Bose–Einstein condensates

  • Article
    | Open Access

    A gas of magnons, quantised magnetic excitations, can be driven into a Bose-Einstein condensation (BEC) state even at room temperature. Here, Divinskiy et al show that it is possible to achieve stationary equilibrium room-temperature magnon BEC via a spin-current.’

    • B. Divinskiy
    • , H. Merbouche
    •  & S. O. Demokritov
  • Article
    | Open Access

    The microscopic nature of neutral collective excitation of the fractional quantum Hall state is still debated. Here the authors show that a macroscopic ensemble of neutral excitations in the 1/3 state exhibits properties of a Bose system with an exceptionally long coherence time.

    • L. V. Kulik
    • , A. S. Zhuravlev
    •  & V. Y. Umansky
  • Article
    | Open Access

    Here, the authors show that the interaction between microcavity photons and excitons in an atomically thin WSe2 results in a hybridized regime of strong light-matter coupling. Coherence build-up is accompanied by a threshold-like behaviour of the emitted light intensity, which is a fingerprint of a polariton laser effect.

    • Hangyong Shan
    • , Lukas Lackner
    •  & Carlos Antón-Solanas
  • Article
    | Open Access

    Semiconductor microcavities allow engineering of artificial lattices with optical write-in and read-out of information. Here, the authors show an optically imprinted system of exciton-polaritons arranged in a Lieb lattice and reveal a nonequilibrium transition from scattered- to trapped polariton condensates.

    • S. Alyatkin
    • , H. Sigurdsson
    •  & P. G. Lagoudakis
  • Article
    | Open Access

    The use of room temperature exciton–polariton Bose–Einstein condensation is limited by the need for external high-finesse microcavities. The authors generate room temperature EPs with single-crystal microribbons as waveguide Fabry–Pérot microcavities, and demonstrate controllable output of coherent light.

    • Ji Tang
    • , Jian Zhang
    •  & Yong Sheng Zhao
  • Article
    | Open Access

    Previous interference experiments on indirect excitons found dislocation-like phase singularities that could not be explained by common phase defects. Here, the authors explain these features in terms of the moiré pattern of interference of condensate matter waves propagating over macroscopic distances.

    • J. R. Leonard
    • , Lunhui Hu
    •  & A. C. Gossard
  • Article
    | Open Access

    Anderson localization has been previously reported in 1D and 3D but it has remained elusive in 2D environments. Here the authors report probable observation of 2D Anderson localization using ultracold atoms in a weak interaction regime.

    • Donald H. White
    • , Thomas A. Haase
    •  & David A. W. Hutchinson
  • Article
    | Open Access

    Efficient generation of phonons is an important ingredient for a prospective electrically-driven phonon laser for coherent control of quantum systems. Here, the authors report on laser-like phonon emission in a hybrid semiconductor microcavity that optomechanically couples BEC polaritons with phonons.

    • D. L. Chafatinos
    • , A. S. Kuznetsov
    •  & A. Fainstein
  • Article
    | Open Access

    To simulate band structures of solid state materials synthetic lattices are usually generated by optical lattices or by irreversible patterning the system. Here, the authors present reconfigurable synthetic band-structures in optical exciton-polariton lattices and generate non-Hermitian topological phases.

    • L. Pickup
    • , H. Sigurdsson
    •  & P. G. Lagoudakis
  • Article
    | Open Access

    Understanding the sub-picosecond dynamics of driven-dissipative condensates of interacting bosons is challenging. Here the authors combine a lattice of plasmonic nanoparticles with a dye molecule solution in strong coupling and reveal distinct lasing, stimulated thermalization, and condensation regimes.

    • Aaro I. Väkeväinen
    • , Antti J. Moilanen
    •  & Päivi Törmä
  • Article
    | Open Access

    Many studies of polariton condensates have been limited to low temperatures. Here the authors demonstrate ambient polariton condensation in lattices using organic traps that profit from the stability of organic excitons and the large Rabi splitting.

    • M. Dusel
    • , S. Betzold
    •  & C. Schneider
  • Article
    | Open Access

    Little is known about the underlying mechanism responsible for the spatial stability of magnon Bose-Einstein condensates. Here experimental evidence is provided for a repulsive interaction of magnons in the condensate resulting in its stabilization.

    • I. V. Borisenko
    • , B. Divinskiy
    •  & S. O. Demokritov
  • Article
    | Open Access

    Description of non-equilibrium phase transitions is problematic, due to the absence of suitable free energy landscapes. Here, the authors experimentally show delayed photon condensation and timing jitter in a dye-filled microcavity, modelled by a non-equilibrium extension of the free-energy landscape.

    • Benjamin T. Walker
    • , João D. Rodrigues
    •  & Robert A. Nyman
  • Article
    | Open Access

    Vortices can be generated in many platforms and are useful due to manipulation of their vorticity. Here the authors show generation and optical switching of a vortex in exciton-polariton condensates using GaAs microcavities.

    • Xuekai Ma
    • , Bernd Berger
    •  & Stefan Schumacher
  • Article
    | Open Access

    Many aspects of polariton condensate behaviour can be captured by mean-field theories but interactions introduce additional quantum effects. Here the authors observe quantum depletion in a driven-dissipative condensate and find that deviations from equilibrium predictions depend on the excitonic fraction.

    • Maciej Pieczarka
    • , Eliezer Estrecho
    •  & Elena A. Ostrovskaya
  • Article
    | Open Access

    Topological defects and textures are universal phenomena across physics. The authors demonstrate that an initial non-singular spinor texture can be controllably transformed into a pair of singular vortices with cores filled by atoms that continuously connect distinct magnetic phases of matter.

    • L. S. Weiss
    • , M. O. Borgh
    •  & D. S. Hall
  • Article
    | Open Access

    Exploration of magnon Bose–Einstein condensate (BEC) may enable intriguing applications in magnonic devices. Here the authors show experimentally the condensed magnons forming compact humps of BEC density can propagate many hundreds of micrometers in the form of Bogoliubov waves.

    • Dmytro A. Bozhko
    • , Alexander J. E. Kreil
    •  & Burkard Hillebrands
  • Article
    | Open Access

    Order parameter and phase characterization of multicomponent quantum system is of fundamental importance. Here the authors show the parameter control of the dynamics and relaxation of the magnetic ordering of the spin-1 Bose-Einstein condensates of sodium atoms in uniform magnetic field.

    • K. Jiménez-García
    • , A. Invernizzi
    •  & F. Gerbier
  • Article
    | Open Access

    There is increasing interest in understanding the non-equilibrium phenomena in quantum fluids. Here, the authors show dissipative, viscous shock and rarefaction wave dynamics emerging from the turbulent, superfluid flow of an elongated BEC of ultracold Rb atoms driven by a quantum-mechanical piston.

    • Maren E. Mossman
    • , Mark A. Hoefer
    •  & P. Engels
  • Article
    | Open Access

    Topologically protected pseudospin transport is difficult to implement for bosonic systems due to the lack of symmetry-protected pseudospins. Here, Bleu et al. propose robust valley pseudospin transport, truly topologically protected by the winding of a quantum vortex propagating between two staggered honeycomb lattices.

    • O. Bleu
    • , G. Malpuech
    •  & D. D. Solnyshkov
  • Article
    | Open Access

    The mechanism for exciton-polariton condensation in the presence of an incoherent reservoir has been long debated. Here the authors demonstrate the role of the spatial hole burning in condensation of long‐lived exciton polaritons by imaging the condensates in a single-shot excitation regime.

    • E. Estrecho
    • , T. Gao
    •  & E. A. Ostrovskaya
  • Article
    | Open Access

    Cold atom quantum simulation has had challenges in realising the tailored, dynamic types of disorder relevant to real materials. Here, the authors use synthetic momentum-space lattices to engineer spatially and dynamically controlled disorder to observe ballistic, diffusive, and arrested atomic transport.

    • Fangzhao Alex An
    • , Eric J. Meier
    •  & Bryce Gadway
  • Article
    | Open Access

    Liquid helium can be treated as an ideal gas or a condensed liquid and displays intriguing features like Bose–Einstein condensation. Here the authors show that roton excitation reveals information on real space dynamic atom-atom correlations in superfluid helium, which could be used to benchmark models.

    • W. Dmowski
    • , S. O. Diallo
    •  & T. Egami
  • Article
    | Open Access

    When a single mode optical cavity is coupled to a Bose-Einstein condensate, one usually observes a single mode of light when strongly pumped. Here the authors observe a supermode in the output of a multimode cavity and relate this to a signature of a nonequilibrium condensation phase transition.

    • Alicia J. Kollár
    • , Alexander T. Papageorge
    •  & Benjamin L. Lev
  • Article
    | Open Access

    The motion of particles in a quantum condensate state are described by a single macroscopic wave function, leading to a host of unusual properties. Here, the authors generate such a condensation of magnetically induced excitons, known as cyclotron magnetoexcitons, in a high-mobility quantum well.

    • L. V. Kulik
    • , A. S. Zhuravlev
    •  & S. Schmult
  • Article
    | Open Access

    The crossover between the weak-coupling limit and strong-coupling limit provides important information for quantum bound states of interacting fermions. Here, Kasahara et al. report thermodynamic evidence for prevailing phase fluctuations of superconductivity, highlighting unusual normal state in the BCS-BEC crossover regime.

    • S. Kasahara
    • , T. Yamashita
    •  & Y. Matsuda
  • Article
    | Open Access

    Magnons, quantized spin excitations in magnetic materials, may undergo Bose-Einstein condensation into a macroscopic correlated quantum state at low temperature. Here, the authors demonstrate how magnon condensation in quantum magnet TlCuCl3generates an electrical polarization.

    • S. Kimura
    • , K. Kakihata
    •  & H. Tanaka
  • Article
    | Open Access

    The optical trapping of ultracold atoms allows for the simulation and controlled exploration of phenomena normally found in condensed matter systems. Here, the authors demonstrate spin–orbit coupling between lattice band pseudospins in a Bose-Einstein condensate of ultracold atoms.

    • M. A. Khamehchi
    • , Chunlei Qu
    •  & P. Engels
  • Article
    | Open Access

    Microcavity polaritons are a fluid of coupled photonic and electronic excitations that share many of the properties of Bose–Einstein condensates. Here, the authors show that the sudden creation of these bosonic fluids at high density results in the concentration of the particles, unlike an atomic gas that would expand.

    • L. Dominici
    • , M. Petrov
    •  & D. Sanvitto
  • Article |

    Interacting quantum many-body systems in low dimensions is an active research area in ultra-cold gases. Here, Chomaz et al.study the dimensional crossover of Bose–Einstein condensation and observe the emergence of phase coherence in an ultra-cold quasi-2D Bose gas confined to a flat-bottom trapping potential.

    • Lauriane Chomaz
    • , Laura Corman
    •  & Jean Dalibard
  • Article |

    Spin-orbit coupling in a Bose–Einstein condensate provides an additional degree of freedom to explore interesting phenomena. Hamner et al.study the ground state of such a system and show that it exhibits a transition between normal and superradiant phases that can be described by the Dicke model.

    • Chris Hamner
    • , Chunlei Qu
    •  & Peter Engels
  • Article
    | Open Access

    Ramsey interferometers are used to measure minute energy shifts, but they are usually only applied to simple, non-interacting ensembles. Here, the authors demonstrate a two-pulse Ramsey-type interferometer built on the motional states of an interacting Bose–Einstein condensate using optimal control.

    • S. van Frank
    • , A. Negretti
    •  & J. Schmiedmayer
  • Article |

    Efimov trimers are bound states of three bosons, which exist even if their attraction is too weak to form a pair state. Here, the authors explore the phase diagram of a unitary Bose gas and find a transition from a normal gas to a superfluid Efimov liquid, held together by the same effects as Efimov trimers.

    • Swann Piatecki
    •  & Werner Krauth
  • Article |

    In contrast to real atoms, Bose–Einstein condensation of quasi-particles does not require low temperature, but is obtained via external pumping. Here, the authors show an unexpected transitional dynamics of a Bose–Einstein condensate of magnons due to a nonlinear evaporative supercooling mechanism.

    • Alexander A. Serga
    • , Vasil S. Tiberkevich
    •  & Burkard Hillebrands
  • Article |

    Ultracold atomic gases provide a playground for exploring exotic quantum phases, like superfluids with staggered orbital currents. Li et al.show that thermal fluctuations can destroy such a state in two stages, revealing a new intermediate chiral Bose liquid with a striking dynamical fingerprint.

    • Xiaopeng Li
    • , Arun Paramekanti
    •  & W. Vincent Liu
  • Article
    | Open Access

    Atom interferometers exploit wave-particle duality and can be used as sensitive measurement devices. Berrada et al.present a Mach–Zehnder interferometer for Bose–Einstein condensates trapped on an atom chip and demonstrate enhanced performance using non-classical states.

    • T. Berrada
    • , S. van Frank
    •  & J Schmiedmayer