Quantum fluids and solids

  • Article
    | Open Access

    The pseudogap phase in cuprate superconductors is predicted to be a pair density wave state (PDW) but experimental evidence has been lacking. Here, the authors detect the temperature evolution of energy gap modulations and scattering interference signature suggesting the Bi2Sr2CaDyCu2O8 pseudogap phase contains a PDW.

    • Shuqiu Wang
    • , Peayush Choubey
    •  & J. C. Séamus Davis
  • Article
    | Open Access

    Quantum spin liquid states are realized in systems with frustrated magnetic interactions. Here, the authors show that tunable frustrated spin-spin interactions can be induced by coupling a quantum antiferromagnet to the quantized light of a driven optical cavity, giving rise to robust quantum spin liquid states.

    • Alessio Chiocchetta
    • , Dominik Kiese
    •  & Sebastian Diehl
  • Article
    | Open Access

    Sr3Ru2O7 exhibits a quantum critical point tunable by magnetic field and has been widely used in the study of criticality. Here, by using inelastic neutron scattering, the authors measure collective magnetic excitations near the quantum critical point and relate them to thermodynamic properties and spin density wave order.

    • C. Lester
    • , S. Ramos
    •  & S. M. Hayden
  • Article
    | Open Access

    Twisted van der Waals systems are known to host flat electronic bands, originating from moire potential. Here, the authors predict from purely geometric considerations a new type of nearly dispersionless bands in twisted bilayer MoS2, resulting from destructive interference between effective lattice hopping matrix elements.

    • Lede Xian
    • , Martin Claassen
    •  & Angel Rubio
  • Article
    | Open Access

    The nonequilibrium regime provides an exciting frontier in the search for novel quantum phases of matter. Here, the authors show that optically driving a lightly-doped semiconductor can lead to the spontaneous formation of a dynamical quantum liquid crystalline phase with a rotating magnetization.

    • Iliya Esin
    • , Gaurav Kumar Gupta
    •  & Netanel H. Lindner
  • Article
    | Open Access

    Surface plasmons have unique physical properties that make them also interesting for technology. Here, the authors observe plasmons in mixed-dimensional heterostructures that can be highly modulated with electrostatic gating, which may be explained by plasmon hybridization

    • Sheng Wang
    • , SeokJae Yoo
    •  & Feng Wang
  • Article
    | Open Access

    Laser-assisted electron scattering (LAES) is a commonly observed strong field process in gas phase systems. Here the authors use helium droplets with core atoms and molecules to observe increased electron energy due to multiple LAES events within the droplets.

    • Leonhard Treiber
    • , Bernhard Thaler
    •  & Markus Koch
  • Article
    | Open Access

    The nature of spin interactions and the field-induced quantum spin liquid phase in the Kitaev material α-RuCl3 have been debated. Here, using a combination of many-body techniques, the authors derive an effective spin model that explains the majority of experimental findings and predicts a new quantum spin liquid phase in strong out-of-plane magnetic field.

    • Han Li
    • , Hao-Kai Zhang
    •  & Wei Li
  • Article
    | Open Access

    In this paper, the authors demonstrate that cryogenic scanning transmission electron microscopy allows for the direct mapping of the local arrangements and symmetries of electronic order, providing a useful method for studying strongly correlated systems. They show this using the example of Nd1/2Sr1/2MnO3, a model charge ordered material.

    • Ismail El Baggari
    • , David J. Baek
    •  & Lena F. Kourkoutis
  • Article
    | Open Access

    The Hall effect has been used as a probe of the normal state of cuprates, when superconductivity is supressed by a magnetic field. Here, the authors report the vanishing of the Hall coefficient at high magnetic field in cuprates with stripe order and interpret it as a signature of the stripe-ordered phase.

    • Zhenzhong Shi
    • , P. G. Baity
    •  & Dragana Popović
  • Article
    | Open Access

    It was recently proposed that the coupling between phonons and fractional excitations of a Kitaev quantum spin liquid can be detected in its phonon dynamics. Here, the authors report signatures of this coupling, manifested in low-energy phonon anomalies measured by inelastic X-ray scattering with meV resolution.

    • Haoxiang Li
    • , T. T. Zhang
    •  & H. Miao
  • Article
    | Open Access

    Previous work has shown the detection of quantum turbulence with mechanical resonators but with limited spatial and temporal resolution. Here, the authors demonstrate real-time detection of single quantum vortices in superfluid 4He with millisecond and micron resolution at temperatures of 10 millikelvin.

    • A. Guthrie
    • , S. Kafanov
    •  & D. E. Presnov
  • Article
    | Open Access

    The dominant mechanism of the excitonic insulator transition in Ta2NiSe5 and the nature of its high-temperature phase are debated. The authors report transient reflectivity measurements indicating a significant electronic contribution to the transition and a gapped state of preformed excitons at high temperatures.

    • Hope M. Bretscher
    • , Paolo Andrich
    •  & Akshay Rao
  • Article
    | Open Access

    Charge transport in strongly correlated electron systems is not fully understood. Here, the authors show that resilient quasiparticles at finite frequency persist into the bad-metal regime near a Mott insulator, where dynamical localization results in a ‘displaced Drude peak’ and strongly enhanced dc resistivity.

    • Andrej Pustogow
    • , Yohei Saito
    •  & Simone Fratini
  • Article
    | Open Access

    Surface states in topological quantum matter are protected by their band structure. Here, on confined superfluid 3He as a model for topological superconductors, the authors report experimental evidence on the fragility of surface Andreev bound states with respect to the details of surface scattering.

    • P. J. Heikkinen
    • , A. Casey
    •  & J. Saunders
  • Article
    | Open Access

    Honeycomb lattices with interacting spins can host rich magnetic behaviour; however, typically features are complicated by additional interactions. Here, the authors perform neutron scattering on YbCl3, which exhibits near perfect two-dimensional magnetism, providing a benchmark for other materials.

    • G. Sala
    • , M. B. Stone
    •  & A. D. Christianson
  • Article
    | Open Access

    Viscous fermionic flow appears in liquid helium but rarely appears in metallic solid. Here, Jaoui et al. report a T-square thermal resistivity due to momentum conserving electronic scattering in semi-metallic antimony, which is in agreement with the hydrodynamic scenario.

    • Alexandre Jaoui
    • , Benoît Fauqué
    •  & Kamran Behnia
  • Article
    | Open Access

    There is a long-standing experimental effort to observe field-induced correlated states in three-dimensional materials. Here, the authors observe an unconventional Hall response in the quantum limit of the bulk semimetal HfTe5 with a plateau-like feature in the Hall conductivity.

    • S. Galeski
    • , X. Zhao
    •  & J. Gooth
  • Article
    | Open Access

    Superfluid 3He under confinement can be used as a model system for topological quantum matter, but few related measurements are reported. Here, the authors report on the thermal conduction of helium-3 in a micro-fabricated channel with unanticipated effects in both the normal and superfluid states.

    • D. Lotnyk
    • , A. Eyal
    •  & J. M. Parpia
  • Article
    | Open Access

    Understanding dynamics of fermionic bound states is important for their potential application in quantum devices. Here the authors study zero temperature dynamics and dissipation of fermions bound on a moving goal-post shaped wire in superfluid 3He-B.

    • S. Autti
    • , S. L. Ahlstrom
    •  & D. E. Zmeev
  • Article
    | Open Access

    Viscous electron fluids are predicted in strongly correlated systems but remain challenging to realize. Here, the authors predict enhanced effective Coulomb interaction and reduced ratio of the shear viscosity over entropy density in a Kagome metal, inferring turbulent flow of viscous electron fluids.

    • Domenico Di Sante
    • , Johanna Erdmenger
    •  & Tim Wehling
  • Article
    | Open Access

    There exist many theoretical models of frustrated quantum magnetism, most of which lack convincing experimental realisations. Here the authors combine several experimental methods to argue that KCu6AlBiO4(SO4)5Cl behaves as a square-kagome-lattice quantum Heisenberg antiferromagnet.

    • Masayoshi Fujihala
    • , Katsuhiro Morita
    •  & Kenji Nakajima
  • Article
    | Open Access

    Among the exotic phases in underdoped cuprates, the evidence of a pair density wave (PDW) remains inconclusive. Here, Shi et al. report transport signatures consistent with the presence of PDW pairing correlations that compete with uniform superconductivity in two underdoped cuprate superconductors.

    • Zhenzhong Shi
    • , P. G. Baity
    •  & Dragana Popović
  • Article
    | Open Access

    Quantum spin liquids have magnetic moments that do not form magnetic order even as the temperature approaches zero, leading to the dominance of quantum fluctuations. Chillal et al. present evidence that the hyper-hyperkagome lattice of PbCuTe2O6 hosts a three-dimensional quantum spin liquid.

    • Shravani Chillal
    • , Yasir Iqbal
    •  & Bella Lake
  • 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

    Polariton condensates undergo continuous driving and dissipation, posing challenges for investigating their collective behaviour. Ballarini et al. adapt an oceanographic technique to measure the asymmetric occupation of the Goldstone mode and identify similarities with equilibrium condensates.

    • Dario Ballarini
    • , Davide Caputo
    •  & Daniele Sanvitto
  • Article
    | Open Access

    Electrons on the surface of helium have strong interactions with each other but weak coupling to dissipation mechanisms, providing opportunities for many-body physics and storing quantum information. Here the authors demonstrate a circuit QED platform for manipulating and probing few-electron clusters.

    • Gerwin Koolstra
    • , Ge Yang
    •  & David I. Schuster
  • 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

    Owing to its driven-dissipative nature, and its solid-state environment, a resonantly driven polariton condensate can be accompanied by an incoherent reservoir of excitons. Stepanov et al. demonstrate that this situation strongly modifies the spectrum of collective excitations, which determines many quantum hydrodynamic features in a polariton fluid.

    • Petr Stepanov
    • , Ivan Amelio
    •  & Maxime Richard
  • Article
    | Open Access

    Power laws are usually associated with a scale invariance due to the absence of a length scale. Here, Jin et al. report experimental evidence of a new type of power law in a GaAs/AlGaAs double quantum-well heterostructure, suggesting existence of a new type of universality that emerges at finite energy and momentum.

    • Y. Jin
    • , O. Tsyplyatyev
    •  & C. J. B. Ford
  • 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

    Low dimensional quantum magnetic excitations are intriguing but the experimental realizations are challenging. Here, the authors demonstrate Tomonaga–Luttinger behavior and spinon confinement in rare-earth perovskite YbAlO3 by inelastic neutron scattering measurements.

    • L. S. Wu
    • , S. E. Nikitin
    •  & A. Podlesnyak
  • Article
    | Open Access

    The emergence of superconductivity from the normal state in the cuprates above the transition temperature (Tc) has been controversial. Here, Pelc et al. report nonlinear conductivity, resulting from superconducting precursors only, vanishing exponentially above Tc both with temperature and with magnetic field.

    • Damjan Pelc
    • , Marija Vučković
    •  & Neven Barišić
  • Article
    | Open Access

    Advances in the fabrication of low-disorder metallic materials have made it possible to reach the hydrodynamic regime of electronic transport. Here the authors investigate a hydrodynamic electron fluid in tungsten diphosphide and find that both electrical and thermal transport are limited by the quantum indeterminacy.

    • J. Gooth
    • , F. Menges
    •  & B. Gotsmann
  • Article
    | Open Access

    Driven-dissipative microcavity polariton experiments find superfluid-like behaviour but the intuition developed from equilibrium systems cannot be straightforwardly applied. Juggins et al. show coherently-driven polaritons are not superfluid and earlier observations instead arise from a distinct rigid state.

    • R. T. Juggins
    • , J. Keeling
    •  & M. H. Szymańska
  • Article
    | Open Access

    Quantum ferromagnetic spin liquids in two dimensions, namely quantum kagome ices, yield exotic magnetic properties but their identification remains challenging. Here the authors investigate a dynamic kagome ice state in the pyrochlore oxide Nd2Zr2O7 by magnetization and neutron scattering measurements.

    • E. Lhotel
    • , S. Petit
    •  & G. Balakrishnan
  • Article
    | Open Access

    Biexciton complexes in atomically thin transition metal dichalcogenides have unusually large binding energies. Here, the authors explore biexciton formation dynamics in monolayer MoSe2 in the presence of magnetic fields up to 25 T.

    • Christopher. E. Stevens
    • , Jagannath Paul
    •  & Denis Karaiskaj
  • 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

    Superfluid flow around a vortex is quantized so that vortices become discrete, particle-like defects, with interactions mediated by the surrounding fluid. Here, the authors use a polariton system to experimentally investigate the behavior and scattering of vortices in a two-component superfluid.

    • Lorenzo Dominici
    • , Ricardo Carretero-González
    •  & Daniele Sanvitto
  • Article
    | Open Access

    When the continuous scale symmetry of a quantum system is broken, anomalies occur which may lead to quantum phase transitions. Here, the authors provide evidence for such a quantum phase transition in the attractive Coulomb potential of vacancies in graphene, and further envision its universality for diverse physical systems.

    • O. Ovdat
    • , Jinhai Mao
    •  & E. Akkermans
  • Article
    | Open Access

    Superfluid helium-3 provides a clean testing ground for the understanding of quantum phases and their transitions. Here the authors show that when helium is confined in a nanofluidic cavity supercooling across the first-order A–B transition is suppressed, indicating an intrinsic nucleation mechanism.

    • N. Zhelev
    • , T. S. Abhilash
    •  & J. M. Parpia
  • 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

    High-mobility graphene can play host to exciton polaritons—hybrid matter–light particles, which can form into a state known as a quantum Hall polariton fluid. Here, the authors show that electron–electron interactions can act to destabilize this state and lead to the formation of a modulated phase.

    • Francesco M. D. Pellegrino
    • , Vittorio Giovannetti
    •  & Marco Polini
  • Article
    | Open Access

    Anisotropic disorder is predicted to change the stability of the superfluid state in3He and leads to new phases. Here, Zhelev et al. report signatures of the phase transitions in 3He confined in an extremely anisotropic ordered aerogel including a new polar phase.

    • N. Zhelev
    • , M. Reichl
    •  & J. M. Parpia
  • Article |

    Half-quantized vortices are the fundamental topological excitations of a two-component superfluid, however, probing the dynamics of their formation is challenging. Manni et al.report real-time observations of polariton vortices unbinding into half-quantized vortex pairs in an exciton-polariton condensate.

    • F. Manni
    • , K. G. Lagoudakis
    •  & B. Deveaud
  • Article |

    Polariton condensates provide an arena in which to study interesting non-equilibrium condensate dynamics. Tosi et al. generate stable vortex lattices in a polariton condensate and study their macroscopic wavefunction, uncovering a nonlinear regime for topological defects at high densities.

    • G. Tosi
    • , G. Christmann
    •  & J.J. Baumberg
  • Article
    | Open Access

    The physical properties of organic metals have generally been described in terms of a highly correlated Luttinger liquid. Using angle-resolved photoelectron spectroscopy, Kisset al. measure the Fermi surface of (BEDT-TTF)3Br(pBIB), and find that, in contrast to other systems, it can be described as a Fermi liquid.

    • T. Kiss
    • , A. Chainani
    •  & S. Shin
  • Article |

    Spin liquids are states of matter in which the constituent spins of a magnet are highly correlated yet fluctuate strongly down to millikelvin temperatures. Here the authors report torque magnetometry measurements of the Mott insulator EtMe3Sb[Pd(dmit)2]2and find it displays an ungapped quantum spin liquid state.

    • D. Watanabe
    • , M. Yamashita
    •  & Y. Matsuda