Atomic, Molecular and Optical Physics Commons^™

Rod-Shape Theranostic Nanoparticles Facilitate Antiretroviral Drug Biodistribution And Activity In Human Immunodeficiency Virus Susceptible Cells And Tissues, Bhavesh D. Kevadiya, Brendan Ottemann, Insiya Z. Mukadam, Laura Castellanos, Kristen Sikora, James R. Hilaire, Jatin Machhi, Jonathan Herskovitz, Dhruvkumar Soni, Mahmudul Hasan, Wenting Zhang, Anandakumar Sarella, Jered Garrison, Joellyn Mcmillan, Benson Edagwa, R. Lee Mosley, Richard W. Vachet, Howard E. Gendelman

Nebraska Center for Materials and Nanoscience: Faculty Publications

Human immunodeficiency virus theranostics facilitates the development of long acting (LA) antiretroviral drugs (ARVs) by defining drug-particle cell depots. Optimal drug formulations are made possible based on precise particle composition, structure, shape and size. Through the creation of rod-shaped particles of defined sizes reflective of native LA drugs, theranostic probes can be deployed to measure particle-cell and tissue biodistribution, antiretroviral activities and drug retention.

Methods: Herein, we created multimodal rilpivirine (RPV) ¹⁷⁷lutetium labeled bismuth sulfide nanorods (¹⁷⁷LuBSNRs) then evaluated their structure, morphology, configuration, chemical composition, biological responses and adverse reactions. Particle biodistribution was analyzed by single …

Svat4: A Computer Program For Visualization And Analysis Of Crystal Structures, Xingzhong Li

Nebraska Center for Materials and Nanoscience: Faculty Publications

SVAT4 is a computer program for interactive visualization of three-dimensional crystal structures, including chemical bonds and magnetic moments. A wide range of functions, e.g. revealing atomic layers and polyhedral clusters, are available for further structural analysis. Atomic sizes, colors, appearance, view directions and view modes (orthographic or perspective views) are adjustable. Customized work for the visualization and analysis can be saved and then reloaded. SVAT4 provides a template to simplify the process of preparation of a new data file. SVAT4 can generate high-quality images for publication and animations for presentations. The usability of SVAT4 is broadened by a software suite …

Stacked Volume Holographic Gratings For Extending The Operational Wavelength Range In Led And Solar Applications, Sanjay Keshri, Julia Marín-Sáez, Izabela Naydenova, Kevin Murphy, Jesús Atencia, Daniel Chemisana, Sean Garner, María-Victoria Collados, Suzanne Martin

Articles

A novel stacking procedure is presented for volume phase holographic gratings (VPHGs) recorded in photopolymer material using Corning Willow Glass as a flexible substrate in order to achieve broader angular and spectral selectivity in a diffractive device with high efficiency for solar and LED applications. For the first time to our knowledge, we have shown a device designed for use with a white LED that has the same input and output angles and high efficiency when illuminated by different wavelengths. In this paper, two VPHGs were designed, experimentally recorded, and tested when illuminated at normal incidence. The experimental approach is …

Generation And Stability Of Structurally Imprinted Target Skyrmions In Magnetic Multilayers, Noah Kent, Robert Streubel, Charles Henri Lambert, Alejandro Ceballos, Soong Gun Je, Scott Dhuey, Mi Young Im, Felix Büttner, Frances Hellman, Sayeef Salahuddin, Peter Fischer

Robert Streubel Papers

Target Skyrmions (TSks) are extended topological spin textures with a constant chirality where the rotation of the z component of the magnetization is larger than π. TSks have topological charge 1 or 0, if the z component of the magnetization Mz goes through a rotation of nπwhere n is an odd or even integer, respectively. TSks with a rotation of the z component of up to 4πhave been imaged via high spatial resolution element-specific X-ray imaging. The TSks were generated by weakly coupling 30 nm thin Permalloy (Ni80Fe20, PY) disks with a 1 μm diameter to asymmetric (Ir 1 nm/Co …

Reconfigurable Ferromagnetic Liquid Droplets, Xubo Liu, Noah Kent, Alejandro Ceballos, Robert Streubel, Yufeng Jiang, Yu Chai, Paul Y. Kim, Joe Forth, Frances Hellman, Shaowei Shi, Dong Wang, Brett A. Helms, Paul D. Ashby, Peter Fischer, Thomas P. Russell

Robert Streubel Papers

Solid ferromagnetic materials are rigid in shape and cannot be reconfigured. Ferrofluids, although reconfigurable, are paramagnetic at room temperature and lose their magnetization when the applied magnetic field is removed. Here, we show a reversible paramagnetic-to-ferromagnetic transformation of ferrofluid droplets by the jamming of a monolayer of magnetic nanoparticles assembled at the water-oil interface. These ferromagnetic liquid droplets exhibit a finite coercivity and remanent magnetization. They can be easily reconfigured into different shapes while preserving themagnetic properties of solid ferromagnets with classic north-south dipole interactions. Their translational and rotational motions can be actuated remotely and precisely by an external magnetic …

New Heusler Compounds In Ni-Mn-In And Ni-Mn-Sn Alloys, Xingzhong Li, W.-Y. Zhang, Shah R. Valloppilly, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Rapidly quenched ternary Ni-Mn-T (T = In, Sn) alloys exhibit features associated with magnetic skyrmions, so that XRD, TEM, EDS, SAED and HREM investigations were carried out for structural characterization on the two alloy systems. In this paper, we report a new type of Mn-rich Heusler compound with a cubic unit cell, a = 0.9150 nm in Ni-Mn-In and a = 0.9051 nm in Ni-Mn-Sn, which coexist with a Ni-rich full-Heusler compound with defects, a = 0.6094 nm in Ni-Mn-In and a = 0.6034 nm in Ni-Mn-Sn. A further analysis of the experimental results reveals a close structural relationship between …

Scope Of Self-Interacting Thermal Wimps In A Minimal U(1) D Extension And Its Future Prospects, Rahool Kumar Barman, Biplob Bhattacherjee, Arindam Chatterjee, Arghya Choudhury, Aritra Gupta

Journal Articles

In this work we have considered a minimal extension of Standard Model by a local U(1) gauge group in order to accommodate a stable (fermionic) Dark Matter (DM) candidate. We have focussed on parameter regions where DM possesses adequate self-interaction, owing to the presence of a light scalar mediator (the dark Higgs), alleviating some of the tensions in the small-scale structures. We have studied the scenario in the light of a variety of data, mostly from dark matter direct searches, collider searches and flavor physics experiments, with an attempt to constrain the interactions of the standard model (SM) particles with …

The Population Densities Of Argon Metastable Levels, Nada Khogeer, Chelsy Gonzalez, Milka Nikolic

Physics and Astronomy

In this experiment, we used the optical emission spectroscopy (OES) method to obtain the main properties of low temperature Argon plasma. The experiment was sustained in powers and pressures that ranges from 30-100 W and 15-100 mTorr. We used numerical methods for the Argon kinetic model to calculate metastable levels and resonant states for the first excited states in low temperature Argon plasma. By finding the ratio of two spectral lines and finding another ratio from a different upper energy level that goes down to the same two lower energy levels, we can construct a system of two nonlinear equations. …

Origin Of Enhanced Anisotropy In Fept-C Granular Films Revealed By Xmcd, Robert Streubel, Alpha T. N'Diaye, Kumar Srinivasan, Antony Ajan, Peter Fischer

Robert Streubel Papers

We study the effect of carbon segregants on the spin and orbital moments of L10 FePt granular media using x-ray magnetic circular dichroism (XMCD) spectroscopy and report an effective decoupling of the structural film properties from the magnetic parameters of the grains. The carbon concentration reduces the grain size from (200 ± 160) nm2 down to (50 ± 20) nm2 for 40 mol. %C and improves sphericity and the order of grains, while preserving the crystalline order, spin and orbital moments, and perpendicular magnetocrystalline anisotropy. We identify the primary cause of enhanced saturation and coercive fields as the reduced demagnetization …

Magnetization Reversal And Local Switching Fields Of Ferromagnetic Co/Pd Microtubes With Radial Magnetization, Norbert Puwenberg, Christopher F. Reiche, Robert Streubel, Mishal Khan, Dipankar Mukherjee, Ivan V. Soldatov, Michael Melzer, Oliver G. Schmidt, Bernd Büchner, Thomas Mühl

Robert Streubel Papers

Three-dimensional nanomagnetism is a rapidly growing field of research covering both noncollinear spin textures and curved magnetic geometries including microtubular structures. We spatially resolve the field-induced magnetization reversal of free-standing ferromagnetic microtubes utilizing multifrequency magnetic force microscopy (MFM). The microtubes are composed of Co/Pd multilayer films with perpendicular magnetic anisotropy that translates to an anisotropy with radial easy axis upon rolling-up. Simultaneously mapping the topography and the perpendicular magnetostatic force derivative, the relation between surface angle and local magnetization configuration is evaluated for a large number of locations with slopes exceeding 45 degrees. The angle-dependence of the switching field is …

X-Ray Ptychography On Low-Dimensional Hard-Condensed Matter Materials, Xiaowen Shi, Nicolas Burdet, Bo Chen, Gang Xiong, Robert Streubel, Ross Harder, Ian K. Robinson

Robert Streubel Papers

Tailoring structural, chemical, and electronic (dis-)order in heterogeneous media is one of the transformative opportunities to enable new functionalities and sciences in energy and quantum materials. This endeavor requires elemental, chemical, and magnetic sensitivities at the nano/atomic scale in two- and three-dimensional space. Soft X-ray radiation and hard X-ray radiation provided by synchrotron facilities have emerged as standard characterization probes owing to their inherent element-specificity and high intensity. One of the most promising methods in view of sensitivity and spatial resolution is coherent diffraction imaging, namely, X-ray ptychography, which is envisioned to take on the dominance of electron imaging techniques …

University Physics I: Classical Mechanics, Julio Gea-Banacloche

Open Educational Resources

This is a textbook for the first semester of University Physics for scientists and engineers. It covers classical mechanics, and a brief introduction to thermodynamics. The presentation and approach are similar to Mazur’s “The Principles and Practice of Physics,” in that conservation laws are introduced before forces, and one-dimensional systems thoroughly covered before moving to two dimensions. Although the course is “calculus based,” the book has been written with the understanding that many students may be taking calculus simultaneously as a corequisite, so the use of calculus is relatively sparse.

This revised version (Fall 2019) takes into account a number …

Femtosecond-Laser-Induced Spin-Polarized Electron Emission From A Gaas Tip, Evan M. Brunkow, Eric R. Jones, Herman Batelaan, Timothy J. Gay

Timothy J. Gay Publications

It is shown that focusing circularly polarized 800nm light pulses of duration 100 fs on the tips of p-GaAs crystalline shards having no negative electron affinity (NEA) activation results in electron emission that is both fast and spin-polarized. The 400 fs duration of the emission process was determined by pump/probe measurements. The three samples we investigated produced electron polarizations of 13.1(0.9)%, 13.3(0.7)%, and 10.4(0.2)%. Emission currents ranged between 50 pA and 3 nA with a sample bias of –100 V and an average laser power of 100 mW. The electron emission exhibited linear dichroism and was obtained under moderate vacuum …

Textured Heterogeneity In Square Artificial Spin Ice, J. C.T. Lee, S. K. Mishra, V. S. Bhat, R. Streubel, B. Farmer, X. Shi, L. E. De Long, I. Mcnulty, P. Fischer, S. D. Kevan, S. Roy

Robert Streubel Papers

We report evidence of spontaneous formation of a heterogeneous network of superdomains in two-dimensional square artificial spin ice nanostructures in externally applied magnetic fields. Coherent resonant soft-x-ray scattering from such textures gives rise to unique internal structure in Bragg peaks. The magnetic heterogeneity is locally disordered but has a zigzag texture at longer length scales. Our result suggests that the macroscopic magnetic texture is derived from the microscopic structure of the Dirac strings.

Boundary Conditions And Berry Phase In Magnetic Nanostructures, A. Ullah, B. Balamurugan, W. Zhang, D. J. Sellmyer, R. Skomski

Nebraska Center for Materials and Nanoscience: Faculty Publications

The effect of micromagnetic boundary conditions on the Berry curvature and topological Hall effect in granular nanostructures is investi- gated by model calculations. Both free surfaces and grain boundaries between interacting particles or grains affect the spin structure. The Dzyaloshinskii-Moriya interactions yield corrections to the Erdmann-Weierstrass boundary conditions, but the Berry curvature remains an exclusive functional of the local spin structure, which greatly simplifies the treatment of nanostructures. An explicit example is a model nanostructure with cylindrical symmetry whose spin structure is described by Bessel function and which yields a mean-field-type Hall-effect contribution that can be related to magnetic-force-microscopy images.

Crystal Structure And Dzyaloshinski–Moriya Micromagnetics, Ahsan Ullah, B. Balamurugan, Wuzhang Fang, Shah R. Valloppilly, Xingzhong Li, Rabindra Pahari, Lanping Yue, Andrei Sokolov, David J. Sellmyer, Ralph Skomski

Nebraska Center for Materials and Nanoscience: Faculty Publications

The relationship between atomic-scale and micromagnetic Dzyaloshinski–Moriya (DM) interactions has been investigated. By analyzing the Lifshitz invariants for different point groups, we have found that there is no unique link between the absence of inversion symmetry and DM interactions. The absence of inversion symmetry is a necessary condition for a net DM interaction in crystals, but several noncentrosymmetric point groups have zero DM interactions. In many cases, the key consideration is whether the crystals are polar and/or chiral. For example, MnSi-type spin spirals, which violate helical spin symmetry, are caused by the insertion of chiral atomic-scale building blocks into an …

Medium-Dependent Antibacterial Properties And Bacterial Filtration Ability Of Reduced Graphene Oxide, Alexander Gusev, Olga Zakharova, Dmitry S. Muratov, Nataliia S. Vorobeva, Mamun Sarker, Iaroslav Rybkin, Daniil Bratashov, Evgeny Kolesnikov, Aleš Lapanje, Denis V. Kuznetsov, Alexander Sinitskii

Nebraska Center for Materials and Nanoscience: Faculty Publications

Toxicity of reduced graphene oxide (rGO) has been a topic of multiple studies and was shown to depend on a variety of characteristics of rGO and biological objects of interest. In this paper, we demonstrate that when studying the same dispersions of rGO and fluorescent Escherichia coli (E. coli) bacteria, the outcome of nanotoxicity experiments also depends on the type of culture medium. We show that rGO inhibits the growth of bacteria in a nutrition medium but shows little effect on the behavior of E. coli in a physiological saline solution. The observed effects of rGO on E. …

Spin- And Angle-Resolved Photoemission Studies Of The Electronic Structure Of Si(110)“16×2” Surfaces, N. K. Lewis, Y. Lassailly, L. Martinelli, I. Vobornik, J. Fujii, C. Bigi, Evan M. Brunkow, Nathan B. Clayburn, Timothy J. Gay, W. R. Flavell, E. A. Seddon

Timothy J. Gay Publications

The electronic structure of Si(110)“16×2” double-domain, single-domain, and 1×1 surfaces have been investigated using spin- and angle-resolved photoemission at sample temperatures of 77K and 300K. Angleresolved photoemission was conducted using horizontally and vertically polarized 60 eV and 80 eV photons. Band-dispersion maps revealed four surface states (S₁ to S₄) which were assigned to silicon dangling bonds on the basis of measured binding energies and photoemission intensity changes between horizontal and vertical light polarizations. Three surface states (S₁, S₂, and S₄), observed in the Si(110)“16×2” reconstruction, were assigned to Si …

Controlling The Magnetocrystalline Anisotropy Of E-Fe2o3, Imran Ahamed, Ralph Skomski, Arti Kashyap

Nebraska Center for Materials and Nanoscience: Faculty Publications

The magnetocrystalline anisotropy of pristine and Co-substituted ε-Fe₂O₃ is investigated by density functional calculations. The epsilon-iron oxide is the only polymorph of Fe₂O₃ magnetoelectric in its antiferromagnetic ground states other crystalline forms being α-Fe₂O₃ (hematite), β-Fe₂O₃, and γ-Fe₂O₃ (maghemite). The magnetizations of the four iron sublattices are antiferromagnetically aligned with slightly different magnetic moments resulting in a ferrimagnetic structure. Compared to the naturally occurring hematite and maghemite, bulk ε-Fe₂O₃ is difficult to prepare, but ε-Fe₂O₃ nanomaterials of different …

High Energy Product Of Mnbi By Field Annealing And Sn Alloying, Wenyong Zhang, Balamurugan Balasubramanian, Parashu Kharel, Rabindra Pahari, Shah R. Valloppilly, Xingzhong Li, Lanping Yue, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Permanent-magnet materials are one cornerstone of today’s technology, abundant in disk drives, motors, medical equipment, wind gen- erators, and cars. A continuing challenge has been to reconcile high permanent-magnet performance with low raw-material costs. This work reports a Mn-Bi-Sn alloy exclusively made from inexpensive elements, exhibiting high values of Curie-temperature, magnetization, anisotropy, coercivity, and energy product. The samples are produced by field annealing of rapidly quenched Sn-containing MnBi alloys, where the improvement of the magnetic properties is caused by the substitutional occupancy of the 2c sites in the hexagonal NiAs structure by Sn. The substitution modifies the electronic structure of …

High Energy Product Of Mnbi By Field Annealing And Sn Alloying, Wenyong Zhang, Balamurugan Balasubramanian, Parashu Kharel, Rabindra Pahari, Shah R. Valloppilly, Xingzhong Li, Lanping Yue, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Permanent-magnet materials are one cornerstone of today’s technology, abundant in disk drives, motors, medical equipment, wind generators, and cars. A continuing challenge has been to reconcile high permanent-magnet performance with low raw-material costs. This work reports a Mn-Bi-Sn alloy exclusively made from inexpensive elements, exhibiting high values of Curie-temperature, magnetization, anisotropy, coercivity, and energy product. The samples are produced by field annealing of rapidly quenched Sn-containing MnBi alloys, where the improvement of the magnetic properties is caused by the substitutional occupancy of the 2c sites in the hexagonal NiAs structure by Sn. The substitution modifies the electronic structure of the …

Comparative Study Of Topological Hall Effect And Skyrmions In Nimnin And Nimnga, Wenyong Zhang, Balamurugan Balasubramanian, Ahsan Ullah, Rabindra Pahari, Xingzhong Li, Lanping Yue, Shah R. Valloppilly, Andrei Sokolov, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

A nonequilibrium rapid-quenching method has been used to fabricate NiMnIn and NiMnGa alloys that are chemically and morphologically similar but crystallographically and physically very different. NiMnGa crystallizes in a Ni2In-type hexagonal structure, whereas NiMnIn is a cubic Heusler alloy. Both alloys yield a topological Hall effect contribution corresponding to bubble-type skyrmion spin structures, but it occurs in much lower magnetic fields in NiMnIn as compared to NiMnGa. The effect is unrelated to net Dzyaloshinskii-Moriya interactions, which are absent in both alloys due to their inversion-symmetric crystal structures. Based on magnetic-force microscopy, we explain the difference between the two alloys by …

Structure And Magnetism Of Co2ge Nanoparticles, Onur Tosun, Frank M. Abel, Balamurugan Balasubramanian, Ralph Skomski, David J. Sellmyer, George C. Hadjipanayis

Nebraska Center for Materials and Nanoscience: Faculty Publications

The structural and magnetic properties of Co₂Ge nanoparticles (NPs) prepared by the cluster-beam deposition (CBD) technique have been investigated. As-made particles with an average size of 5.5 nm exhibit a mixture of hexagonal and orthorhombic crystal structures. Thermomagnetic measurements showed that the as-made particles are superparamagnetic at room temperature with a blocking temperature (T_B) of 20 K. When the particles are annealed at 823 K for 12 h, their size is increased to 13 nm and they develop a new orthorhombic crystal structure, with a Curie temperature (T_C) of 815 K. This …

Radiation Tolerance In Nano-Structured Crystalline Fe(Cr)/Amorphous Sioc Composite, Qing Su, Tianyao Wang, Lin Shao, Michael Nastasi

Nebraska Center for Materials and Nanoscience: Faculty Publications

The management of irradiation defects is one of key challenges for structural materials in current and future reactor systems. To develop radiation tolerant alloys for service in extreme irradiation environments, the Fe self-ion radiation response of nanocomposites composed of amorphous silicon oxycarbide (SiOC) and crystalline Fe(Cr) were examined at 10, 20, and 50 displacements per atom damage levels. Grain growth in width direction was observed to increase with increasing irradiation dose in both Fe(Cr) films and Fe(Cr) layers in the nanocomposite after irradiation at room temperature. However, compared to the Fe(Cr) film, the Fe(Cr) layers in the nanocomposite exhibited ~50% …

Magnetic And Magnetocaloric Properties Of Pr2-Xndxfe17 Ribbons, Bishnu Dahal, Parashu Kharel, Thomas Ott, Wenyong Zhang, Shah R. Valloppilly, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The structural, magnetic and magnetocaloric properties of Fe deficient Pr_2-xNd_xFe₁₇ (x = 0.5, 0.7) alloys prepared by arc-melting and melt- spinning have been investigated. The room temperature x-ray diffraction patterns show that the samples are nearly single-phase and crystallize in the rhombohedral Th₂Zn₁₇-type crystal structure. The Curie temperatures determined from the thermomagnetic curves are 302 K and 307 K for Pr_1.5Nd_0.5Fe₁₇ and Pr_1.3Nd_0.7Fe₁₇, respectively. The peak magnetic entropy change and the relative cooling power at field change of 50 kOe …

Quantum Phase Transition And Ferromagnetism In Co1+XSn, Rabindra Pahari, Balamurugan Balasubramanian, Rohit Pathak, Manh Coung Nguyen, Shah R. Valloppilly, Ralph Skomski, Arti Kashyap, Cai-Zhuang Wang, Kai-Ming Ho, George C. Hadjipanayis, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The onset of ferromagnetism in cobalt-tin alloys is investigated experimentally and theoretically. The Co₁₊xSn alloys were prepared by rapid quenching from the melt and form a modified hexagonal NiAs-type crystal structure for 0.45 ≤ x ≤ 1. The magnetic behavior is described analytically and by density-functional theory using supercells and the coherent-potential approximation. The excess of Co concentration x, which enters the interstitial 2d sites in the hypothetical NiAs-ordered parent alloy CoSn, yields a Griffiths-like phase and, above a quantum critical point (x_c ≈ 0.65), a quantum phase …

Searching For Clean Observables In $B -> D* /Tau- \Bar{\Nu}_{\Tau}$ Decays, Michael D. Williams Jr.

Theses and Dissertations

In this thesis, the clean angular observables in the $\bar{B} \to D^{*+} \ell^- \bar{\nu}_{\ell}$ angular distribution is studied. Similar angular observables are widely studied in $B \to K^* \mu^+ \mu^-$ decays. We believed that these angular observables may have different sensitivities to different new physics structures.

Crystal Structure, Magnetism And Magnetocaloric Properties Of Mn2−XSn0.5Ga0.5 (X=0, 0.3, 0.5, 0.8) Alloys, H. Qian, Rabindra Pahari, K. Schroeder, Shah R. Valloppilly, Y. Huh, Pavel V. Lukashev, J. Hu, Parashu Kharel, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Magnetic refrigeration based on the magnetocaloric effect has attracted recent attention due to advantages such as high efficiency and environmental friendliness. We have investigated the structural, magnetic and magnetocaloric properties of Mn_2−xSn_0.5Ga_0.5 (x=0, 0.3, 0.5, 0.8) alloys prepared using arc-melting and meltspinning techniques with prospects for magnetic refrigeration. The Mn_2−xSn_0.5Ga_0.5 alloys, except for Mn_1.2Sn_0.5Ga_0.5, have a single-phase hexagonal crystal structure. The Mn_1.2Sn_0.5Ga_0.5 alloy also contains a small amount of MnSn₂ impurity phase. The Curie temperature and high-field (30 kOe) …

Completely Top–Down Hierarchical Structure In Quantum Mechanics, Yakir Aharonov, Eliahu Cohen, Jeff Tollaksen

Mathematics, Physics, and Computer Science Faculty Articles and Research

Can a large system be fully characterized using its subsystems via inductive reasoning? Is it possible to completely reduce the behavior of a complex system to the behavior of its simplest “atoms”? In this paper we answer these questions in the negative for a specific class of systems and measurements. After a general introduction of the topic, we present the main idea with a simple two-particle example, where strong correlations arise between two apparently empty boxes. This leads to surprising effects within atomic and electromagnetic systems. A general construction based on preand postselected ensembles is then suggested, wherein the Nbody …

Spatial And Temporal Correlations Of Xy Macro Spins, Robert Streubel, Noah Kent, Scott Dhuey, Andreas Scholl, Steve Kevan, Peter Fischer

Robert Streubel Papers

We use nano disk arrays with square and honeycomb symmetry to investigate magnetic phases and spin correlations of XY dipolar systems at the micro scale. Utilizing magnetization sensitive X-ray photoemission electron microscopy, we probe magnetic ground states and the “order-by-disorder” phenomenon predicted 30 years ago. We observe the antiferromagnetic striped ground state in square lattices, and 6-fold symmetric structures, including trigonal vortex lattices and disordered floating vortices, in the honeycomb lattice. The spin frustration in the honeycomb lattice causes a phase transition from a long-range ordered locked phase over a floating phase with quasi long-range order and indications of a …