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Showing papers in "Physical Review Letters in 2013"


Journal ArticleDOI
TL;DR: In this article, a rigorous framework for quantification of coherence and identification of intuitive and easily computable measures for coherence has been proposed by adopting coherence as a physical resource.
Abstract: We introduce a rigorous framework for the quantification of coherence and identify intuitive and easily computable measures of coherence We achieve this by adopting the viewpoint of coherence as a physical resource By determining defining conditions for measures of coherence we identify classes of functionals that satisfy these conditions and other, at first glance natural quantities, that do not qualify as coherence measure We conclude with an outline of the questions that remain to be answered to complete the theory of coherence as a resource

1,862 citations


Journal ArticleDOI
TL;DR: Huygens' principle is applied to develop designer surfaces that provide extreme control of electromagnetic wave fronts across electrically thin layers to find a wide range of applications over the entire electromagnetic spectrum including single-surface lenses, polarization controlling devices, stealth technologies, and perfect absorbers.
Abstract: Huygens' principle is a well-known concept in electromagnetics that dates back to 1690. Here, it is applied to develop designer surfaces that provide extreme control of electromagnetic wave fronts across electrically thin layers. These reflectionless surfaces, referred to as metamaterial Huygens' surfaces, provide new beam shaping, steering, and focusing capabilities. The metamaterial Huygens' surfaces are realized with two-dimensional arrays of polarizable particles that provide both electric and magnetic polarization currents to generate prescribed wave fronts. A straightforward design methodology is demonstrated and applied to develop a beam-refracting surface and a Gaussian-to-Bessel beam transformer. Metamaterial Huygens' surfaces could find a wide range of applications over the entire electromagnetic spectrum including single-surface lenses, polarization controlling devices, stealth technologies, and perfect absorbers.

1,418 citations


Journal ArticleDOI
TL;DR: It is shown that monolayer MoS2 possesses a large and diverse number of strongly bound excitonic states with novel k-space characteristics that were not previously seen experimentally or theoretically.
Abstract: We present first-principles calculations of the optical response of monolayer molybdenum disulfide employing the GW-Bethe-Salpeter equation (GW-BSE) approach including self-energy, excitonic, and electron-phonon effects. We show that monolayer MoS2 possesses a large and diverse number of strongly bound excitonic states with novel k-space characteristics that were not previously seen experimentally or theoretically. The absorption spectrum is shown to be dominated by excitonic states with a binding energy close to 1 eV and by strong electron-phonon broadening in the visible to ultraviolet range. Our results explain recent experimental measurements and resolve inconsistencies between previous GW-BSE calculations.

1,340 citations


Journal ArticleDOI
TL;DR: The result derived in this Letter completes the set of NNLO QCD corrections to the total top pair-production cross section at hadron colliders and allows a new level of scrutiny in parton distribution functions and new physics searches.
Abstract: We compute the next-to-next-to-leading order (NNLO) quantum chromodynamics (QCD) correction to the total cross section for the reaction $gg\ensuremath{\rightarrow}t\overline{t}+X$. Together with the partonic channels we computed previously, the result derived in this Letter completes the set of NNLO QCD corrections to the total top pair-production cross section at hadron colliders. Supplementing the fixed order results with soft-gluon resummation with next-to-next-to-leading logarithmic accuracy, we estimate that the theoretical uncertainty of this observable due to unknown higher order corrections is about 3% at the LHC and 2.2% at the Tevatron. We observe a good agreement between the standard model predictions and the available experimental measurements. The very high theoretical precision of this observable allows a new level of scrutiny in parton distribution functions and new physics searches.

1,319 citations


Journal ArticleDOI
TL;DR: It is shown that for two atomic spin states with opposite magnetic moments, the experimental implementation of an optical lattice that allows for the generation of large homogeneous and tunable artificial magnetic fields with ultracold atoms naturally realizes the time-reversal-symmetric Hamiltonian underlying the quantum spin Hall effect.
Abstract: We demonstrate the experimental implementation of an optical lattice that allows for the generation of large homogeneous and tunable artificial magnetic fields with ultracold atoms. Using laser-assisted tunneling in a tilted optical potential, we engineer spatially dependent complex tunneling amplitudes. Thereby, atoms hopping in the lattice accumulate a phase shift equivalent to the Aharonov-Bohm phase of charged particles in a magnetic field. We determine the local distribution of fluxes through the observation of cyclotron orbits of the atoms on lattice plaquettes, showing that the system is described by the Hofstadter model. Furthermore, we show that for two atomic spin states with opposite magnetic moments, our system naturally realizes the time-reversal-symmetric Hamiltonian underlying the quantum spin Hall effect; i.e., two different spin components experience opposite directions of the magnetic field.

1,130 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that two-dimensional tin films are QSH insulators with sizable bulk gaps of 0.3 eV, sufficiently large for practical applications at room temperature.
Abstract: The search for large-gap quantum spin Hall (QSH) insulators and effective approaches to tune QSH states is important for both fundamental and practical interests. Based on first-principles calculations we find two-dimensional tin films are QSH insulators with sizable bulk gaps of 0.3 eV, sufficiently large for practical applications at room temperature. These QSH states can be effectively tuned by chemical functionalization and by external strain. The mechanism for the QSH effect in this system is band inversion at the $\ensuremath{\Gamma}$ point, similar to the case of a HgTe quantum well. With surface doping of magnetic elements, the quantum anomalous Hall effect could also be realized.

1,113 citations


Journal ArticleDOI
M. Aguilar1, G Alberti2, Behcet Alpat, A. Alvino2  +344 moreInstitutions (39)
TL;DR: The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude, showing the existence of new physical phenomena.
Abstract: A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

1,100 citations


Journal ArticleDOI
TL;DR: A (quasi-)two-dimensional colloidal suspension of self-propelled spherical particles propelled due to diffusiophoresis in a near-critical water-lutidine mixture finds that the driving stabilizes small clusters and undergoes a phase separation into large clusters and a dilute gas phase.
Abstract: We study experimentally and numerically a (quasi-)two-dimensional colloidal suspension of self-propelled spherical particles. The particles are carbon-coated Janus particles, which are propelled due to diffusiophoresis in a near-critical water-lutidine mixture. At low densities, we find that the driving stabilizes small clusters. At higher densities, the suspension undergoes a phase separation into large clusters and a dilute gas phase. The same qualitative behavior is observed in simulations of a minimal model for repulsive self-propelled particles lacking any alignment interactions. The observed behavior is rationalized in terms of a dynamical instability due to the self-trapping of self-propelled particles.

1,004 citations


Journal ArticleDOI
TL;DR: It is argued that a good choice of basis for (multi)loop integrals can lead to significant simplifications of the differential equations, and criteria for finding an optimal basis are proposed.
Abstract: Scattering amplitudes at loop level can be expressed in terms of Feynman integrals. The latter satisfy partial differential equations in the kinematical variables. We argue that a good choice of basis for (multi)loop integrals can lead to significant simplifications of the differential equations, and propose criteria for finding an optimal basis. This builds on experience obtained in supersymmetric field theories that can be applied successfully to generic quantum field theory integrals. It involves studying leading singularities and explicit integral representations. When the differential equations are cast into canonical form, their solution becomes elementary. The class of functions involved is easily identified, and the solution can be written down to any desired order in ϵ within dimensional regularization. Results obtained in this way are particularly simple and compact. In this Letter, we outline the general ideas of the method and apply them to a two-loop example.

979 citations


Journal ArticleDOI
TL;DR: The Harper Hamiltonian for neutral particles in optical lattices is implemented using laser-assisted tunneling and a potential energy gradient provided by gravity or magnetic field gradients to describe the motion of charged particles in strong magnetic fields.
Abstract: We experimentally implement the Harper Hamiltonian for neutral particles in optical lattices using laser-assisted tunneling and a potential energy gradient provided by gravity or magnetic field gradients. This Hamiltonian describes the motion of charged particles in strong magnetic fields. Laser-assisted tunneling processes are characterized by studying the expansion of the atoms in the lattice. The band structure of this Hamiltonian should display Hofstadter's butterfly. For fermions, this scheme should realize the quantum Hall effect and chiral edge states.

946 citations


Journal ArticleDOI
TL;DR: It is shown that the effect originates from concerted actions of the direct and inverse spin Hall effects and therefore it is called "spin Hall magnetoresistance."
Abstract: We report anisotropic magnetoresistance in Pt|Y3Fe5O12 bilayers. In spite of Y3Fe5O12 being a very good electrical insulator, the resistance of the Pt layer reflects its magnetization direction. The effect persists even when a Cu layer is inserted between Pt and Y3Fe5O12, excluding the contribution of induced equilibrium magnetization at the interface. Instead, we show that the effect originates from concerted actions of the direct and inverse spin Hall effects and therefore call it “spin Hall magnetoresistance.”

Journal ArticleDOI
TL;DR: P perturbative analysis is used to reveal analytically the structure of eigenvectors and eigenvalues of the complete network in terms of the spectral properties of the individual layers of the multiplex network, and allows us to understand the physics of diffusionlike processes on top of multiplex networks.
Abstract: We study the time scales associated with diffusion processes that take place on multiplex networks, i.e., on a set of networks linked through interconnected layers. To this end, we propose the construction of a supra-Laplacian matrix, which consists of a dimensional lifting of the Laplacian matrix of each layer of the multiplex network. We use perturbative analysis to reveal analytically the structure of eigenvectors and eigenvalues of the complete network in terms of the spectral properties of the individual layers. The spectrum of the supra-Laplacian allows us to understand the physics of diffusionlike processes on top of multiplex networks.

Journal ArticleDOI
TL;DR: It is argued that the many-body localization can be used to protect coherence in the system by suppressing relaxation between eigenstates with different local integrals of motion.
Abstract: We construct a complete set of local integrals of motion that characterize the many-body localized (MBL) phase. Our approach relies on the assumption that local perturbations act locally on the eigenstates in the MBL phase, which is supported by numerical simulations of the random-field $XXZ$ spin chain. We describe the structure of the eigenstates in the MBL phase and discuss the implications of local conservation laws for its nonequilibrium quantum dynamics. We argue that the many-body localization can be used to protect coherence in the system by suppressing relaxation between eigenstates with different local integrals of motion.

Journal ArticleDOI
M. G. Aartsen1, Rasha Abbasi2, Y. Abdou3, Markus Ackermann  +284 moreInstitutions (36)
TL;DR: These two neutrino-induced events could be a first indication of an astrophysical neutrinos flux; the moderate significance, however, does not permit a definitive conclusion at this time.
Abstract: We report on the observation of two neutrino-induced events which have an estimated deposited energy in the IceCube detector of 1.04 +/- 0.16 and 1.14 +/- 0.17 PeV, respectively, the highest neutrino energies observed so far. These events are consistent with fully contained particle showers induced by neutral-current nu(e,mu,tau) ((nu) over bar (e,mu,tau)) or charged-current nu(e) ((nu) over bar (e)) interactions within the IceCube detector. The events were discovered in a search for ultrahigh energy neutrinos using data corresponding to 615.9 days effective live time. The expected number of atmospheric background is 0.082 +/- 0.004(stat)(-0.057)(+0.041)(syst). The probability of observing two or more candidate events under the atmospheric background-only hypothesis is 2.9 x 10(-3) (2.8 sigma) taking into account the uncertainty on the expected number of background events. These two events could be a first indication of an astrophysical neutrino flux; the moderate significance, however, does not permit a definitive conclusion at this time.

Journal ArticleDOI
TL;DR: The analysis of the interrelation between two processes accounting for the spreading of an epidemic, and the information awareness to prevent its infection, on top of multiplex networks reveals the phase diagram of the incidence of the epidemics and allows the evolution of the epidemic threshold depending on the topological structure of the multiplex and the inter correlation with the awareness process.
Abstract: We present the analysis of the interrelation between two processes accounting for the spreading of an epidemic, and the information awareness to prevent its infection, on top of multiplex networks. This scenario is representative of an epidemic process spreading on a network of persistent real contacts, and a cyclic information awareness process diffusing in the network of virtual social contacts between the same individuals. The topology corresponds to a multiplex network where two diffusive processes are interacting affecting each other. The analysis using a microscopic Markov chain approach reveals the phase diagram of the incidence of the epidemics and allows us to capture the evolution of the epidemic threshold depending on the topological structure of the multiplex and the interrelation with the awareness process. Interestingly, the critical point for the onset of the epidemics has a critical value (metacritical point) defined by the awareness dynamics and the topology of the virtual network, from which the onset increases and the epidemics incidence decreases.

Journal ArticleDOI
TL;DR: By applying the optical nanocircuit concepts to metasurfaces, an effective route to locally control light transmission over a deeply subwavelength scale is proposed, which may lead to large improvements in the manipulation of optical transmission and processing of nanoscale optical signals over conformal and Si-compatible substrates.
Abstract: By applying the optical nanocircuit concepts to metasurfaces, we propose an effective route to locally control light transmission over a deeply subwavelength scale. This concept realizes the optical equivalent of a transmit-array, whose use is demonstrated for light bending and focusing with unprecedented efficiency over a subwavelength distance, with crucial benefits for nano-optics applications. These findings may lead to large improvements in the manipulation of optical transmission and processing of nanoscale optical signals over conformal and Si-compatible substrates.

Journal ArticleDOI
TL;DR: The authors' Wigner-like surmises are shown to be very accurate when compared to numerics and exact calculations in the large matrix size limit, and quantitative improvements are found through a polynomial expansion.
Abstract: We derive expressions for the probability distribution of the ratio of two consecutive level spacings for the classical ensembles of random matrices. This ratio distribution was recently introduced to study spectral properties of many-body problems, as, contrary to the standard level spacing distributions, it does not depend on the local density of states. Our Wigner-like surmises are shown to be very accurate when compared to numerics and exact calculations in the large matrix size limit. Quantitative improvements are found through a polynomial expansion. Examples from a quantum many-body lattice model and from zeros of the Riemann zeta function are presented.

Journal ArticleDOI
TL;DR: This work demonstrates a planar, tunable superconducting qubit with energy relaxation times up to 44 μs and finds a fine structure in the qubit energy lifetime as a function of frequency, indicating the presence of a sparse population of incoherent, weakly coupled two-level defects.
Abstract: We demonstrate a planar, tunable superconducting qubit with energy relaxation times up to 44 μs. This is achieved by using a geometry designed to both minimize radiative loss and reduce coupling to materials-related defects. At these levels of coherence, we find a fine structure in the qubit energy lifetime as a function of frequency, indicating the presence of a sparse population of incoherent, weakly coupled two-level defects. We elucidate this defect physics by experimentally varying the geometry and by a model analysis. Our "Xmon" qubit combines facile fabrication, straightforward connectivity, fast control, and long coherence, opening a viable route to constructing a chip-based quantum computer.

Journal ArticleDOI
TL;DR: A new integrable nonlocal nonlinear Schrödinger equation is introduced that possesses a Lax pair and an infinite number of conservation laws and is PT symmetric.
Abstract: A new integrable nonlocal nonlinear Schrodinger equation is introduced. It possesses a Lax pair and an infinite number of conservation laws and is PT symmetric. The inverse scattering transform and scattering data with suitable symmetries are discussed. A method to find pure soliton solutions is given. An explicit breathing one soliton solution is found. Key properties are discussed and contrasted with the classical nonlinear Schrodinger equation.

Journal ArticleDOI
M. Ablikim, M. N. Achasov1, Xiaocong Ai, O. Albayrak2  +365 moreInstitutions (50)
TL;DR: In this article, the process e(+)e(-) -> pi(+)pi(-) J/psi at a center-of-mass energy of 4.260 GeV using a 525 pb(-1) data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider was studied.
Abstract: We study the process e(+)e(-) -> pi(+)pi(-) J/psi at a center-of-mass energy of 4.260 GeV using a 525 pb(-1) data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross section is measured to be (62.9 +/- 1.9 +/- 3.7) pb, consistent with the production of the Y(4260). We observe a structure at around 3.9 GeV/c(2) in the pi(+/-) J/psi mass spectrum, which we refer to as the Z(c)(3900). If interpreted as a new particle, it is unusual in that it carries an electric charge and couples to charmonium. A fit to the pi(+/-) J/psi invariant mass spectrum, neglecting interference, results in a mass of (3899.0 +/- 3.6 +/- 4.9) MeV/c(2) and a width of (46 +/- 10 +/- 20) MeV. Its production ratio is measured to be R = (sigma(e(+)e(-) -> pi(+/-) Z(c)(3900)(-/+) -> pi(+)pi(-) J/psi)/sigma(e(+)e(-) -> pi(+)pi(-) J/psi)) = (21.5 +/- 3.3 +/- 7.5)%. In all measurements the first errors are statistical and the second are systematic.

Journal ArticleDOI
TL;DR: A self-consistent electromagnetic theory of the coupling between dipole emitters and dissipative nanoresonators that predicts that a spectral detuning between the emitter and the resonance does not necessarily result in a Lorentzian response in the presence of dissipation.
Abstract: We provide a self-consistent electromagnetic theory of the coupling between dipole emitters and dissipative nanoresonators. The theory that relies on the concept of quasinormal modes with complex frequencies provides an accurate closed-form expression for the electromagnetic local density of states of any photonic or plasmonic resonator with strong radiation leakage, absorption, and material dispersion. It represents a powerful tool to calculate and conceptualize the electromagnetic response of systems that are governed by a small number of resonance modes. We use the formalism to revisit Purcell's factor. The new formula substantially differs from the usual one; in particular, it predicts that a spectral detuning between the emitter and the resonance does not necessarily result in a Lorentzian response in the presence of dissipation. Comparisons with fully vectorial numerical calculations for plasmonic nanoresonators made of gold nanorods evidence the high accuracy of the predictions achieved by our semianalytical treatment.

Journal ArticleDOI
TL;DR: It is shown that the equilibrium quantum phase transition and the dynamical phase transition in the transverse-field Ising model are intimately related.
Abstract: A phase transition indicates a sudden change in the properties of a large system. For temperature-driven phase transitions this is related to nonanalytic behavior of the free energy density at the critical temperature: The knowledge of the free energy density in one phase is insufficient to predict the properties of the other phase. In this Letter we show that a close analogue of this behavior can occur in the real time evolution of quantum systems, namely nonanalytic behavior at a critical time. We denote such behavior a dynamical phase transition and explore its properties in the transverse-field Ising model. Specifically, we show that the equilibrium quantum phase transition and the dynamical phase transition in this model are intimately related.

Journal ArticleDOI
TL;DR: In this article, the authors examined a minimal model for an active colloidal fluid in the form of self-propelled Brownian spheres that interact purely through excluded volume with no aligning interaction.
Abstract: We examine a minimal model for an active colloidal fluid in the form of self-propelled Brownian spheres that interact purely through excluded volume with no aligning interaction. Using simulations and analytic modeling, we quantify the phase diagram and separation kinetics. We show that this nonequilibrium active system undergoes an analog of an equilibrium continuous phase transition, with a binodal curve beneath which the system separates into dense and dilute phases whose concentrations depend only on activity. The dense phase is a unique material that we call an active solid, which exhibits the structural signatures of a crystalline solid near the crystal-hexatic transition point, and anomalous dynamics including superdiffusive motion on intermediate time scales.

Journal ArticleDOI
Roel Aaij1, Bernardo Adeva2, Marco Adinolfi3, C. Adrover4  +653 moreInstitutions (44)
TL;DR: A measurement of form-factor-independent angular observables in the decay B(0)→K*(892)(0)μ(+)μ(-) is presented, based on a data sample collected by the LHCb experiment in pp collisions at a center-of-mass energy of 7 TeV.
Abstract: We present a measurement of form-factor-independent angular observables in the decay B-0 -> K*(892)(0)mu(+)mu(-). The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb experiment in pp collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared q(2) in the range 0.1 < q(2) < 19.0 GeV2/c(4). Agreement with recent theoretical predictions of the standard model is found for 23 of the 24 measurements. A local discrepancy, corresponding to 3.7 Gaussian standard deviations is observed in one q(2) bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is 0.5%.

Journal ArticleDOI
TL;DR: It is shown that the free energy of thermodynamics emerges naturally from the resource theory of energy-preserving transformations, provided that a sublinear amount of coherent superposition over energy levels is available, a situation analogous to the sub linear amount of classical communication required for entanglement dilution.
Abstract: The ideas of thermodynamics have proved fruitful in the setting of quantum information theory, in particular the notion that when the allowed transformations of a system are restricted, certain states of the system become useful resources with which one can prepare previously inaccessible states. The theory of entanglement is perhaps the best-known and most well-understood resource theory in this sense. Here, we return to the basic questions of thermodynamics using the formalism of resource theories developed in quantum information theory and show that the free energy of thermodynamics emerges naturally from the resource theory of energy-preserving transformations. Specifically, the free energy quantifies the amount of useful work which can be extracted from asymptotically many copies of a quantum system when using only reversible energy-preserving transformations and a thermal bath at fixed temperature. The free energy also quantifies the rate at which resource states can be reversibly interconverted asymptotically, provided that a sublinear amount of coherent superposition over energy levels is available, a situation analogous to the sublinear amount of classical communication required for entanglement dilution.

Journal ArticleDOI
TL;DR: Transport measurements of an InAs nanowire coupled to niobium nitride leads at high magnetic fields observe a zero-bias anomaly (ZBA) in the differential conductance of the nanowires for certain ranges of magnetic field and chemical potential.
Abstract: We report on transport measurements of an InAs nanowire coupled to niobium nitride leads at high magnetic fields. We observe a zero-bias anomaly (ZBA) in the differential conductance of the nanowire for certain ranges of magnetic field and chemical potential. The ZBA can oscillate in width with either the magnetic field or chemical potential; it can even split and re-form. We discuss how our results relate to recent predictions of hybridizing Majorana fermions in semiconducting nanowires, while considering more mundane explanations.

Journal ArticleDOI
Z. Q. Liu, C. P. Shen1, C. Z. Yuan, I. Adachi  +188 moreInstitutions (56)
TL;DR: In a study of Y(4260) → π+ π- J/φ decays, a structure is observed in the M(π(±)J/ψ) mass spectrum with 5.2σ significance that can be interpreted as a new charged charmoniumlike state.
Abstract: The cross section for ee+ e- → π+ π- J/ψ between 3.8 and 5.5 GeV is measured with a 967 fb(-1) data sample collected by the Belle detector at or near the Υ(nS) (n = 1,2,…,5) resonances. The Y(4260) state is observed, and its resonance parameters are determined. In addition, an excess of π+ π- J/ψ production around 4 GeV is observed. This feature can be described by a Breit-Wigner parametrization with properties that are consistent with the Y(4008) state that was previously reported by Belle. In a study of Y(4260) → π+ π- J/ψ decays, a structure is observed in the M(π(±)J/ψ) mass spectrum with 5.2σ significance, with mass M = (3894.5 ± 6.6 ± 4.5) MeV/c2 and width Γ = (63 ± 24 ± 26) MeV/c2, where the errors are statistical and systematic, respectively. This structure can be interpreted as a new charged charmoniumlike state.

Journal ArticleDOI
TL;DR: The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of 5.7 × 10(-13) (90% confidence level).
Abstract: The analysis of a combined data set, totaling $3.6\ifmmode\times\else\texttimes\fi{}{10}^{14}$ stopped muons on target, in the search for the lepton flavor violating decay ${\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\gamma}$ is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of $5.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.

Journal ArticleDOI
TL;DR: In this article, the Bose-Einstein condensation of an atomic gas in the (quasi)uniform three-dimensional potential of an optical box trap was observed.
Abstract: We have observed the Bose-Einstein condensation of an atomic gas in the (quasi)uniform three-dimensional potential of an optical box trap. Condensation is seen in the bimodal momentum distribution and the anisotropic time-of-flight expansion of the condensate. The critical temperature agrees with the theoretical prediction for a uniform Bose gas. The momentum distribution of a noncondensed quantum-degenerate gas is also clearly distinct from the conventional case of a harmonically trapped sample and close to the expected distribution in a uniform system. We confirm the coherence of our condensate in a matter-wave interference experiment. Our experiments open many new possibilities for fundamental studies of many-body physics.

Journal ArticleDOI
Matteo Agostini1, M. Allardt, E. Andreotti, A. M. Bakalyarov, M. Balata, I. R. Barabanov, M. Heider Barnabé, N. Barros, Laura Baudis, C. Bauer, N. Becerici-Schmidt, E. Bellotti, S. Belogurov, S. T. Belyaev, Giovanni Benato, Alessandro Bettini, L. B. Bezrukov, T. Bode, V. B. Brudanin, R. Brugnera, D. Budjáš, Allen Caldwell, C. Cattadori, A. Chernogorov, F. Cossavella, E. V. Demidova, A. Domula, V. G. Egorov, R. Falkenstein, A. D. Ferella, K. Freund, N. Frodyma, A. M. Gangapshev, A. Garfagnini, C. Gotti, P. Grabmayr, V. I. Gurentsov, K. N. Gusev, K. K. Guthikonda, W. Hampel, A. Hegai, M. Heisel2, S. Hemmer, G. Heusser, Werner Hofmann2, Mikael Hult, L. V. Inzhechik, L. Ioannucci, J. Janicskó Csáthy, J. Jochum, M. Junker, Th. Kihm, I. V. Kirpichnikov, A. Kirsch, A. A. Klimenko, K. T. Knoepfle2, O.I. Kochetov, V. N. Kornoukhov, V. V. Kuzminov, M. Laubenstein, A. Lazzaro, V. I. Lebedev, B. Lehnert, H. Y. Liao, Manfred Lindner2, Ivano Lippi, X. Liu, A. Lubashevskiy2, B. K. Lubsandorzhiev, Guillaume Lutter, C. Macolino, A. A. Machado, Bela Majorovits, W. Maneschg2, M. Misiaszek, Igor Nemchenok, Stefano Nisi, C. O'Shaughnessy, Luciano Pandola, K. Pelczar, G. Pessina, F. Potenza, A. Pullia, Stefano Riboldi, N. Rumyantseva, Cinzia Sada, M. Salathe, C. Schmitt, Jochen Schreiner2, O. Schulz, B. Schwingenheuer2, Stefan Schönert2, E. Shevchik, M. Shirchenko, Hardy Simgen, A.A. Smolnikov, L. Stanco, H. Strecker2, M. Tarka, C. A. Ur, A. A. Vasenko, O. Volynets, K. von Sturm, V. Wagner, M. Walter, A. Wegmann2, T. Wester, M. M. Wojcik, E. A. Yanovich, P. Zavarise, I. Zhitnikov, S. V. Zhukov, D. R. Zinatulina, Kai Zuber, G. Zuzel 
TL;DR: The results from phase I of the Germanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory (Italy) searching for neutrinoless double beta decay of the isotope (76)Ge are reported.
Abstract: Neutrinoless double beta decay is a process that violates lepton number conservation. It is predicted to occur in extensions of the standard model of particle physics. This Letter reports the results from phase I of the Germanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory (Italy) searching for neutrinoless double beta decay of the isotope $^{76}\mathrm{Ge}$. Data considered in the present analysis have been collected between November 2011 and May 2013 with a total exposure of 21.6 kg yr. A blind analysis is performed. The background index is about $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\text{ }\text{ }\mathrm{counts}/(\mathrm{keV}\text{ }\mathrm{kg}\text{ }\mathrm{yr})$ after pulse shape discrimination. No signal is observed and a lower limit is derived for the half-life of neutrinoless double beta decay of $^{76}\mathrm{Ge}$, ${T}_{1/2}^{0\ensuremath{ u}}g2.1\ifmmode\times\else\texttimes\fi{}{10}^{25}\text{ }\text{ }\mathrm{yr}$ (90% C.L.). The combination with the results from the previous experiments with $^{76}\mathrm{Ge}$ yields ${T}_{1/2}^{0\ensuremath{ u}}g3.0\ifmmode\times\else\texttimes\fi{}{10}^{25}\text{ }\text{ }\mathrm{yr}$ (90% C.L.).