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1
Andreev, Pavel A. « Simultaneous dipole and quadrupole moment contribution in the Bogoliubov spectrum : Application of the non-integral Gross–Pitaevskii equation ». Modern Physics Letters B 31, no 13 (10 mai 2017) : 1750152. http://dx.doi.org/10.1142/s0217984917501524.
Texte intégralRésumé :
We present the Gross–Pitaevskii equation for Bose–Einstein condensates (BECs) possessing the electric dipole and the electric quadrupole moments in a non-integral form. These equations are coupled with the Maxwell equations. The model under consideration includes the dipole–dipole, the dipole–quadrupole, and the quadrupole–quadrupole interactions in terms of the electric field created by the dipoles and quadrupoles. We apply this model to obtain the Bogoliubov spectrum for three-dimensional BECs with a repulsive short-range interaction. We obtain an extra term in the Bogoliubov spectrum in comparison with the dipolar BECs. We show that the quadrupole–quadrupole interaction gives a positive contribution in the Bogoliubov spectrum. Hence, this spectrum is stable.
2
Khalyavin, Dmitry D., Roger D. Johnson, Fabio Orlandi, Paolo G. Radaelli, Pascal Manuel et Alexei A. Belik. « Emergent helical texture of electric dipoles ». Science 369, no 6504 (6 août 2020) : 680–84. http://dx.doi.org/10.1126/science.aay7356.
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Long-range ordering of magnetic dipoles in bulk materials gives rise to a broad range of magnetic structures, from simple collinear ferromagnets and antiferromagnets, to complex magnetic helicoidal textures stabilized by competing exchange interactions. In contrast, dipolar order in dielectric crystals is typically limited to parallel (ferroelectric) and antiparallel (antiferroelectric) collinear alignments of electric dipoles. Here, we report an observation of incommensurate helical ordering of electric dipoles by light hole doping of the quadruple perovskite BiMn7O12. In analogy with magnetism, the electric dipole helicoidal texture is stabilized by competing instabilities. Specifically, orbital ordering and lone electron pair stereochemical activity compete, giving rise to phase transitions from a nonchiral cubic structure to an incommensurate electric dipole and orbital helix via an intermediate density wave.
3
Kusmartsev, F. V., et M. Saarela. « Dipolar clusters and ferroelectricity in high Tc superconductors ». International Journal of Modern Physics B 29, no 25n26 (14 octobre 2015) : 1542002. http://dx.doi.org/10.1142/s0217979215420023.
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In this paper, we show that doping of hole charge carriers induces formation of resonance plaquettes (RPs) having electric dipolar moments and fluctuating stripes in cuprates. A single RP is created by many-body interactions between the dopant ion or a charge fluctuation outside and holes inside the CuO plane. In such a process, Coulomb interacting holes in the CuO plane are self-organized into four-particles resonance valence bond plaquettes bound with dopants or polarons located in the spacer layer between CuO planes. Such RPs have ordered and disordered phases. They are ordered into charge density waves (CDW) or stripes only at certain conditions. The lowest energy of the ordered phase corresponds to a local antiferroelectric ordering. The RPs mobility is very low at low temperatures and they are bound into dipole–dipole pairs. Electromagnetic radiation interacts strongly with RPs electric dipoles and when the sample is subjected to it, the mobility changes significantly. This leads to a fractal growth of dipolar RP clusters. The existence of electric dipoles and CDW reveal a series of new phenomena such as ferroelectricity, strong light and microwave absorption and the field induced superconductivity.
4
Chan, Chin Han, et Hans-Werner Kammer. « Characterization of polymer electrolytes by dielectric response using electrochemical impedance spectroscopy ». Pure and Applied Chemistry 90, no 6 (27 juin 2018) : 939–53. http://dx.doi.org/10.1515/pac-2017-0911.
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Abstract Authors present a phenomenological view on dielectric relaxation in polymer electrolytes, which is monitored by electrochemical impedance spectroscopy. Molecular interaction of polymer chains with salt molecules (or dipole-dipole interaction between segments and salt molecules) leads to dipolar molecular entities. Frequency-dependant impedance spectra are the key quantities of the interest for determination of electric properties of materials and their interfaces with conducting electrodes. Salt concentration serves as parameter. Bulk and interfacial properties of the samples are discussed in terms of impedance (Z*) and modulus (M*) spectra. We focus on two different classes of systems, i.e. high molar mass of poly(ethylene oxide) (PEO)+lithium perchlorate (LiClO4) (i.e. the inorganic salt) and epoxidized natural rubber (ENR-25) with 25 mol% of epoxide content+LiClO4. Impedance spectra with salt content as parameter tell us that we have interaction between dipolar entities leading to dispersion of relaxation times. However, as scaling relations show, dispersion of relaxation times does not depend on salt content in the PEO system. The relaxation peak for the imaginary part of electric modulus (M″) provides information on long-range motion of dipoles. Summarizing the results from imaginary part of impedance spectrum (Z″), tan δ (imaginary/real of permittivities) and M″ for the two systems under the discussion, PEO behaves like a mixture of chains with dipoles. There are interactions between the dipoles, but they are relaxing individually. Therefore, we see PEO-salt system as a polymer electrolyte where only a tiny fraction of added salt molecules becomes electrically active in promoting conductance. However, ENR-25-salt system behaves just as a macroscopic dipole and it can not display electrode polarization or electric relaxation because there is no mobility of individual dipoles. Hence, ENR-25-salt does not form a polymer electrolyte in the classic sense.
5
Tobias, William G., Kyle Matsuda, Jun-Ru Li, Calder Miller, Annette N. Carroll, Thomas Bilitewski, Ana Maria Rey et Jun Ye. « Reactions between layer-resolved molecules mediated by dipolar spin exchange ». Science 375, no 6586 (18 mars 2022) : 1299–303. http://dx.doi.org/10.1126/science.abn8525.
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Microscopic control over polar molecules with tunable interactions enables the realization of distinct quantum phenomena. Using an electric field gradient, we demonstrated layer-resolved state preparation and imaging of ultracold potassium-rubidium molecules confined to two-dimensional planes in an optical lattice. The rotational coherence was maximized by rotating the electric field relative to the light polarization for state-insensitive trapping. Spatially separated molecules in adjacent layers interact through dipolar spin exchange of rotational angular momentum; by adjusting these interactions, we regulated the local chemical reaction rate. The resonance width of the exchange process vastly exceeded the dipolar interaction energy, an effect attributed to thermal energy. This work realized precise control of interacting molecules, enabling electric field microscopy on subwavelength scales and allowing access to unexplored physics in two-dimensional systems.
6
Rosenberg, Itamar, Dror Liran, Yotam Mazuz-Harpaz, Kenneth West, Loren Pfeiffer et Ronen Rapaport. « Strongly interacting dipolar-polaritons ». Science Advances 4, no 10 (octobre 2018) : eaat8880. http://dx.doi.org/10.1126/sciadv.aat8880.
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Exciton-polaritons are mutually interacting quantum hybridizations of confined photons and electronic excitations. Here, we demonstrate a system of optically guided, electrically polarized exciton-polaritons (“dipolaritons”) that displays up to 200-fold enhancement of the polariton-polariton interaction strength compared to unpolarized polaritons. The magnitude of the dipolar interaction enhancement can be turned on and off and can be easily tuned over a very wide range by varying the applied polarizing electric field. The large interaction strengths and the very long propagation distances of these fully guided dipolaritons open up new opportunities for realizing complex quantum circuitry and quantum simulators, as well as topological states based on exciton-polaritons, for which the interactions between polaritons need to be large and spatially or temporally controlled. The results also raise fundamental questions on the origin of these large enhancements.
7
Shih, Chunyu, John J. Molina et Ryoichi Yamamoto. « Field-induced dipolar attraction between like-charged colloids ». Soft Matter 14, no 22 (2018) : 4520–29. http://dx.doi.org/10.1039/c8sm00395e.
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The field induced anisotropic interactions between like-charged colloidal particles is studied using direct numerical simulations, where the polarization of the electric double layer is explicitly computed under external AC electric fields.
8
Peshkovsky, Alexey, et Ann E. McDermott. « Dipolar Interactions in Molecules Aligned by Strong AC Electric Fields ». Journal of Magnetic Resonance 147, no 1 (novembre 2000) : 104–9. http://dx.doi.org/10.1006/jmre.2000.2167.
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Guerrero, Tomás, Rosa Santillan, Héctor García-Ortega, Omar G. Morales-Saavedra, Norberto Farfán et Pascal G. Lacroix. « Bis(4-nitroanilines) in interactions through a π-conjugated bridge : conformational effects and potential molecular switches ». New Journal of Chemistry 41, no 20 (2017) : 11881–90. http://dx.doi.org/10.1039/c7nj02622f.
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Freeman, G. R., L. D. Coulson et N. H. March. « On the Ehrenberg–Siday–Aharonov–Bohm (ESAB) and Aharonov–Casher (AC) Effects ». Modern Physics Letters B 12, no 22 (20 septembre 1998) : 933–42. http://dx.doi.org/10.1142/s0217984998001086.
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When an electron beam passes outside a confined magnetic flux, the motional magnetic field of the electrons overlaps the confined flux. The potential energy of the magnetic dipolar interaction of the motional magnetic field with the confined magnetic flux causes the velocity of the electrons to change slightly, which shifts the phase of the electron de Broglie wave. When portions of an electron beam pass on different sides of a confined flux and are then mixed, they produce an interference pattern. There is a similar magnetic dipolar interaction, with resulting velocity and phase changes, when a beam of magnetic particles interacts with the motional magnetic flux produced by their crossing a strong electric field. These are classical electromagnetic dipolar (not Lorentz) interactions that causes changes in Berry's geometrical phase, but are not ESAB or AC effects. Data that were suggested to demonstrate the ESAB and AC effects have been quantitatively interpreted in terms of motional magnetic fields and velocity changes.
11
Paczwa, Mateusz, Aleksej A. Sapiga, Marcin Olszewski, Nikolaj Sergeev et Aleksej V. Sapiga. « 23Na Nuclear Magnetic Resonance Study of the Structure and Dynamic of Natrolite ». Zeitschrift für Naturforschung A 70, no 4 (1 avril 2015) : 295–300. http://dx.doi.org/10.1515/zna-2014-0371.
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AbstractThe temperature dependences of nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR spectra of 23Na nuclei in natrolite (Na2Al2Si3O10·2H2O) have been studied. The temperature dependences of the spin-lattice relaxation times T1 in natrolite have also been studied. It has been shown that the spin-lattice relaxation of the 23Na is governed by the electric quadrupole interaction with the crystal electric field gradients modulated by translational motion of H2O molecules in the natrolite pores. The dipolar interactions with paramagnetic impurities become significant as a relaxation mechanism of the 23Na nuclei only at low temperature (<270 K).
12
Kowalczyk, Radoslaw M., Patrick J. Murphy et Jamie Tibble-Howlings. « Sensing Magnetic Field and Intermolecular Interactions in Diamagnetic Solution Using Residual Dipolar Couplings of Zephycandidine ». International Journal of Molecular Sciences 23, no 23 (1 décembre 2022) : 15118. http://dx.doi.org/10.3390/ijms232315118.
Texte intégralRésumé :
An unusual residual dipolar coupling of methylene protons was recorded in NMR spectra because aromatic zephycandidine has preferential orientation at the external magnetic field. The observed splitting contains contribution from the dipole–dipole D-coupling and the anisotropic component of J-coupling. Absolute values of the anisotropy of magnetic susceptibility |Δχax| are larger for protic solvents because of the hydrogen-bonding compared to aprotic solvents for which polar and dispersion forces are more important. The energy barrier for the reorientation due to hydrogen-bonding is 1.22 kJ/mol in methanol-d4, 0.85 kJ/mol in ethanol-d6 and 0.87 kJ/mol in acetic acid-d6. In dimethyl sulfoxide-d6, 1.08 kJ/mol corresponds to the interaction of solvent lone pair electrons with π-electrons of zephycandidine. This energy barrier decreases for acetone-d6 which has smaller electric dipole moment. In acetonitrile-d3, there is no energy barrier which suggests solvent ordering around the solute due to the solvent-solvent interactions. The largest absolute values of the magnetic anisotropy are observed for aromatic benezene-d6 and tolune-d8 which have their own preferential orientation and enhance the order in the solution. The magnetic anisotropy of “isolated” zephycandidine, not hindered by intermolecular interaction could be estimated from the correlation between Δχax and cohesion energy density.
13
Bentley, Nathan P., et Stephen J. Blundell. « The interaction between a positive muon and multiple quadrupolar nuclei ». Journal of Physics : Conference Series 2462, no 1 (1 mars 2023) : 012043. http://dx.doi.org/10.1088/1742-6596/2462/1/012043.
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Abstract A positively charged muon implanted in copper sits at an octahedral interstitial site and experiences a magnetic dipolar coupling with six nearest-neighbour quadrupolar I = 3/2 copper nuclei. The resulting avoided level crossing resonance observed as a function of magnetic field provides a means of studying these interactions and understanding the effect of the electric-field gradient due to the muon acting on the quadrupolar nuclei. The effect is usually modelled by considering the interaction between the positive muon and a single copper nucleus, but the other five copper nuclei are equally important. By solving the problem in the full 2(2I + 1)6 = 8192-dimensional Hilbert space, we demonstrate the effect of these additional interactions.
14
Yuan, Shaohua, Chaowei Sui, Jiyong Kang et Chenglong Jia. « Electric readout of Bloch sphere spanned by twisted magnon modes ». Applied Physics Letters 120, no 13 (28 mars 2022) : 132402. http://dx.doi.org/10.1063/5.0085775.
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We present a magnonic type of Bloch sphere based on twisted spin-wave (magnon) eigenmodes with opposite intrinsic orbital angular momentum, which is topology-protected and damping-resistant. Taking advantage of the release of the chiral degeneracy of magnons by dynamic dipolar interactions and/or interfacial Dzyaloshinskii–Moriya interactions in ferromagnetic nanodisks, we show how these magnonic “qubit” states can be precisely launched and electrically detected through combined spin pumping and inverse spin Hall effect. The experimental feasibility is verified using full-edged numerical micromagnetic simulations for FeB nanodisks. Our investigations demonstrate the potential of twisted spin waves for magnonic information encoding in a flexible and realizable approach.
15
Matsuda, Kyle, Luigi De Marco, Jun-Ru Li, William G. Tobias, Giacomo Valtolina, Goulven Quéméner et Jun Ye. « Resonant collisional shielding of reactive molecules using electric fields ». Science 370, no 6522 (10 décembre 2020) : 1324–27. http://dx.doi.org/10.1126/science.abe7370.
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Full control of molecular interactions, including reactive losses, would open new frontiers in quantum science. We demonstrate extreme tunability of ultracold chemical reaction rates by inducing resonant dipolar interactions by means of an external electric field. We prepared fermionic potassium-rubidium molecules in their first excited rotational state and observed a modulation of the chemical reaction rate by three orders of magnitude as we tuned the electric field strength by a few percent across resonance. In a quasi–two-dimensional geometry, we accurately determined the contributions from the three dominant angular momentum projections of the collisions. Using the resonant features, we shielded the molecules from loss and suppressed the reaction rate by an order of magnitude below the background value, thereby realizing a long-lived sample of polar molecules in large electric fields.
16
Mitra-Delmotte, Gargi, et Asoke Nath Mitra. « Softening the “Crystal Scaffold” for Life’s Emergence ». Physics Research International 2012 (21 février 2012) : 1–13. http://dx.doi.org/10.1155/2012/232864.
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Del Giudice’s group studies how water can organize on hydrophilic surfaces forming coherent domains (loaning energy from the quantum vacuum), plus quasifree electrons, whose excitations produce cold vortices, aligning to ambient fields. Their electric and magnetic dipolar modes can couple to oscillatory (electric-organic dipoles) and/or rotary (magnetic-mineral dipoles), besides responding to magnetic potentials. Thus, imprinted electromagnetic patterns of catalytic colloids—compared with Cairns-Smith’s “crystal scaffold”—on their structured water partners could have equipped the latter with a selection basis for “choosing” their context-based “soft-matter” (de Gennes) replacements. We consider the potential of the scenario of an external control on magnetic colloids forming in the Hadean hydrothermal setting (of Russell and coworkers)—via a magnetic rock field—conceptually enabling self-assembly, induction of asymmetries, response effects towards close-to-equilibrium dynamics, and associative networks, besides providing a coherent environment for stabilizing associated symmetry-broken quanta and their feedback interactions with those of coherent water domains, to address the emergence of metabolism and replication.
17
Schindewolf, Andreas, Roman Bause, Xing-Yan Chen, Marcel Duda, Tijs Karman, Immanuel Bloch et Xin-Yu Luo. « Evaporation of microwave-shielded polar molecules to quantum degeneracy ». Nature 607, no 7920 (27 juillet 2022) : 677–81. http://dx.doi.org/10.1038/s41586-022-04900-0.
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AbstractUltracold polar molecules offer strong electric dipole moments and rich internal structure, which makes them ideal building blocks to explore exotic quantum matter1–9, implement quantum information schemes10–12 and test the fundamental symmetries of nature13. Realizing their full potential requires cooling interacting molecular gases deeply into the quantum-degenerate regime. However, the intrinsically unstable collisions between molecules at short range have so far prevented direct cooling through elastic collisions to quantum degeneracy in three dimensions. Here we demonstrate evaporative cooling of a three-dimensional gas of fermionic sodium–potassium molecules to well below the Fermi temperature using microwave shielding. The molecules are protected from reaching short range with a repulsive barrier engineered by coupling rotational states with a blue-detuned circularly polarized microwave. The microwave dressing induces strong tunable dipolar interactions between the molecules, leading to high elastic collision rates that can exceed the inelastic ones by at least a factor of 460. This large elastic-to-inelastic collision ratio allows us to cool the molecular gas to 21 nanokelvin, corresponding to 0.36 times the Fermi temperature. Such cold and dense samples of polar molecules open the path to the exploration of many-body phenomena with strong dipolar interactions.
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Eichele, Klaus, et Arnd-Rüdiger Grimmer. « Phosphorus-31 and vanadium-51 solid-state nuclear magnetic resonance spectroscopy of β-vanadyl phosphate — Effects of homo- and heteronuclear spin-spin, electrostatic, and paramagnetic interactions ». Canadian Journal of Chemistry 89, no 7 (juillet 2011) : 870–84. http://dx.doi.org/10.1139/v11-025.
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Field-dependent 31P solid-state NMR studies demonstrate that the line shape in spectra of β-VOPO4 depends on 51V–31P direct and indirect spin-spin interactions (M2 (51V, 31P) = 101(23) × 106 rad2 s–2, 2Jiso (51V, 31P) = 48(5) Hz) and, to a lesser extent, on 31P chemical shift anisotropy (δiso = –10.4(2), Ω = δ11 – δ33 = 22(2) ppm) and 31P–31P interactions (M2 (31P, 31P) = 6.7(1) × 106 rad2 s–2). In contrast, homonuclear dipolar interactions play an important role for the field and spinning rate dependent 31P spin-lattice relaxation via paramagnetic impurities (T1 = 20–60 s). Vanadium-51 magic-angle spinning NMR spectra indicate a sizeable chemical shift anisotropy (δiso = –754(1), δ11 = –336(10), δ22 = –344(6), δ33 = –1581(8) ppm) and nuclear quadrupole interaction (χ = 1.5(1) MHz, η = 0.35(5)); the principal axis systems of both interactions are clearly not coincident, with an angle of 35(5)° between the greatest component of the electric field gradient tensor and δ33.
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Trpišová, B., et J. A. Brown. « Ordering of Dipoles in Different Types of Microtubule Lattice ». International Journal of Modern Physics B 12, no 05 (20 février 1998) : 543–78. http://dx.doi.org/10.1142/s0217979298000338.
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Microtubules (MTs) are the largest protein polymers in the cytoskeleton of eucaryotic cells in which they perform various functions. They are important in cell division, cell movement, they seem to be the devices through which are transferred signals in the nervous system. In this paper we continued to investigate the hypothesis that MTs can be viewed as assemblies of dipoles which are carried by the MT subunits, tubulin heterodimers. These assemblies were studied by means of the two-dimensional Ising model for both the A- and B-type arrangements of the tubulin subunits in a MT and the number of protofilaments 12, 13 and 14. We found that depending on these parameters and the magnitudes and orientations of the dipoles a MT may be at body temperature in an ordered phase or in a phase characterized by a random configuration of dipoles. The type of the ordered phase is determined by the above parameters as well, and it can be ferroelectric, antiferroelectric or ferrielectric. The dipolar ordering also depends on the presence of microtubule associated proteins, assuming that they can locally alter the dipolar interactions by binding to a MT, and external electric fields. The model presented here started by Tuszyński1–3 can be one of the first steps in the theoretical investigation of the electromagnetic features of MTs and their role in the MT behavior.
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Holland, Connor M., Yukai Lu et Lawrence W. Cheuk. « On-demand entanglement of molecules in a reconfigurable optical tweezer array ». Science 382, no 6675 (8 décembre 2023) : 1143–47. http://dx.doi.org/10.1126/science.adf4272.
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Entanglement is crucial to many quantum applications, including quantum information processing, quantum simulation, and quantum-enhanced sensing. Because of their rich internal structure and interactions, molecules have been proposed as a promising platform for quantum science. Deterministic entanglement of individually controlled molecules has nevertheless been a long-standing experimental challenge. We demonstrate on-demand entanglement of individually prepared molecules. Using the electric dipolar interaction between pairs of molecules prepared by using a reconfigurable optical tweezer array, we deterministically created Bell pairs of molecules. Our results demonstrate the key building blocks needed for quantum applications and may advance quantum-enhanced fundamental physics tests that use trapped molecules.
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Ma, Fuduo, Sijia Wang, David T. Wu et Ning Wu. « Electric-field–induced assembly and propulsion of chiral colloidal clusters ». Proceedings of the National Academy of Sciences 112, no 20 (4 mai 2015) : 6307–12. http://dx.doi.org/10.1073/pnas.1502141112.
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Chiral molecules with opposite handedness exhibit distinct physical, chemical, or biological properties. They pose challenges as well as opportunities in understanding the phase behavior of soft matter, designing enantioselective catalysts, and manufacturing single-handed pharmaceuticals. Microscopic particles, arranged in a chiral configuration, could also exhibit unusual optical, electric, or magnetic responses. Here we report a simple method to assemble achiral building blocks, i.e., the asymmetric colloidal dimers, into a family of chiral clusters. Under alternating current electric fields, two to four lying dimers associate closely with a central standing dimer and form both right- and left-handed clusters on a conducting substrate. The cluster configuration is primarily determined by the induced dipolar interactions between constituent dimers. Our theoretical model reveals that in-plane dipolar repulsion between petals in the cluster favors the achiral configuration, whereas out-of-plane attraction between the central dimer and surrounding petals favors a chiral arrangement. It is the competition between these two interactions that dictates the final configuration. The theoretical chirality phase diagram is found to be in excellent agreement with experimental observations. We further demonstrate that the broken symmetry in chiral clusters induces an unbalanced electrohydrodynamic flow surrounding them. As a result, they rotate in opposite directions according to their handedness. Both the assembly and propulsion mechanisms revealed here can be potentially applied to other types of asymmetric particles. Such kinds of chiral colloids will be useful for fabricating metamaterials, making model systems for both chiral molecules and active matter, or building propellers for microscale transport.
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Tao, R. « Apply the Electrorheological Effect to Produce Three-Dimensional Photonic Crystals for Laser Applications ». International Journal of Modern Physics B 13, no 14n16 (30 juin 1999) : 2189–96. http://dx.doi.org/10.1142/s0217979299002307.
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We have applied the electrorheological (ER) effect to produce three-dimensional (3-D) photonic crystals for laser applications. When polyester resin is in a strong electric field, bubbles are generated as a result of a chemical reaction. Because the resin has much high dielectric constant and conductivity than that of the bubbles, the bubbles are negatively polarized. Strong dipolar interactions force the bubbles align in the field direction to form chains and aggregate into a body-centered tetragonal lattice. This crystallization process can be controlled by varying the electric field strength, temperature, and amount of hardener. The final product, a 3-D photonic crystal, has good optical properties for laser applications.
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PRÉVOT, GEOFFROY, et BERNARD CROSET. « EQUILIBRIUM CONFIGURATIONS OF TWO-DIMENSIONAL STRESSED DOMAINS ON THE SURFACE OF ISOTROPIC AND CUBIC CRYSTALS ». Surface Review and Letters 16, no 04 (août 2009) : 545–62. http://dx.doi.org/10.1142/s0218625x09012925.
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In this paper, we derive analytical formulations of the elastic energy of a stressed domain on a crystalline substrate. Taking care of the singularity of the elastic Green function at r = 0, we obtain a universal expression for the isotropic case. By using the analogy between electric dipolar and elastic interactions, we developed similar analytical calculations for the (001) surface of a cubic crystal. We showed that the anisotropy of the boundary energy and the anisotropy of the substrate govern the shape of the domains, favoring either compact shapes or stripe configurations. The analytical approach adopted in this paper also allows us to discuss the role of elastic anisotropy for the existence of attractive interactions between domains.
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Park, Jae Sung, et David Saintillan. « Direct Numerical Simulations of Electrophoretic Deposition of Charged Colloidal Suspensions ». Key Engineering Materials 507 (mars 2012) : 47–51. http://dx.doi.org/10.4028/www.scientific.net/kem.507.47.
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Motivated by applications in the field of nanomanufacturing, we perform large-scale numerical simulations of the electrophoretic deposition of suspensions of charged colloids in an electrolyte. A simulation method is developed to model the full deposition process that captures linear electrophoresis, dipolar interactions, van-der-Waals forces, steric interactions, Brownian motion, as well as electric and hydrodynamic interactions with the electrodes. Using a fast algorithm, suspensions of up to 5,000 particles are simulated, and results are reported for the final deposit microstructure as a function of field strength. The simulation results demonstrate that regular crystalline colloidal assemblies are obtained at low field strengths and volume fractions, while more random structures with frequent defects are formed in stronger fields and at higher volume fractions, in agreement with recent deposition experiments.
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Zuckermann, M. J., A. Georgallas et D. A. Pink. « The effect of electrostatic interactions and water polarization on the properties of charged lipid membranes : a theoretical approach ». Canadian Journal of Physics 63, no 9 (1 septembre 1985) : 1228–34. http://dx.doi.org/10.1139/p85-201.
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We describe the physical properties of a planar interface between an electrolyte and a charged lipid membrane. The model differs from the usual Gouy–Chapman–Debye–Huckel theory for electrolytes in that the dipolar nature of the water molecules is explicitly included. The polarization, dielectric constant, and electric potential of the electrolyte are calculated as functions of distance from the interface. The change in gel – liquid-crystal transition temperature is obtained as a function of pH and salt concentration from the free energy of the system. The results are compared to previous calculations using the Gouy–Chapman–Debye–Huckel theory and to experimental data for dimyristoyl-methylphosphoric acid.
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Shen, Fei, Ning An, Yifei Tao, Hongping Zhou, Zhaoneng Jiang et Zhongyi Guo. « Anomalous forward scattering of gain-assisted dielectric shell-coated metallic core spherical particles ». Nanophotonics 6, no 5 (9 décembre 2016) : 1063–72. http://dx.doi.org/10.1515/nanoph-2016-0141.
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AbstractWe have investigated the scattering properties of an individual core-shell nanoparticle using the Mie theory, which can be tuned to support both electric and magnetic modes simultaneously. In general, the suppression of forward scattering can be realized by the second Kerker condition. Here, a novel mechanism has to be adopted to explain zero-forward scattering, which originates from the complex interactions between dipolar and quadrupolar modes. However, for lossy and lossless core-shell spherical nanoparticles, zero-forward scattering can never be achieved because the real parts of Mie expansion coefficients are always positive. By adding proper gain in dielectric shell, zero-forward scattering can be found at certain incident wavelengths, which means that all electric and magnetic responses in Mie scattering can be counteracted totally in the forward direction. In addition, if the absolute values of dipolar and quadrupolar terms are in the same order of magnitude, the local scattering minimum and maximum can be produced away from the forward and backward directions due to the interacting effect between the dipolar and quadrupolar terms. Furthermore, by adding suitable gain in shell, super-forward scattering can also be realized at certain incident wavelengths. We also demonstrated that anomalously weak scattering or superscattering could be obtained for the core-shell nanoparticles with suitable gain in shell. In particular, for such a choice of suitable gain in shell, we can obtain zero-forward scattering and anomalously weak scattering at the same wavelength as well as super-forward scattering at another wavelength. These features may provide new opportunities for cloaking, plasmonic lasers, optical antennas, and so on.
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YETHIRAJ, ANAND, et ALFONS VAN BLAADEREN. « MONODISPERSE COLLOIDAL SUSPENSIONS OF SILICA AND PMMA SPHERES AS MODEL ELECTRORHEOLOGICAL FLUIDS : A REAL-SPACE STUDY OF STRUCTURE FORMATION ». International Journal of Modern Physics B 16, no 17n18 (20 juillet 2002) : 2328–33. http://dx.doi.org/10.1142/s0217979202012311.
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Colloidal particle coordinates in three dimensions can be obtained in 3D samples with a combination of the increased resolution and optical sectioning capabilities of confocal microscopy and fluorescently labeled model core-shell silica colloids. In this work we show how this capability can be used to analyze structure formation in electrorheological fluids on a quantitative basis. We find body-centered-tetragonal (BCT) crystals for colloidal particles in an electric field. Metastable sheet like structures were identified as an intermediate phase prior to BCT crystal formation. Due to finite-size effects induced by the electrode surface the sheets are not randomly oriented, but grow preferentially with a 60° tilt with respect to the electric field. Preliminary measurements indicate that flow-aligned sheets form under shear. Finally, we show that in the case that the ionic strength is very low, electric-field-induced dipolar interactions can be present in addition to long-range repulsions between the colloids leading to interesting metastable and equilibrium structures with possibilities for applications in photonic bandgap crystals as well as in model ER studies.
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Singh, Charu, et Nirat Ray. « Micromagnetic Simulations of Emergent Monopole Defects and Magnetization Reversal in Connected and Dipolar Kagome Artificial Spin Ice ». Journal of Physics : Conference Series 2518, no 1 (1 juin 2023) : 012017. http://dx.doi.org/10.1088/1742-6596/2518/1/012017.
Texte intégralRésumé :
Abstract Artificial spin ice (ASI) materials, created by lithographically patterning nanoscale magnets in desired geometries, have shown a number of interesting phenomena, such as emergent magnetic monopoles (monopole defects), collective dynamics and phase transitions. The control of monopole defects with external stimuli such as magnetic and electric fields, strain, electric currents etc. would be of much interest in fabrication of future devices. In this work, we investigate the magnetization reversal as a function of the connectivity of the Kagome ASI, using micromagnetic simulations. The domain wall motion is expected to play an important role in the connected spin ice, whereas the dipolar interactions dominate for the unconnected case. The magnetic microstate of each lattice is uniquely determined by the vertex configuration, with the Kagome lattice supporting a six-fold-degenerate vertex state, obeying either a two-in/one-out (vertex charge +q) or one-in/two-out (vertex charge q) ice rule. We analyze the fraction of each vertex type to highlight changes in the magnetic microstate as a function of applied magnetic field. Our results could be correlated with magneto-transport measurements and direct imaging of vertex states in ASI using magnetic force microscopy.
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Wang, Ming Wen, Niann I. Yu et Wen Hao Liao. « Aligned MWCNT-Reinforced Bulk Epoxy-Matrix Composites by Dielectrophoretic Force ». Advanced Materials Research 538-541 (juin 2012) : 2224–31. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.2224.
Texte intégralRésumé :
Studies have proved that enhancing epoxy matrices by adding carbon nanotubes to form structural reinforcements has significantly improved mechanical properties at very low carbon nanotube loading. That mechanical properties of aligned composites are better than those of random ones has been demonstrated in past studies; however, alignment is not easy to achieve in carbon nanotube epoxy-matrix bulk composite by conventional techniques. In this study, epoxy-matrix bulk composites reinforced by aligned multi-walled carbon nanotubes (MWCNTs) are prepared using an RF electric field to elicit dipolar interactions among the nanotubes in a viscous matrix following immobilization by curing under continuous application of an anisotropic electric field and the fracture toughness is experimentally characterized later. The processes of actively aligned MWCNTs epoxy-matrix bulk composite were controlled as a function of CNT weight fraction, the frequency of dielectrophoretic field and processing time. Carbon nanotubes are not only aligned along the field but also migrate laterally to enhance thickness. Eventually, addition of nanotubes improved the mechanical properties of the MWCNT/epoxy bulk composites, and the increase in the flexural modulus and fracture toughness with the aligned nanotube composite is two times greater than the improvement for the randomly oriented composite.
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Wang, Ming Wen. « Alignment and Surface Modification of Multiwall Carbon Nanotubes Polymeric Composites ». Advanced Materials Research 881-883 (janvier 2014) : 872–81. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.872.
Texte intégralRésumé :
Polymer matrices add carbon nanotubes have significantly improved mechanical and electrical properties at very low carbon nanotube loading. That mechanical and electrical properties of aligned composites are better than those of random ones has been demonstrated in past studies. The non-conductive barriers of surface contaminants and weakly bound polymer layers will deform on the surface of composite resulted from the effects of micro gravity and oxidization. Addition of the adaptive plasma modification makes improvement in the surface properties of the composites is necessary. In this study, we actively align and network multiwall carbon nanotubes (MWCNTs) in a polymer matrix, then adopt O2/CF4radio frequency (RF) plasma to modify the surface of polymeric composite. MWCNTs were aligned using an AC electric field to elicit dipolar interactions among the nanotubes in a viscous matrix following immobilization by curing under continuous application of an anisotropic electric field, and the barriers of surface contaminants and weakly bound polymer layers can be reduced to the smallest degree or eliminated by RF plasma modification. Consequently, the MWCNTs polymeric composite amplify the flexural modulus, wear resistance, and electrical conductivity in the reality.
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Massana-Cid, Helena, Antonio Ortiz-Ambriz, Andrej Vilfan et Pietro Tierno. « Emergent collective colloidal currents generated via exchange dynamics in a broken dimer state ». Science Advances 6, no 10 (mars 2020) : eaaz2257. http://dx.doi.org/10.1126/sciadv.aaz2257.
Texte intégralRésumé :
Controlling the flow of matter down to micrometer-scale confinement is of central importance in material and environmental sciences, with direct applications in nano and microfluidics, drug delivery, and biotechnology. Currents of microparticles are usually generated with external field gradients of different nature (e.g., electric, magnetic, optical, thermal, or chemical ones), which are difficult to control over spatially extended regions and samples. Here, we demonstrate a general strategy to assemble and transport polarizable microparticles in fluid media through combination of confinement and magnetic dipolar interactions. We use a homogeneous magnetic modulation to assemble dispersed particles into rotating dimeric state and frustrated binary lattices, and generate collective currents that arise from a novel, field-synchronized particle exchange process. These dynamic states are similar to cyclotron and skipping orbits in electronic and molecular systems, thus paving the way toward understanding and engineering similar processes at different length scales across condensed matter.
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ANDREEV, PAVEL A. « NONINTEGRAL FORM OF THE GROSS–PITAEVSKII EQUATION FOR POLARIZED MOLECULES ». Modern Physics Letters B 27, no 13 (10 mai 2013) : 1350096. http://dx.doi.org/10.1142/s0217984913500966.
Texte intégralRésumé :
The Gross–Pitaevskii equation for polarized molecules is an integro-differential equation, consequently it is complicated for solving. We find a possibility to represent it as a nonintegral nonlinear Schrödinger equation, but this equation should be coupled with two linear equations describing the electric field. These two equations are the Maxwell equations. We recapture the dispersion of collective excitations in the three-dimensional electrically polarized BEC with no evolution of the electric dipole moment directions. We trace the contribution of the electric dipole moment. We explicitly consider the contribution of the electric dipole moment in the interaction constant for the short-range interaction. We show that the spectrum of dipolar BEC does not reveal instability at repulsive short-range interaction. Nonlinear excitations are also considered. We present dependence of the bright soliton characteristics on the electric dipole moment.
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Juusola, Liisa, Sanni Hoilijoki, Yann Pfau-Kempf, Urs Ganse, Riku Jarvinen, Markus Battarbee, Emilia Kilpua, Lucile Turc et Minna Palmroth. « Fast plasma sheet flows and X line motion in the Earth's magnetotail : results from a global hybrid-Vlasov simulation ». Annales Geophysicae 36, no 5 (10 septembre 2018) : 1183–99. http://dx.doi.org/10.5194/angeo-36-1183-2018.
Texte intégralRésumé :
Abstract. Fast plasma flows produced as outflow jets from reconnection sites or X lines are a key feature of the dynamics in the Earth's magnetosphere. We have used a polar plane simulation of the hybrid-Vlasov model Vlasiator, driven by steady southward interplanetary magnetic field and fast solar wind, to study fast plasma sheet ion flows and related magnetic field structures in the Earth's magnetotail. In the simulation, lobe reconnection starts to produce fast flows after the increasing pressure in the lobes has caused the plasma sheet to thin sufficiently. The characteristics of the earthward and tailward fast flows and embedded magnetic field structures produced by multi-point tail reconnection are in general agreement with spacecraft measurements reported in the literature. The structuring of the flows is caused by internal processes: interactions between major X points determine the earthward or tailward direction of the flow, while interactions between minor X points, associated with leading edges of magnetic islands carried by the flow, induce local minima and maxima in the flow speed. Earthward moving flows are stopped and diverted duskward in an oscillatory (bouncing) manner at the transition region between tail-like and dipolar magnetic fields. Increasing and decreasing dynamic pressure of the flows causes the transition region to shift earthward and tailward, respectively. The leading edge of the train of earthward flow bursts is associated with an earthward propagating dipolarization front, while the leading edge of the train of tailward flow bursts is associated with a tailward propagating plasmoid. The impact of the dipolarization front with the dipole field causes magnetic field variations in the Pi2 range. Major X points can move either earthward or tailward, although tailward motion is more common. They are generally not advected by the ambient flow. Instead, their velocity is better described by local parameters, such that an X point moves in the direction of increasing reconnection electric field strength. Our results indicate that ion kinetics might be sufficient to describe the behavior of plasma sheet bulk ion flows produced by tail reconnection in global near-Earth simulations. Keywords. Magnetospheric physics (magnetospheric configuration and dynamics; plasma sheet) – space plasma physics (numerical simulation studies)
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Lucier, Bryan E. G., Alex R. Reidel et Robert W. Schurko. « Multinuclear solid-state NMR of square-planar platinum complexes — Cisplatin and related systems ». Canadian Journal of Chemistry 89, no 7 (juillet 2011) : 919–37. http://dx.doi.org/10.1139/v11-033.
Texte intégralRésumé :
Multinuclear solid-state nuclear magnetic resonance (SSNMR) experiments have been performed on cisplatin and four related square-planar compounds. The wideband uniform rate smooth truncation – Carr–Purcell–Meiboom–Gill (WURST–CPMG) pulse sequence was utilized in NMR experiments to acquire 195Pt, 14N, and 35Cl ultra-wideline NMR spectra of high quality. Standard Hahn-echo and magic-angle spinning 195Pt NMR experiments are also performed to refine extracted chemical shielding (CS) tensor parameters. Platinum magnetic shielding (MS) tensor orientations are calculated using both plane-wave density functional theory (DFT) and standard DFT methods. The tensor orientations are shown to be highly constrained by molecular symmetry elements, but also influenced to some degree by intermolecular interactions. 14N WURST–CPMG experiments were performed on three compounds and electric field gradient (EFG) parameters (the quadrupolar coupling constant, CQ, and the asymmetry parameter, ηQ) are reported. First principles calculations of the 14N EFG tensor parameters and orientations and affirm their dependence on the local hydrogen bonding environment. 35Cl WURST–CPMG experiments on cisplatin and transplatin are reported, using two different static magnetic fields to extract EFG and CS tensor parameters, and 35Cl EFG tensor magnitudes and orientations are predicted using first principles calculations. Transverse (T2) relaxation data for all nuclei are used to investigate heteronuclear dipolar relaxation mechanisms, as well as the nature of the local hydrogen bonding environments.
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Kang, Yongqiang, Jialin Zhang, Zhipeng Shi, Xuhong Pu, Shuaibing Li et Hongwei Li. « A Novel Mutual-Coupling Dipole Model Considering the Interactions between Particles ». Coatings 12, no 8 (30 juillet 2022) : 1079. http://dx.doi.org/10.3390/coatings12081079.
Texte intégralRésumé :
The interactions between two or more particles and the calculation of the local electric field are widely applied in many fields, such as those of insulation, biology, medicine, and microfluidics. The dipole approximation model, which is a classical electric field calculation method, has been widely used in many fields to solve for the local electric field in a multi-particle system, but it does not consider the interactions between particles; as a result, it is easily limited by the calculation situation, and it generates a large calculation error when the distance between particles is small. Based on the physical essence of an interaction between two particles, a concept of the mutual-coupling dipole moment caused by the interactions between particles is defined for the first time. Moreover, by combining the calculation process of the dipole moment and the electric field of polarization, a novel mutual-coupling dipole model considering the interactions between particles is proposed in this paper, and analytical expressions of the local electric field that consider the interaction between two particles are obtained, thus compensating for the large error in the electric field calculation caused by the dipole approximation model when the distance between particles is small. In this paper, a mutual-coupling dipole model considering particle interactions is proposed. This model can effectively reflect the interactions between particles when the distance between particles D/R is less than 0.6 and accurately calculate the local electric fields of the particles. These results can be effectively used to investigate the interactions between particles and the control of particles in electric fields in many fields, such as in the calculation of the insulation of mixed dielectrics, the microscopic transport of medicines, the control of bio-cells and micro-fluids in electric fields, and environmental governance.
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Man, Dariusz, Marian Podolak et Ryszard Olchawa. « Computer Simulations of the Electric Interactions between the Phospholipid Head-Groups and Ionic Admixtures in the Membrane Surface ». Zeitschrift für Naturforschung C 56, no 5-6 (1 juin 2001) : 402–6. http://dx.doi.org/10.1515/znc-2001-5-613.
Texte intégralRésumé :
Some phospholipids (e.g. lecithin) form a system of electric dipoles on the membrane surface layer. In the case of lecithin the positive dipole charge is located on the choline and the negative one on the phosphoric molecule group. These dipoles are arranged almost parallel to the membrane surface. Taking the dipole membrane structure as a base for further investigations, a computer model of the electrostatic interaction between the dipole system and the ionic admixture was investigated. The model presumes hexagonal centered or a rectangular flat geometry of the 121 dipoles distribution. The dipoles may rotate freely around round the motionless symmetry axis perpendicular to the system surface. The initial state is given by fixing the geometry of the dipole matrix and ionic admixture distribution. Subsequently this system underwent a computer simulation which consisted of a calculation of resultant force moments acting on each dipole caused by other dipoles and ions. These force moments lead the system to the equilibrium state (minimum of the binding energy). The minimum energy value of the dipoles system depends on concentration and charge of the admixtured ions. The results of repeated simulations indicate that the system achieve the least of all binding energy (the most stable equilibrium state) at 1.5% concentration of admixtured ions in case of ion charge equal to 1Q (where Q denotes arbitrary unit of ion charge) and at 2.5% concentration of admixtured ions in case of ion charge equal to 2Q. The calculated results are in a good agreement with the experimental.
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Lykakh, V. A., et E. S. Syrkin. « Carriers Spectra of Functionalized Semiconducting Nanowire and Conformational Transition in Molecules ». Ukrainian Journal of Physics 57, no 7 (30 juillet 2012) : 710. http://dx.doi.org/10.15407/ujpe57.7.710.
Texte intégralRésumé :
The tuning of the spectrum of semiconducting nanowires as a result of the functionalization by a layer of molecules with a conformational transition is investigated. The situation where the electric charge carrier induces the conformational transition with a change of the orientation of the intrinsic electric dipole moments of molecules is expected. The spectrum of a carrier and the parameters of the arising quantum well are determined by the derived self-consistent system of transcendent equations. The system includes the Schrödinger equation for a charge carrier, nonlinear equations for the intrinsic electric-dipole moments, the material equations de4scribing the interaction of an extra carrier in the nanowire and molecular electric dipoles. In a semiconductor nanowire, the hole and electron spectra are symmetric. It is shown that the layer of adsorbed molecules breaks this symmetry when themolecular dipoles create the conditions for a localization of carriers of only one kind, which depends on the charge sign and the orientation of dipoles. The functionalized nanowires can be used as a semiconductor rectifier.
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Manikas, Konstantinos, Georgios G. Vogiatzis, Markus Hütter et Patrick D. Anderson. « Structure formation in suspensions under uniform electric or magnetic field ». Multiscale and Multidisciplinary Modeling, Experiments and Design 4, no 2 (20 mars 2021) : 77–97. http://dx.doi.org/10.1007/s41939-021-00091-9.
Texte intégralRésumé :
AbstractThe structure formation of particles with induced dipoles dispersed in a viscous fluid, under a spatially and temporarily uniform external electric or magnetic field, is investigated by means of Brownian Dynamics simulations. Dipole–dipole interactions forces, excluded volume forces and thermal fluctuations are accounted for. The resulting structures are characterized in terms of average orientation of their inter-particle vectors (second Legendre polynomial), network structure, size of particle clusters, anisotropy of the gyration tensor of every cluster and existence of (cluster) percolation. The magnitude of the strength of the external field and the volume fraction of particles are varied and the structural evolution of the system is followed in time. The results show that the characteristic timescale calculated from the interaction of only two dipoles is also valid for the collective dynamics of many-particle simulations. In addition, the magnitude of the strength of the external field in the range of values we investigate influences only the magnitude of the deviations around the average behavior. The main characteristics (number density of branch-points and thickness of branches) of the structure are mainly affected by the volume fraction. The possibility of 3D printing these systems is explored. While the paper provides the details about the case of an electric field, all results presented here can be translated directly into the case of a magnetic field and paramagnetic particles.
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Hutson, Ross B., William R. Milner, Lingfeng Yan, Jun Ye et Christian Sanner. « Observation of millihertz-level cooperative Lamb shifts in an optical atomic clock ». Science 383, no 6681 (26 janvier 2024) : 384–87. http://dx.doi.org/10.1126/science.adh4477.
Texte intégralRésumé :
Collective couplings of atomic dipoles to a shared electromagnetic environment produce a wide range of many-body phenomena. We report on the direct observation of resonant electric dipole-dipole interactions in a cubic array of atoms in the many-excitation limit. The interactions produce spatially dependent cooperative Lamb shifts when spectroscopically interrogating the millihertz-wide optical clock transition in strontium-87. We show that the ensemble-averaged shifts can be suppressed below the level of evaluated systematic uncertainties for optical atomic clocks. Additionally, we demonstrate that excitation of the atomic dipoles near a Bragg angle can enhance these effects by nearly an order of magnitude compared with nonresonant geometries. Our work demonstrates a platform for precise studies of the quantum many-body physics of spins with long-range interactions mediated by propagating photons.
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ILTAN, E. O. « THE SCALAR UNPARTICLE EFFECT ON THE CHARGED LEPTON ELECTRIC DIPOLE MOMENT ». International Journal of Modern Physics A 24, no 14 (10 juin 2009) : 2729–40. http://dx.doi.org/10.1142/s0217751x09043201.
Texte intégralRésumé :
We study the charged lepton electric dipole moment which is induced by the scalar unparticle mediation and we predict the appropriate range for the free parameters appearing in the effective Lagrangian which drives the unparticle-standard model lepton interactions. We observe that the charged lepton electric dipole moment is strongly sensitive to the scaling dimension du of the unparticle and the new couplings in the effective interaction. Furthermore, we see that the current experimental limits of charged lepton electric dipole moments can ensure an appropriate range for these free parameters.
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Hsu, Wei-Ting, Bo-Han Lin, Li-Syuan Lu, Ming-Hao Lee, Ming-Wen Chu, Lain-Jong Li, Wang Yao, Wen-Hao Chang et Chih-Kang Shih. « Tailoring excitonic states of van der Waals bilayers through stacking configuration, band alignment, and valley spin ». Science Advances 5, no 12 (20 décembre 2019) : eaax7407. http://dx.doi.org/10.1126/sciadv.aax7407.
Texte intégralRésumé :
Excitons in monolayer semiconductors have a large optical transition dipole for strong coupling with light. Interlayer excitons in heterobilayers feature a large electric dipole that enables strong coupling with an electric field and exciton-exciton interaction at the cost of a small optical dipole. We demonstrate the ability to create a new class of excitons in hetero- and homobilayers that combines advantages of monolayer and interlayer excitons, i.e., featuring both large optical and electric dipoles. These excitons consist of an electron confined in an individual layer, and a hole extended in both layers, where the carrier-species–dependent layer hybridization can be controlled through rotational, translational, band offset, and valley-spin degrees of freedom. We observe different species of layer-hybridized valley excitons, which can be used for realizing strongly interacting polaritonic gases and optical quantum controls of bidirectional interlayer carrier transfer.
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Parker, G. W. « Derivation of the electric dipole–dipole interaction as an electric hyperfine interaction ». American Journal of Physics 54, no 8 (août 1986) : 715–17. http://dx.doi.org/10.1119/1.14478.
Texte intégral
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Czajkowski, Krzysztof M., Maria Bancerek, Alexander Korneluk, Dominika Świtlik et Tomasz J. Antosiewicz. « Polarization-dependent mode coupling in hyperbolic nanospheres ». Nanophotonics 10, no 10 (21 juillet 2021) : 2737–51. http://dx.doi.org/10.1515/nanoph-2021-0247.
Texte intégralRésumé :
Abstract Hyperbolic materials offer much wider freedom in designing optical properties of nanostructures than ones with isotropic and elliptical dispersion, both metallic or dielectric. Here, we present a detailed theoretical and numerical study on the unique optical properties of spherical nanoantennas composed of such materials. Hyperbolic nanospheres exhibit a rich modal structure that, depending on the polarization and direction of incident light, can exhibit either a full plasmonic-like response with multiple electric resonances, a single, dominant electric dipole or one with mixed magnetic and electric modes with an atypical reversed modal order. We derive conditions for observing these resonances in the dipolar approximation and offer insight into how the modal response evolves with the size, material composition, and illumination. Specifically, the origin of the magnetic dipole mode lies in the hyperbolic dispersion and its existence is determined by two diagonal permittivity components of different sign. Our analysis shows that the origin of this unusual behavior stems from complex coupling between electric and magnetic multipoles, which leads to very strong scattering or absorbing modes. These observations assert that hyperbolic nanoantennas offer a promising route towards novel light–matter interaction regimes.
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JIBU, MARI, KARL H. PRIBRAM et KUNIO YASUE. « FROM CONSCIOUS EXPERIENCE TO MEMORY STORAGE AND RETRIEVAL : THE ROLE OF QUANTUM BRAIN DYNAMICS AND BOSON CONDENSATION OF EVANESCENT PHOTONS ». International Journal of Modern Physics B 10, no 13n14 (30 juin 1996) : 1735–54. http://dx.doi.org/10.1142/s0217979296000805.
Texte intégralRésumé :
A quantum field theoretical formulation of an interaction between the radiation field and the electric dipole field of intracellular and extracellular water in perimembranous dendritic compartments is proposed. The intercellular spaces filled mostly with water are shown to be not just a filler but a proper substrate for dendritic processing composed of a boson condensation of evanescent photons. Macroscopic ordered dynamics of the electric dipoles of water in the perimembranous region immediately adjacent to dendritic membranes provides interactions with the radiation field to produce evanescent photons that ensure that the critical temperature of the boson condensation can be higher than the body temperature. Thus, superconducting phenomena can take place. Such a high-temperature boson condensate of evanescent photons can be understood as a physical substrate for distributed saltatory processing in dendritic arborizations. Memory storage can be understood in terms of processing involving the ionic coating of the dynamically ordered structure of water facilitated by the boson condensate of evanescent photons.
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Han, Jianing, Juliet Mitchell et Morgan Umstead. « Electric Field Excitation Suppression in Cold Atoms ». Atoms 8, no 3 (20 août 2020) : 47. http://dx.doi.org/10.3390/atoms8030047.
Texte intégralRésumé :
In this article, the atom excitation suppression is studied in two mechanisms. The first mechanism for excitation suppression is caused by an external DC electric field. The second mechanism is due to the energy shift caused by an electric field generated by free charges, which are created by ionizing atoms. The latter mechanism is known as the Coulomb blockade. Here, the Coulomb forces originate from ions created by ionizing atoms with a UV laser. The interaction, which causes the suppression, is treated theoretically as dipole–charge interactions. In the model, the charge is an ion, and the dipole is an atom. From measurements, we use 85Rb atoms. The valence electron and the ion core are the two poles of an electric dipole. The interaction potential energy between the ion and the atom is proportional to 1R2, and the frequency shift caused by this interaction is proportional to 1R4, where R is the distance between the ion and the dipole considered. This research is motivated by potential applications for quantum information storage, remote control, creating hot plasmas using cold atoms, as well as electronic devices.
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Kholmetskii, Alexander L., Oleg V. Missevitch et Tolga Yarman. « Quantum phases for electric charges and electric (magnetic) dipoles : physical meaning and implication ». Journal of the Belarusian State University. Physics, no 1 (9 février 2021) : 50–61. http://dx.doi.org/10.33581/2520-2243-2021-1-50-61.
Texte intégralRésumé :
We analyse the physical meaning of quantum phase effects for point-like charges and electric (magnetic) dipoles in an electromagnetic (EM) field. At present, there are known eight effects of such a kind: four of them (the magnetic and electric Aharonov – Bohm phases for electrons, the Aharonov – Casher phase for a moving magnetic dipole and the He – McKellar – Wilkens phase for a moving electric dipole) had been disclosed in 20th century, while four new quantum phases had recently been found by our team (A. L. Kholmetskii, O. V. Missevitch, T. Yarman). In our analysis of physical meaning of these phases, we adopt that a quantum phase for a dipole represents a superposition of quantum phases for each charge, composing the dipole. In this way, we demonstrate the failure of the Schrödinger equation for a charged particle in an EM field to describe new quantum phase effects, when the standard definition of the momentum operator is used. We further show that a consistent description of quantum phase effects for moving particles is achieved under appropriate re-definition of this operator, where the canonical momentum of particle in EM field is replaced by the interactional EM field momentum. Some implications of this result are discussed.
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Bossa, Guilherme Volpe, et Sylvio May. « Integral Representation of Electrostatic Interactions inside a Lipid Membrane ». Molecules 25, no 17 (22 août 2020) : 3824. http://dx.doi.org/10.3390/molecules25173824.
Texte intégralRésumé :
Interactions between charges and dipoles inside a lipid membrane are partially screened. The screening arises both from the polarization of water and from the structure of the electric double layer formed by the salt ions outside the membrane. Assuming that the membrane can be represented as a dielectric slab of low dielectric constant sandwiched by an aqueous solution containing mobile ions, a theoretical model is developed to quantify the strength of electrostatic interactions inside a lipid membrane that is valid in the linear limit of Poisson-Boltzmann theory. We determine the electrostatic potential produced by a single point charge that resides inside the slab and from that calculate charge-charge and dipole-dipole interactions as a function of separation. Our approach yields integral representations for these interactions that can easily be evaluated numerically for any choice of parameters and be further simplified in limiting cases.
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Gong, Feng-Hui, Yun-Long Tang, Yin-Lian Zhu, Heng Zhang, Yu-Jia Wang, Yu-Ting Chen, Yan-Peng Feng et al. « Atomic mapping of periodic dipole waves in ferroelectric oxide ». Science Advances 7, no 28 (juillet 2021) : eabg5503. http://dx.doi.org/10.1126/sciadv.abg5503.
Texte intégralRésumé :
A dipole wave is composed of head-to-tail connected electric dipoles in the form of sine function. Potential applications in information carrying, transporting, and processing are expected, and logic circuits based on nonlinear wave interaction are promising for dipole waves. Although similar spin waves are well known in ferromagnetic materials for their roles in some physical essence, electric dipole wave behavior and even its existence in ferroelectric materials are still elusive. Here, we observe the atomic morphology of large-scale dipole waves in PbTiO3/SrTiO3 superlattice mediated by tensile epitaxial strains on scandate substrates. The dipole waves can be expressed in the formula of y = Asin (2πx/L) + y0, where the wave amplitude (A) and wavelength (L) correspond to 1.5 and 6.6 nm, respectively. This study suggests that by engineering strain at the nanoscale, it should be possible to fabricate unknown polar textures, which could facilitate the development of nanoscale ferroelectric devices.
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Hoffmann, Michael, Prasanna Venkatesan Ravindran et Asif Islam Khan. « Why Do Ferroelectrics Exhibit Negative Capacitance ? » Materials 12, no 22 (13 novembre 2019) : 3743. http://dx.doi.org/10.3390/ma12223743.
Texte intégralRésumé :
The Landau theory of phase transitions predicts the presence of a negative capacitance in ferroelectric materials based on a mean-field approach. While recent experimental results confirm this prediction, the microscopic origin of negative capacitance in ferroelectrics is often debated. This study provides a simple, physical explanation of the negative capacitance phenomenon—i.e., ‘S’-shaped polarization vs. electric field curve—without having to invoke the Landau phenomenology. The discussion is inspired by pedagogical models of ferroelectricity as often presented in classic text-books such as the Feynman lectures on Physics and the Introduction of Solid State Physics by Charles Kittel, which are routinely used to describe the quintessential ferroelectric phenomena such as the Curie-Weiss law and the emergence of spontaneous polarization below the Curie temperature. The model presented herein is overly simplified and ignores many of the complex interactions in real ferroelectrics; however, this model reveals an important insight: The polarization catastrophe phenomenon that is required to describe the onset of ferroelectricity naturally leads to the thermodynamic instability that is negative capacitance. Considering the interaction of electric dipoles and saturation of the dipole moments at large local electric fields we derive the full ‘S’-curve relating the ferroelectric polarization and the electric field, in qualitative agreement with Landau theory.
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Qian, Wei, et David E. Boerner. « Electromagnetic response of a discretely grounded circuit—An integral equation solution ». GEOPHYSICS 59, no 11 (novembre 1994) : 1680–94. http://dx.doi.org/10.1190/1.1443556.
Texte intégralRésumé :
We derive an integral equation to describe the electromagnetic response of a discretely grounded circuit. This investigation is relevant to the study of man‐made structures such as metallic fences, grounded powerlines, and pipelines, all of which may fall into the class of discretely grounded conductors. The solution developed here is an extension to existing circuit theory and takes into account the self and mutual interaction of the circuit elements. It is possible to ignore these interactions at low frequencies where the grounding impedances dominate the effective impedance of the circuit. However, at frequencies where the electromagnetic skin depth is comparable to the length between adjacent grounding points, the effective impedance of the circuit is proportional to frequency, and the inductance of the circuit dominates its electromagnetic response. Within the quasi‐static limit (i.e., where displacement currents can be neglected) electromagnetic excitation by either horizontal electric or vertical magnetic dipoles produces a constant primary electric field at high frequencies (far‐field). Thus, the electric current in the discretely grounded circuit will always be inversely proportional to frequency for these types of sources. Horizontal magnetic dipole or vertical electric dipole sources generate primary electric fields that are proportional to the inverse square root of frequency in the high frequency limit of the quasi‐static domain, and thus the current in a circuit excited by such sources will decrease as the inverse of square root of frequency. The integral equation solution derived here can be used to investigate the influence from cultural conductors on actual electromagnetic surveys and also provides further insights into the current channeling response of surficial conductors.