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Nature Materials

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https://www.readbyqxmd.com/read/28805826/violation-of-ohm-s-law-in-a-weyl-metal
#1
Dongwoo Shin, Yongwoo Lee, M Sasaki, Yoon Hee Jeong, Franziska Weickert, Jon B Betts, Heon-Jung Kim, Ki-Seok Kim, Jeehoon Kim
Ohm's law is a fundamental paradigm in the electrical transport of metals. Any transport signatures violating Ohm's law would give an indisputable fingerprint for a novel metallic state. Here, we uncover the breakdown of Ohm's law owing to a topological structure of the chiral anomaly in the Weyl metal phase. We observe nonlinear I-V characteristics in Bi0.96Sb0.04 single crystals in the diffusive limit, which occurs only for a magnetic-field-aligned electric field (E∥B). The Boltzmann transport theory with the charge pumping effect reveals the topological-in-origin nonlinear conductivity, and it leads to a universal scaling function of the longitudinal magnetoconductivity, which completely describes our experimental results...
August 14, 2017: Nature Materials
https://www.readbyqxmd.com/read/28805825/the-processing-and-heterostructuring-of-silk-with%C3%A2-light
#2
Mehra S Sidhu, Bhupesh Kumar, Kamal P Singh
Spider silk is a tough, elastic and lightweight biomaterial, although there is a lack of tools available for non-invasive processing of silk structures. Here we show that nonlinear multiphoton interactions of silk with few-cycle femtosecond pulses allow the processing and heterostructuring of the material in ambient air. Two qualitatively different responses, bulging by multiphoton absorption and plasma-assisted ablation, are observed for low- and high-peak intensities, respectively. Plasma ablation allows us to make localized nanocuts, microrods, nanotips and periodic patterns with minimal damage while preserving molecular structure...
August 14, 2017: Nature Materials
https://www.readbyqxmd.com/read/28805824/flexible-shape-memory-scaffold-for-minimally-invasive-delivery-of-functional-tissues
#3
Miles Montgomery, Samad Ahadian, Locke Davenport Huyer, Mauro Lo Rito, Robert A Civitarese, Rachel D Vanderlaan, Jun Wu, Lewis A Reis, Abdul Momen, Saeed Akbari, Aric Pahnke, Ren-Ke Li, Christopher A Caldarone, Milica Radisic
Despite great progress in engineering functional tissues for organ repair, including the heart, an invasive surgical approach is still required for their implantation. Here, we designed an elastic and microfabricated scaffold using a biodegradable polymer (poly(octamethylene maleate (anhydride) citrate)) for functional tissue delivery via injection. The scaffold's shape memory was due to the microfabricated lattice design. Scaffolds and cardiac patches (1 cm × 1 cm) were delivered through an orifice as small as 1 mm, recovering their initial shape following injection without affecting cardiomyocyte viability and function...
August 14, 2017: Nature Materials
https://www.readbyqxmd.com/read/28805823/bronze-mean-hexagonal-quasicrystal
#4
Tomonari Dotera, Shinichi Bekku, Primož Ziherl
The most striking feature of conventional quasicrystals is their non-traditional symmetry characterized by icosahedral, dodecagonal, decagonal or octagonal axes. The symmetry and the aperiodicity of these materials stem from an irrational ratio of two or more length scales controlling their structure, the best-known examples being the Penrose and the Ammann-Beenker tiling as two-dimensional models related to the golden and the silver mean, respectively. Surprisingly, no other metallic-mean tilings have been discovered so far...
August 14, 2017: Nature Materials
https://www.readbyqxmd.com/read/28783161/phase-coexistence-and-electric-field-control-of-toroidal-order-in-oxide-superlattices
#5
A R Damodaran, J D Clarkson, Z Hong, H Liu, A K Yadav, C T Nelson, S-L Hsu, M R McCarter, K-D Park, V Kravtsov, A Farhan, Y Dong, Z Cai, H Zhou, P Aguado-Puente, P García-Fernández, J Íñiguez, J Junquera, A Scholl, M B Raschke, L-Q Chen, D D Fong, R Ramesh, L W Martin
Systems that exhibit phase competition, order parameter coexistence, and emergent order parameter topologies constitute a major part of modern condensed-matter physics. Here, by applying a range of characterization techniques, and simulations, we observe that in PbTiO3/SrTiO3 superlattices all of these effects can be found. By exploring superlattice period-, temperature- and field-dependent evolution of these structures, we observe several new features. First, it is possible to engineer phase coexistence mediated by a first-order phase transition between an emergent, low-temperature vortex phase with electric toroidal order and a high-temperature ferroelectric a1/a2 phase...
August 7, 2017: Nature Materials
https://www.readbyqxmd.com/read/28783160/measurement-of-the-spin-temperature-of-optically-cooled-nuclei-and-gaas-hyperfine-constants-in-gaas-algaas-quantum-dots
#6
E A Chekhovich, A Ulhaq, E Zallo, F Ding, O G Schmidt, M S Skolnick
Deep cooling of electron and nuclear spins is equivalent to achieving polarization degrees close to 100% and is a key requirement in solid-state quantum information technologies. While polarization of individual nuclear spins in diamond and SiC (ref. ) reaches 99% and beyond, it has been limited to 50-65% for the nuclei in quantum dots. Theoretical models have attributed this limit to formation of coherent 'dark' nuclear spin states but experimental verification is lacking, especially due to the poor accuracy of polarization degree measurements...
August 7, 2017: Nature Materials
https://www.readbyqxmd.com/read/28783159/oxide-superlattices-balancing-polar-vortices-and-stripes
#7
Matthew Dawber
No abstract text is available yet for this article.
August 7, 2017: Nature Materials
https://www.readbyqxmd.com/read/28783158/raman-spectroscopy-enhanced-by-organic-surfaces
#8
John R Lombardi
No abstract text is available yet for this article.
August 7, 2017: Nature Materials
https://www.readbyqxmd.com/read/28783157/nanostructured-organic-semiconductor-films-for-molecular-detection-with-surface-enhanced-raman-spectroscopy
#9
Mehmet Yilmaz, Esra Babur, Mehmet Ozdemir, Rebecca L Gieseking, Yavuz Dede, Ugur Tamer, George C Schatz, Antonio Facchetti, Hakan Usta, Gokhan Demirel
π-Conjugated organic semiconductors have been explored in several optoelectronic devices, yet their use in molecular detection as surface-enhanced Raman spectroscopy (SERS)-active platforms is unknown. Herein, we demonstrate that SERS-active, superhydrophobic and ivy-like nanostructured films of a molecular semiconductor, α,ω-diperfluorohexylquaterthiophene (DFH-4T), can be easily fabricated by vapour deposition. DFH-4T films without any additional plasmonic layer exhibit unprecedented Raman signal enhancements up to 3...
August 7, 2017: Nature Materials
https://www.readbyqxmd.com/read/28783156/hydrogels-with-precisely-controlled-integrin-activation-dictate-vascular-patterning-and%C3%A2-permeability
#10
Shuoran Li, Lina R Nih, Haylee Bachman, Peng Fei, Yilei Li, Eunwoo Nam, Robert Dimatteo, S Thomas Carmichael, Thomas H Barker, Tatiana Segura
Integrin binding to bioengineered hydrogel scaffolds is essential for tissue regrowth and regeneration, yet not all integrin binding can lead to tissue repair. Here, we show that through engineering hydrogel materials to promote α3/α5β1 integrin binding, we can promote the formation of a space-filling and mature vasculature compared with hydrogel materials that promote αvβ3 integrin binding. In vitro, α3/α5β1 scaffolds promoted endothelial cells to sprout and branch, forming organized extensive networks that eventually reached and anastomosed with neighbouring branches...
August 7, 2017: Nature Materials
https://www.readbyqxmd.com/read/28759034/microporous-polymers-ultrapermeable-membranes
#11
Yan Yin, Michael D Guiver
No abstract text is available yet for this article.
July 31, 2017: Nature Materials
https://www.readbyqxmd.com/read/28759033/one-pot-synthesis-of-silanol-free-nanosized-mfi%C3%A2-zeolite
#12
Julien Grand, Siddulu Naidu Talapaneni, Aurélie Vicente, Christian Fernandez, Eddy Dib, Hristiyan A Aleksandrov, Georgi N Vayssilov, Richard Retoux, Philippe Boullay, Jean-Pierre Gilson, Valentin Valtchev, Svetlana Mintova
The synthesis of nanostructured zeolites enables modification of catalytically relevant properties such as effective surface area and diffusion path length. Nanostructured zeolites may be synthesized either in alkaline media, and so contain significant numbers of hydrophilic silanol groups, or in expensive and harmful fluoride-containing media. Here, we report and characterize, using a combination of experimental and theoretical techniques, the one-pot synthesis of silanol-free nanosized MFI-type zeolites by introducing atomically dispersed tungsten; this prevents silanol group occurrence by forming flexible W-O-Si bridges...
July 31, 2017: Nature Materials
https://www.readbyqxmd.com/read/28759032/formation-of-porous-crystals-via-viscoelastic-phase-separation
#13
Hideyo Tsurusawa, John Russo, Mathieu Leocmach, Hajime Tanaka
Viscoelastic phase separation of colloidal suspensions can be interrupted to form gels either by glass transition or by crystallization. With a new confocal microscopy protocol, we follow the entire kinetics of phase separation, from homogeneous phase to different arrested states. For the first time in experiments, our results unveil a novel crystallization pathway to sponge-like porous crystal structures. In the early stages, we show that nucleation requires a structural reorganization of the liquid phase, called stress-driven ageing...
July 31, 2017: Nature Materials
https://www.readbyqxmd.com/read/28759031/modulation-of-thermal-and-thermoelectric-transport-in-individual-carbon-nanotubes-by-fullerene-encapsulation
#14
Takashi Kodama, Masato Ohnishi, Woosung Park, Takuma Shiga, Joonsuk Park, Takashi Shimada, Hisanori Shinohara, Junichiro Shiomi, Kenneth E Goodson
The potential impact of encapsulated molecules on the thermal properties of individual carbon nanotubes (CNTs) has been an important open question since the first reports of the strong modulation of electrical properties in 2002. However, thermal property modulation has not been demonstrated experimentally because of the difficulty of realizing CNT-encapsulated molecules as part of thermal transport microstructures. Here we develop a nanofabrication strategy that enables measurement of the impact of encapsulation on the thermal conductivity (κ) and thermopower (S) of single CNT bundles that encapsulate C 60, Gd@C 82 and Er 2@C 82...
July 31, 2017: Nature Materials
https://www.readbyqxmd.com/read/28759030/polymer-ultrapermeability-from-the-inefficient-packing-of-2d-chains
#15
Ian Rose, C Grazia Bezzu, Mariolino Carta, Bibiana Comesaña-Gándara, Elsa Lasseuguette, M Chiara Ferrari, Paola Bernardo, Gabriele Clarizia, Alessio Fuoco, Johannes C Jansen, Kyle E Hart, Thilanga P Liyana-Arachchi, Coray M Colina, Neil B McKeown
The promise of ultrapermeable polymers, such as poly(trimethylsilylpropyne) (PTMSP), for reducing the size and increasing the efficiency of membranes for gas separations remains unfulfilled due to their poor selectivity. We report an ultrapermeable polymer of intrinsic microporosity (PIM-TMN-Trip) that is substantially more selective than PTMSP. From molecular simulations and experimental measurement we find that the inefficient packing of the two-dimensional (2D) chains of PIM-TMN-Trip generates a high concentration of both small (<0...
July 31, 2017: Nature Materials
https://www.readbyqxmd.com/read/28740190/a-magnetic-topological-semimetal-sr1-ymn1-zsb2-y-z-0-1
#16
J Y Liu, J Hu, Q Zhang, D Graf, H B Cao, S M A Radmanesh, D J Adams, Y L Zhu, G F Cheng, X Liu, W A Phelan, J Wei, M Jaime, F Balakirev, D A Tennant, J F DiTusa, I Chiorescu, L Spinu, Z Q Mao
Weyl (WSMs) evolve from Dirac semimetals in the presence of broken time-reversal symmetry (TRS) or space-inversion symmetry. The WSM phases in TaAs-class materials and photonic crystals are due to the loss of space-inversion symmetry. For TRS-breaking WSMs, despite numerous theoretical and experimental efforts, few examples have been reported. In this Article, we report a new type of magnetic semimetal Sr1-yMn1-zSb2 (y, z < 0.1) with nearly massless relativistic fermion behaviour (m(∗) =  0.04 - 0.05m0, where m0 is the free-electron mass)...
July 24, 2017: Nature Materials
https://www.readbyqxmd.com/read/28714985/electrical-pumping-and-tuning-of-exciton-polaritons-in-carbon-nanotube-microcavities
#17
Arko Graf, Martin Held, Yuriy Zakharko, Laura Tropf, Malte C Gather, Jana Zaumseil
Exciton-polaritons are hybrid light-matter particles that form upon strong coupling of an excitonic transition to a cavity mode. As bosons, polaritons can form condensates with coherent laser-like emission. For organic materials, optically pumped condensation was achieved at room temperature but electrically pumped condensation remains elusive due to insufficient polariton densities. Here we combine the outstanding optical and electronic properties of purified, solution-processed semiconducting (6,5) single-walled carbon nanotubes (SWCNTs) in a microcavity-integrated light-emitting field-effect transistor to realize efficient electrical pumping of exciton-polaritons at room temperature with high current densities (>10 kA cm(-2)) and tunability in the near-infrared (1,060 nm to 1,530 nm)...
July 17, 2017: Nature Materials
https://www.readbyqxmd.com/read/28714984/carbon-nanotubes-wiry-matter-light-coupling
#18
Jeremy J Baumberg
No abstract text is available yet for this article.
July 17, 2017: Nature Materials
https://www.readbyqxmd.com/read/28714983/tunable-room-temperature-magnetic-skyrmions-in-ir-fe-co-pt-multilayers
#19
Anjan Soumyanarayanan, M Raju, A L Gonzalez Oyarce, Anthony K C Tan, Mi-Young Im, A P Petrović, Pin Ho, K H Khoo, M Tran, C K Gan, F Ernult, C Panagopoulos
Magnetic skyrmions are nanoscale topological spin structures offering great promise for next-generation information storage technologies. The recent discovery of sub-100-nm room-temperature (RT) skyrmions in several multilayer films has triggered vigorous efforts to modulate their physical properties for their use in devices. Here we present a tunable RT skyrmion platform based on multilayer stacks of Ir/Fe/Co/Pt, which we study using X-ray microscopy, magnetic force microscopy and Hall transport techniques...
July 17, 2017: Nature Materials
https://www.readbyqxmd.com/read/28714982/dynamic-surface-self-reconstruction-is-the-key-of-highly-active-perovskite-nano-electrocatalysts-for-water-splitting
#20
Emiliana Fabbri, Maarten Nachtegaal, Tobias Binninger, Xi Cheng, Bae-Jung Kim, Julien Durst, Francesco Bozza, Thomas Graule, Robin Schäublin, Luke Wiles, Morgan Pertoso, Nemanja Danilovic, Katherine E Ayers, Thomas J Schmidt
The growing need to store increasing amounts of renewable energy has recently triggered substantial R&D efforts towards efficient and stable water electrolysis technologies. The oxygen evolution reaction (OER) occurring at the electrolyser anode is central to the development of a clean, reliable and emission-free hydrogen economy. The development of robust and highly active anode materials for OER is therefore a great challenge and has been the main focus of research. Among potential candidates, perovskites have emerged as promising OER electrocatalysts...
July 17, 2017: Nature Materials
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