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Dynamic nuclear polarization is the transfer of electronic angular momentum to nuclear spins and is a potential route for coherently manipulating spin in quantum information. Here, the authors show that spin–orbit coupling can quench dynamic nuclear polarization in a gallium arsenide quantum dot.

A superconductor–graphene junction is shown to exhibit the quantum Hall effect, with the chemical potential of the edge state displaying a sign reversal. Such a system could provide a platform for observing isolated non-Abelian anyonic zero modes.

The spin state of two electrons in a double well is a promising qubit. Now, such qubits can be arbitrarily rotated around two different axes by applying a magnetic field of different magnitude to each electron. This can be done in nanoseconds, before the stored information is lost.

In most electrical conductors, heat is transported by charge carriers and so both usually flow in the same direction; but in two-dimensional electron systems subject to strong magnetic fields, certain fractional quantum Hall states can cause charge and heat to flow in opposite directions.

Graphene multilayers can host heavy electrons in flat bands alongside light electrons in Dirac cones. Local probes now reveal that a finite Dirac electron population persists at the Fermi level while correlated states form in the flat bands.

Samples of graphene supported on boron nitride demonstrate superior electrical properties, achieving levels of performance that are comparable to those observed with suspended samples.

Monolayer graphene is a semimetal with no bandgap, and bilayer graphene is a semiconductor with a tunable gap. A trio of studies now shows that trilayer graphene can be either, depending on how its layers are stacked — behaviour that could support exotic new electronic states.

The presence of disorder makes it difficult to determine the intrinsic properties of graphene in its ideal form. Measurements of high-quality bilayer graphene flakes suspended above a substrate identify the persistence of quantum Hall behaviour at magnetic fields an order of magnitude lower than seen before, and previously unseen symmetry breaking of the lowest Landau level is also observed.

Majorana fermions, which are their own antiparticles, are expected to exist in topological superconductors. A study using superconducting leads in contact with a quantum well reveals the presence of supercurrents along one-dimensional sample edges of a quantum spin Hall state. These edge supercurrents are topological.

This study measures 'puddles' of charge in a fractional quantum Hall device and finds new evidence for the existence of quarter charge particles, thereby boosting confidence in the prospects for topological quantum computation.

Diract imaging of supercurrent flow at a Josephson junction has been inaccessible in experiment. Here, using nanoscale magnetometry, the authors find large kinetic inductance of thin film superconductors can lead to competing Josephson vortex states hidden below the critical current, and also provide a new route towards the Josephson diode effect.

An on-chip platform with in situ adjustable interfacial properties, using a microelectromechanical system, provides multi-degree-of-freedom control of two-dimensional materials, including twisting and pressurizing.

Exploring magnetic excitations and spin textures on the nanoscale may lead to new spintronic technologies and new understanding of condensed matter. Here, the authors demonstrate the potential of single electron spins in diamond to image such excitations by characterizing spin waves in a ferromagnetic microdisc.

By integrating a moiré photonic structure on-chip with advanced microelectromechanical system (MEMS) technology, an in situ twisted moiré photonic platform that can be tuned is realized, enabling nanometre-scale positioning of two optical nanostructures in either the near- or far-field coupling regime.

A study using local compressibility measurements reports fractional Chern insulator states at low magnetic field in magic-angle twisted bilayer graphene, and establishes the applied magnetic field as a means to tune the Berry curvature distribution.

Majorana bound states are created in a two-dimensional architecture by confining Majorana channels within a planar Josephson junction, using the phase difference across the junction and an in-plane magnetic field.

An antiferromagnetic diode effect was observed in a centrosymmetric crystal without directional charge separation. This effect could be used to create in-plane field-effect transistors and microwave-energy-harvesting devices.

Viscous Dirac fluid flow in room-temperature graphene is imaged using quantum diamond magnetometry, revealing a parabolic Poiseuille profile for electron flow in a high-mobility graphene channel near the charge-neutrality point.

Measurements of the superfluid stiffness in twisted trilayer graphene reveal unconventional nodal-gap superconductivity, where the superconducting transition is controlled by phase fluctuations rather than Cooper-pair breaking.

Directly embedding single nitrogen–vacancy centres into ordered arrays of plasmonic nanostructures can enhance their radiative emission rate and thus give greater scalability over previous bottom-up approaches for the realization of on-chip quantum networks.

This paper reports magnetic imaging of immunolabeled mammalian cells using nitrogen-vacancy centers in diamond and shows that the method can be used for quantitative profiling of markers.

Electron spins in semiconductor structures are quantum bits with good prospects, but the information stored in the spin states tends to degrade quickly owing to interactions with nuclei in the host material. A study of GaAs quantum dots now provides a fuller understanding of this memory loss and how it can be suppressed. Quantum-memory times exceeding 200 μs are demonstrated, two orders of magnitude longer than previously reported for this system.

A nitrogen–vacancy centre in diamond can be used as a probe for nanoscale NMR and MRI of multiple nuclear species.

Luttinger-liquid theory describes interacting electrons in one dimension, so long as their energies are linear as a function of momentum. When the energies become nonlinear, particles and holes behave differently, with particles able to relax when injected into a quantum wire.

The interplay between spin physics and superconductivity is examined in HgTe quantum wells, revealing a tunable momentum of the Cooper pairs that drives changes in their superconducting behaviour.

Previous measurements of interferometers based on quantum Hall (QH) edge channels have suggested potential electron pairing effects. Here, the authors investigate the coupling between QH edge channels in graphene Aharonov-Bohm (AB) interferometers, proposing a possible single-particle explanation for the apparent interference phase jumps and AB frequency doubling.

Local probes of quantum Hall states are still in their infancy. Now scanning tunnelling measurements were used to extract the energy gap of candidate non-Abelian fractional states, which are found to be encouragingly large for applications.

Interferometers can probe the wave-nature and exchange statistics of indistinguishable particles. Quantum Hall interferometers from graphite-encapsulated graphene heterostructures now enable the observation of the Aharonov–Bohm effect and of robust fractional quantum Hall states.

The sensitivity of a magnetometer based on a nitrogen–vacancy centre can be enhanced by three orders of magnitude by using a ferromagnetic nanoparticle.

In addition to the broken time-reversal symmetry that typifies Chern insulators, twisted bilayer graphene hosts a set of topological states with broken translational symmetry.

Although magnons in the quantum Hall regime of graphene have been detected, their thermodynamic properties have not yet been measured. Now, a local probe technique enables the detection of the magnon density and chemical potential.

When interactions between electrons in a material are strong, they can start to behave hydrodynamically. Spatially resolved imaging of current flow in a three-dimensional material suggests that electron–electron interactions are mediated by phonons.

Here, the authors develop a spectroscopic technique whereby individual defects in an ultrathin hBN dielectric, placed in proximity to graphene, act as quantum dots. Dot-assisted tunneling is highly sensitive to the nearby graphene excitation spectrum, and allows probing of energy splitting in the excited Landau levels.

The spin of the nitrogen-vacancy (NV) defect in diamond acts as a sensitive, atomic-sized magnetic field sensor that provides nanoscale access to the properties of condensed matter systems. This Review introduces NV magnetometry and discusses its application to the exploration of static and dynamic magnetism and electric current distributions.

The authors report a superconducting transition beginning at 13 K in films of the quintuple-layer nickelate Nd₆Ni₅O₁₂.

Typically, quasiparticles are injected into superconductors at energies comparable to the pairing energy in order to gain insights into quasiparticle dynamics. Tunnelling spectroscopy of a mesoscopic superconductor under high electric field now provides insights into a regime where electrons impinge with 10⁶ times the pairing energy.

To efficiently optimize soft magnets for high-frequency applications, simultaneous imaging of both amplitude and phase of AC stray fields is essential. Here, an imaging technique for analyzing AC magnetization response from DC to 2.3 MHz is developed using diamond quantum sensors with nitrogen-vacancy centers.

Electrons in strongly interacting materials can flow collectively, exhibiting hydrodynamic phenomena such as viscous flow. This Review highlights recent experimental advances, including high-quality materials growth, that have enabled these observations and surveys the spatially resolved theoretical frameworks necessary to interpret and predict these phenomena.

Variations in unconventional superconductors are increasing in number and diversity in recent years, and so it is increasingly important to develop analytical methods to distinguish and categorise their different features. Here, the authors study two types of collective modes of the order parameter unique to time-reversal symmetry breaking superconductors and propose using them to identify these exotic states.