Featured
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News & Views |
Bringing the noise
Noise is usually viewed as the bane of measurements. But a neat experiment has confirmed a long-standing prediction for an exotic electronic state of matter through the increase of noise in charge transmission.
- Chetan Nayak
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Letter |
Binary nanocrystal superlattice membranes self-assembled at the liquid–air interface
The spontaneous assembly of two different types of nanoparticle into ordered superlattices offers a route to designing materials with precisely controlled properties, but available synthesis strategies have many practical limitations. These authors report a fabrication process which overcomes these limitations. They generate large-scale (square-millimetre) binary superlattice structures at a liquid–air interface, allowing the material to be free standing or transferred to any substrate ready for fabrication into useful devices.
- Angang Dong
- , Jun Chen
- & Christopher B. Murray
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Letter |
Transmission of topological surface states through surface barriers
Topological surface states are a class of electronic states that might be of interest in quantum computing or spintronic applications. They are predicted to be robust against imperfections, but so far there has been no evidence that these states do transmit through naturally occurring surface defects. Here, scanning tunnelling microscopy has been used to show that topological surface states of antimony can be transmitted through naturally occurring barriers that block non-topological surface states of common metals.
- Jungpil Seo
- , Pedram Roushan
- & Ali Yazdani
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Letter |
Intra-unit-cell electronic nematicity of the high-Tc copper-oxide pseudogap states
In the high-transition-temperature superconductors, the pseudogap phase becomes predominant when the density of doped holes is reduced. In this phase it has been unclear which electronic symmetries (if any) are broken, what the identity of any associated order parameter might be, and which microscopic electronic degrees of freedom are active. Here, images of the intra-unit-cell states in underdoped Bi2Sr2CaCu2O8 + δ are studied, revealing electronic nematicity of the states close to the pseudogap energy.
- M. J. Lawler
- , K. Fujita
- & Eun-Ah Kim
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News & Views |
U-turns strictly prohibited
According to theory, electrons on the surface of a topological insulator are not allowed to make U-turns. This notion, and some of its main consequences, has now been tested experimentally.
- Marcel Franz
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News Feature |
Topological insulators: Star material
A new class of materials is poised to take condensed-matter physics by storm. Geoff Brumfiel looks at what is making topological insulators all the rage.
- Geoff Brumfiel
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Article |
Femtosecond electronic response of atoms to ultra-intense X-rays
With the start-up of the first X-ray free-electron laser, a new era has begun in dynamical studies of atoms. Here the facility is used to study the fundamental nature of the electronic response in free neon atoms. During a single X-ray pulse, they sequentially eject all their ten electrons to produce fully stripped neon. The authors explain this electron-stripping in a straightforward model, auguring favourably for further studies of interactions of X-rays with more complex systems.
- L. Young
- , E. P. Kanter
- & M. Messerschmidt
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Letter |
Coherent control of Rydberg states in silicon
When an atom is excited into a Rydberg state, its electronic wavefunction can extend to several nanometres. This process can be used to induce and coherently control interactions between atoms that are far enough apart to be non-interacting in their normal states. Now, such behaviour has been realized in a solid-state context, by demonstrating coherent control of the wavefunctions of phosphorus dopant atoms in silicon.
- P. T. Greenland
- , S. A. Lynch
- & G. Aeppli
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News & Views |
Single skyrmions spotted
Skyrmions are a special type of particle that has long been predicted to exist in many fields of physics. Direct images of these structures have now been made in a magnetic material.
- Christian Pfleiderer
- & Achim Rosch
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Letter |
Quantum simulation of frustrated Ising spins with trapped ions
A network is frustrated when competing interactions between nodes prevent each bond from being satisfied. Frustration in quantum networks can lead to massively entangled ground states, as occurs in exotic materials such as quantum spin liquids and spin glasses. Here, a quantum simulation of a frustrated spin system is described, in which there are three trapped atomic ions whose interactions are controlled using optical forces.
- K. Kim
- , M.-S. Chang
- & C. Monroe
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News & Views |
The emergent and hidden unveiled
The appearance of an unexplained electronic state in the uranium metal URu2Si2 at low temperatures has long puzzled condensed-matter physicists. The latest experiment on the material sheds light on the process.
- Andrew J. Schofield
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Letter |
Distinguishing the ultrafast dynamics of spin and orbital moments in solids
The magnetism produced by electrons in a solid can have two components — the spin and orbital moments — that are interchangeable on femtosecond timescales. Here it is shown how rapid changes in these two components can be disentangled, providing insights into the underlying dynamical processes that could be of value for the ultrafast control of information in magnetic recording media.
- C. Boeglin
- , E. Beaurepaire
- & J.-Y. Bigot
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Letter |
GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies
Although compound semiconductors like gallium arsenide (GaAs) offer advantages over silicon for photovoltaic and optoelectronic applications, these do not outweigh the costly process of growing large layers of these materials and transferring them to appropriate substrates. However, a new fabrication approach is now demonstrated: films of GaAs and AlGaAs are grown in thick, multilayered assemblies in a single sequence; the individual layers are then released and distributed over foreign substrates by printing.
- Jongseung Yoon
- , Sungjin Jo
- & John A. Rogers
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News |
Solar cells sliced and diced
Peel-and-stamp technique could pave the way for more efficient semiconductors.
- Geoff Brumfiel
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Letter |
Polymorphism control of superconductivity and magnetism in Cs3C60 close to the Mott transition
Superconductivity and magnetic order are well known in C60 compounds of the form A3C60 (where A = alkali metal). The spherical C60 molecular ions in these crystals are almost always arranged in a face-centred cubic (f.c.c.) packing, except in Cs3C60, where the known superconducting phase has a body-centred cubic (b.c.c) packing. Now the f.c.c. polymorph for Cs3C60 has been isolated; it too is superconducting, although its magnetic properties are very different to those of its b.c.c counterpart.
- Alexey Y. Ganin
- , Yasuhiro Takabayashi
- & Kosmas Prassides
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Research Highlights |
Quantum information: Leak-proof chips
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News & Views |
A condensate's main squeeze
Entanglement between particles permits the quantum uncertainty in one variable to be reduced at the cost of increasing that in another. Condensates are an ideal system in which this technique can be studied.
- Charles A. Sackett
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Article |
Quantum spin liquid emerging in two-dimensional correlated Dirac fermions
A quantum spin liquid is a hypothetical system of spins (such as those carried by electrons), the orientations of which continue to fluctuate even at absolute zero. Theoretical and experimental evidence for the existence of such states at the microscopic level is elusive, but these authors have modelled correlated electrons arranged on a honeycomb lattice (such as in graphene), and identified the conditions under which a microscopic quantum spin liquid would be realized in two dimensions.
- Z. Y. Meng
- , T. C. Lang
- & A. Muramatsu
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News & Views |
Atoms in chequerboard order
Bose–Einstein condensates are ideal tools with which exotic phenomena can be investigated. The hitherto-unrealized Dicke quantum phase transition has now been observed with one such system in an optical cavity.
- Cheng Chin
- & Nathan Gemelke
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Letter |
Atom-chip-based generation of entanglement for quantum metrology
Atom chips provide a versatile quantum laboratory for experiments with ultracold atomic gases, but techniques to control atomic interactions and to generate entanglement have been unavailable so far. Here, the experimental generation of multi-particle entanglement on an atom chip is described. The technique is used to produce spin-squeezed states of a two-component Bose–Einstein condensate, which should be useful for quantum metrology.
- Max F. Riedel
- , Pascal Böhi
- & Philipp Treutlein
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Letter |
Nonlinear atom interferometer surpasses classical precision limit
The precision of interferometers — used in metrology and in the state-of-the-art time standard — is generally limited by classical statistics. Here it is shown that the classical precision limit can be beaten by using nonlinear atom interferometry with Bose–Einstein condensates.
- C. Gross
- , T. Zibold
- & M. K. Oberthaler
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Letter |
A trapped single ion inside a Bose–Einstein condensate
Until now, quantum atomic gases and single trapped ions have been treated separately in experiments. Now a hybrid system has been investigated, involving the immersion of a single trapped ion into a Bose–Einstein condensate of neutral atoms. The two systems could be controlled independently and the fundamental interaction processes were studied. Sympathetic cooling of the single ion by the condensate was observed, hinting at the possibility of using these condensates as refrigerators for ion-trap quantum computers.
- Christoph Zipkes
- , Stefan Palzer
- & Michael Köhl
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News & Views |
Golden ratio seen in a magnet
The golden ratio — an exact 'magic' number often claimed to be observed when taking ratios of distances in ancient and modern architecture, sculpture and painting — has been spotted in a magnetic compound.
- Ian Affleck
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News |
Are the Universe's secrets hiding on a chip?
Topological insulator could help to test quantum field theory.
- Geoff Brumfiel
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Letter |
Transmission of electrical signals by spin-wave interconversion in a magnetic insulator
An insulator does not conduct electricity, and so cannot in general be used to transmit an electrical signal. But an insulator's electrons possess spin in addition to charge, and so can transmit a signal in the form of a spin wave. Here a hybrid metal–insulator–metal structure is reported, in which an electrical signal in one metal layer is directly converted to a spin wave in the insulating layer; this wave is then transmitted to the second metal layer, where the signal can be directly recovered as an electrical voltage.
- Y. Kajiwara
- , K. Harii
- & E. Saitoh
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Review Article |
Electron liquids and solids in one dimension
- Vikram V. Deshpande
- , Marc Bockrath
- & Amir Yacoby
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Letter |
Superconductivity in alkali-metal-doped picene
The phenomenon of superconductivity continues to intrigue, and several new superconducting materials have been discovered in recent years — but in the case of organic superconductors, no new material system with a high superconducting transition temperature has been identified in the past decade. Now it has been shown that the introduction of potassium into crystals of organic molecule picene can yield superconductivity at temperatures as high as 18 K.
- Ryoji Mitsuhashi
- , Yuta Suzuki
- & Yoshihiro Kubozono
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Research Highlights |
Condensed matter: Cutting it fine
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Letter |
Above-room-temperature ferroelectricity in a single-component molecular crystal
Ferroelectrics are electro-active materials that can store and switch their polarity, sense temperature changes, interchange electric and mechanical functions, and manipulate light. Subtle changes in the topology of certain chemical bonds have long been identified as a possible route for achieving ferroelectricity in organic molecular crystals. Ferroelectricity above room temperature is now demonstrated by applying an electric field to coherently align the molecular polarities in crystalline croconic acid.
- Sachio Horiuchi
- , Yusuke Tokunaga
- & Yoshinori Tokura
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Letter |
Broken rotational symmetry in the pseudogap phase of a high-Tc superconductor
In the study of high-transition-temperature (high-Tc) copper oxide superconductors, a fundamental question is what symmetries are broken when the pseudogap phase sets in below a temperature T*. A large in-plane anisotropy of the Nernst effect is now observed in a high-Tc copper oxide superconductor that sets in precisely at T* throughout the doping phase diagram. It is concluded that the pseudogap phase is an electronic state that strongly breaks four-fold rotational symmetry.
- R. Daou
- , J. Chang
- & Louis Taillefer
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News & Views |
Membrane magic
The use of magnetic fields to assemble particles into membranes provides a powerful tool for exploring the physics of self-assembly and a practical method for synthesizing functional materials.
- Jack F. Douglas
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