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Philipp T Dumitrescu, Romain Vasseur, Andrew C Potter
We simulate the dynamics of a disordered interacting spin chain subject to a quasiperiodic time-dependent drive, corresponding to a stroboscopic Fibonacci sequence of two distinct Hamiltonians. Exploiting the recursive drive structure, we can efficiently simulate exponentially long times. After an initial transient, the system exhibits a long-lived glassy regime characterized by a logarithmically slow growth of entanglement and decay of correlations analogous to the dynamics at the many-body delocalization transition...
February 16, 2018: Physical Review Letters
Nikita P Kryuchkov, Stanislav O Yurchenko, Yury D Fomin, Elena N Tsiok, Valentin N Ryzhov
A transition from a square to a hexagonal lattice is studied in a 2D system of particles interacting via a core-softened potential. Due to the presence of two length scales of repulsion, different local configurations with four, five, and six neighbors are possible, leading to the formation of complex crystals. The previously proposed interpolation method is generalized to calculate pair correlations in crystals whose unit cell consists of more than one particle. The high efficiency of the method is illustrated using a snub square lattice as a representative example...
February 28, 2018: Soft Matter
Beth A Lindquist, Ryan B Jadrich, William Pineros, Thomas M Truskett
We discuss how a machine learning approach based on relative entropy optimization can be used as an inverse design strategy to discover isotropic pair interactions that self-assemble single- or multi-component particle systems into Frank-Kasper phases. In doing so, we also gain insights into self-assembly of quasicrystals.
February 27, 2018: Journal of Physical Chemistry. B
Junpeng Hou, Haiping Hu, Kuei Sun, Chuanwei Zhang
A quasicrystal is a class of ordered structures defying conventional classification of solid crystals and may carry classically forbidden (e.g., fivefold) rotational symmetries. In view of long-sought supersolids, a natural question is whether a superfluid can spontaneously form quasicrystalline order that is not possessed by the underlying Hamiltonian, forming "superfluid-quasicrystals." Here we show that a superfluid-quasicrystal stripe state with the minimal fivefold rotational symmetry can be realized as the ground state of a Bose-Einstein condensate within a practical experimental scheme...
February 9, 2018: Physical Review Letters
Zhiqing Yang, Lifeng Zhang, Matthew F Chisholm, Xinzhe Zhou, Hengqiang Ye, Stephen J Pennycook
Dislocations in crystals naturally break the symmetry of the bulk, introducing local atomic configurations with symmetries such as fivefold rings. But dislocations do not usually nucleate aperiodic structure along their length. Here we demonstrate the formation of extended binary quasicrystalline precipitates with Penrose-like random-tiling structures, beginning with chemical ordering within the pentagonal structure at cores of prismatic dislocations in Mg-Zn alloys. Atomic resolution observations indicate that icosahedral chains centered along [0001] pillars of Zn interstitial atoms are formed templated by the fivefold rings at dislocation cores...
February 23, 2018: Nature Communications
Daniel C Fredrickson
The structural diversity of intermetallic phases poses a great challenge to chemical theory and materials design. In this Account, two examples are used to illustrate how a focus on the most complex of these structures (and their relationships to simpler ones) can reveal how chemical principles underlie structure for broad families of compounds. First, we show how experimental investigations into the Fe-Al-Si system, inspired by host-guest like features in the structure of Fe25Al78Si20, led to a theoretical approach to deriving isolobal analogies between molecular and intermetallic compounds and a more general electron counting rule...
January 31, 2018: Accounts of Chemical Research
Ryan D Brown, Steven A Corcelli, S Alex Kandel
Traditionally, the goal of self-assembly and supramolecular chemistry is to engineer an equilibrium structure with a desired geometry and functionality; this is achieved through careful choice of molecular monomers, growth conditions, and substrate. Supramolecular assemblies produced under nonequilibrium conditions, in contrast, can form metastable structures with conformations quite different from those accessible in equilibrium self-assembly. The study of nonequilibrium growth of clusters potentially impacts the study of nucleation in atmospheric aerosols, nucleation in organic crystallization, and mesoscale organization for systems ranging from biological molecules to molecular electronics...
January 30, 2018: Accounts of Chemical Research
M Schmiedeberg, C V Achim, J Hielscher, S C Kapfer, H Löwen
We explore the growth of two-dimensional quasicrystals, i.e., aperiodic structures that possess long-range order, from two seeds at various distances and with different orientations by using dynamical phase-field crystal calculations. We compare the results to the growth of periodic crystals from two seeds. There, a domain border consisting of dislocations is observed in case of large distances between the seed and large angles between their orientation. Furthermore, a domain border is found if the seeds are placed at a distance that does not fit to the periodic lattice...
July 2017: Physical Review. E
K Kamiya, T Takeuchi, N Kabeya, N Wada, T Ishimasa, A Ochiai, K Deguchi, K Imura, N K Sato
Superconductivity is ubiquitous as evidenced by the observation in many crystals including carrier-doped oxides and diamond. Amorphous solids are no exception. However, it remains to be discovered in quasicrystals, in which atoms are ordered over long distances but not in a periodically repeating arrangement. Here we report electrical resistivity, magnetization, and specific-heat measurements of Al-Zn-Mg quasicrystal, presenting convincing evidence for the emergence of bulk superconductivity at a very low transition temperature of [Formula: see text] K...
January 11, 2018: Nature Communications
Joyce Pham, Fanqiang Meng, Matthew J Lynn, Tao Ma, Andreas Kreyssig, Matthew J Kramer, Alan I Goldman, Gordon J Miller
The irreversible transformation from an icosahedral quasicrystal (i-QC) CaAu4.39Al1.61 to its cubic 2/1 crystalline approximant (CA) Ca13Au56.31(3)Al21.69 (CaAu4.33(1)Al1.67, Pa ̅ 3(No. 205); Pearson symbol: cP728; a = 23.8934(4) Å), starting at ~570 ○C and complete by ~650 ○C, is discovered from in-situ, high-energy, variable-temperature powder X-ray diffraction (PXRD), thereby providing direct experimental evidence for the relationship between QCs and their associated CAs. The new cubic phase crystallizes in a Tsai-type approximant structure under the broader classification of polar intermetallic compounds, in which atoms of different electronegativities, viz...
December 29, 2017: Journal of the American Chemical Society
Qisheng Lin, Gordon J Miller
Intermetallic compounds represent an extensive pool of candidates for energy related applications stemming from magnetic, electric, optic, caloric, and catalytic properties. The discovery of novel intermetallic compounds can enhance understanding of the chemical principles that govern structural stability and chemical bonding as well as finding new applications. Valence electron-poor polar intermetallics with valence electron concentrations (VECs) between 2.0 and 3.0 e-/atom show a plethora of unprecedented and fascinating structural motifs and bonding features...
December 18, 2017: Accounts of Chemical Research
Insung Han, Xianghui Xiao, Ashwin J Shahani
How does a quasicrystal grow? Despite the decades of research that have been dedicated to this area of study, it remains one of the fundamental puzzles in the field of crystal growth. Although there has been no lack of theoretical studies on quasicrystal growth, there have been very few experimental investigations with which to test their various hypotheses. In particular, evidence of the in situ and three-dimensional (3D) growth of a quasicrystal from a parent liquid phase is lacking. To fill-in-the-gaps in our understanding of the solidification and melting pathways of quasicrystals, we performed synchrotron-based X-ray imaging experiments on a decagonal phase with composition of Al-15at%Ni-15at%Co...
December 12, 2017: Scientific Reports
Mengjie Zu, Peng Tan, Ning Xu
In traditional approaches to form quasicrystals, multiple competing length scales involved in particle size, shape, or interaction potential are believed to be necessary. It is unexpected that quasicrystals can be formed by monodisperse, isotropic particles interacting via a simple potential that does not contain explicit multiple length scales to stabilize quasicrystals. Here, we report the surprising finding of the formation of such quasicrystals in high-density systems of soft-core particles. Although there are length scales naturally introduced in our model systems, they do not establish the quasicrystalline order...
December 12, 2017: Nature Communications
A Dareau, E Levy, M Bosch Aguilera, R Bouganne, E Akkermans, F Gerbier, J Beugnon
Topological properties of crystals and quasicrystals is a subject of recent and growing interest. This Letter reports an experiment where, for certain quasicrystals, these properties can be directly retrieved from diffraction. We directly observe, using an interferometric approach, all of the topological invariants of finite-length Fibonacci chains in their diffraction pattern. We also quantitatively demonstrate the stability of these topological invariants with respect to structural disorder.
November 24, 2017: Physical Review Letters
Julius Oppenheim, Chi Ma, Jinping Hu, Luca Bindi, Paul J Steinhardt, Paul D Asimow
Five-component icosahedral quasicrystals with compositions in the range Al68-73 Fe11-16 Cu10-12 Cr1-4 Ni1-2 were recently recovered after shocking metallic CuAl5 and (Mg0.75 Fe0.25 )2 SiO4 olivine in a stainless steel 304 chamber, intended to replicate a natural shock that affected the Khatyrka meteorite. The iron in those quasicrystals might have originated either from reduction of Fe2+ in olivine or from the stainless steel chamber. In this study, we clarify the shock synthesis mechanism of icosahedral quasicrystals through two new shock recovery experiments...
November 15, 2017: Scientific Reports
J Oppenheim, C Ma, J Hu, L Bindi, P J Steinhardt, P D Asimow
The Khatyrka meteorite contains both icosahedral and decagonal quasicrystals. In our previous studies, icosahedral quasicrystals have been synthesized and recovered from shock experiments at the interface between CuAl5 and stainless steel 304 alloys. In this study, we report a new shock recovery experiment aimed at synthesizing decagonal quasicrystals similar to decagonite, natural Al71 Ni24 Fe5 . Aluminum 2024 and permalloy 80 alloys were stacked together and shocked in a stainless steel 304 recovery chamber...
November 15, 2017: Scientific Reports
Abdullah Sirindil, Marianne Quiquandon, Denis Gratias
An analysis is presented of the new types of defects that can appear in crystalline structures where the positions of the atoms and the unit cell belong to the same {\bb Z}-module, i.e. are irrational projections of an N > 3-dimensional (N-D) lattice Λ as in the case of quasicrystals. Beyond coherent irrationally oriented twins already discussed in a previous paper [Quiquandon et al. (2016). Acta Cryst. A72, 55-61], new two-dimensional translational defects are expected, the translation vectors of which, being projections of nodes of Λ, have irrational coordinates with respect to the unit-cell reference frame...
November 1, 2017: Acta Crystallographica. Section A, Foundations and Advances
M Valliammai, S Sivabalan
We report a polarization maintaining chalcogenide (ChG) photonic quasicrystal fiber (PQF) for wide-band mid-IR (MIR) supercontinuum (SC) generation. The numerical demonstration of SC generation in the proposed PQF spans from 2 to 15 μm wavelengths for a pulse power of 2 kW. Besides, the proposed PQF offers a high birefringence (10(-3) to 10(-2)) from 3.5 to 15 μm wavelengths and exhibits a low confinement loss (10(-7) to 10(-1)) for the wavelengths from 2 to 15 μm with single mode behavior. The proposed Ge11...
June 1, 2017: Applied Optics
Zongdai Liu, Rui Chen, Yanjun Liu, Xinhai Zhang, Xiaowei Sun, Wenbin Huang, Dan Luo
Organic microcavity lasers based on liquid crystals have attracted substantial attention due to their easy processing, compact volume and excellent tunable properties. However, the threshold of traditional holographic polymer dispersed liquid crystals (H-PDLCs) laser doped with dye is usually as high as several tens of μJ/pulse, which hinders its broad applications. Herein, we demonstrate a low-threshold lasing from quasicrystal based on H-PDLCs. An conjugated polymer poly (2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylenevinylene (MEH-PPV) film is coated on the inner surface of glass substrate to dramatically reduce the lasing threshold, which is 20 times lower than that of dye-doped microcavity laser...
September 4, 2017: Optics Express
Quanlong Yang, Jianqiang Gu, Yuehong Xu, Yanfeng Li, Xueqian Zhang, Zhen Tian, Chunmei Ouyang, Jiaguang Han, Weili Zhang
The control of light-matter interaction in metasurfaces offers an unexplored potential for the excitation and manipulation of light. Here, we combine experimental terahertz time-domain spectroscopy and near-field scanning terahertz microscopy to demonstrate the role of reciprocal vectors in the transmission and plasmonic resonances of quasicrystal metasurfaces. An investigation of two-dimensional metasurface structures with different rotationally symmetric quasicrystal arrangements demonstrates that the transmission minima resulting from Wood's anomaly are directly related to the surface plasmon resonances...
October 2, 2017: Optics Express
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