Flat bands in magic-angle twisted bilayer graphene (MATBG) have recently emerged as a rich platform to explore strong correlations1, superconductivity2,3,4,5 and magnetism3,6,7. However, the phases of MATBG in a magnetic field and what they reveal about the zero-field phase diagram remain relatively uncharted. Here we report a rich sequence of wedge-like regions of quantized Hall conductance with Chern

Multiplexing increases the capacity of optical communication, but it is limited by the number of modes and their orbital angular momentum. A robust vortex laser now solves this problem by emitting several beams, all carrying large topological charges.

SARS, MERS and now SARS-CoV-2 are unlikely to be the last emerging infections we face during our lifetimes. Tracing contacts both forward and backward through our heterogeneous populations will prove essential to future response strategies.

The quantum Hall effect involves electrons confined to a two-dimensional plane subject to a perpendicular magnetic field, but it also has a photonic analogue1,2,3,4,5,6. Using heterostructures based on structured semiconductors on a magnetic substrate, we introduce compact and integrated coherent light sources of large orbital angular momenta7 based on the photonic quantum Hall effect1,2,3,4,5,6. The

Advancing our understanding of non-equilibrium phenomena in quantum many-body systems remains one of the greatest challenges in physics. Here we report on the experimental observation of a paradigmatic many-body problem, namely the non-equilibrium dynamics of a quantum impurity immersed in a bosonic environment1,2. We use an interferometric technique to prepare coherent superposition states of atoms

Effective control of an epidemic relies on the rapid discovery and isolation of infected individuals. Because many infectious diseases spread through interaction, contact tracing is widely used to facilitate case discovery and control. However, what determines the efficacy of contact tracing has not been fully understood. Here we reveal that, compared with ‘forward’ tracing (tracing to whom disease

The ability to tailor the hopping interactions between the constituent elements of a physical system could enable the observation of unusual phenomena that are otherwise inaccessible in standard settings1,2. In this regard, a number of recent theoretical studies have indicated that an asymmetry in either the short- or long-range complex exchange constants can lead to counterintuitive effects, for example

A Correction to this paper has been published: https://doi.org/10.1038/s41567-021-01192-5.

Optical spectroscopy in the gas phase is a key tool for elucidating the structure of atoms and molecules and their interaction with external fields. The line resolution is usually limited by a combination of first-order Doppler broadening due to particle thermal motion and a short transit time through the excitation beam. For trapped particles, suitable laser cooling techniques can lead to strong confinement

Understanding and tuning correlated states is of great interest and importance to modern condensed-matter physics. The recent discovery of unconventional superconductivity and Mott-like insulating states in magic-angle twisted bilayer graphene presents a unique platform to study correlation phenomena, in which the Coulomb energy dominates over the quenched kinetic energy as a result of hybridized flat

The ability to learn new tasks and generalize to others is a remarkable characteristic of both human brains and recent artificial intelligence systems. The ability to perform multiple tasks simultaneously is also a key characteristic of parallel architectures, as is evident in the human brain and exploited in traditional parallel architectures. Here we show that these two characteristics reflect a

A quantum dot has been used to detect a single excitation among the tens of thousands of atomic nuclear spins comprising it. This result is an important step towards treating nuclear spins as a quantum memory rather than a troublesome source of noise.

Electron and X-ray beams originating from compact laser-wakefield accelerators have very small source sizes that are typically on the micrometre scale. Therefore, the beam divergences are relatively high, which makes it difficult to preserve their high quality during transport to applications. To improve on this, tremendous efforts have been invested in controlling the divergence of the electron beams

Collective effects leading to spatial, temporal or spatiotemporal pattern formation in complex nonlinear systems driven out of equilibrium cannot be described at the single-particle level and are therefore often called emergent phenomena. They are characterized by length scales exceeding the characteristic interaction length and by spontaneous symmetry breaking. Recent advances in integrated photonics

The strong electron interactions in the minibands formed in moiré superlattices of van der Waals materials, such as twisted graphene and transition metal dichalcogenides, make such systems a fascinating platform with which to study strongly correlated states1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19. In most systems, the correlated states appear when the moiré lattice is filled by an integer number

Accessing an ensemble of coherently interacting objects at the level of single quanta via a proxy qubit is transformative in the investigations of emergent quantum phenomena. An isolated nuclear spin ensemble is a remarkable platform owing to its coherence, but sensing its excitations with single spin precision has remained elusive. Here we achieve quantum sensing of a single nuclear-spin excitation

Antiferromagnets can encode information in their ordered magnetic structure, providing the basis for future spintronic devices1,2,3. The control and understanding of antiferromagnetic domain walls, which are the interfaces between domains with differing order parameter orientations, are key ingredients for advancing antiferromagnetic spintronic technologies. However, studies of the intrinsic mechanics

Many cellular processes, such as cell division1,2,3, cell motility4, wound healing5 and tissue folding6,7, rely on the precise positioning of proteins on the membrane. Such protein patterns emerge from a combination of protein interactions, transport, conformational state changes and chemical reactions at the molecular level8. Recent experimental and theoretical work clearly demonstrates the role of

In twisted bilayers of semiconducting transition metal dichalcogenides, a combination of structural rippling and electronic coupling gives rise to periodic moiré potentials that can confine charged and neutral excitations1,2,3,4,5. Here we show that the moiré potential in these bilayers at small angles is unexpectedly large, reaching values above 300 meV for the valence band and 150 meV for the conduction

Two experiments using entangled photons have successfully generated more randomness than consumed — at a level of security that is all but certain. They did so by exploiting non-locality, one of the most counterintuitive aspects of quantum mechanics.

Topological invariants characterizing filled Bloch bands underpin electronic topological insulators and analogous artificial lattices for Bose–Einstein condensates, photonics and acoustic waves. In bosonic systems, there is no Fermi exclusion principle to enforce uniform band filling, which makes measuring their bulk topological invariants challenging. Here we show how to achieve the controllable filling

The ability to produce random numbers that are unknown to any outside party is crucial for many applications. Device-independent randomness generation1,2,3,4 does not require trusted devices and therefore provides strong guarantees of the security of the output, but it comes at the price of requiring the violation of a Bell inequality for implementation. A further challenge is to make the bounds in

The unavoidable effects of noise make quantum error correction necessary to realize the full potential of quantum computers. Devices that correct errors autonomously can avoid the computational and hardware overheads of traditional approaches.

The metric system is one of the enduring achievements of the French Revolution. Martin Milton recounts how it was also intended to unite nations.

Unlike their predecessors in the White House, Joe Biden and Kamala Harris are placing research and development at the centre of their policy agenda. This change was as sorely needed as it is welcome, but the stakes for the new US administration remain high.

The short lifetime of light-induced superconductivity prevents the measurement of its transport properties. Encouraging this state to stay a little longer in K3C60 allows the observation of vanishing electrical resistance.

Quantum computing combines great promise with daunting challenges — the road to devices that solve real-world problems is still long. Now, an implementation of a quantum algorithm maps the problems we want to solve to the devices we already have.

Faster algorithms for combinatorial optimization could prove transformative for diverse areas such as logistics, finance and machine learning. Accordingly, the possibility of quantum enhanced optimization has driven much interest in quantum technologies. Here we demonstrate the application of the Google Sycamore superconducting qubit quantum processor to combinatorial optimization problems with the

Holography is a cornerstone characterization and imaging technique that can be applied to the full electromagnetic spectrum, from X-rays to radio waves or even particles such as neutrons. The key property in all these holographic approaches is coherence, which is required to extract the phase information through interference with a reference beam. Without this, holography is not possible. Here we introduce

Various phenomena occur when two-dimensional materials, such as graphene or transition metal dichalcogenides, are assembled into bilayers with a twist between the individual layers. As an application of this paradigm, we predict that structures composed of two-monolayer-thin d-wave superconductors with a twist angle form a robust, fully gapped topological phase with spontaneously broken time-reversal

Excitation of high-Tc cuprates and certain organic superconductors with intense far-infrared optical pulses has been shown to create non-equilibrium states with optical properties that are consistent with transient high-temperature superconductivity. These non-equilibrium phases have been generated using femtosecond drives, and have been observed to disappear immediately after excitation, which is

Twisted van der Waals heterostructures have latterly received prominent attention for their many remarkable experimental properties and the promise that they hold for realizing elusive states of matter in the laboratory. We propose that these systems can, in fact, be used as a robust quantum simulation platform that enables the study of strongly correlated physics and topology in quantum materials

A Correction to this paper has been published: https://doi.org/10.1038/s41567-021-01181-8.

Table-top superfluid experiments offer a way of bringing the physics of astrophysical black holes into the lab. But the presence of two event horizons in these superfluid black holes complicates matters — and makes them more interesting.

With increasing neutron number, the size of a nucleus grows, subject to subtle effects that act as fingerprints of its internal structure. A fresh look at potassium calls for theory to decipher the details.

Muon colliders offer enormous potential for the exploration of the particle physics frontier but are challenging to realize. A new international collaboration is forming to make such a muon collider a reality.

With the growing availability of experimental loophole-free Bell tests1,2,3,4,5, it has become possible to implement a new class of device-independent random number generators whose output can be certified6,7 to be uniformly random without requiring a detailed model of the quantum devices used8,9,10. However, all these experiments require many input bits to certify a small number of output bits, and

Liquid–liquid phase separation1,2 occurs not only in bulk liquid, but also on surfaces. In physiology, the nature and function of condensates on cellular structures remain unexplored. Here we study how the condensed protein TPX2 behaves on microtubules to initiate branching microtubule nucleation3,4,5, which is critical for spindle assembly in eukaryotic cells6,7,8,9,10. Using fluorescence, electron

Nuclear charge radii are sensitive probes of different aspects of the nucleon–nucleon interaction and the bulk properties of nuclear matter, providing a stringent test and challenge for nuclear theory. Experimental evidence suggested a new magic neutron number at N = 32 (refs. 1,2,3) in the calcium region, whereas the unexpectedly large increases in the charge radii4,5 open new questions about the

A Correction to this paper has been published: https://doi.org/10.1038/s41567-021-01180-9.

Among the many reasons a signal may deviate from perfect periodicity, quantum-limited jitter is arguably the most fundamental. A clever experiment has now stripped away technical noise to unveil quantum-limited jitter of ultrafast soliton frequency combs.

Coherently pumped (Kerr) solitons in an ideal optical microcavity are expected to undergo random quantum motion that determines fundamental performance limits in applications of the soliton microcombs1. Here this random walk and its impact on Kerr soliton timing jitter are studied experimentally. The quantum limit is discerned by measuring the relative position of counter-propagating solitons2. Their

A Correction to this paper has been published: https://doi.org/10.1038/s41567-021-01178-3.

The magnetic properties of intercalated metal dichalcogenides are dramatically affected by small crystal imperfections, potentially providing design principles and materials for spintronic devices.

The use of coherent light for precision measurements has been a key driving force for numerous research directions, ranging from biomedical optics1,2 to semiconductor manufacturing3. Recent work demonstrates that the precision of such measurements can be substantially improved by tailoring the spatial profile of light fields used for estimating an observable system parameter4,5,6,7,8,9,10. These advances

Exchange bias is a property of widespread technological utility, but its underlying mechanism remains elusive, in part because it is rooted in the interaction of coexisting order parameters in the presence of complex magnetic disorder. Here we show that a giant exchange bias housed within a spin-glass phase arises in a disordered antiferromagnet. The magnitude and robustness of the exchange bias emerges

A Correction to this paper has been published: https://doi.org/10.1038/s41567-021-01169-4 .

Recent advances in spectroscopy give access to the decay time of excitations in disordered insulating silicon close to the metal–insulator transition, revealing similarities to high-temperature cuprate superconductors.

A long-standing open problem in condensed-matter physics is whether or not a strongly disordered interacting insulator can be mapped to a system of effectively non-interacting localized excitations. Using terahertz two-dimensional coherent spectroscopy, we investigate this issue in phosphorus-doped silicon, a classic example of a correlated disordered electron system in three dimensions. Despite the

Gaussian models provide an excellent effective description of many quantum many-body systems ranging from condensed-matter systems1,2 all the way to neutron stars3. Gaussian states are common at equilibrium when the interactions are weak. Recently it was proposed that they can also emerge dynamically from a non-Gaussian initial state evolving under non-interacting dynamics4,5,6,7,8,9,10,11. Here we

Epithelial tissues provide an important barrier function in animals, but these tissues are subjected to extreme strains during day-to-day activities such as feeding and locomotion. Understanding tissue mechanics and the adaptive response in dynamic force landscapes remains an important area of research. Here we carry out a multi-modal study of a simple yet highly dynamic organism, Trichoplax adhaerens

Intense X-ray free-electron lasers (XFELs) can rapidly excite matter, leaving it in inherently unstable states that decay on femtosecond timescales. The relaxation occurs primarily via Auger emission, so excited-state observations are constrained by Auger decay. In situ measurement of this process is therefore crucial, yet it has thus far remained elusive in XFELs owing to inherent timing and phase

Methodology adapted from data science sparked the field of materials informatics, and materials databases are at the heart of it. Applying artificial intelligence to these databases will allow the prediction of the properties of complex organic crystals.

Physicists and biologists have different conceptions of beauty. A better appreciation of these differences may bring the disciplines closer and help develop a more integrated view of life.

Biophysicists have long sought to probe the physical properties of the cell nucleus, but the sheer size of this tiny organelle puts limits on its exploration. The coarsening of biomolecular droplets looks set to give us the inside scoop.

When the twist angle between two layers of graphene is approximately 1.1°, interlayer tunnelling and rotational misalignment conspire to create a pair of flat bands1 that are known to host various insulating, superconducting and magnetic states when they are partially filled2,3,4,5,6,7. Most work has focused on the zero-magnetic-field phase diagram, but here we show that twisted bilayer graphene in

Identifying efficient pathways to control and modify the order parameter of a macroscopic phase in materials is an important ongoing challenge. One way to do this is via the excitation of a high-frequency mode that couples to the order, and this is the ultimate goal of the field of ultrafast phase transitions1,2. This is an especially interesting research direction in magnetism, where the coupling

DNA is organized into chromatin, a complex polymeric material that stores information and controls gene expression. An emerging mechanism for biological organization, particularly within the crowded nucleus, is biomolecular phase separation into condensed droplets of protein and nucleic acids. However, the way in which chromatin impacts the dynamics of phase separation and condensate formation is poorly

Simulations are as much a part of science as hypothesis and experiment. But can their outcomes be considered observations? Wendy S. Parker investigates.

Along with five other journals in the Nature Portfolio, Nature Physics will pilot a new Guided Open Access trial in 2021. We explain how it works.