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https://www.readbyqxmd.com/read/29044098/ferrotoroidic-ground-state-in-a-heterometallic-cr-iii-dy-iii-6-complex-displaying-slow-magnetic-relaxation
#1
Kuduva R Vignesh, Alessandro Soncini, Stuart K Langley, Wolfgang Wernsdorfer, Keith S Murray, Gopalan Rajaraman
Toroidal quantum states are most promising for building quantum computing and information storage devices, as they are insensitive to homogeneous magnetic fields, but interact with charge and spin currents, allowing this moment to be manipulated purely by electrical means. Coupling molecular toroids into larger toroidal moments via ferrotoroidic interactions can be pivotal not only to enhance ground state toroidicity, but also to develop materials displaying ferrotoroidic ordered phases, which sustain linear magneto-electric coupling and multiferroic behavior...
October 18, 2017: Nature Communications
https://www.readbyqxmd.com/read/29041433/second-harmonic-generation-enhancement-from-a-nonlinear-nanocrystal-integrated-hyperbolic-metamaterial-cavity
#2
Wenyang Wu, Lingling Fan, Wenbo Zang, Xin Yang, Peng Zhan, Zhuo Chen, Zhenlin Wang
We theoretically investigate the dipolar whispering-gallery modes (WGMs) with different mode orders supported by spherical hyperbolic metamaterial (HMM) cavities consisting of alternating metal and dielectric layers. Associated with the excitations of the WGMs with the highest and the second highest mode orders, the HMM cavities are capable of creating highly enhanced and uniformly distributed local fields in the entire dielectric core region. Variation on the metal filling ratio allows for easily tuning the resonant wavelengths of WGMs over a wide spectral range...
September 4, 2017: Optics Express
https://www.readbyqxmd.com/read/28975150/ferroelectric-self-assembled-molecular-materials-showing-both-rectifying-and-switchable-conductivity
#3
Andrey V Gorbunov, Miguel Garcia Iglesias, Julia Guilleme, Tim D Cornelissen, W S Christian Roelofs, Tomas Torres, David González-Rodríguez, E W Meijer, Martijn Kemerink
Advanced molecular materials that combine two or more physical properties are typically constructed by combining different molecules, each being responsible for one of the properties required. Ideally, single molecules could take care of this combined functionality, provided they are self-assembled correctly and endowed with different functional subunits whose strong electronic coupling may lead to the emergence of unprecedented and exciting properties. We present a class of disc-like semiconducting organic molecules that are functionalized with strong dipolar side groups...
September 2017: Science Advances
https://www.readbyqxmd.com/read/28972785/change-the-collective-behaviors-of-colloidal-motors-by-tuning-electrohydrodynamic-flow-at-the-subparticle-level
#4
Xingfu Yang, Ning Wu
As demonstrated in biological systems, breaking the symmetry of surrounding hydrodynamic flow is the key to achieve autonomous locomotion of microscopic objects. In recent years, a variety of synthetic motors have been developed based on different propulsion mechanisms. Most work, however, focuses on the propulsion of individual motors. Here, we study the collective behaviors of colloidal dimers actuated by a perpendicularly applied AC electric field, which controls the electrohydrodynamic flow at subparticle levels...
October 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28961343/ultrafast-magnetization-manipulation-using-single-femtosecond-light-and-hot-electron-pulses
#5
Yong Xu, Marwan Deb, Grégory Malinowski, Michel Hehn, Weisheng Zhao, Stéphane Mangin
Current-induced magnetization manipulation is a key issue for spintronic applications. This manipulation must be fast, deterministic, and nondestructive in order to function in device applications. Therefore, single- electronic-pulse-driven deterministic switching of the magnetization on the picosecond timescale represents a major step toward future developments of ultrafast spintronic systems. Here, the ultrafast magnetization dynamics in engineered Gdx [FeCo]1-x -based structures are studied to compare the effect of femtosecond laser and hot-electron pulses...
September 29, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28957174/patterned-multilayer-metamaterial-for-fast-and-efficient-photon-collection-from-dipolar-emitters
#6
O A Makarova, M Y Shalaginov, S Bogdanov, A V Kildishev, A Boltasseva, V M Shalaev
Solid-state quantum emitters are prime candidates for the realization of fast, on-demand single-photon sources. The improvement in photon emission rate and collection efficiency for point-like emitters can be achieved by using a near-field coupling to nanophotonic structures. Plasmonic metamaterials with hyperbolic dispersion have previously been demonstrated to significantly increase the fluorescence decay rates from dipolar emitters due to a large broadband density of plasmonic modes supported by such metamaterials...
October 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28957111/electron-beam-excited-photon-emission-from-monopole-modes-of-a-plasmonic-nano-disc
#7
Xianglong Miao, Kai Guo, Cheng Qian, Jin Wang, Degang Zhao, Kin Hung Fung
Plasmonic dark modes are not easy to be observed in the far field due to their weak photon emission. By contrast, it has been shown that a dark mode can be excited effectively by a near-field source such as an electron beam. In this Letter, we show theoretically that the photon emission from the monopole-like dark mode supported on a plasmonic nano-disc could be unexpectedly strong when excited by an electron beam through its hole. Even though this monopole mode is considered to be dark, it is found that the emission can be even "brighter" than the dipolar bright modes when the electron speed is higher than 0...
September 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28957083/plasmon-coherence-determination-by-nanoscattering
#8
Yahong Chen, Andreas Norrman, Sergey A Ponomarenko, Ari T Friberg
We present a simple and robust protocol to recover the second-order field correlations of polychromatic, statistically stationary surface plasmon polaritons (SPPs) from a spectrum measurement in the far zone of a dipolar nanoscatterer. The recovered correlations carry comprehensive information about the spectral, spatial, and temporal coherence of the SPPs. We also introduce and exemplify for the first time, to the best of our knowledge, the two-point Stokes parameters associated with partially coherent SPP fields...
September 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28949743/quantum-fluctuations-in-quasi-one-dimensional-dipolar-bose-einstein-condensates
#9
D Edler, C Mishra, F Wächtler, R Nath, S Sinha, L Santos
Recent experiments have revealed that beyond-mean-field corrections are much more relevant in weakly interacting dipolar condensates than in their nondipolar counterparts. We show that in quasi-one-dimensional geometries quantum corrections in dipolar and nondipolar condensates are strikingly different due to the peculiar momentum dependence of the dipolar interactions. The energy correction of the condensate presents not only a modified density dependence, but it may even change from attractive to repulsive at a critical density due to the surprising role played by the transversal directions...
August 4, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28949736/frustrated-magnetism-of-dipolar-molecules-on-a-square-optical-lattice-prediction-of-a-quantum-paramagnetic-ground-state
#10
Haiyuan Zou, Erhai Zhao, W Vincent Liu
Motivated by the experimental realization of quantum spin models of polar molecule KRb in optical lattices, we analyze the spin 1/2 dipolar Heisenberg model with competing anisotropic, long-range exchange interactions. We show that, by tilting the orientation of dipoles using an external electric field, the dipolar spin system on square lattice comes close to a maximally frustrated region similar, but not identical, to that of the J_{1}-J_{2} model. This provides a simple yet powerful route to potentially realize a quantum spin liquid without the need for a triangular or kagome lattice...
August 4, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28938818/comparative-monte-carlo-simulations-of-charge-carrier-transport-in-amorphous-molecular-solids-as-given-by-three-most-common-models-of-disorder-the-dipolar-glass-the-gaussian-disorder-and-their-mix
#11
A P Tyutnev, S V Novikov, V S Saenko, E D Pozhidaev
We have performed Monte-Carlo simulations of the charge carrier transport in a model molecularly doped polymer using three most popular hopping theories (the dipolar glass model, the Gaussian disorder model, and an intermediate between them) in a wide range of applied electric fields and temperatures. Time of flight transients have been computed and analyzed in logarithmic coordinates to study the Poole-Frenkel field dependence, the non-Arrhenius mobility temperature dependence, and the nondispersive versus dispersive current shapes...
September 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28920118/hybrid-magnetic-iron-oxide-nanoparticles-with-tunable-field-directed-self-assembly
#12
Vikash Malik, Antara Pal, Olivier Pravaz, Jérôme J Crassous, Simon Granville, Bernard Grobety, Ann M Hirt, Hervé Dietsch, Peter Schurtenberger
We describe the synthesis of hybrid magnetic ellipsoidal nanoparticles that consist of a mixture of two different iron oxide phases, hematite (α-Fe2O3) and maghemite (γ-Fe2O3), and characterize their magnetic field-driven self-assembly. We demonstrate that the relative amount of the two phases can be adjusted in a continuous way by varying the reaction time during the synthesis, leading to strongly varying magnetic properties of the particles. Not only does the saturation magnetization increase dramatically as the composition of the spindles changes from hematite to maghemite, but also the direction of the induced magnetic moment changes from being parallel to the short axis of the spindle to being perpendicular to it...
October 5, 2017: Nanoscale
https://www.readbyqxmd.com/read/28912470/the-sensitivity-of-a-radical-pair-compass-magnetoreceptor-can-be-significantly-amplified-by-radical-scavengers
#13
Daniel R Kattnig, P J Hore
Birds have a remarkable ability to obtain navigational information from the Earth's magnetic field. The primary detection mechanism of this compass sense is uncertain but appears to involve the quantum spin dynamics of radical pairs formed transiently in cryptochrome proteins. We propose here a new version of the current model in which spin-selective recombination of the radical pair is not essential. One of the two radicals is imagined to react with a paramagnetic scavenger via spin-selective electron transfer...
September 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28894256/a-scaling-law-for-distinct-electrocaloric-cooling-performance-in-low-dimensional-organic-relaxor-and-anti-ferroelectrics
#14
Yuping Shi, Limin Huang, Ai Kah Soh, George J Weng, Shuangyi Liu, Simon A T Redfern
Electrocaloric (EC) materials show promise in eco-friendly solid-state refrigeration and integrable on-chip thermal management. While direct measurement of EC thin-films still remains challenging, a generic theoretical framework for quantifying the cooling properties of rich EC materials including normal-, relaxor-, organic- and anti-ferroelectrics is imperative for exploiting new flexible and room-temperature cooling alternatives. Here, we present a versatile theory that combines Master equation with Maxwell relations and analytically relates the macroscopic cooling responses in EC materials with the intrinsic diffuseness of phase transitions and correlation characteristics...
September 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28875033/exploring-the-salt-cocrystal-continuum-with-solid-state-nmr-using-natural-abundance-samples-implications-for-crystal-engineering
#15
Lalit Rajput, Manas Banik, Jayasubba Reddy Yarava, Sumy Joseph, Manoj Kumar Pandey, Yusuke Nishiyama, Gautam R Desiraju
There has been significant recent interest in differentiating multicomponent solid forms, such as salts and cocrystals, and, where appropriate, in determining the position of the proton in the X-H⋯A-YX(-)⋯H-A(+)-Y continuum in these systems, owing to the direct relationship of this property to the clinical, regulatory and legal requirements for an active pharmaceutical ingredient (API). In the present study, solid forms of simple cocrystals/salts were investigated by high-field (700 MHz) solid-state NMR (ssNMR) using samples with naturally abundant (15)N nuclei...
July 1, 2017: IUCrJ
https://www.readbyqxmd.com/read/28871959/dipolar-extracellular-potentials-generated-by-axonal-projections
#16
Thomas McColgan, Ji Liu, Paula Tuulia Kuokkanen, Catherine Emily Carr, Hermann Wagner, Richard Kempter
Extracellular field potentials (EFPs) are an important source of information in neuroscience, but their physiological basis is in many cases still a matter of debate. Axonal sources are typically discounted in modeling and data analysis because their contributions are assumed to be negligible. Here, we established experimentally and theoretically that contributions of axons to EFPs can be significant. Modeling action potentials propagating along axons, we showed that EFPs were prominent in the presence of terminal zones where axons branch and terminate in close succession, as found in many brain regions...
September 5, 2017: ELife
https://www.readbyqxmd.com/read/28867557/imaging-the-spatial-distribution-of-radiofrequency-field-sample-and-temperature-in-mas-nmr-rotor
#17
Hiroki Nagashima, Julien Trébosc, Olivier Lafon, Frédérique Pourpoint, Piotr Paluch, Marek J Potrzebowski, Jean-Paul Amoureux
We investigate using nutation experiments the spatial distribution of radiofrequency (rf) field, sample, temperature and cross-polarization transfer efficiency in 1.3 mm rotor. First, two-dimensional (2D) (1)H nutation experiments on silicone thin cylinders in the presence of B0 field gradient generated by shim coils are used to image the spatial distribution of rf field inside the rotor. These experiments show that the rf field is asymmetrical with respect to the center of the rotor. Moreover, they show the large inhomogeneity that still remains across the sample when using spacers, and that even in this case, the rf-field close to the drive cap is decreased to ca...
August 12, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28863524/nuclear-magnetic-relaxation-by-the-dipolar-emor-mechanism-multi-spin-systems
#18
Zhiwei Chang, Bertil Halle
In aqueous systems with immobilized macromolecules, including biological tissues, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have previously developed a rigorous EMOR relaxation theory for dipole-coupled two-spin and three-spin systems. Here, we extend the stochastic Liouville theory to four-spin systems and use these exact results as a guide for constructing an approximate multi-spin theory, valid for spin systems of arbitrary size...
August 28, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28862151/relaxation-dynamics-of-a-driven-two-level-system-coupled-to-a-bose-einstein-condensate-application-to-quantum-dot-dipolar-exciton-gas-hybrid-systems
#19
Vadim Mikhailovich Kovalev, Wang-Kong Tse
We develop a microscopic theory for the relaxation dynamics of an optically pumped two-level system (TLS) coupled to a bath of weakly interacting Bose gas. Using Keldysh formalism and diagrammatic perturbation theory, expressions for the relaxation times of the TLS Rabi oscillations are derived when the boson bath is in the normal state and the Bose-Einstein condensate (BEC) state. We apply our general theory to consider an irradiated quantum dot coupled with a boson bath consisting of a two-dimensional dipolar exciton gas...
September 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28844220/self-diffusion-studies-by-intra-and-inter-molecular-spin-lattice-relaxometry-using-field-cycling-liquids-plastic-crystals-porous-media-and-polymer-segments
#20
REVIEW
Rainer Kimmich, Nail Fatkullin
Field-cycling NMR relaxometry is a well-established technique for probing molecular dynamics in a frequency range from typically a few kHz up to several tens of MHz. For the interpretation of relaxometry data, it is quite often assumed that the spin-lattice relaxation process is of an intra-molecular nature so that rotational fluctuations dominate. However, dipolar interactions as the main type of couplings between protons and other dipolar species without quadrupole moments can imply appreciable inter-molecular contributions...
August 2017: Progress in Nuclear Magnetic Resonance Spectroscopy
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