Physics

  • Article
    | Open Access

    Nanocrystals are used in light-emitting diodes and solar cells, but their charge transport in films is unclear. Here, the study of PbS nanocrystal films reveals the role of mid-gap states in their charge transport, suggesting different design needs for devices operated in dark (transistors) versus light (solar cells) conditions.

    • Prashant Nagpal
    •  & Victor I. Klimov
  • Article
    | Open Access

    Inertial sensors using atom interferometry have applications in geophysics, navigation- and space-based tests of fundamental physics. Here, the first operation of an atom accelerometer during parabolic flights is reported, demonstrating high-resolution measurements at both 1g and 0g.

    • R. Geiger
    • , V. Ménoret
    •  & P. Bouyer
  • Article
    | Open Access

    The paradigm of reservoir computing shows that, like the human brain, complex networks can perform efficient information processing. Here, a simple delay dynamical system is demonstrated that can efficiently perform computations capable of replacing a complex network in reservoir computing.

    • L. Appeltant
    • , M.C. Soriano
    •  & I. Fischer
  • Article |

    Quadrupoles have many engineering applications, but experimental observations of fluidic multipoles have not been reported. This study presents an experimental two-dimensional microfluidic quadrupole, a theoretical analysis consistent with observations, and a first application as a channel-free floating gradient generator.

    • Mohammad A. Qasaimeh
    • , Thomas Gervais
    •  & David Juncker
  • Article |

    Property coupling by heteroepitaxy is severely limited in material combinations with highly dissimilar bonding. This report presents a chemical boundary condition methodology to actively engineer two-dimensional film growth in such systems that otherwise collapse into island formation and rough morphologies.

    • Elizabeth A. Paisley
    • , Mark. D. Losego
    •  & Jon-Paul Maria
  • Article
    | Open Access

    The measurement of the total cross-section of proton–proton collisions is of fundamental importance for particle physics. Here, the first measurement of the inelastic cross-section is presented for proton–proton collisions at an energy of 7 teraelectronvolts using the ATLAS detector at the Large Hadron Collider.

    • G. Aad
    • , B. Abbott
    •  & L. Zwalinski
  • Article |

    Photodetection is believed to be among the most promising potential applications for graphene. Here, by combining graphene with plasmonic nanostructures, the efficiency of graphene-based photodetectors is increased by up to two orders of magnitude.

    • T.J. Echtermeyer
    • , L. Britnell
    •  & K.S. Novoselov
  • Article
    | Open Access

    Determining the direction of the magnetic field of light is important for optical applications. Here, scattering of light from a subwavelength aperture in a metal plane is shown to be governed by its magnetic vector, providing the magnetic field orientation independently of the electric field.

    • H.W. Kihm
    • , S.M. Koo
    •  & D.-S. Kim
  • Article
    | Open Access

    At extreme temperature and pressure, materials can form new dense phases with unusual physical properties. Here, laser-induced microexplosions are used to produce a superdense, stable, body-centred-cubic form of aluminium, which was previously predicted to exist at pressures above 380GPa.

    • Arturas Vailionis
    • , Eugene G. Gamaly
    •  & Saulius Juodkazis
  • Article
    | Open Access

    Single atoms can be detected using optical resonators that extend the lifetime of the photon. Here, the authors demonstrate fast, high-fidelity detection of very low atom densities using a microfabricated optical cavity to couple the detection light with the atoms.

    • J. Goldwin
    • , M. Trupke
    •  & E.A. Hinds
  • Article
    | Open Access

    Quantum-mechanical predictions are generally probabilistic. Here, assuming freely chosen measurements, it is shown that enhanced predictions are not possible and, thus, randomness is inherent in quantum theory: a result that has applications in fields such as quantum cryptography.

    • Roger Colbeck
    •  & Renato Renner
  • Article
    | Open Access

    Quantum computing has advantages over conventional computing, but the complexity of quantum algorithms creates technological challenges. Here, an architecture-independent technique, that simplifies adding control qubits to arbitrary quantum operations, is developed and demonstrated.

    • Xiao-Qi Zhou
    • , Timothy C. Ralph
    •  & Jeremy L. O'Brien
  • Article |

    Brillouin interactions between sound and light can excite mechanical resonances in photonic microsystems, with potential for sensing and frequency reference applications. The authors demonstrate experimental excitation of mechanical resonances ranging from 49 to 1,400 MHz using forward Brillouin scattering.

    • Gaurav Bahl
    • , John Zehnpfennig
    •  & Tal Carmon
  • Article |

    Pagerank is widely used to rank web content; however, it is unknown how network topology affects its performance. The authors demonstrate that, in random networks, pagerank is sensitive to perturbations in topology, whereas scale-free networks contain a few super-stable nodes whose ranking is exceptionally stable.

    • Gourab Ghoshal
    •  & Albert-László Barabási
  • Article
    | Open Access

    In some iron-based materials, unconventional superconductivity can emerge near a quantum phase transition where long-range magnetic order vanishes. Giovannettiet al.show that the magnetic quantum phase transition in an iron pnictide superconductor is very close to the quantum tricritical point.

    • Gianluca Giovannetti
    • , Carmine Ortix
    •  & José Lorenzana
  • Article
    | Open Access

    The fractional quantum Hall effect occurs when electrons move in Landau levels. In this study, using a theoretical flat-band lattice model, the fractional quantum Hall effect is observed in the presence of repulsive interactions when the band is one third full and in the absence of Landau levels.

    • D.N. Sheng
    • , Zheng-Cheng Gu
    •  & L. Sheng
  • Article |

    A quantum simulator can follow the evolution of a prescribed model, whose behaviour may be difficult to determine. Here, the emergence of magnetism is simulated by implementing a quantum Ising model, providing a benchmark for simulations in larger systems.

    • R. Islam
    • , E.E. Edwards
    •  & C. Monroe
  • Article
    | Open Access

    Two-qubit operation is an essential part of quantum computation, but implementation has been difficult. Gotoet al.introduce optically controllable internuclear coupling in semiconductors providing a simple way of switching inter-qubit couplings in semiconductor-based quantum computers.

    • Atsushi Goto
    • , Shinobu Ohki
    •  & Tadashi Shimizu
  • Article |

    Interactions between charge, orbital and lattice degrees of freedom in correlated electron systems have resulted in predictions of new electronic phases of matter. Carlson and Dahmen propose two protocols for detecting disordered electron nematics in condensed matter systems using non-equilibrium methods.

    • E.W. Carlson
    •  & K.A. Dahmen
  • Article |

    The unoccupied electronic levels of graphene are modified by corrugation, doping and presence of impurities. Here, the authors map discrete electronic domains within a single graphene sheet using scanning transmission X-ray microscopy and provide insight into the modification of unoccupied levels.

    • Brian J. Schultz
    • , Christopher J. Patridge
    •  & Sarbajit Banerjee
  • Article |

    Anyons are particles with fractional statistics that interpolate between bosons and fermions, and are thought to exist in low-dimensional systems. Keilmannet al. propose an experimental system to create anyons in one-dimensional optical lattices using assisted Raman tunnelling.

    • Tassilo Keilmann
    • , Simon Lanzmich
    •  & Marco Roncaglia
  • Article
    | Open Access

    A bubble at an air–liquid interface can form a liquid jet upon bursting, spraying aerosol droplets into the air. Leeet al. show that jetting is analogous to pinching-off in liquid coalescence, which may be useful in applications that prevent jet formation and in the improved incorporation of aerosols in climate models.

    • Ji San Lee
    • , Byung Mook Weon
    •  & Wah-Keat Lee
  • Article
    | Open Access

    Light–matter interactions can be used to manipulate magnetization in solids, but light-controlled magnetization vector motion has not been demonstrated. Here, two-dimensional magnetic oscillations in NiO are manipulated with optical pulses leading to vectorial control of magnetization by light.

    • Natsuki Kanda
    • , Takuya Higuchi
    •  & Makoto Kuwata-Gonokami
  • Article |

    Waveplates are used in optoelectronics to alter the polarization of light, but they do not typically perform achromatically, which is important for applications such as three-dimensional displays. Here, biologically inspired periodically multilayered structures are produced, which function as achromatic visible-light waveplates.

    • Yi-Jun Jen
    • , Akhlesh Lakhtakia
    •  & Jyun-Rong Lai
  • Article |

    Optoelectronic devices such as conventional semiconductor lasers are used to study the chaotic behaviour of nonlinear systems. Here chaos is observed for quantum-dot microlasers operating close to the quantum limit with potential for new directions in the study of chaos in quantum systems.

    • Ferdinand Albert
    • , Caspar Hopfmann
    •  & Ido Kanter
  • Article |

    A quantum key distribution system allows two remote parties to communicate in secret by a shared key code. This work demonstrates a complete and undetected eavesdropping attack on a quantum key distribution connection, highlighting the need for further security updates on secure communication systems.

    • Ilja Gerhardt
    • , Qin Liu
    •  & Vadim Makarov
  • Article
    | Open Access

    Negative thermal expansion—contraction upon heating—is an unusual process that may be exploited to produce materials with zero or other controlled thermal expansion values. Azumaet al. observe negative thermal expansion in BiNiO3which is a result of Bi/Ni charge-transfer transitions.

    • Masaki Azuma
    • , Wei-tin Chen
    •  & J. Paul Attfield
  • Article
    | Open Access

    Understanding how the high-energy physics of Mott-like excitations affects condensate formation is a key challenge in high-temperature superconductivity. Giannettiet al. clarify the relationship of many-body CuO2excitations and the onset of superconductivity using a new optical pump supercontinuum-probe technique.

    • Claudio Giannetti
    • , Federico Cilento
    •  & Fulvio Parmigiani
  • Article
    | Open Access

    Bose–Einstein condensation of excitons in thermal equilibrium is a predicted quantum statistical phenomenon that has been difficult to observe. Yoshiokaet al. cool trapped excitons to sub-Kelvin temperatures and show that condensation manifests itself as a relaxation explosion as has been observed for atomic hydrogen.

    • Kosuke Yoshioka
    • , Eunmi Chae
    •  & Makoto Kuwata-Gonokami
  • Article
    | Open Access

    Two-dimensional fluid interfaces are ubiquitous, but studying their surface dynamic properties is difficult because of coupling between the film and bulk fluid. Choiet al.combine active microrheology with fluorescence microscopy to image fluid interfaces under applied stress.

    • S.Q. Choi
    • , S. Steltenkamp
    •  & T.M. Squires
  • Article
    | Open Access

    The conductance of single-molecule junctions is affected by the structure of the molecule and how it is bound to the electrodes, which may be examined using Raman spectroscopy. Liuet al. have developed 'fishing-mode' tip-enhanced Raman spectroscopy, which allows the simultaneous determination of conductance and Raman spectra.

    • Zheng Liu
    • , Song-Yuan Ding
    •  & Zhong-Qun Tian
  • Article |

    Sintering is the basis for the production of many metallic and composite materials. Gruppet al. use a new technique to measure the rotation of microscopic copper particles during sintering and find intrinsic rotations to be the dominant movement.

    • R. Grupp
    • , M. Nöthe
    •  & J. Banhart
  • Article
    | Open Access

    Wave mixing in optical resonators suffers from strong bandwidth constraints, hindering practical implementation. Morichettiet al. report travelling-wave four-wavemixing in coupled ring resonators, which combines the efficiency enhancement of resonant propagation with a wide-band conversion process.

    • Francesco Morichetti
    • , Antonio Canciamilla
    •  & Andrea Melloni
  • Article |

    Speckle patterns are a manifestation of decoherence and can result from two-particle interference. Here, the authors image atomic speckle for guided matter waves and link this to atom bunching in the second-order correlation function, suggesting potential use in squeezed-atom interferometry applications.

    • R.G. Dall
    • , S.S. Hodgman
    •  & A.G. Truscott
  • Article
    | Open Access

    Theory and simulations predict scale-invariant concentration fluctuations during diffusion in liquids, but on Earth, large-scale fluctuations are damped by gravity. Microgravity experiments by Vailatiet al. reveal the scale-invariant nature of diffusion, associated with fractal fronts and long-ranged correlations.

    • Alberto Vailati
    • , Roberto Cerbino
    •  & Marzio Giglio
  • Article
    | Open Access

    Temperature-controlled regulation of thermal conductivity is difficult to achieve because thermal properties do not change significantly through solid-state phase transitions. Here temperature control of thermal conductivities is demonstrated using liquid–solid phase transitions in a nanoparticle suspension.

    • Ruiting Zheng
    • , Jinwei Gao
    •  & Gang Chen
  • Article |

    Melting-related phenomena are of fundamental and applied interest, but the melting theory is poorly understood. Levitas and Samani develop an advanced phase-field theory of melting coupled to mechanics that resolves existing contradictions and reveals the features of melting phenomena.

    • Valery I Levitas
    •  & Kamran Samani
  • Article
    | Open Access

    Pattern-forming processes in simple fluids and suspensions are well understood, but displacement morphologies in frictional fluids and granular mixtures have not been studied extensively. Sandneset al. consider the effects of Coulomb friction and compressibility on the fluid dynamics of granular mixtures.

    • B. Sandnes
    • , E.G. Flekkøy
    •  & H. See
  • Article
    | Open Access

    In the pseudogap state of cuprates, although diamagnetic signals have been detected, a Meissner effect has never been observed. Morenzoni and colleagues probe the local diamagnetic response in the normal state of an underdoped layer showing that a 'barrier' layer exhibits a Meissner effect.

    • Elvezio Morenzoni
    • , Bastian M. Wojek
    •  & Ivan Božović
  • Article
    | Open Access

    Observing superposition states of mesoscopic quantum systems is an ongoing challenge. Gerlichet al. report quantum interference of large tailor-made organic compounds, demonstrating delocalization and the quantum wave nature of entire molecules composed of up to 430 atoms.

    • Stefan Gerlich
    • , Sandra Eibenberger
    •  & Markus Arndt
  • Article |

    Monitoring the impact of annealing on nanometre-thick polymer layers provides new insight into the changes in the performance of macromolecular materials. Here, the authors present results showing a correlation between the deviations from bulk behaviour and the growth of an irreversibly adsorbed layer.

    • Simone Napolitano
    •  & Michael Wübbenhorst
  • Article |

    Single-molecule force spectroscopy is used to study single molecule interactions, but probing short-lived events is difficult. Here, a nanomechanical interface is developed, which allows the study of microsecond timescale interactions.

    • Mingdong Dong
    •  & Ozgur Sahin
  • Article |

    Skyrmions are particle-like topological entities in a continuous field that have a role in various condensed matter systems. Here, numerical methods are used to show that a chiral nematic liquid crystal could be used as a model system to facilitate direct structural investigation of Skyrmions.

    • Jun-ichi Fukuda
    •  & Slobodan Žumer
  • Article |

    Cold ion traps have not previously been used to study sliding friction between crystal lattices. Here, Benassiet al. use simulations to show that cold ion traps could be used for detailed investigation of atomic scale friction.

    • A. Benassi
    • , A. Vanossi
    •  & E. Tosatti
  • Article |

    Graphene and InAs nanowires are both promising materials for coherent spin manipulation, but coupling between a quantum system and its environment leads to decoherence. Here, the contribution of electron–phonon coupling to decoherence in graphene and InAs nanowire is studied.

    • P. Roulleau
    • , S. Baer
    •  & T. Ihn