ecole Normale Supérieure de Paris
      • • Laboratoire Pierre Aigrain
      • • Laboratoire Kastler-Brossel
      Paris, Ile-de-France, France
  • 2006
    • Politecnico di Torino
      Torino, Piedmont, Italy
  • 2000–2003
    • European Laboratory for Non-Linear Spectroscopy
      Sesto, Tuscany, Italy
  • 2000–2001
    • Università degli Studi di Salerno
      • Department of Physics "E. R. Caianiello" DF
      Salerno, Campania, Italy
  • 1997–2001
    • Scuola Normale Superiore di Pisa
      • Laboratory NEST: National Enterprise for Nano-Science and Nano-Technology
      Pisa, Tuscany, Italy