Order In Matter Research Articles

Terahertz electric-field-driven dynamical multiferroicity in SrTiO3

The emergence of collective order in matter is among the most fundamental and intriguing phenomena in physics. In recent years, the dynamical control and creation of novel ordered states of matter not accessible in thermodynamic equilibrium is receiving much attention1–6. The theoretical concept of dynamical multiferroicity has been introduced to describe the emergence of magnetization due to time-dependent electric polarization in non-ferromagnetic materials7,8. In simple terms, the coherent rotating motion of the ions in a crystal induces a magnetic moment along the axis of rotation. Here we provide experimental evidence of room-temperature magnetization in the archetypal paraelectric perovskite SrTiO3 due to this mechanism. We resonantly drive the infrared-active soft phonon mode with an intense circularly polarized terahertz electric field and detect the time-resolved magneto-optical Kerr effect. A simple model, which includes two coupled nonlinear oscillators whose forces and couplings are derived with ab initio calculations using self-consistent phonon theory at a finite temperature9, reproduces qualitatively our experimental observations. A quantitatively correct magnitude was obtained for the effect by also considering the phonon analogue of the reciprocal of the Einstein–de Haas effect, which is also called the Barnett effect, in which the total angular momentum from the phonon order is transferred to the electronic one. Our findings show a new path for the control of magnetism, for example, for ultrafast magnetic switches, by coherently controlling the lattice vibrations with light.

Evolution of Ecosystems under an Anthropogenic Load: From Disorganization to Self-Organization

The paper presents a concept of the sustainability of aquatic ecosystems, their disorganization when impacted by anthropogenic pollution, and evolutionary development after the effect of the toxicants decreased. The general laws of the ecosystem transformations are explained from the viewpoint of the ecological theory and the mechanism of thermodynamic ordering of matter in living systems. The evolutionary development of ecosystems after weakening of induced anthropogenic perturbations is demonstrated to be consistent with the trends of ecosystem successions: from a natural stage through critical one to a stable modification. The latter is characterized by a higher ordering of the matter and a decrease in the entropy. Ecosystems are not able to return to their natural state because they evolved through a critical state to a new stable one, which is characterized by highly ordered state of the matter.

Phase stability and electronic structure of iridium metal at the megabar range

The 5d transition metals have attracted specific interest for high-pressure studies due to their extraordinary stability and intriguing electronic properties. In particular, iridium metal has been proposed to exhibit a recently discovered pressure-induced electronic transition, the so-called core-level crossing transition at the lowest pressure among all the 5d transition metals. Here, we report an experimental structural characterization of iridium by x-ray probes sensitive to both long- and short-range order in matter. Synchrotron-based powder x-ray diffraction results highlight a large stability range (up to 1.4 Mbar) of the low-pressure phase. The compressibility behaviour was characterized by an accurate determination of the pressure-volume equation of state, with a bulk modulus of 339(3) GPa and its derivative of 5.3(1). X-ray absorption spectroscopy, which probes the local structure and the empty density of electronic states above the Fermi level, was also utilized. The remarkable agreement observed between experimental and calculated spectra validates the reliability of theoretical predictions of the pressure dependence of the electronic structure of iridium in the studied interval of compressions.

Tilted-pulse-front excitation of strong quasistatic precursors.

It was recently predicted [M. I. Bakunov, A. V. Maslov, and M. V. Tsarev, Phys. Rev. A95, 063817 (2017)10.1103/PhysRevA.95.063817] that concurrent processes of optical rectification and multiphoton absorption of an ultrashort laser pulse in an electro-optic crystal can generate a quasistatic electromagnetic precursor propagating ahead of the laser pulse. The electric and magnetic fields in the precursor can exceed the fields in the ordinary terahertz wave generated behind the laser pulse. We propose a way to enhance the precursor's magnitude tremendously, by at least two orders of magnitude, by using tilted-pulse-front excitation technique and higher orders of multiphoton absorption. In particular, we show that a pulse of 500 fs duration and 70 GW/cm2 peak intensity from a Yb-doped laser amplifier can generate in a 5-mm-thick LiNbO3 crystal a 0.5-mm-long precursor with the strengths of the electric and magnetic fields as high as 0.4 MV/cm and 0.13 T, respectively. Strong quasistatic (subterahertz) fields can be a useful tool for particle acceleration, molecular orientation, ultrafast control of magnetic order in matter, and in terahertz streaking techniques.

The hidden structure of liquids.

From its earliest days, crystallography has been viewed as a means to probe order in matter. J. D. Bernal's work on the structure of water reframed it as a means of examining the extent to which matter can be regarded as orderly.

Layers, Flows, and Switches: Individuals in Next Society

Next society is a society under pressure to find a structural and a cultural answer to the overflow of meaning that the introduction of computers, conceived of as complex units, has provoked not just into everyday communication but also into exacting, indeed professional kinds of communication. In markets, on the battlefield, in hospitals, in laboratories, in bureaucracies, and even in social networks, computers set out not only to provide support but also to make appropriate or less appropriate decisions. Once again, ‘structure’ means ensuring the differentiation, distribution, and dissemination of new kinds of communication, and ‘culture’ means providing communication with ideas of what makes sense and is of value. If Manuel Castells, Harrison C. White, Bruno Latour, and others are right, the structure of next society is a network structure, molding good old modernity’s fields of functional endeavor into new clusters and profiles of activities that defy rational ordering. Instead of the functional ordering of matter and cause so typical of modern reason, we are beginning to deal with a nervous ordering of flows and switches that gain their profile from an idiosyncratic exploitation of heterogeneity.

Reaction-Map of Organic Chemistry

The Reaction-Map of Organic Chemistry has been designed to give organic chemistry students an overview of most of the reactions needed for the organic chemistry course. The chart has been partially organized according to the periodic table on the horizontal axis and according to carbon oxidation level on the vertical axis. In addition the carboxyls are grouped vertically according to decreasing reactivity, and carbon–carbon bond forming reactions are emphasized with bold arrows. The chart provides a study aid for students and should help students develop synthetic routes from one functional group to another. The chart should be especially useful for students studying for the final examination for the two-semester organic chemistry course. In addition to the chart, three keys are available that organize the reactions according to mechanism, functional group preparations, and functional group reactions. Chemistry can be thought of as a search for order in matter and this chart attempts to provide some insig...

Articulation: a working paper on rhetoric and taxis

This essay suggests a way to historicize different rhetorical practices—in effect, alternative ways to write genealogies of diverse rhetorics. A certain distinction between culture and nature is a fundamental organizing concept in humanistic rhetoric that has circumscribed scholars' ability to appreciate rhetoric that does not emanate from the subject as conceptualized in Greco‐Roman theory and the theory derived from it. Accordingly, scholarship is preoccupied with the ways that the motivated discourse of subjects leaps the gap between discourse and things to affect the material world. Rather than treating it as natural, the formation of a gap between discourse and things is defined in this essay as a performance articulated through everyday practices, which shifts the focus from human agents to practices. Articulation is a performative concept about the ordering of matter and meaning. To articulate is to produce bodies, language, and the space of their relative disposition through shared acts. Ultimately, practices establish different orders of discourse and things and, thus, condition the relationships that enable diverse modes of rhetoric to function. Historicizing the order articulated by practices becomes a way to trace genealogies of diverse rhetorics.

Fluctuation X-ray Microscopy for Measuring Medium-Range Order

ABSTRACTMany x-ray techniques exist to probe long- and short-range order in matter, in real space by imaging and in reciprocal space by diffraction and scattering. However, measuring mediumrange order (MRO) in disordered materials is a long-standing problem. Based on fluctuation electron microscopy, which was applied successfully to the understanding of MRO in amorphous materials, we have developed fluctuation x-ray microscopy (FXM). This novel approach offers quantitative insight into medium-range correlations in materials at nanometer and larger length scales. It examines spatially resolved fluctuations in the intensity of a series of x-ray speckle patterns. The speckle variance depends on higher order correlations that are more sensitive to MRO. Systematically measuring the speckle variance as function of the momentum transfer and x-ray illumination size produces a fluctuation map that contains information about the degree of MRO and the correlation length. This approach can be used for the exploration of MRO and subtle spatial structural changes in a wide range of disordered materials from soft condensed matter to nanowire arrays, semiconductor quantum dot arrays and magnetic materials. It will also help us to understand the mechanisms of order-disorder transitions and may lead to control of ordering, which is important in developing ordered structures tailored for particular applications. A theory for FXM and preliminary experimental results from polystyrene latex spheres are discussed in this paper.

Spherical crystals

The structure of condensed matter order may change when the medium is curved. This is illustrated for the case of spherical crystals formed by self-assembled colloidal beads on water droplets in oil. Beyond a minimum crystal size novel grain boundary scars proliferate in the ground state.

Role of crystallography

Fundamental advances in materials research depend heavily on crystallographic information. Modern crystallography is concerned with the structural topology of the various states of order in matter; in particular, with the atomic arrangement, collective excitations, and electron and defect distributions in solids. The crystallographic techniques of importance to materials research cover a wide range; an overview was published recently.

Determination of Radial Distribution Functions by Elastic Electron Diffraction

THE ordering of matter in amorphous materials can be characterized by a radial distribution function of density 4πr2ρ(r), and a difference radial distribution function 4πr2(ρ(r) − ρ0). The latter is obtained1 from experimental scattering data I(s) by the Fourier inversion: where s = 2sin½β/λ, β is the scattering angle, and f is the atomic scattering factor. f is a smoothly decreasing function of s and the quantity to be inverted is the ratio of the ripple of I(s) about f2(s), to the smooth curve f2(s).

Ontology and the Possibility of Religious Knowledge

ontological determinants of human experience in terms of which religious knowledge (as well as other types of knowledge) can become an ontic possibility? The formulation of our question suggests that the question of knowing is inseparable from the question of being and that any ontic analysis of the sources, methods, and criteria of the special types of knowledge presupposes an ontological understanding of the conditions which make human knowledge possible. Knowledge presupposes being. Cognitive attitudes and methodological procedures, if they are to be anything more than arbitrary constructions, are referential to regions or orders of being and intentional structures within these orders which determine their adequacy or legitimacy of application. The order of matter, for example (independent now of the question concerning its nature and status), as circumscribing the province of the physical sciences, has a peculiar propriety for experimental investigation and quantitative analysis. And, strictly defined, the scientific method possesses precisely this character. Logical empiricism, more than any other contemporary philosophical movement, has concerned itself with a clarification of the methods and criteria of meaning which are applicable to scientific knowledge and has emerged with some notable (and probably noteworthy) results. The logical empiricist argues that the meaning and truth of logical statements are rooted in the criterion of rational intelligibility. Logical propositions, or what Hume had already referred to as relations of ideas, are true if their denial entails a contradiction. A square has four sides or all bachelors are males is a logical truth which carries meaning by virtue of its self-evident character. Empirical state* Calvin O. Schrag is currently an associate professor of philosophy at Purdue University. He was formerly a teaching fellow at Harvard University and a visiting lecturer in philosophy at the University of Illinois (1959-60). He holds the degrees of B.A. (Bethel College, Newton, Kansas) ; B.D. (Yale Divinity School); and Ph.D. (Harvard University). He is the author of Existence and Freedom: Towards an Ontology of Human Finitude, published by Northwestern University Press in 1961. He has also served on a staff of twenty distinguished American scholars who compiled and edited Masterpieces of World Philosophy in Summary Form, published in 1961. In addition, he has contributed articles to such scholarly periodicals as Revue internationale de philosophie; Dialectics; Review of Metaphysics; Ethics; the Personalist; the Journal of Religious Thought; and the Modern Schoolman. This past summer a research grant from the Purdue Research Foundation sent him to the Sorbonne in Paris and the University of Louvain, Belgium, to study contemporary European phenomenology in the Edmund Husserl archives.