This article reviews advances in the theory and practice of producing spin-polarized 3_He by spin-exchange and metastability-exchange optical pumping. The advances have enhanced applications to charged particle and photon scattering targets, neutron spin filters, magnetic resonance imaging, and precision measurements.

[Rev. Mod. Phys. 89, 045004] Published Mon Dec 11, 2017

]]>The subject of this Colloquium is related to the topic of the 2016 Physics Nobel Prize that was awarded to David J. Thouless, F. Duncan M. Haldane, and J. Michael Kosterlitz “for theoretical discoveries of topological phase transitions and topological phases of matter.” The Colloquium provides a pedagogical introduction to topological phases of matter from comprehensive point of view of many-body entanglement which is important in quantum physics.

[Rev. Mod. Phys. 89, 041004] Published Mon Dec 04, 2017

]]>Optical fibers provide much more than a means to transport light between different locations. This article reviews how integration of functional fluid, solid, and gaseous materials in photonic crystal fibers enables control of their linear and nonlinear properties with applications in optoelectronics, sensing, and laser science.

[Rev. Mod. Phys. 89, 045003] Published Mon Nov 27, 2017

]]>What happens to nucleon-nucleon interactions at very short distances, below the radius of the proton? Does the structure of a nucleon bound in a nucleus differ from that of a free nucleon? The answer to both questions can be provided in terms of the internal quark structure of a nucleon. This article reviews current experimental and theoretical developments providing the high-resolution picture of correlated nucleonic pairs at a short distance scale.

[Rev. Mod. Phys. 89, 045002] Published Mon Nov 13, 2017

]]>Dynamical systems in science with examples ranging from physics, chemistry, and biology up to population dynamics, communication, and climate are rarely isolated but generally interact with each other. One particular way of characterizing the interactions is to use coupling functions which possess the property of enabling one not only to understand but also to control and predict the underlying interaction dynamics. This article demonstrates the usefulness of coupling functions for studying the interaction mechanisms of dynamical systems in different research fields.

[Rev. Mod. Phys. 89, 045001] Published Mon Nov 06, 2017

]]>The dictum that “information is physical” indicates that we should understand how features of quantum physics, in particular, the phenomenon of quantum coherence, can be understood to be, and quantified as, a resource for the processing of information. This Colloquium discusses how to characterize, quantify, and manipulate quantum coherence, in application areas ranging from many-body and solid state physics to biological and nanoscale systems.

[Rev. Mod. Phys. 89, 041003] Published Mon Oct 30, 2017

]]>What is the nature of matter in the interior of cold white dwarfs and in the crust of neutron stars? To shed light on this question, theoretical simulations have been carried out to describe intricate phases of nucleonic matter, such as “pasta” structures in terms of competition between nuclear attraction and electrostatic repulsion. This Colloquium reviews current theoretical developments in astromaterial science relevant to multimessenger astronomical observations.

[Rev. Mod. Phys. 89, 041002] Published Mon Oct 23, 2017

]]>One of the fundamental processes in physics is the interaction of matter with light. One learns early in quantum mechanics how electrons in a hydrogen atom absorb light with well-defined energy or frequency and make transitions between different quantized energy levels. However, the physical behavior is rather different when an atom interacts with multiple light beams with different frequencies because the optical forces change tremendously. This Colloquium discusses this and its consequences in atom cooling.

[Rev. Mod. Phys. 89, 041001] Published Thu Oct 19, 2017

]]>The 2016 Nobel Prize for Physics was shared by David J. Thouless, F. Duncan M. Haldane, and John Michael Kosterlitz. These papers are the text of the address given in conjunction with the award.

[Rev. Mod. Phys. 89, 040501] Published Mon Oct 09, 2017

]]>The 2016 Nobel Prize for Physics was shared by David J. Thouless, F. Duncan M. Haldane, and John Michael Kosterlitz. These papers are the text of the address given in conjunction with the award.

[Rev. Mod. Phys. 89, 040502] Published Mon Oct 09, 2017

]]>At the LHC the production of two or more gauge bosons is completely predicted by the standard model to high precision. Departures from those predictions are very sensitive probes of new physics. This article reviews the theoretical framework for probing such non-standard-model effects and summarizes the results from LHC operation at 7 and 8 TeV.

[Rev. Mod. Phys. 89, 035008] Published Wed Sep 20, 2017

]]>Living systems are undoubtedly complicated. The complicated behaviors result from interactions between many different components. In this Colloquium colloidal systems are shown to exhibit lifelike behavior such as spontaneous assembly of complex structures, the ability to self-replicate, and the ability to perform complex and coordinated metaboliclike behavior. This behavior arises from programming of the interactions between components of the colloidal system.

[Rev. Mod. Phys. 89, 031001] Published Wed Sep 13, 2017

]]>The ${}^{12}$C(α,γ)${}^{16}$O reaction is essential for the the production of carbon and oxygen in the Universe, and also for the composition of stellar cores after helium burning, a key determinant for supernova explosions. This review summarizes the current experimental understanding, theoretical underpinning, and the interpretation of reaction data for this critical reaction. It is shown that the desired level of uncertainty, ≈10%, may be in sight, but several inconsistencies need to be overcome. Ways to move forward beyond the state of the art are discussed.

[Rev. Mod. Phys. 89, 035007] Published Thu Sep 07, 2017

]]>A comprehensive account of the theoretical analyses of the Efimov effect and the universal properties of three-body bound states is provided. Recent experimental studies are reviewed and shown how the few-body analysis also yields insights into many-body phenomena, accessible by the experimental ability to tune the range and strength of the forces between cold atoms.

[Rev. Mod. Phys. 89, 035006] Published Mon Aug 28, 2017

]]>This review discusses disordered materials that only flow if the imposed stress is beyond a certain threshold value. These so-called yield stress materials cannot be described as elastic solids nor as simple Newtonian fluids. Examples include whipped cream, toothpaste, cement, ketchup, and mayonnaise. The physical origin of the yield stress, the nonlinear flow behavior, and experimental techniques to investigate these materials are discussed. Also an overview of the microscopic theoretical descriptions of the nonlinear flow dynamics is presented.

[Rev. Mod. Phys. 89, 035005] Published Mon Aug 21, 2017

]]>This article presents a review on electron vortex beams highlighting both its experimental and its theoretical aspects. The unique characteristics of electron vortex states as well as their similarities with orbital angular momentum states of light are discussed and perspectives are offered for their application in a number of technologies.

[Rev. Mod. Phys. 89, 035004] Published Wed Aug 16, 2017

]]>Solids formed by light atoms or molecules have, at experimentally realizable low temperatures, a kinetic energy per particle that is large compared to the thermal energy. Examples include solid helium, hydrogen, and methane, which are important in a variety of contexts. This review provides an introduction to these quantum crystals, with a focus on simulation techniques suitable for describing and understanding them.

[Rev. Mod. Phys. 89, 035003] Published Thu Aug 03, 2017

]]>Quantum technologies are increasingly driving the field of precision metrology. While current techniques for sensing and recording time rely on classical devices, quantum sensors exploit quantum systems to reach unprecedented levels of precision. The working part of the sensor contains one or a few qubits, and resources like quantum entanglement are chosen and tailored to maximize sensitivity. This review introduces quantum sensing from the perspective of working experimentalists, with specific sensor implementations, concepts and methods, and recent developments.

[Rev. Mod. Phys. 89, 035002] Published Tue Jul 25, 2017

]]>The field of relativistic heavy ion collisions spans over five decades ranging from the formulation of scientific goals and early experiments at Berkeley in the 1960s with mostly lighter heavy ions via the start of operation of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven in the year 2000 up to the Large Hadron Collider (LHC) at CERN, where the first experiments took place in 2010. The data from the RHIC and LHC experiments and their theoretical explanations outlined in this review provide convincing evidence for the creation of a strongly coupled quark-gluon plasma, i.e., a nearly perfect fluid with large entropy density to viscosity ratio formed during collision.

[Rev. Mod. Phys. 89, 035001] Published Wed Jul 19, 2017

]]>In spintronics devices, magnetic materials are used as polarizers or analyzers for electron spin. Magnetic anisotropy defines the orientation for magnetization and polarization of spin currents traversing the material. This review focuses on perpendicular magnetic anisotropy which arises at magnetic metal/oxide interfaces. This anisotropy plays a role in the magnetic memory based on magnetic tunnel junctions. Aspects of the anisotropy are described in various applications and in the field of spintronics research.

[Rev. Mod. Phys. 89, 025008] Published Wed Jun 28, 2017

]]>The physics of chaotic advection is a field that emerged at the intersection of nonlinear dynamics and fluid mechanics. An older term for the field is Langrangian turbulence. This review deals with mathematical physics descriptions and perspectives of chaotic features in transport and mixing in fluid systems of sizes ranging from micrometers to hundreds of kilometers.

[Rev. Mod. Phys. 89, 025007] Published Wed Jun 14, 2017

]]>Magnetism at interfaces often takes on a fundamentally completely different character when compared to magnetism in bulk. This review focuses on these differences and provides an overview of magnetic interfaces relevant to modern spintronics beginning from the most basic and well-understood questions and reaching to the frontiers of knowledge. Topics covered include interfacial spin-orbit coupling, spin-transfer torques, interface-induced exotic spin textures, interface-dependent magnetization dynamics, and the interplay between charge, spin, orbital, and lattice degrees of freedom. The review provides perspectives in key areas and poses questions that may inspire unanticipated control strategies for magnetic interfaces for future magnetic recording and memory applications.

[Rev. Mod. Phys. 89, 025006] Published Mon Jun 05, 2017

]]>The quantum Hall effects by now are recognized as prime examples of the importance of topological considerations in condensed-matter physics. The fractional Quantum Hall effect in particular has proven to display a large number of topologically ordered states that have been classified and understood in terms of hierarchical schemes. This review explains the current understanding of such classifications, with particular emphasis on conformal-field-theory approaches.

[Rev. Mod. Phys. 89, 025005] Published Tue May 23, 2017

]]>Photons, the particles of light, are in most conditions very weakly interacting. Nevertheless, it is possible to make them interact by altering environmental conditions, for instance, in the interior of certain materials or by squeezing them in confined geometries. In this Colloquium the topic of photons interacting strongly when confined to a one-dimensional geometry is discussed from experimental and theoretical perspectives.

[Rev. Mod. Phys. 89, 021001] Published Wed May 10, 2017

]]>If gravitation propagates via a massive field, the velocity of gravitational waves (gravitons) depends on their frequency. Gravitational waves emitted early during the inspiral of compact binaries would travel slower than those emitted later, causing an offset in relative arrival times. This review utilizes the first direct detections of gravitons from two inspiraling black holes for setting an upper mass bound, examines it within the framework of massive gravity theories, and compares to observational bounds obtained from other related effects.

[Rev. Mod. Phys. 89, 025004] Published Wed May 03, 2017

]]>The concept of a quantum spin liquid is important for problems ranging from quantum spin chains to high-temperature superconductivity. This review gives a pedagogical introduction to the theoretical concepts behind this fascinating topic, and also discusses the current experimental situation.

[Rev. Mod. Phys. 89, 025003] Published Tue Apr 18, 2017

]]>Soft condensed matter refers to materials where the constituent building blocks are larger than atoms but smaller than the system itself. The large size of the constituent particles makes these soft materials distinctive from hard condensed matter systems. Soft matter is easily deformable, dissipative, disordered, nonlinear, far from equilibrium, thermal and entropic, slow, observable, susceptible to external fields, patterned, nonlocal, interfacial elastic, memory retaining, and active. This article surveys soft-matter science and discusses different classes of systems including colloids; emulsions; foams; glassy, granular, and jammed matter; liquid crystals; polymers; adaptive mechanical metamaterials; and active matter.

[Rev. Mod. Phys. 89, 025002] Published Wed Apr 12, 2017

]]>Can one determine the black hole nature of an observed object by electromagnetic observations? As astrophysical black holes are expected to result from collapse with nonzero angular momentum, the spacetime geometry would correspond to the Kerr metric. This review discusses how electromagnetic radiation emitted by gas or stars orbiting these objects can potentially be utilized to test the Kerr black hole hypothesis with current and future observational facilities.

[Rev. Mod. Phys. 89, 025001] Published Thu Apr 06, 2017

]]>[Rev. Mod. Phys. 89, 029901] Published Thu Apr 06, 2017

]]>Dynamics of quantum many-body systems is one of the most complex problems in physics since it involves the time evolution of a large number of particles that interact with each other under the influence of external forces. With ultracold atoms in optical atomic lattices it can be done in a controlled environment by applying a periodic force. This Colloquium covers the experimental and theoretical developments in this exciting field of physics.

[Rev. Mod. Phys. 89, 011004] Published Fri Mar 31, 2017

]]>What are the thermodynamic properties of matter at extreme densities, even exceeding nuclear matter density severely? How can we describe the composition of matter for such conditions, the resulting pressure, and the maximum mass of cold neutron stars? How is this affected by finite temperatures, as they occur in core collapse supernovae and in compact star mergers? This review addresses these points within the framework of constraints from experiments as well as astronomical observations.

[Rev. Mod. Phys. 89, 015007] Published Wed Mar 15, 2017

]]>By use of a pulse sequence, the technique of stimulated Raman adiabatic passage transfers population without loss between quantum states via unstable intermediate states. This article reviews many applications of stimulated Raman adiabatic passage to control quantum states in physics and chemistry, from precision spectroscopy over molecular reactions to quantum information processing.

[Rev. Mod. Phys. 89, 015006] Published Wed Mar 08, 2017

]]>Wave front shaping, the ability to manipulate light fields both spatially and temporally, in complex media is an emerging field with many applications. This review summarizes how insights from mesoscopic scattering theory have direct relevance for optical wave control experiments and vice versa. The results are expected to have an impact on a number of fields ranging from biomedical imaging to nanophotonics, quantum information, and communication technology.

[Rev. Mod. Phys. 89, 015005] Published Thu Mar 02, 2017

]]>In mathematics and computer science, random numbers have the role of a resource for assisting proofs, making cryptography secure, and enabling computational protocols. This role motivates efforts to produce random numbers as a physical process. Potential physical sources abound, but arguably the most fundamental are those based on elementary quantum mechanical processes. This review discusses the current status of devices that generate quantum random numbers.

[Rev. Mod. Phys. 89, 015004] Published Wed Feb 22, 2017

]]>The electron-phonon interaction in solids is important for many interesting properties of solids, among them the critical temperature of phonon-mediated superconductors, the effective electron mass in metals and semiconductors, and the carrier dynamics in semiconductors. Modern density-functional techniques have made it possible to perform $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations of the electron-phonon interaction. This review explains these techniques and discusses their applications.

[Rev. Mod. Phys. 89, 015003] Published Thu Feb 16, 2017

]]>The Heisenberg uncertainty principle has a more precise formulation in terms of inequalities involving quantum entropies. Currently known entropic uncertainty relations are presented; they capture and extend Heisenberg’s idea of the unpredictability of the outcomes of incompatible measurements. Distinct results are obtained for finite- and infinite-dimensional Hilbert spaces. Applications are surveyed, including the formulation of entanglement witnesses, current ideas about wave-particle duality, and the analysis of quantum cryptography.

[Rev. Mod. Phys. 89, 015002] Published Mon Feb 06, 2017

]]>[Rev. Mod. Phys. 89, 010001] Published Fri Feb 03, 2017

]]>Localized surface plasmons are collective modes of the conduction electrons excited by light in metal nanoparticles. Although plasmons have been known for some time, their use for controlling light at the nanometer scale only became possible with developments in near field optics. To model interactions between such collective modes is a complex problem that requires heavy computation. In this Colloquium an algebraic model for plasmons is discussed that elucidates the physics of these collective modes and their interactions.

[Rev. Mod. Phys. 89, 011003] Published Mon Jan 30, 2017

]]>In 1954, Fred Hoyle made a prediction regarding the existence of a resonant state of carbon-12 that would be associated with a triple-alpha process which would be fundamental in nucleosynthesis in stars and would explain the amount of carbon-12 in the Universe. This prediction was spectacularly confirmed by experiments. Nevertheless, the precise properties of the Hoyle state are still the subject of investigation. This Colloquium describes the current theoretical and experimental investigation of this important prediction.

[Rev. Mod. Phys. 89, 011002] Published Thu Jan 26, 2017

]]>This review gives a summary of the many techniques that are used in the analysis of open quantum systems. Emphasis is on those cases where it is unsuitable to use a memoryless or Markovian point of view, generally because there is no large separation of time scales between system and environment dynamics. The approaches reviewed include master equations, Heisenberg equations of motion, chain mapping representations, and various stochastic methods such as path integral Monte Carlo and stochastic equations. Guidance is given on how to evaluate the suitability of each of these methods for application in different physical problems.

[Rev. Mod. Phys. 89, 015001] Published Fri Jan 20, 2017

]]>Spintronics continues to be a field of fast evolution where new concepts and devices are continuously being developed. One of the limiting factors in spintronics is the decoherence time in the materials used. This Colloquium reviews the current situation in the understanding of decoherence in some important semiconductors which are being considered in applications.

[Rev. Mod. Phys. 89, 011001] Published Thu Jan 05, 2017

]]>By variation of the photon statistics and the entanglement between time and frequency components, quantum states of light feature spectroscopy signals which are not subject to classical Fourier limitations on temporal and spectral resolution. This review surveys the properties of entangled photon pairs relevant to spectroscopic applications and it presents an intuitive diagrammatic approach which allows calculation of a variety of ultrafast, nonlinear spectroscopy signals from multilevel model systems exposed to quantum light.

[Rev. Mod. Phys. 88, 045008] Published Wed Dec 28, 2016

]]>Progress in the physical sciences depends as much on innovations in instrumentation that enable more refined experiments as on new theoretical ideas. This article reviews the instrumentation developments in particle and nuclear physics that have brought new understanding in those fields, their impact upon broader societal issues, and their interdependence with commercial advances.

[Rev. Mod. Phys. 88, 045007] Published Tue Dec 20, 2016

]]>Quantum spin liquids form a novel class of matter where, despite the existence of strong exchange interactions, spins do not order down to the lowest measured temperature. Typically, these occur in lattices that act to frustrate the appearance of magnetism. In two dimensions, the classic example is ...

[Rev. Mod. Phys. 88, 041002] Published Fri Dec 02, 2016

]]>This article reviews both experimental and theoretical advances in the field of active matter which consists of natural and artificial objects capable of self-propulsion. Prime examples of active particles are Brownian particles, biological or manmade microscopic and nanoscopic objects, that can propel themselfes by taking up energy from their environment and converting it into directed motion. The review provides a guided tour through the basic principles and fabrication of active particles and discusses also many interesting future directions these manmade micromachines and nanomachines could take as autonomous agents for healthcare, sustainability, and security applications.

[Rev. Mod. Phys. 88, 045006] Published Wed Nov 23, 2016

]]>While the typical scenario for quantum error correction involves active intervention there are advantages to a passive quantum memory, for which a suitably designed interaction Hamiltonian will naturally protect the coherence of low-lying states from decoherence induced by a thermal environment. This review summarizes and discusses the various theoretical attempts to find a workable scenario for a passive quantum memory.

[Rev. Mod. Phys. 88, 045005] Published Tue Nov 15, 2016

]]>Many excitation modes of atomic nuclei and their reactions can be described as time-dependent processes, in which nuclei oscillate, rotate, collide, and split. A theoretical framework to describe nuclear dynamics at low energy is the time-dependent density functional theory. This reviews the foundations and extensions of this theory and its applications to nuclear collective motion, including giant resonances, heavy-ion collisions, and shape coexistence. Conceptual differences between nuclear and electronic applications are also discussed.

[Rev. Mod. Phys. 88, 045004] Published Wed Nov 09, 2016

]]>Electromagnetic fluctuation-induced interactions known as van der Waals, Casimir, and Casimir-Polder forces are an active and exciting area of research. This review summarizes recent progress in this field with emphasis on theoretical and computational developments and their applications to materials including molecular structures, Dirac-like systems, optical metamaterials, composites with nontrivial boundary conditions, and biological matter.

[Rev. Mod. Phys. 88, 045003] Published Wed Nov 02, 2016

]]>Sources of $C\phantom{\rule{0}{0ex}}P$ violation beyond those of the standard model of particle physics are needed to explain the dominance of matter over antimatter in the universe. The bound state of a bottom antiquark and a strange quark and its charge conjugate is a fertile hunting ground, as standard model $C\phantom{\rule{0}{0ex}}P$ violating effects are typically small. This article reviews the many studies of $C\phantom{\rule{0}{0ex}}P$ violation in ${B}_{s}$ decays, the quantum mixing of ${B}_{s}$ and anti-${B}_{s}$, and their interference.

[Rev. Mod. Phys. 88, 045002] Published Thu Oct 13, 2016

]]>Quantum-mechanical systems retain their properties so long as the phase of quantum superpositions evolve stably over time. Contact with an environment can disrupt this phase evolution. But for environments that do not exchange energy with the quantum system, strategies exist where the controlled driving of the system can recover or maintain the quantum phase. This Colloquium surveys the host of techniques that are available to “refocus” the phase when disturbed by various forms of classical or quantum environment. While the first such techniques were developed long ago, ideas from quantum information theory have introduced new strategies for accomplishing this goal.

[Rev. Mod. Phys. 88, 041001] Published Mon Oct 10, 2016

]]>Experiments point to the Higgs particle being the excitation of an elementary scalar field, as originally proposed in the standard model. To many theorists, however, its low mass suggests it may be more than that. This article provides a comprehensive review of these alternative Higgs models. The current run of the LHC will test the nature of the Higgs with greater precision. Particle physicists will find this review to serve as a guide to interpret the experimental results to come.

[Rev. Mod. Phys. 88, 045001] Published Thu Oct 06, 2016

]]>This review article contains the 2014 self-consistent set of values of the constants and conversion factors of physics and chemistry recommended by the Committee on Data for Science and Technology (CODATA). The CODATA values are based on a least-squares adjustment that that takes into account all data available up to the end of 2014. Details of the data selection and methodology are described.

[Rev. Mod. Phys. 88, 035009] Published Mon Sep 26, 2016

]]>In the standard model of particle physics, the strong and weak interaction eigenstates of the three generations of quarks differ and are related by the unitary Cabibbo-Kobayashi-Maskawa matrix. This article reviews measurements of the decays of the mesons containing a bottom quark into final states with leptons. These measurements provide determinations of the matrix elements and other observables, and offer constraints on the standard model as well as pointers to possible new physics.

[Rev. Mod. Phys. 88, 035008] Published Wed Sep 21, 2016

]]>[Rev. Mod. Phys. 88, 039905] Published Tue Sep 20, 2016

]]>Green plants harvest the energy of the Sun in the leaves by converting light energy into chemical energy in the bonds of sugar molecules, using water from the soil and carbon dioxide from the air. This review provides an overview of the vascular anatomy of plants and the physical models that describe the long-distance transport of water and minerals from root to leaf, and, in particular, of sugars from the leaves to the entire body of the plant sustaining growth and communication throughout even the tallest tree.

[Rev. Mod. Phys. 88, 035007] Published Fri Sep 16, 2016

]]>Complex networks range from subcellular biological networks to the Internet. Our ability to control these systems deeply challenges our understanding. Control also may well be a guiding principle in their design. This article reviews the emerging science of the control of complex networks.

[Rev. Mod. Phys. 88, 035006] Published Tue Sep 06, 2016

]]>In recent years an increasing amount of attention has been devoted to quantum materials with topological characteristics that are robust against disorder and other perturbations. In this context it was discovered that topological materials can be classified with respect to their dimension and symmetry properties. This review provides an overview of the classification schemes of both fully gapped and gapless topological materials and gives a pedagogical introduction into the field of topological band theory.

[Rev. Mod. Phys. 88, 035005] Published Wed Aug 31, 2016

]]>Everyday matter is made of the lightest up and down quarks. The strange quark is the third lightest of all quarks. Strangeness, a property of particles associated with the number of strange quarks, preceded the theory and discovery of the quark by about two decades. Recent experimental and theoretical developments in the field of strangeness in nuclei are reviewed. Topics include the production of strange particles, properties of hypernuclei, and strange dense matter.

[Rev. Mod. Phys. 88, 035004] Published Fri Aug 26, 2016

]]>[Rev. Mod. Phys. 88, 039904] Published Thu Aug 11, 2016

]]>It is of societal importance to advance the understanding of emerging patterns of biodiversity from biological and ecological systems. The neutral theory offers a statistical-mechanical framework that relates key biological properties at the individual scale with macroecological properties at the community scale. This article surveys the quantitative aspects of neutral theory and its extensions for physicists who are interested in what important problems remain unresolved for studying ecological systems.

[Rev. Mod. Phys. 88, 035003] Published Tue Jul 26, 2016

]]>The concept of parity-time symmetric systems is rooted in non-Hermitian quantum mechanics where complex potentials obeying this symmetry could exhibit real spectra. The concept has applications in many fields of physics, e.g., in optics, metamaterials, acoustics, Bose-Einstein condensation, electronic circuitry, etc. The inclusion of nonlinearity has led to a number of new phenomena for which no counterparts exist in traditional dissipative systems. Several examples of nonlinear parity-time symmetric systems in different physical disciplines are presented and their implications discussed.

[Rev. Mod. Phys. 88, 035002] Published Mon Jul 18, 2016

]]>[Rev. Mod. Phys. 88, 039902] Published Fri Jul 15, 2016

]]>[Rev. Mod. Phys. 88, 039903] Published Fri Jul 15, 2016

]]>Symmetry-protected phases of matter have been at the forefront of condensed matter physics in recent years. Bosonic symmetry-protected phases have been interpreted in terms of anomalies and group cohomology. The present article aims to develop an analogous description of fermionic symmetry-protected phases, such as the topological insulators that have been seen experimentally in 2 or 3 space dimensions. The relevant mathematical concepts include the Atiyah-Singer index theorem and the Atiyah-Patodi-Singer eta invariant.

[Rev. Mod. Phys. 88, 035001] Published Wed Jul 13, 2016

]]>[Rev. Mod. Phys. 88, 039901] Published Mon Jul 11, 2016

]]>The 2015 Nobel Prize for Physics was shared by Takaaki Kajita and Arthur B. McDonald. These papers are the text of the address given in conjunction with the award.

[Rev. Mod. Phys. 88, 030501] Published Wed Jul 06, 2016

]]>The 2015 Nobel Prize for Physics was shared by Takaaki Kajita and Arthur B. McDonald. These papers are the text of the address given in conjunction with the award.

[Rev. Mod. Phys. 88, 030502] Published Wed Jul 06, 2016

]]>First-principles band theory, properly augmented by topological considerations, has provided a remarkably successful framework for predicting new classes of topological materials. This Colloquium discusses the underpinnings of the topological band theory and its materials applications.

[Rev. Mod. Phys. 88, 021004] Published Wed Jun 29, 2016

]]>A full understanding of long range ferromagnetic order in metallic systems reflects a variety of phenomena which are best understood in the context of quantum phase transitions (QPTs). This review presents experimental data on ferromagnetic QPTs in metals, confronting results with currently available theory. The coverage of clean materials, materials with varying degrees of disorder, and materials with phase diagrams is exhaustive, revealing a trend where the QPTs of clean systems driven by a control parameter are first order compared to more disordered systems where the QPTs are second order.

[Rev. Mod. Phys. 88, 025006] Published Tue May 31, 2016

]]>This review focuses on the fundamental physical properties of low-dimensional carbon nanostructures (graphene, graphene nanoribbons, and carbon nanotubes), with an emphasis on understanding and utilizing the unique physical properties that make this class of materials ideal building blocks for future nanoscience and nanotechnology development. In depth discussions of the structural, electronic, vibrational, and transport properties of these carbon nanostructures from both theoretical and experimental standpoints provide a coherent and foundational overview for researchers interested in broader areas of carbon science and related noncarbon systems.

[Rev. Mod. Phys. 88, 025005] Published Tue May 24, 2016

]]>Electron-atom and electron-molecule collisional cross sections are needed in the modeling and understanding of phenomena ranging from planetary atmosphere science to industrial applications of plasmas. This article reviews the Born approximation and phenomenological scaling approaches that provide accurate excitation cross sections over a range of electron impact energies. The methods are illustrated for a variety of atomic and molecular systems.

[Rev. Mod. Phys. 88, 025004] Published Thu May 19, 2016

]]>Coulomb drag, a term coined in analogy to phonon drag, refers to the effect of mutual friction between nonequilibrium conduction electrons belonging to two electrically isolated but closely spaced conductors. Coulomb drag experiments provide unique insight into microscopic properties of interacting many-body systems and are important in systems of small size or of reduced dimensionality. This review provides an overview of the effect in semiconductor heterostructures, double-layers devices, and nanostructures.

[Rev. Mod. Phys. 88, 025003] Published Tue May 10, 2016

]]>Looking back into 10-12 billion years of cosmic history this Colloquium paper summarizes what is presently known about the proton-to-electron mass ratio and its variation with time. The hydrogen spectra of quasars and how they reveal fundamental information on some of the most important constants in physics and cosmology are reviewed.

[Rev. Mod. Phys. 88, 021003] Published Wed May 04, 2016

]]>Epigenetics is essential in understanding the development, from a common undifferentiated cell, of different cell types that share the same hereditary materials in their genome. A meaningful decoration of chemical marks on chromosomes selects the genes to be expressed by directing the differential folding of the genome in the cell nucleus. This article surveys plausible physical mechanisms involved in setting up epigenetic marks and their role in genome folding and expression.

[Rev. Mod. Phys. 88, 025002] Published Tue Apr 26, 2016

]]>An ongoing theme in quantum physics is the interaction of small quantum systems with an environment. If that environment has many degrees of freedom and is weakly coupled, it can often be reasonable to treat its decohering effect on the small system using a “memoryless,” or Markovian description. This Colloquium shows that for many phenomena a more refined, non-Markovian, treatment is necessary. The suite of developing theoretical tools is reviewed, with which recent progress on this problem has been based.

[Rev. Mod. Phys. 88, 021002] Published Tue Apr 19, 2016

]]>How are two essential quantities of neutron stars (the mass and radius), which provide constraints for the equation of state in their interiors where supranuclear densities are experienced, precisely determined? This Colloquium discusses major techniques for how this information can be inferred from x-ray observations of neutron stars that accrete matter from a binary companion, or of isolated neutron stars that experience seismic vibrations, taking into account rotation, relativistic effects, and magnetic fields.

[Rev. Mod. Phys. 88, 021001] Published Wed Apr 13, 2016

]]>This review addresses the current theoretical understanding of hadronic matter at large magnetic fields. Applications include heavy-ion collisions, neutron stars, and the early Universe. Models used describe the thermodynamic properties and phases of quantum chromodynamics as functions of temperature and magnetic field strength. These models are examined and directions for future research are pointed out.

[Rev. Mod. Phys. 88, 025001] Published Fri Apr 08, 2016

]]>In magnetic fusion reactors relying on the burning of deuterium and tritium, sufficient confinement of the alpha particles produced in the nuclear reactions is crucial to sustaining the burning plasma. In this article the interactions of these energetic particles with linear and nonlinear Alfve’n waves generated in the magnetized plasma are reviewed.

[Rev. Mod. Phys. 88, 015008] Published Wed Mar 23, 2016

]]>The advent of x-ray free electron lasers has made possible the study of matter at the characteristic space and time scales of atomic and molecular phenomena using intense coherent x-ray pulses. This article describes the physical principles and the theoretical models governing the interaction of charged particles, electromagnetic waves, and external magnetic fields that comprise the x-ray free-electron lasers. It also includes a discussion of existing facilities and avenues for increasing the peak power and improving the control of spectral and coherence properties to allow the exploration of an even larger range of phenomena.

[Rev. Mod. Phys. 88, 015006] Published Wed Mar 09, 2016

]]>In the five years since achieving first light at the Linac Coherent Light Source, transformative studies have been conducted in a new regime with femtosecond pulses of short wavelength, high intensity x rays. This article summarizes these results in atomic, molecular and optical physics; condensed matter physics; matter in extreme density, temperature and pressure conditions; chemistry and soft matter; and biological structure and dynamics. In each of these areas, perspectives for future research are discussed.

[Rev. Mod. Phys. 88, 015007] Published Wed Mar 09, 2016

]]>Wave-particle duality lies at the root of quantum mechanics and is central in the description of interferences observed with elementary objects. In a delayed-choice experiment, the decision to observe the particle or wave character of a quantum system is delayed with respect to the time at which the system enters the interferometer. This paper reviews the history of the delayed-choice idea, introduced as a challenge to a realistic explanation of the wave-particle duality. It also describes recent experimental realizations of this idea and discusses intriguing extensions, such as the duality between separability and entanglement in multiple quantum systems.

[Rev. Mod. Phys. 88, 015005] Published Thu Mar 03, 2016

]]>How do we understand the production of the lightest nuclides from H to Li during the first seconds of cosmic time? This article reviews recent developments based on new precision cosmic microwave background measurements from the Planck satellite and observational abundance data. Utilizing updated input on nuclear reactions and the neutron lifetime as well as limits on the baryon density of the Universe obtained from Planck data leads to a number of neutrino flavors.

[Rev. Mod. Phys. 88, 015004] Published Tue Feb 23, 2016

]]>Besides being fundamental for life on Earth, water is one of the complex materials in nature. Due to the unusual properties of the hydrogen bonds water has a large number of phases as a function of temperature and pressure. Furthermore, the phase transitions between these different phases are still the object of much discussion. In this Colloquium the nature of these amazing properties of water is reviewed.

[Rev. Mod. Phys. 88, 011002] Published Wed Feb 17, 2016

]]>Methods of measuring the energies of jets have relied on detection of photons, charged hadrons, and neutral hadrons in a sampling calorimeter. However, the response for each particle is different, leading to poor jet energy resolution. Improved energy resolution for future studies of Higgs bosons and new particles decaying to jets requires improved energy resolution. The particle flow algorithm recognizes that charged particle momenta are better measured than their energies, so considerable improvement in energy resolution can be made using track momenta and substituting the energy deposited in the calorimeter. This article describes beam tests of the particle flow algorithm and the confrontation of data and simulations.

[Rev. Mod. Phys. 88, 015003] Published Mon Feb 08, 2016

]]>The quantum mechanics of black holes, and particularly the information paradox, have been a crucial arena for testing theories of quantum gravity. This review covers the quantum physics of black holes, anti-de Sitter/conformal field theory duality and holography, and the recent firewall paradox, with a focus on ideas from quantum information theory.

[Rev. Mod. Phys. 88, 015002] Published Tue Feb 02, 2016

]]>Physical phenomena at the nanoscale can be considerably different from the behavior in the macroscopic world. This rule is also true for plasmas at the nanoscale. This Colloquium discusses nanoplasmas from the experimental and theoretical point of view and shows that nanoplasmas can also have applications in certain technological areas.

[Rev. Mod. Phys. 88, 011001] Published Mon Jan 25, 2016

]]>Originally developed for quantum chromodynamics at strong coupling, lattice approximations provide an essential tool applicable to any strongly coupled gauge theory. The resolution of the lightweight Higgs puzzle may require new strongly coupled gauge theories at shorter distances. This review introduces the modern lattice tool kit as a combination of analytical and numerical techniques. Numerous applications to new physics with strong coupling gauge theories are presented, and results analyzed.

[Rev. Mod. Phys. 88, 015001] Published Tue Jan 19, 2016

]]>Experimental searches for new physics beyond the standard model of particle physics are not constrained to the high energy sector alone. This article shows examples on symmetry violations, possible breaking of time reversal and Lorentz invariance, from nuclear and neutron beta decay experiments and discusses how the accuracy of standard model parameters could be improved in the search for new physics.

[Rev. Mod. Phys. 87, 1483] Published Tue Dec 15, 2015

]]>How can the electric noise in the vicinity of a metallic body be measured and understood? Trapped ions, known as unique tools for metrology and quantum information processing, also constitute very sensitive probes of this electric noise for distances from micrometers to millimeters. This paper presents various models for the origin of the electric noise, provides a critical review of the experimental findings, and summarizes the important questions that are still open in this active research area.

[Rev. Mod. Phys. 87, 1419] Published Fri Dec 11, 2015

]]>A vision has formed in recent years of the components necessary for a large-scale quantum network. Single trapped atoms can serve as the nodes of this network, with the links established by flying photons that are coupled to the atoms using optical resonators. This review describes progress towards the goal of multinode networks using the current generation of experiments, which have achieved unprecedented levels of atomic qubit control and light-matter coupling efficiencies.

[Rev. Mod. Phys. 87, 1379] Published Tue Dec 01, 2015

]]>The occurrence of high-temperature ferromagnetism in transition metal semiconductors holds promise for devices with spintronic functionalities. This review focuses on transition metal aggregation process, which leads to random patterns of high-temperature material doped beyond the solubility limit. A computational description of nanodecomposition and the relevant experimental results are presented for a range of semiconductor compounds. The correlation of high-temperature ferromagnetism with spinodal nanodecomposition points to promising nanotechnology utilizing materials with transition metal rich nanoclusters coherently embedded within semiconducting hosts.

[Rev. Mod. Phys. 87, 1311] Published Thu Nov 19, 2015

]]>How can information from communication and social networks in modern societies be processed, classified, and retrieved? For this new mathematical methods have to be invented for a precise characterization of the existing networks and their search engines. This article describes the properties of the Google matrix and its efficiency in analyzing directed networks by way of several examples like the World Wide Web, Wikipedia, world trade, social and citation networks, DNA sequences and Ulam networks, and others. The underlying analytical and numerical tools used thereby originate from fields like quantum chaos and random matrix theory.

[Rev. Mod. Phys. 87, 1261] Published Mon Nov 02, 2015

]]>In solid-state materials with strong relativistic spin-orbit coupling, charge currents generate transverse spin currents. The associated spin Hall and inverse spin Hall effects distinguish between charge and spin current where electron charge is a conserved quantity but its spin direction is not. This review provides a theoretical and experimental treatment of this subfield of spintronics, beginning with distinct microscopic mechanisms seen in ferromagnets and concluding with a discussion of optical-, transport-, and magnetization-dynamics-based experiments closely linked to the microscopic and phenomenological theories presented.

[Rev. Mod. Phys. 87, 1213] Published Tue Oct 27, 2015

]]>The 2014 Nobel Prize for Chemistry was shared by Eric Betzig, Stefan W. Hell, and William E. Moerner. These papers are the text of the address given in conjunction with the award.

[Rev. Mod. Phys. 87, 1153] Published Wed Oct 21, 2015

]]>The 2014 Nobel Prize for Chemistry was shared by Eric Betzig, Stefan W. Hell, and William E. Moerner. These papers are the text of the address given in conjunction with the award.

[Rev. Mod. Phys. 87, 1169] Published Wed Oct 21, 2015

]]>The 2014 Nobel Prize for Chemistry was shared by Eric Betzig, Stefan W. Hell, and William E. Moerner. These papers are the text of the address given in conjunction with the award.

[Rev. Mod. Phys. 87, 1183] Published Wed Oct 21, 2015

]]>[Rev. Mod. Phys. 87, 1119] Published Mon Oct 05, 2015

]]>This is a personal history of one of the Japanese researchers engaged in developing a method for growing GaN on a sapphire substrate, paving the way for the realization of smart television and display systems using blue LEDs. The most important work was done in the mid to late 1980s. The background ...

[Rev. Mod. Phys. 87, 1133] Published Mon Oct 05, 2015

]]>[Rev. Mod. Phys. 87, 1139] Published Mon Oct 05, 2015

]]>Quantum Monte Carlo techniques aim at providing a description of complex quantum systems such as nuclei and nucleonic matter from first principles, i.e., realistic nuclear interactions and currents. The methods are similar to those used for many-electron systems in quantum chemistry and condensed matter physics, but are extended to include spin-isospin, tensor, spin-orbit, and three-body interactions. This review shows how to build the atomic nucleus from the ground up. Examples include the structure of light nuclei, electroweak response of nuclei relevant in electron and neutrino scattering, and the properties of dense nucleonic matter.

[Rev. Mod. Phys. 87, 1067] Published Wed Sep 09, 2015

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