The dynamic charge susceptibility, χ(q, ω), is a fundamental observable of all materials, in one, two, and three dimensions, quantifying the collective charge modes and the ability of a material to screen charge, as well as its electronic compressibility. Here, we review the current state of efforts to measure the charge susceptibility of quantum materials using inelastic electron scattering, which

This article is the result of a transcribed recording of an interview that Ram Seshadri [Materials and Chemistry, University of California, Santa Barbara (UCSB)] conducted with Fyl Pincus who recently retired from UCSB (Physics and Materials). Its focus is an autobiographical account of Fyl's academic career and includes a personal view of the early days of soft condensed matter as a subdiscipline

Understanding superconductivity in its myriad forms arising in numerous different crystal architectures is one of the major quests of modern condensed matter physics. One promising avenue to gain local information about novel superconductors is the use of local probes to measure properties inside the unit cell. The application of muon spin spectroscopy to the study of various superconducting materials

Feedback control is essential to the performance of dynamical systems, helping to drive nonequilibrium systems from one state to another. In this review, we discuss feedback control applied to living and synthetic active matter—systems that are constantly dynamical and out of equilibrium. We review the experimental and theoretical work in controlling the trajectory and distribution of active matter

Turbulent motion of fluids is often thought of as a grand problem, but what exactly is this “turbulence problem”? Because it has often been proclaimed as very difficult and unsolved, when can we claim that it is solved? How does this situation in turbulence compare with other complex problems in physical sciences? Addressing these questions is not trivial because everyone has their favorite idea of

Nearly thirty years after its inception, the field of DNA-programmed colloidal self-assembly has begun to realize its initial promise. In this review, we summarize recent developments in designing effective interactions and understanding the dynamic self-assembly pathways of DNA-coated nanoparticles and microparticles, as well as how these advances have propelled tremendous progress in crystal engineering

Over the past approximately 10 years, it has become routine to use piezoelectric actuators to apply large anisotropic stresses to correlated electron materials. Elastic strains exceeding 1% can often be achieved, which is sufficient to qualitatively alter the magnetic and/or electronic structures of a wide range of correlated electron materials. Experiments fall into two broad groups. In one, explicit

We review a key subset of the experimental studies that have recently focused on cubic pyrochlore magnets whose pseudospin-1/2 degrees of freedom have mixed dipolar and octupolar character. We discuss how this comes about and how the character of the pseudospin-1/2 can be experimentally determined. The minimal spin Hamiltonian for such magnetic insulators is known to give rise to a rich phase diagram

Antibiotics are a cornerstone of modern medicine, and antibiotic resistance is a growing threat to public health. The evolution of resistance is a multiscale process shaped by many of the same phenomena that have fascinated condensed matter physicists for decades: fluctuations, disorder, scaling, and the emergence of structure from local heterogeneous interactions. In this review, we offer a brief

We discuss the emerging advances and opportunities at the intersection of machine learning (ML) and climate physics, highlighting the use of ML techniques, including supervised, unsupervised, and equation discovery, to accelerate climate knowledge discoveries and simulations. We delineate two distinct yet complementary aspects: (a) ML for climate physics and (b) ML for climate simulations. Although

Active matter theories naturally describe the mechanics of living systems. As biological matter is overwhelmingly chiral, an understanding of the implications of chirality for the mechanics and statistical mechanics of active materials is a priority. This article examines active, chiral materials from a liquid-crystal physicist's point of view, extracting general features of broken-symmetry-ordered

Organisms maintain the status quo, holding key physiological variables constant to within an acceptable tolerance, and yet adapt with precision and plasticity to dynamic changes in externalities. What organizational principles ensure such exquisite yet robust control of systems-level “state variables” in complex systems with an extraordinary number of moving parts and fluctuating variables? Here, we

The flattening of single-particle band structures plays an important role in the quest for novel quantum states of matter owing to the crucial role of interactions. Recent advances in theory and experiment made it possible to construct and tune systems with nearly flat bands, ranging from graphene multilayers and moiré materials to kagome metals and ruthenates. Although theoretical models predict exactly

Even when ideal solids are insulating, their states with crystallographic defects may have superfluid properties. It became clear recently that edge dislocations in 4He featuring a combination of microscopic quantum roughness and superfluidity of their cores may represent a new paradigmatic class of quasi-one-dimensional superfluids. The new state of matter, termed transverse quantum fluid (TQF), is

With the growing number of microscale devices from computer memory to microelectromechanical systems, such as lab-on-a-chip biosensors, and the increased ability to experimentally measure at the micro- and nanoscale, modeling systems with stochastic processes is a growing need across science. In particular, stochastic partial differential equations (SPDEs) naturally arise from continuum models—for

The shape of a soft solid is largely determined by the balance between elastic and surface energies with capillarity becoming important at length scales smaller than the elastocapillary length, which approaches the millimeter scale for the softest hydrogels, leading to many new and surprising phenomena. This review is focused on describing recent experimental and theoretical progress on the deformations

Trapped ions offer long coherence times and high-fidelity, programmable quantum operations, making them a promising platform for quantum simulation of condensed matter systems, quantum dynamics, and problems related to high-energy physics. We review selected developments in trapped-ion qubits and architectures and discuss quantum simulation applications that utilize these emerging capabilities. This

Spin-polarized antiferromagnets have recently gained significant interest because they combine the advantages of both ferromagnets (spin polarization) and antiferromagnets (absence of net magnetization) for spintronics applications. In particular, spin-polarized antiferromagnetic metals can be useful as active spintronics materials because of their high electrical and thermal conductivities and their

Fractons emerge from many-body systems, featuring subdimensional particles with restricted mobility. These particles have attracted interest for their roles across disciplines, including topological quantum codes, quantum field theory, emergent gravity, and quantum information. They display unique nonequilibrium behaviors such as nonergodicity and glassy dynamics. This review offers a structured overview

Solids are rigid, which means that when left undisturbed, their structures are nearly static. It follows that these structures depend on history—but it is surprising that they hold readable memories of past events. Here, we review the research that has recently flourished around mechanical memory formation, beginning with amorphous solids’ various memories of deformation and mesoscopic models based

Colloidal dispersions exhibit rich equilibrium and nonequilibrium thermodynamic properties, self-assemble into diverse structures at different length scales, and display transport behavior under bulk conditions. In confinement or under geometrical restrictions, new phenomena emerge that have no counterpart when the colloids are embedded in an open, noncurved space. In this review, we focus on the effects

I describe some of my activities, academic and personal, since coming to the United States in 1946 at the age of 16. It has been a long journey with many ups and downs. I selectively and briefly describe my experiences in a rabbinical school with an attached (parochial) high school, at Brooklyn College, in graduate school at Syracuse University, during a postdoc with Lars Onsager at Yale University

The quantum-mechanical description of assemblies of particles whose motion is confined to two (or one) spatial dimensions offers many possibilities that are distinct from bosons and fermions. We call such particles anyons. The simplest anyons are parameterized by an angular phase parameter θ. θ = 0, π correspond to bosons and fermions, respectively; at intermediate values, we say that we have fractional

Understanding the physics of behavior in animals is a challenging and fascinating area of research that has gained increasing attention in recent years. In this review, we delve into the intricate temporal and spatial scales of animal behavior for both individuals and collectives. We explore the experimental and theoretical approaches used to study behavior, highlighting the importance of feedback

The “flow” of electric currents and heat in standard metals is diffusive with electronic motion randomized by impurities. However, for ultraclean metals, electrons can flow like water with their flow being described by the equations of hydrodynamics. While theoretically postulated, this situation was highly elusive for decades. In the past decade, several experimental groups have found strong indications

We review aspects of the evolution from Bardeen–Cooper–Schrieffer (BCS) to Bose–Einstein condensation (BEC) in two dimensions, which have now become relevant in systems with low densities, such as gated superconductors Li xZrNCl, magic-angle twisted trilayer graphene, FeSe, FeSe1− xS x, and ultracold Fermi superfluids. We emphasize the important role played by chemical potentials in determining crossovers

Living cells are spatially organized by compartments that can nucleate, grow, and dissolve. Compartmentalization can emerge by phase separation, leading to the formation of droplets in the cell's nucleo- or cytoplasm, also called biomolecular condensates. Such droplets can organize the biochemistry of the cell by providing specific chemical environments in space and time. These compartments provide

Life evolved organisms to adapt dynamically to their environment and autonomously exhibit behaviors. Although complex behaviors in organisms are typically associated with the capability of neurons to process information, the unicellular organism Physarum polycephalum disabuses us by solving complex tasks despite being just a single although gigantic cell shaped into a mesmerizing tubular network. In

The superconducting nickelates were first proposed as potential analogs to the cuprate unconventional superconductors in 1999, but it took twenty years before superconductivity was successfully stabilized in epitaxial thin films. Since then, a flurry of both experimental and theoretical efforts have sought to understand the similarities and differences between the two systems and how they manifest

At the scale of drops, water either sticks to inclined solids or moves, yet slowly—without the mobility we expect of a liquid of low viscosity. We first recall that the contact line that bounds a drop is responsible for these special adhesion and enhanced friction properties. Then, we discuss how inducing nonwetting states (pearls and marbles) minimizes the role of this line, restores mobility, and

Rich out-of-equilibrium collective dynamics of strongly interacting large assemblies emerge in many areas of science. Some intriguing and not fully understood examples are the glassy arrest in atomic, molecular, or colloidal systems; flocking in natural or artificial active matter; and the organization and subsistence of ecosystems. The learning process, and ensuing amazing performance, of deep neural

High-temperature superconductivity, with transition temperatures up to ≈134 K at ambient pressure, occurs in layered cuprate compounds. The conducting CuO2 planes, which are universally present, are responsible for the superconductivity but also show a disposition to other competing states including spin and charge order. Charge-density-wave (CDW) order appears to be a universal property of cuprate

The Heisenberg spin chain is a canonical integrable model. As such, it features stable ballistically propagating quasiparticles, but spin transport is subballistic at any nonzero temperature: An initially localized spin fluctuation spreads in time t to a width t2/3. This exponent as well as the functional form of the dynamical spin correlation function suggest that spin transport is in the Kardar–Parisi–Zhang

Magnetoelectric multiferroics, which display both ferroelectric and magnetic orders, are appealing because of their rich fundamental physics and promising technological applications. The revival of multiferroics since 2003 led to a comprehensive understanding of the mechanisms that facilitate the coexistence of electric and magnetic orders and conceptually new design strategies for device architectures

Underwater soft robots are typically constructed from soft and flexible materials, which enable them to adapt to aquatic environments where the terrain can be complex. They are often inspired by soft-bodied aquatic animals and can be used for a range of tasks, such as underwater exploration, environmental monitoring, and rescue operations. However, the design of these robots presents significant challenges

In noncentrosymmetric materials, the responses (for example, electrical and optical) generally depend on the direction of the external stimuli, called nonreciprocal phenomena. In quantum materials, these nonreciprocal responses are governed by the quantum geometric properties and symmetries of the electronic states. In particular, spatial inversion ([Formula: see text]) and time-reversal ([Formula:

The thermal Green's function formalism bridging between macroscopic observables and microscopic processes via linear response theory was established in the early 1960s, when I started my research career. I recall stimulating experiences with the help of this technique in exploring transport and thermodynamic properties of Bloch electrons in magnetic fields, especially orbital magnetism and the Hall

Soft matter is a field of condensed matter physics that began to develop in France in the 1970s under the impulse of Pierre-Gilles de Gennes. I had the chance to participate in this adventure, and I describe in this article some of the memorable events. Soft matter is not only linked to physics but also to chemistry and biology, and working in this multidisciplinary field is quite stimulating. My particular

Learning is traditionally studied in biological or computational systems. The power of learning frameworks in solving hard inverse problems provides an appealing case for the development of physical learning in which physical systems adopt desirable properties on their own without computational design. It was recently realized that large classes of physical systems can physically learn through local

Elasticity typically refers to a material's ability to store energy, whereas viscosity refers to a material's tendency to dissipate it. In this review, we discuss fluids and solids for which this is not the case. These materials display additional linear response coefficients known as odd viscosity and odd elasticity. We first introduce odd viscosity and odd elasticity from a continuum perspective

Weakly interacting quasiparticles play a central role in the low-energy description of many phases of quantum matter. At higher energies, however, quasiparticles cease to be well defined in generic many-body systems owing to a proliferation of decay channels. In this review, we discuss the phenomenon of quantum many-body scars, which can give rise to certain species of stable quasiparticles throughout

We review the literature on swimming in complex fluids. A classification is proposed by comparing the length- and timescales of a swimmer with those of nearby obstacles, interpreted broadly, extending from rigid or soft confining boundaries to molecules that confer the bulk fluid with complex stresses. A third dimension in the classification is the concentration of swimmers, which incorporates fluids

Quantum circuits—built from local unitary gates and local measurements—are a new playground for quantum many-body physics and a tractable setting to explore universal collective phenomena far from equilibrium. These models have shed light on longstanding questions about thermalization and chaos, and on the underlying universal dynamics of quantum information and entanglement. In addition, such models

The modern scope of fermiology encompasses not just the classical geometry of Fermi surfaces but also the geometry of quantum wave functions over the Fermi surface. This enlarged scope is motivated by the advent of topological metals—metals whose Fermi surfaces are characterized by a robustly nontrivial Berry phase. We review the extent to which topological metals can be diagnosed from magnetic-field-induced

Understanding the behavior of human crowds is a key step toward a safer society and more livable cities. Despite the individual variability and will of single individuals, human crowds, from dilute to dense, invariably display a remarkable set of universal features and statistically reproducible behaviors. Here, we review ideas and recent progress in employing the language and tools from physics to

The solar–to–chemical energy conversion of Earth-abundant resources like water or greenhouse gas pollutants like CO2 promises an alternate energy source that is clean, renewable, and environmentally friendly. The eventual large-scale application of such photo-based energy conversion devices can be realized through the discovery of novel photocatalytic materials that are efficient, selective, and robust

Life is a nonequilibrium phenomenon: Metabolism provides a continuous supply of energy that drives nearly all cellular processes. However, very little is known about how much energy different cellular processes use, i.e., their energetic costs. The most direct experimental measurements of these costs involve modulating the activity of cellular processes and determining the resulting changes in energetic

Tensor networks provide extremely powerful tools for the study of complex classical and quantum many-body problems. Over the past two decades, the increment in the number of techniques and applications has been relentless, and especially the last ten years have seen an explosion of new ideas and results that may be overwhelming for the newcomer. This short review introduces the basic ideas, the best

DNA molecules with a total length of two meters contain the genetic information in every cell in our body. To control access to the genes, to organize its spatial structure in the nucleus, and to duplicate and faithfully separate the genetic material, the cell makes use of sophisticated physical mechanisms. Base pair sequences multiplex various layers of information, chromatin remodelers mobilize nucleosomes

Inversion and time reversal are essential symmetries for the structure of Cooper pairs in superconductors. The loss of one or both leads to modifications to this structure and can change the properties of the superconducting phases in profound ways. Superconductivity in materials lacking inversion symmetry, or noncentrosymmetric materials, has become an important topic. These materials show unusual

The spin Seebeck effect (SSE) refers to the generation of a spin current as a result of a temperature gradient in a magnetic material, which can be detected electrically via the inverse spin Hall effect in a metallic contact. Since the discovery of the SSE in 2008, intensive studies on the SSE have been conducted to elucidate its origin. SSEs appear in a wide range of magnetic materials including ferro-

The past decades have witnessed an explosion of interest in topological materials, and a lot of mathematical concepts have been introduced in condensed matter physics. Among them, the bulk-boundary correspondence is the central topic in topological physics, which has inspired researchers to focus on boundary physics. Recently, the concepts of topological phases have been extended to non-Hermitian Hamiltonians

Active colloids are self-propelled particles moving in viscous fluids by consuming fuel from their surroundings. Here, we review the numerical and theoretical modeling of active colloids propelled by self-generated near-surface flows. We start with the generic model of an active Brownian particle taking into account potential forces and effective pairwise interaction, which include hydrodynamic and

Recent advances in our understanding of symmetry in quantum many-body systems offer the possibility of a generalized Landau paradigm that encompasses all equilibrium phases of matter. This is a brief and elementary review of some of these developments.

In Floquet engineering, periodic driving is used to realize novel phases of matter that are inaccessible in thermal equilibrium. For this purpose, the Floquet theory provides us a recipe for obtaining a static effective Hamiltonian. Although many existing works have treated closed systems, it is important to consider the effect of dissipation, which is ubiquitous in nature. Understanding the interplay

The overall effect of temperature gradients is stressed for the Earth's core and surface, but also for the Sun's surface. Using Rayleigh–Bénard convection in helium and mercury, we measured all of the scaling properties of the period-doubling cascade and quasiperiodicity. Hard turbulence scaling properties are presented in an experiment using helium gas at low temperature. A [Formula: see text] scaling

This article summarizes some of the relevant features exhibited by binary mixtures of Bose–Einstein condensates in the presence of coherent coupling at zero temperature. The coupling, which is experimentally produced by proper photon transitions, can involve either negligible momentum transfer from the electromagnetic radiation (Rabi coupling) or large momentum transfer (Raman coupling) associated

Electronic correlations give rise to fascinating macroscopic phenomena such as superconductivity, magnetism, and topological phases of matter. Although these phenomena manifest themselves macroscopically, fully understanding the underlying microscopic mechanisms often requires probing on multiple length scales. Spatial modulations on the mesoscopic scale are especially challenging to probe, owing to

Cytoskeletal networks are the main actuators of cellular mechanics, and a foundational example for active matter physics. In cytoskeletal networks, motion is generated on small scales by filaments that push and pull on each other via molecular-scale motors. These local actuations give rise to large-scale stresses and motion. To understand how microscopic processes can give rise to self-organized behavior

Taking a historical perspective, we provide a brief overview of the first-principles modeling of ferroelectric perovskite oxides over the past 30 years. We emphasize how the work done by a relatively small community on the fundamental understanding of ferroelectricity and related phenomena has been at the origin of consecutive theoretical breakthroughs, with an impact going often well beyond the limit