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Pr₂Ir₂O₇ is a candidate for a metallic spin liquid with a quantum critical point; however, the exact nature of its ground state and quantum criticality is unknown. Here, the authors report strong deviations from dipolar spin-ice ground state and find normal electronic behavior near quantum criticality.

Although LaAlO₃ and SrTiO₃ are both insulators, when they are brought together at a (100) interface, a highly conducting two-dimensional electron gas forms between them. Annandi et al.show that this also happens at a (110) interface, counter to expectations that it should not.

Strong correlation effects in metals lead to unconventional emergent behavior that depends on the nature of interactions at the microscopic scale. Deng et al. identify distinct signatures of the so-called Mott and Hund regimes, which may guide the theoretical understanding of correlated materials.

Metallic systems in magnetic fields enter the quantum limit when the cyclotron energy exceeds the Fermi energy. Here the authors introduce the analogue of the quantum limit for insulators, where the Zeeman energy exceeds the cyclotron energy, and show that it explains key features of the Kondo insulator YbB₁₂.

LaNiO₃ is a strange metal, for reasons that are not well understood. Here, Liu et al. report evidence for scattering of charge carriers by antiferromagnetic quantum fluctuations in high-purity epitaxial thin films of LaNiO₃, suggesting it is close to an antiferromagnetic quantum critical point.

A study of the magnetic fine structure of the electronic states in a semiconductor quantum dot coupled to a superconducting contact highlights important elements that should be taken into account in the search for Majorana modes in the solid state.

Achieving deep blue emission and high practical efficiency in organic light-emitting devices remains a considerable challenge. Here, the authors report late-stage double borylation of boron/nitrogen based multi-resonance frameworks, achieving maximum efficiency of over 32% in stable devices.

Thermoelectric performances depend on phonon and electron transport. Here, Takahashi et al. show that the large Seebeck coefficient observed in high-purity single-crystal FeSb₂ is due to the phonon-drag effect and to the high effective mass of delectrons interacting with quasi-ballistic phonons.

Detailed investigation of a single atomic spin on a surface reveals that its Kondo interaction with the substrate electrons depends strongly on the spin's relative orientation.

Quantum aspects of transport through single molecules are observable at room temperature. In this Technical Review, we discuss the different processes and energy scales involved in charge transport through single-molecule junctions, the resulting electronic functionalities and the new possibilities for controlling these functionalities for the realization of nanoscale devices.

The heavy fermion compound URu₂Si₂displays a hidden order phase and superconductivity at low temperatures. Here, the authors perform substitution studies—partially replacing silicon with phosphorus—and study the effects on hidden order and superconductivity.

The back-action of electrons can cool a nanomechanical oscillator to a few-quantum state when a current flows through a suspended nanotube. The electron back-action, which is attributed to an electrothermal effect, also induces self-oscillations.

Despite much recent effort, the highest reported T_c of the infinite-layer nickelates remains lower than 15 K. Here, the authors apply pressure to Pr_0.82Sr_0.18NiO₂ thin films and observe a monotonic increase of T_c to 31 K at 12.1 GPa, an increase that does not level off with increasing pressure.

Plutonium has unusual physical properties due to strong electronic correlation, but its α-phase has not been studied much in this respect. Using sophisticated numerical methods, Zhu et al. show that in this phase different atomic sites have different degrees of electronic correlation.

Using the two stable electronic states of alkaline-earth atoms, an orbital spin-exchange interaction—the building block of orbital quantum magnetism—has been observed in a fermionic quantum gas.

Understanding the strange metal behavior, characterized by linear-in-temperature resistivity, could shed light on the mechanism of unconventional superconductivity. Here, by using electrical resistivity measurements into the micro-Kelvin regime, the authors report evidence of unconventional superconductivity in the strange metal YbRh₂Si₂ and propose a possible pairing mechanism.

Indium antimonide nanowires have large spin-orbit coupling, which can give rise to helical states that are an important part of proposals for topological quantum computing. Here the authors measure conductance through the helical states and extract a larger spin-orbit energy than obtained before.

In compounds containing 4f and 5f elements, hidden-order phases exist which are undetectable by many methods, the origins of which are debated. Here, the authors use photoemission and neutron scattering methods to show how such a multipolar-ordered phase emerges due to Fermi surface instability in CeB₆.

Experimental observations and theoretical analysis provide evidence that the spin polarization of the spin-spiral type II multiferroic NiI₂ exhibits p-wave magnetism and its spin chirality is related to ferroelectric polarization, which can be electrically controlled. 

A neutron-scattering study provides quantitative evidence for magnetically mediated superconductivity close to a quantum critical point in the heavy fermion superconductor CeCu₂Si₂.

The authors study a YbCoIn5/CeCoIn5/YbRhIn5 heterostructure. Using non-reciprocity in the second harmonic transport response, they demonstrate the existence of a specific form of finite-momentum pairing called a helical superconducting state, where the phase of the order parameter is spontaneously spatially modulated.

Understanding the magnetic properties of molecules at the atomic level is a crucial aspect in the growing area of organic spintronics. This study brings further insight into the mechanisms of electron-spin interactions by investigating an iron-based organic molecule deposited on gold substrates.

Previous studies of magnetic adatom chains on superconducting substrates have mostly focused on the regime of dense chains and classical spins. Here, using scanning tunnelling microscopy, the authors study the excitation spectra of Fe chains on a NbSe₂ surface, adatom by adatom, in the regime of quantum spins.

The heavy-fermion material PuCoGa₅ is characterized by unconventional superconducting properties. By combining point-contact spectroscopy and first-principles calculations, this study reveals a d-wave symmetry in the system's order parameter.

Dilanthanide complexes that possess radical bridges exhibit enhanced magnetic exchange coupling, affording molecular magnets with high blocking temperatures. Here, the authors explore a series of dilanthanide-encapsulated fullerenes where the radical bridge is taken to its limit and the role is played by a single unpaired electron.

The symmetry, microscopy and spectroscopy signatures of altermagnetism are reviewed, and compared with traditional ferromagnetism and Néel antiferromagnetism, and magnetic phases with symmetry-protected compensated non-collinear spin orders.

The insulator-to-metal transition in vanadium dioxide still has many unexplored properties. Here the authors use multi-modal THz and mid-IR nano-imaging to examine the phase transition in VO₂ thin films, and discuss the unexpectedly smooth transition at THz frequencies in the context of a dimer Hubbard model.

Magnetic interactions in solids are usually short-range or else they involve itinerant electrons. Here, the authors evidence a long-range magnetic coupling mediated by orbital moments in a polar spacer layer of nonmagnetic insulating oxide, with a sign which oscillates with spacer thickness.

By means of a sensitive neutron spectroscopy approach the magnetic excitations in the heavy fermion superconductor CeRhIn₅ are probed, revealing a uniaxial anisotropy that can be tuned with an external magnetic field.

A first principles understanding of the origins of the Earth's magnetic field requires the study of iron and nickel at high temperatures and pressures. Here, the authors find anomalies in the electronic properties of nickel and iron-nickel alloys, which may be important for the physics of geomagnetism.

In topological insulators, topology imposes a quantum phase transition between the trivial and nontrivial phases. Here, Xu et al. demonstrate how properties of the topological surface states emerge in the trivial phase of BiTl(S_1-δSe_δ)₂when close to its chemically tuned phase transition.

The zero-bias state in FeTe_0.55Se_0.45 is conjectured to be related to Majorana physics, but most in-gap impurity states are not well understood. Here, the authors detect spatially dispersing Yu-Shiba-Rusinov states which can be tuned using an STM tip with varying tip-sample distance.

Local magnetic properties that can be controlled by an applied electric field are desirable for spintronics applications. Nair et al.show that tuning carrier concentration by molecular doping or electric field can be used to control adatoms magnetism on graphene, enabling magnetic moments to be switched on and off.

In addition to its low-field superconducting state, UTe₂ features a re-entrant superconducting state when high magnetic fields are applied at a particular range of angles. Here, the authors demonstrate that the high-field re-entrant superconducting state survives even when the low-field superconducting state is destroyed by disorder.

This study reveals a non-monotonic evolution of the mixed-valence character in the Sm_xLa_1−xB₆ series, with near-complete suppression of valence fluctuations in the intermediate substitution regime, followed by a re-emergent mixed-valence behavior in the dilute-impurity limit.