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, Stefen 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, Stefen 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, Stefen 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

]]>Random-matrix theory has a long history of applications, from nuclear physics to electron localization to quantum dots. This review discusses yet another application of this very versatile framework: topological superconductors. An introduction to the basic concepts is followed by a discussion of transport properties that are susceptible to the predicted existence of Majorana excitations in these exotic materials.

[Rev. Mod. Phys. 87, 1037] Published Thu Sep 03, 2015

]]>Complex networks arise in a wide range of biological and sociotechnical systems. Epidemic spreading is central to our understanding of dynamical processes in complex networks, and is of interest to physicists, mathematicians, epidemiologists, and computer and social scientists. This review presents the main results and paradigmatic models in infectious disease modeling and generalized social contagion processes.

[Rev. Mod. Phys. 87, 925] Published Mon Aug 31, 2015

]]>Surface nanobubbles are nanoscopic gaseous domains on immersed substrates which can survive for days. They were first speculated to exist about 20 years ago, based on stepwise features in force curves between two hydrophobic surfaces, eventually leading to the first atomic force microscopy (AFM) ima…

[Rev. Mod. Phys. 87, 981] Published Mon Aug 31, 2015

]]>Density functional theory has been spectacularly successful in physics, chemistry, and related fields, and it keeps finding new applications. This paper gives an overview of the history of the method and its many applications since it gained wide acceptance, as well as a discussion of its likely future.

[Rev. Mod. Phys. 87, 897] Published Tue Aug 25, 2015

]]>In contrast to conventional BCS superconductors, the observation that superconductivity in unconventional high-temperature materials appears in close proximity to a static antiferromagnetic phase suggests that magnetism plays a fundamental role in the microscopic origins of superconductivity. This review provides an overview of how elastic and inelastic neutron scattering is used to determine the magnetic structures and the doping evolution of spin excitations in iron-based superconductors. The interplay between magnetism and superconductivity is contrasted with related behavior in the copper oxide and heavy fermion superconductors and is important to future theoretical efforts.

[Rev. Mod. Phys. 87, 855] Published Thu Aug 20, 2015

]]>The aim of this review, based on Anderson’s ideas on phase slippage in superfluid helium, is to convey a physical meaning to the superfluid order parameter and its phase. This embraces an understanding of the superfluid order parameter phase and the associated processes that involve phase slip, the motion of vortices, critical velocities, Josephson effects, and phase slip associated with flow through small apertures. The review proceeds from a historical overview to a description of how the hydrodynamics of superfluid helium evolves from large to small scale, ultimately breaking down at close distance revealing the perplexingly elusive quantum properties of these fluids.

[Rev. Mod. Phys. 87, 803] Published Mon Aug 17, 2015

]]>Recent advances in ultrafast laser spectroscopy have made it possible to study the electron dynamics for physical and chemical processes at the atomic level in real time. This article reviews the concepts and techniques that are necessary to understand and interpret these experiments with the focus on time-resolved photoemission.

[Rev. Mod. Phys. 87, 765] Published Wed Aug 12, 2015

]]>Carbon nanotubes with multifunctional capabilities are prime candidates for quantum wires for use in a variety of novel electronic devices. Unlike conventional semiconductor nanowires, electrons confined to nanotubes have two angular momentum quantum numbers from spin and valley degrees of freedom. This review describes the energy levels associated with the interplay of each of these degrees of freedom and how the spin-orbit interaction affects electronic transport through single and multiple quantum dots created by external field gating. The emphasis on experimental evidence provides essential concepts which are placed into context with recent theoretical advances such as on electron-electron interactions in one dimension.

[Rev. Mod. Phys. 87, 703] Published Tue Jul 28, 2015

]]>Since 1967 the primary time standard is the cesium atomic clock, based on a hyperfine transition in the microwave domain. The development of ultrastable laser sources now allows one to operate on electronic transitions in the optical domain, corresponding to a 5-order-of-magnitude increase in the clock frequency. This article reviews the spectacular accuracy and stability gains that can be obtained when working with laser cooled ions or neutral atoms. It also discusses some important applications of these optical clocks, from geodesy to tests of fundamental theories to many-body physics.

[Rev. Mod. Phys. 87, 637] Published Fri Jun 26, 2015

]]>The statistical mechanics of systems out of equilibrium provides a formidable challenge. This review describes an approach to a subset of such problems, viz., stationary nonequilibrium states. The review includes what is known as the macroscopic fluctuation theory, which allows for the definition of nonequilibrium analogs of thermodynamics potentials, and is applied to various illustrative models.

[Rev. Mod. Phys. 87, 593] Published Wed Jun 24, 2015

]]>With the observation of neutrino masses and mixings, the study of their electromagnetic interactions has assumed greater relevance both as verification of the $\nu $ standard model, and as a guide to new physics. After a standard description of massive neutrinos, this review assembles the present state of the art in the study of their electromagnetic interactions. Possible measurements of their static properties as test of new physics are described, a well as their behavior in strong magnetic fields. As such it should be helpful to both particle physicists and astrophysicists.

[Rev. Mod. Phys. 87, 531] Published Tue Jun 16, 2015

]]>Lévy walks are random walks in which the distribution of step length does not decay exponentially and the velocity of the moving particle is finite. Building on earlier concepts, they reconcile anomalously fast diffusion with a finite propagation speed and have applications that range from basic statistical mechanics and transport theory to optics, cold atom dynamics, and biophysics. This review gives an introduction to this important class of models and discusses applications in both physics and biology.

[Rev. Mod. Phys. 87, 483] Published Tue Jun 09, 2015

]]>Understanding high temperature superconductors is a central problem in condensed matter physics. Many experiments have uncovered ordering tendencies which are responsible for the complex phase diagram of high temperature superconductors. This Colloquium discusses the interplay between different order parameters in these materials. Considering the intertwining of these orders leads to new experimentally observable consequences, shedding new light into the physics of these fascinating materials.

[Rev. Mod. Phys. 87, 457] Published Tue May 26, 2015

]]>Several years ago measurements at the Fermilab Tevatron proton-antiproton collider showed top quarks to be produced preferably in the proton direction and the antitop quarks in the antiproton direction. The size of such asymmetries was not expected in the standard model and this sparked intensive effort. This article reviews the current theoretical and experimental progress in understanding the asymmetries. The revised measurements and calculations are now in relatively good agreement. The LHC now produces large quantities of top quarks and can study related, but different, measures of asymmetric top quark production. The prospects for the LHC to extend our understanding and to probe for new physics beyond the standard model paradigm are also discussed.

[Rev. Mod. Phys. 87, 421] Published Mon May 18, 2015

]]>This Colloquium presents recent progress in understanding constraints and consequences of close-packing geometry of filamentous or columnar materials possessing nontrivial textures, focusing, in particular, on the common motifs of twisted and toroidal structures. The mathematical framework is presen…

[Rev. Mod. Phys. 87, 401] Published Thu May 14, 2015

]]>Quantum dots embedded in photonics nanostructures provide unprecedented control over the interaction between light and matter. This review gives an overview of the theoretical principles involved, as well as applications ranging from high-precision quantum electrodynamics experiments to quantum-information processing.

[Rev. Mod. Phys. 87, 347] Published Mon May 11, 2015

]]>It may seem inevitable that highly entangled quantum states are susceptible to disturbance through interaction with a decohering environment. However, certain multiqubit entangled states are well protected from common forms of decoherence as the quantum information is hidden in inherently nonlocal degrees of freedom. This review shows that this robustness is enabled by specific measurements on subsets of qubits, implementing a quantum version of an error correction process. Beginning with the basics, the latest understanding of the relation between this form of error correction and the concept of two-dimensional topological order in many-body physics is reviewed.

[Rev. Mod. Phys. 87, 307] Published Tue Apr 07, 2015

]]>In recent years, there has been a wealth of new science involving low-energy antimatter (i.e., positrons and antiprotons) at energies ranging from ${10}^{2}$ to less than ${10}^{-3}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{eV}$. Much of this progress has been driven by the development of new plasma-based techniques to accumulate, manipulate, and deliver…

[Rev. Mod. Phys. 87, 247] Published Tue Mar 17, 2015

]]>The current status and open challenges of large ${N}_{c}$ QCD baryon spectroscopy are reviewed. After introducing the $1/{N}_{c}$ expansion method, the latest achievements for the ground state properties are revisited. Next the applicability of this method to excited states is presented using two different approa…

[Rev. Mod. Phys. 87, 211] Published Tue Mar 10, 2015

]]>The routine transformation of a liquid, as it is rapidly cooled, resulting in glass formation, is remarkably complex. A theoretical explanation of the dynamics associated with this process has remained one of the major unsolved problems in condensed matter physics. The random first order transition …

[Rev. Mod. Phys. 87, 183] Published Tue Mar 03, 2015

]]>Symmetry transformations have been proven a bedrock tool for understanding the nature of particle interactions, formulating, and testing fundamental theories. Based on the up to now unbroken $CPT$ symmetry, the violation of the $CP$ symmetry between matter and antimatter by weak interactions, discovered…

[Rev. Mod. Phys. 87, 165] Published Mon Feb 23, 2015

]]>Ettore Majorana (1906–1938) disappeared while traveling by ship from Palermo to Naples in 1938. His fate has never been fully resolved and several articles have been written that explore the mystery itself. His demise intrigues us still today because of his seminal work, published the previous year,…

[Rev. Mod. Phys. 87, 137] Published Wed Feb 11, 2015

]]>Mass spectrometry (MS) is widely regarded as the most sensitive and specific general purpose analytical technique. More than a century has passed for MS since the ground-breaking work of Nobel laureate Sir Joseph John Thomson in 1913. This Colloquium aims to (1) give an historical overview of the ma…

[Rev. Mod. Phys. 87, 113] Published Wed Jan 28, 2015

]]>This is a review on theoretical and experimental studies on dielectric microcavities, which play a significant role in fundamental and applied research. The basic concepts and theories are introduced. Experimental techniques for fabrication of microcavities and optical characterization are described…

[Rev. Mod. Phys. 87, 61] Published Thu Jan 22, 2015

]]>*Compass models* are theories of matter in which the couplings between the internal spin (or other relevant field) components are inherently spatially (typically, direction) dependent. A simple illustrative example is furnished by the *90° compass model* on a square lattice in which only couplings of th…

[Rev. Mod. Phys. 87, 1] Published Mon Jan 12, 2015

]]>[Rev. Mod. Phys. 86, 1453] Published Wed Dec 31, 2014

]]>The field of cavity optomechanics is reviewed. This field explores the interaction between electromagnetic radiation and nanomechanical or micromechanical motion. This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radi…

[Rev. Mod. Phys. 86, 1391] Published Tue Dec 30, 2014

]]>The use of infrared lasers to power optical-scale lithographically fabricated particle accelerators is a developing area of research that has garnered increasing interest in recent years. The physics and technology of this approach is reviewed, which is referred to as dielectric laser acceleration (…

[Rev. Mod. Phys. 86, 1337] Published Tue Dec 23, 2014

]]>This article reviews the role of hidden symmetries of dynamics in the study of physical systems, from the basic concepts of symmetries in phase space to the forefront of current research. Such symmetries emerge naturally in the description of physical systems as varied as nonrelativistic, relativist…

[Rev. Mod. Phys. 86, 1283] Published Mon Dec 22, 2014

]]>Recent years have witnessed a controversy over Heisenberg’s famous error-disturbance relation. Here the conflict is resolved by way of an analysis of the possible conceptualizations of measurement error and disturbance in quantum mechanics. Two approaches to adapting the classic notion of root-mean-…

[Rev. Mod. Phys. 86, 1261] Published Thu Dec 18, 2014

]]>Any physical process can be represented as a quantum channel mapping an initial state to a final state. Hence it can be characterized from the point of view of communication theory, i.e., in terms of its ability to transfer information. Quantum information provides a theoretical framework and the pr…

[Rev. Mod. Phys. 86, 1203] Published Wed Dec 10, 2014

]]>Finding new collective electronic states in materials is one of the fundamental goals of condensed matter physics. Atomic-scale superlattices formed from transition metal oxides are a particularly appealing hunting ground for new physics. In bulk form, transition metal oxides exhibit a remarkable ra…

[Rev. Mod. Phys. 86, 1189] Published Mon Oct 13, 2014

]]>The fractional calculus has been part of the mathematics and science literature for 310 years. However, it is only in the past decade or so that it has drawn the attention of mainstream science as a way to describe the dynamics of complex phenomena with long-term memory, spatial heterogeneity, along…

[Rev. Mod. Phys. 86, 1169] Published Thu Oct 09, 2014

]]>[Rev. Mod. Phys. 86, 1187] Published Thu Oct 09, 2014

]]>Experimental investigations of spin-polarized electron confinement in nanostructures by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) are reviewed. To appreciate the experimental results on the electronic level, the physical basis of STM is elucidated with special emp…

[Rev. Mod. Phys. 86, 1127] Published Fri Oct 03, 2014

]]>[Rev. Mod. Phys. 86, 1125] Published Mon Sep 22, 2014

]]>This Colloquium presents an overview of the research on nonlinear electromagnetic metamaterials. The developed theoretical approaches and experimental designs are summarized, along with a systematic description of various phenomena available with nonlinear metamaterials.

[Rev. Mod. Phys. 86, 1093] Published Fri Sep 12, 2014

]]>The hadronic final state in electron-proton collisions at HERA has provided a rich testing ground for development of the theory of the strong force, QCD. In this review, over 200 publications from the H1 and ZEUS Collaborations are summarized. Short distance physics, the measurement of processes at …

[Rev. Mod. Phys. 86, 1037] Published Fri Aug 22, 2014

]]>This is an overview of theoretical approaches to semiflexible polymers and their networks. Such semiflexible polymers have large bending rigidities that can compete with the entropic tendency of a chain to crumple up into a random coil. Many studies on semiflexible polymers and their assemblies have…

[Rev. Mod. Phys. 86, 995] Published Thu Jul 24, 2014

]]>Spectroscopic studies of electronic phenomena in graphene are reviewed. A variety of methods and techniques are surveyed, from quasiparticle spectroscopies (tunneling, photoemission) to methods probing density and current response (infrared optics, Raman) to scanning probe nanoscopy and ultrafast pu…

[Rev. Mod. Phys. 86, 959] Published Wed Jul 23, 2014

]]>Biological locomotion, movement within environments through self-deformation, encompasses a range of time and length scales in an organism. These include the electrophysiology of the nervous system, the dynamics of muscle activation, the mechanics of the skeletal system, and the interaction mechanic…

[Rev. Mod. Phys. 86, 943] Published Thu Jul 17, 2014

]]>Accelerator-based light sources such as storage rings and free-electron lasers use relativistic electron beams to produce intense radiation over a wide spectral range for fundamental research in physics, chemistry, materials science, biology, and medicine. More than a dozen such sources operate worl…

[Rev. Mod. Phys. 86, 897] Published Mon Jul 14, 2014

]]>Over the past two decades, the research of (Ga,Mn)As has led to a deeper understanding of relativistic spin-dependent phenomena in magnetic systems. It has also led to discoveries of new effects and demonstrations of unprecedented functionalities of experimental spintronic devices with general appli…

[Rev. Mod. Phys. 86, 855] Published Fri Jul 11, 2014

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