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https://www.readbyqxmd.com/read/28339249/electric-control-of-dirac-quasiparticles-by-spin-orbit-torque-in-an-antiferromagnet
#1
L Šmejkal, J Železný, J Sinova, T Jungwirth
Spin orbitronics and Dirac quasiparticles are two fields of condensed matter physics initiated independently about a decade ago. Here we predict that Dirac quasiparticles can be controlled by the spin-orbit torque reorientation of the Néel vector in an antiferromagnet. Using CuMnAs as an example, we formulate symmetry criteria allowing for the coexistence of topological Dirac quasiparticles and Néel spin-orbit torques. We identify the nonsymmorphic crystal symmetry protection of Dirac band crossings whose on and off switching is mediated by the Néel vector reorientation...
March 10, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28333454/sub-structural-components-of-organic-colloids-from-a-pu-polluted-soil-with-implications-for-pu-mobilization
#2
Nicole DiDonato, Chen Xu, Peter H Santschi, Patrick G Hatcher
Contaminated soil organic matter from the Rocky Flats Environmental Technology Site (RFETS) has been previously shown to accumulate plutonium (Pu) in a colloidal sub-fraction and hypothesized to contain cutin-like chemical structures cross-linked with hydroxamate functionality. The present study further characterizes this high Pu-affinity sub-fraction using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) and discovers additional sub-structural components. The Pu-enriched fraction was extracted and purified through a series of ultrafiltration and isoelectric focusing (IEF) electrophoresis steps...
March 23, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28333435/laser-desorption-ionization-coupled-to-ft-icr-mass-spectrometry-for-studies-of-natural-organic-matter
#3
John W T Blackburn, Will Kew, Margaret C Graham, Dusan Uhrin
Laser desorption/ionization (LDI) was investigated as an ionization method for Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) studies of natural organic matter (NOM). Using International Humic Substances Society standards, Suwannee River fulvic acid (SRFA) and Suwannee River natural organic matter (SRNOM), LDI was found to ionize very similar set of compounds (> 90 % of molecular formulae identity) to the matrix assisted laser desorption/ionization (MALDI), while producing higher quality spectra...
March 23, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28332533/condensed-matter-physics-vibrations-mapped-by-an-electron-beam
#4
Christian Colliex
No abstract text is available yet for this article.
March 22, 2017: Nature
https://www.readbyqxmd.com/read/28329445/nanoscale-imaging-of-current-density-with-a-single-spin-magnetometer
#5
K Chang, A Eichler, J Rhensius, L Lorenzelli, C L Degen
Charge transport in nanostructures and thin films is fundamental to many phenomena and processes in science and technology, ranging from quantum effects and electronic correlations in mesoscopic physics, to integrated charge- or spin-based electronic circuits, to photoactive layers in energy research. Direct visualization of the charge flow in such structures is challenging due to their nanometer size and the itinerant nature of currents. In this work, we demonstrate noninvasive magnetic imaging of current density in two-dimensional conductor networks including metallic nanowires and carbon nanotubes...
March 24, 2017: Nano Letters
https://www.readbyqxmd.com/read/28322214/optical-signatures-of-parity-anomaly-in-a-gapped-graphene-like-system
#6
C X Zhang, X G Qiu
Parity anomaly refers to the violation of coordinate reflection symmetry induced by the quantum fluctuations. It is proposed to exist in a graphene-like system with a finite bare mass for Dirac fermions, and manifests itself as a parity- violating quantum correction to the current of each species of fermions. Coulomb interaction greatly increases the fermion mass, and produces various types of excitons. Of particular interest is the ρ-exciton, which is directly connected to parity anomaly and can be generated by absorbing a specific photon...
March 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28320903/phase-space-methods-for-the-spin-dynamics-in-condensed-matter-systems
#7
Jérôme Hurst, Paul-Antoine Hervieux, Giovanni Manfredi
Using the phase-space formulation of quantum mechanics, we derive a four-component Wigner equation for a system composed of spin-[Formula: see text] fermions (typically, electrons) including the Zeeman effect and the spin-orbit coupling. This Wigner equation is coupled to the appropriate Maxwell equations to form a self-consistent mean-field model. A set of semiclassical Vlasov equations with spin effects is obtained by expanding the full quantum model to first order in the Planck constant. The corresponding hydrodynamic equations are derived by taking velocity moments of the phase-space distribution function...
April 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28320902/a-global-optimization-perspective-on-molecular-clusters
#8
REVIEW
J M C Marques, F B Pereira, J L Llanio-Trujillo, P E Abreu, M Albertí, A Aguilar, F Pirani, M Bartolomei
Although there is a long history behind the idea of chemical structure, this is a key concept that continues to challenge chemists. Chemical structure is fundamental to understanding most of the properties of matter and its knowledge for complex systems requires the use of state-of-the-art techniques, either experimental or theoretical. From the theoretical view point, one needs to establish the interaction potential among the atoms or molecules of the system, which contains all the information regarding the energy landscape, and employ optimization algorithms to discover the relevant stationary points...
April 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/28306244/recent-advances-in-ultrathin-two-dimensional-nanomaterials
#9
Chaoliang Tan, Xiehong Cao, Xue-Jun Wu, Qiyuan He, Jian Yang, Xiao Zhang, Junze Chen, Wei Zhao, Shikui Han, Gwang-Hyeon Nam, Melinda Sindoro, Hua Zhang
Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances...
March 17, 2017: Chemical Reviews
https://www.readbyqxmd.com/read/28306166/noncentrosymmetric-magnets-hosting-magnetic-skyrmions
#10
REVIEW
Naoya Kanazawa, Shinichiro Seki, Yoshinori Tokura
The concept of a skyrmion, which was first introduced by Tony Skyrme in the field of particle physics, has become widespread in condensed matter physics to describe various topological orders. Skyrmions in magnetic materials have recently received particular attention; they represent vortex-like spin structures with the character of nanometric particles and produce fascinating physical properties rooted in their topological nature. Here, a series of noncentrosymmetric ferromagnets hosting skyrmions is reviewed: B20 metals, Cu2 OSeO3 , Co-Zn-Mn alloys, and GaV4 S8 , where Dzyaloshinskii-Moriya interaction plays a key role in the stabilization of skyrmion spin texture...
March 17, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28304035/nuclear-dynamics-and-phase-polymorphism-in-solid-formic-acid
#11
Maciej Krzystyniak, Kacper Drużbicki, Giovanni Romanelli, Matthias J Gutmann, Svemir Rudić, Silvia Imberti, Felix Fernandez-Alonso
We apply a unique sequence of structural and dynamical neutron-scattering techniques, augmented with density-functional electronic-structure calculations, to establish the degree of polymorphism in an archetypal hydrogen-bonded system - crystalline formic acid. Using this combination of experimental and theoretical techniques, the hypothesis by Zelsmann on the coexistence of the β1 and β2 phases above 220 K is tested. Contrary to the postulated scenario of proton-transfer-driven phase coexistence, the emerging picture is one of a quantitatively different structural change over this temperature range, whereby the loosening of crystal packing promotes temperature-induced shearing of the hydrogen-bonded chains...
March 17, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28300118/strongly-baryon-dominated-disk-galaxies-at-the-peak-of-galaxy-formation-ten-billion-years-ago
#12
R Genzel, N M Förster Schreiber, H Übler, P Lang, T Naab, R Bender, L J Tacconi, E Wisnioski, S Wuyts, T Alexander, A Beifiori, S Belli, G Brammer, A Burkert, C M Carollo, J Chan, R Davies, M Fossati, A Galametz, S Genel, O Gerhard, D Lutz, J T Mendel, I Momcheva, E J Nelson, A Renzini, R Saglia, A Sternberg, S Tacchella, K Tadaki, D Wilman
In the cold dark matter cosmology, the baryonic components of galaxies-stars and gas-are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark-matter halo. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius-a hallmark of the dark-matter model...
March 15, 2017: Nature
https://www.readbyqxmd.com/read/28297991/solvent-free-molecular-level-modeling-of-self-assembling-amphiphiles-in-water
#13
Somajit Dey, Jayashree Saha
Aggregation mesophases of self-assembling amphiphiles in water are highly important in the context of biology (biomembranes), therapy (liposomes), industry (polymer surfactants), and condensed-matter physics (lyotropic liquid crystals). Besides helping to increase fundamental understanding of collective molecular behavior, simulations of these lyotropic phases are pivotal to technological and medical developments such as smart drug carriers for gene therapy. Implicit-solvent, coarse-grained, low resolution modeling with a simple pair potential is the key to realizing the larger length and time scales associated with such mesoscopic phenomena during a computer simulation...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28297917/free-energy-of-singular-sticky-sphere-clusters
#14
Yoav Kallus, Miranda Holmes-Cerfon
Networks of particles connected by springs model many condensed-matter systems, from colloids interacting with a short-range potential and complex fluids near jamming, to self-assembled lattices and various metamaterials. Under small thermal fluctuations the vibrational entropy of a ground state is given by the harmonic approximation if it has no zero-frequency vibrational modes, yet such singular modes are at the epicenter of many interesting behaviors in the systems above. We consider a system of N spherical particles, and directly account for the singularities that arise in the sticky limit where the pairwise interaction is strong and short ranged...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28294118/ground-state-selection-under-pressure-in-the-quantum-pyrochlore-magnet-yb2ti2o7
#15
E Kermarrec, J Gaudet, K Fritsch, R Khasanov, Z Guguchia, C Ritter, K A Ross, H A Dabkowska, B D Gaulin
A quantum spin liquid is a state of matter characterized by quantum entanglement and the absence of any broken symmetry. In condensed matter, the frustrated rare-earth pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7, so-called spin ices, exhibit a classical spin liquid state with fractionalized thermal excitations (magnetic monopoles). Evidence for a quantum spin ice, in which the magnetic monopoles become long range entangled and an emergent quantum electrodynamics arises, seems within reach. The magnetic properties of the quantum spin ice candidate Yb2Ti2O7 have eluded a global understanding and even the presence or absence of static magnetic order at low temperatures is controversial...
March 15, 2017: Nature Communications
https://www.readbyqxmd.com/read/28277520/condensed-matter-physics-marching-to-a-different-quantum-beat
#16
Chetan Nayak
No abstract text is available yet for this article.
March 8, 2017: Nature
https://www.readbyqxmd.com/read/28277505/observation-of-a-discrete-time-crystal
#17
J Zhang, P W Hess, A Kyprianidis, P Becker, A Lee, J Smith, G Pagano, I-D Potirniche, A C Potter, A Vishwanath, N Y Yao, C Monroe
Spontaneous symmetry breaking is a fundamental concept in many areas of physics, including cosmology, particle physics and condensed matter. An example is the breaking of spatial translational symmetry, which underlies the formation of crystals and the phase transition from liquid to solid. Using the analogy of crystals in space, the breaking of translational symmetry in time and the emergence of a 'time crystal' was recently proposed, but was later shown to be forbidden in thermal equilibrium. However, non-equilibrium Floquet systems, which are subject to a periodic drive, can exhibit persistent time correlations at an emergent subharmonic frequency...
March 8, 2017: Nature
https://www.readbyqxmd.com/read/28272466/designing-exotic-many-body-states-of-atomic-spin-and-motion-in-photonic-crystals
#18
Marco T Manzoni, Ludwig Mathey, Darrick E Chang
Cold atoms coupled to photonic crystals constitute an exciting platform for exploring quantum many-body physics. For example, such systems offer the potential to realize strong photon-mediated forces between atoms, which depend on the atomic internal (spin) states, and where both the motional and spin degrees of freedom can exhibit long coherence times. An intriguing question then is whether exotic phases could arise, wherein crystalline or other spatial patterns and spin correlations are fundamentally tied together, an effect that is atypical in condensed matter systems...
March 8, 2017: Nature Communications
https://www.readbyqxmd.com/read/28266499/hidden-phase-in-a-two-dimensional-sn-layer-stabilized-by-modulation-hole-doping
#19
Fangfei Ming, Daniel Mulugeta, Weisong Tu, Tyler S Smith, Paolo Vilmercati, Geunseop Lee, Ying-Tzu Huang, Renee D Diehl, Paul C Snijders, Hanno H Weitering
Semiconductor surfaces and ultrathin interfaces exhibit an interesting variety of two-dimensional quantum matter phases, such as charge density waves, spin density waves and superconducting condensates. Yet, the electronic properties of these broken symmetry phases are extremely difficult to control due to the inherent difficulty of doping a strictly two-dimensional material without introducing chemical disorder. Here we successfully exploit a modulation doping scheme to uncover, in conjunction with a scanning tunnelling microscope tip-assist, a hidden equilibrium phase in a hole-doped bilayer of Sn on Si(111)...
March 7, 2017: Nature Communications
https://www.readbyqxmd.com/read/28263585/acute-responses-of-microorganisms-from-membrane-bioreactors-in-the-presence-of-naocl-protective-mechanisms-of-extracellular-polymeric-substances
#20
Xiaomeng Han, Zhiwei Wang, Mei Chen, Xingran Zhang, Chuyang Y Tang, Zhichao Wu
Extracellular polymeric substances (EPS) are key foulants in membrane bioreactors (MBRs). However, their positive functions of protecting microorganisms from environmental stresses, e.g., during in situ hypochlorite chemical cleaning of membranes, have not been adequately elucidated. In this work, we investigated the response of microorganisms in an MBR to various dosages of NaOCl, with a particular emphasis on the mechanistic roles of EPS. Results showed that functional groups in EPS such as the hydroxyl and amino groups were attacked by NaOCl, causing the oxidation of polysaccharides, denaturation of amino acids, damage to protein secondary structure, and transformation of tryptophan protein-like substances to condensed aromatic ring substances...
March 21, 2017: Environmental Science & Technology
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