Search

Tuning the structure in the atomic scale enables manipulation of the quantum state in a molecular based system. Here, Hiraokaet al. tune the Kondo coupling between molecular spins and the Au electrode by controlling the position of Fe²⁺ions in the molecular cage with a tip.

The study and application of the conductive surface states of topological insulators are often restricted by the presence of bulk conduction states. Here, Xu et al. present evidence for such topological surface states with true bulk insulation in the strongly correlated Kondo insulator SmB₆.

In the Kondo effect, a bath of conduction electrons screens a localized magnetic moment. Here, the authors demonstrate Kondo screening of a normally isolated 4f-like moment in a magnetic molecule on a Cu(001) surface that is modulated by strong ligand-mediated coupling.

The competition between interactions promoting magnetic order and those suppressing magnetism causes unusual electronic behaviour in Kondo lattice materials. Here, the authors show the energy scale for valence fluctuations is not controlled by the Kondo scale, contrary to expectations from single-site models.

The Kondo effect from magnetic impurities has been proposed as a probe of fractionalized excitations in a topological quantum spin liquid. Lee et al. experimentally demonstrate the Kondo effect in a Kitaev candidate material α-RuCl3 with dilute Cr impurities.

Kondo materials exhibit extremely rich physics, from unconventional superconductivity to topological phases. Unfortunately, for a real material, direct solution of the Kondo lattice is practically impossible. Here, Simeth et al. present a tractable approach to this problem, showing how a multi-orbital periodic Anderson model can be reduced to a Kondo lattice model, and be applied to relevant materials and quantitatively validated with neutron spectroscopy.

In rare-earth intermetallics, interaction between localized 4f electrons and itinerant electrons can result in exotic states of matter. Here, the authors use photoemission spectroscopy to reveal and study this interaction in the bulk and at the surface of the Kondo lattice antiferromagnet CeRh₂Si₂.

Pyrochlore iridates lie at a tuning-free magnetic quantum critical point hosting several complex exotic phenomena. Here, the authors discover an electronic phase separation in single crystalline Pr₂Ir₂O₇, where well-defined Kondo resonances are interweaved with a non-magnetic metallic phase with Kondo-destruction.

Understanding the physics of transition metal oxides that move beyond the commonly studied 3d orbital state is important for future studies. Taking the (CaCu₃)B₄O₁₂ family as an example, Meyers et al.examine the electronic and magnetic structure as the B-site changes from Co to Rh and Ir.

Samarium hexaboride, a well-known Kondo insulator, shows transport anomalies at low temperatures, which recently have been proposed to be of topological origin. Using laser- and synchrotron-based photoemission techniques, Neupane et al. find evidence for a topological Fermi surface.

Experimental study of the Kondo insulator SmB₆ provides an alternative route to realize a Fermi surface in the absence of a conventional Fermi liquid.

Transitions between stable quantum phases of matter typically involve going through an unstable quantum critical point, the unique properties of which have become a focus of research in the past decade or so. Extensive bulk measurements on the nickel oxypnictide system CeNiAsO uncover heavy-fermion behaviour, suggesting the family of oxipnictides may be ideal materials for examining quantum criticality more broadly.

Isocyanate groups are excellent precursors for the synthesis of polyurethanes and polyureas however they degrade with atmospheric moisture. Here, the authors report the encapsulation of isocyanates within crystalline pillar[n]arene macrocycles that provides both high protection efficiency and facile deprotection of isocyanate compounds.

We present comprehensive thermodynamic and spectroscopic evidence for an antiferromagnetically ordered heavy-fermion ground state in the van der Waals metal CeSiI.

Anisotropic hybridization between conduction and unpaired f electrons is rarely observed. Now, a lanthanide-based two-dimensional compound exhibits nodal hybridization, giving rise to heavy-fermion behaviour.

The authors report that the metallic spin-1/2 chain compound Ti₄MnBi₂ forms near a quantum critical point with inherent frustration. They identify strong 1D spin and 3D electron coupling that should stimulate the search for materials exhibiting a 1D Kondo effect and heavy fermions.

Three-body low-energy s-wave states play an important role in few-body physics and associated universal phenomena, yet their experimental observation in nuclear system has been elusive. Here, the authors identify the three-body s-wave properties in neutron-rich ¹⁰He nuclei with improved statistics and sensitivities.

Under chemical pressure, two phase transitions that were seemingly linked become detached in YbRh₂Si₂, thereby clarifying a long-standing mystery in the heavy-electron metals. Moreover, a new quantum phase appears under negative pressure.

Despite all of the fundamental research carried out on them, artificial atoms continue to be a source of surprise. The intersection between the electrons in a quantum dot and a nearby sea of electrons can create unusual many-body states. A spectroscopic study now makes these states observable.

Manipulating spin states of molecules in a controllable manner is essential to develop the molecule-based spintronics technologies. Here, Ormaza et al. show how to use the interaction between a single metallocene molecule and a metallic surface to reversibly switch spin from 1 to ½ in a junction.

Heavy-fermion materials have unusual electronic behavior due to a dual localized-itinerant character of 4f electrons. Here, by studying divalent EuRh₂Si₂, the authors gain insight into the electronic states of the trivalent heavy fermion system YbRh₂Si₂ and show that it experimentally demonstrates Luttinger’s theorem.

The interactions of quasiparticles can be described by renormalizing their masses, such that some materials have a vanishingly small effective mass, whereas others have a very high effective mass. The observation by Vyalikh and colleagues of both extremes occurring on the surface and interior of the same material offers a new view of many-body interactions.

Electrically manipulating molecular magnetism is a challenge to overcome for applications in high-density storage. Here, the authors use inelastic electron tunneling spectroscopy to show that a vibron-assisted spin excitation in a nickel-nickelocene complex exceeds a pure spin excitation in energy and amplitude.

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.

It remains difficult to distinguish single-Q and multi-Q magnetic states experimentally. Here, Gastiasoro et al. show that the magnetic configuration of an itinerant system can be mapped out to the local density of states near a magnetic impurity, distinguishing unambiguously between single-Q and multi-Qphases.

The realization of the anomalous Hall effect in high-mobility two dimensional electron systems has so far remained elusive. Here, the authors observe its emergence in MgZnO/ZnO heterostructures and attribute it to skew scattering of electrons by localized paramagnetic centres.

In heavy fermion metals, exotic states such as superconductivity depend to a large extent on whether unpaired electrons can become delocalized from the magnetic sites. The authors demonstrate that the primary driving force behind delocalization is the local environment of the rare earth ions and the strength of the resulting charge fluctuations.

Samarium hexahoride is argued to be a topological Kondo insulator, but this claim remains under debate. Here, Hlawenka et al. provide a topologically trivial explanation for the conducting states at the (100) surface of samarium hexaboride; an explanation based on Rashba splitting and a surface shift of the Kondo resonance.

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.

Energy gaps can be induced by spatial modulation of the electronic potential. Here, the authors demonstrate a large and robust energy gap in a free-standing carbon nanotube utilizing a 15-gate keyboard that spatially modulates the local potential.

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.

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.

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.

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.

Resonant magnetic excitations are common in unconventional superconductors, but the mechanism for their formation is elusive. Using inelastic neutron scattering, this study finds similar excitations in the non-superconducting heavy-fermion metal CeB₆, suggesting common behaviour between the two ground states.