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Ultrafast electron microscopy reveals how conductive paths in VO₂ form and dissolve under rapid electrical pulses, uncovering switching mechanisms relevant for brain-inspired and next generation electronics.

Dielectric breakdown in Mott insulators induced by strong electric fields is thought to take place via a Zener mechanism. Guiot et al. show that the breakdown characteristics are instead similar to the avalanche breakdown in conventional semiconductors, although with much longer delay times.

Ultrafast photoexcitation stabilizes new states of matter with rich out-of-equilibrium behaviours. Here, Lantzet al. report a transient non-thermal phase developing immediately after photoexcitation in V₂O₃, shedding a light on optical manipulation of strongly correlated systems.

There has been significant interest in using spin-waves or magnons for information processing, due to their low energy dissipation and short wavelength at terahertz frequencies, however, manipulating magnons can be challenging. Here, Kim et al show that magnons in Sr2IrO4 are extremely strain sensitive, with small applied strains leading to large variation in the magnon energy.

Detailed knowledge of the low-energy electronic structure is required to understand the Mott insulating phase of Ca₂RuO₄. Here, Sutter et al. provide directly the experimental band structure of the paramagnetic insulating phase of Ca₂RuO₄and unveil the electronic origin of its Mott phase.

The organic material κ-H₃(Cat-EDT-TTF)₂ has been suggested to exhibit a quantum spin liquid phase in which quantum fluctuations prevent the formation of magnetic order. Here, the authors show that this may be a result of fluctuations of hydrogen atoms, rather than more conventional geometric frustration.

Exciton transport in 2D Ruddlesden−Popper perovskite plays a key role for their optoelectronic performance. Here, authors significantly enhance free exciton mobilities in exfoliated thin flakes by anchoring butyl ammonium cation with polymethyl methacrylate, which also improves lattice rigidity.

Doped Sr₂IrO₄ is of interest because of its close similarities to La₂CuO₄, a parent compound of the cuprates. Nelson et al. reveal the intrinsic evolution of its electronic structure with hole doping by avoiding the strong in-plane disorder introduced by previously used chemical substitutions.

The influence of spin–orbit coupling on itinerant electrons underlies the formation of spin–orbit Mott states. Here, the authors demonstrate a temperature-hysteretic cascade between charge-ordered phases stabilized by localized 5dspin–orbit Mott dimer states in metallic iridium ditelluride.

A single component built from sputtered niobium dioxide, a Mott insulator–metal transition material, can simultaneously exhibit both visible light emission and electrical threshold switching with neuron-like oscillations.

Many of the fundamental effects in condensed matter physics can be described in the framework of quasiparticles. Here, the authors observe quasiparticles related to the antiferromagnetic state in quasi-two-dimensional Sr₂IrO₄, showing close resemblances to elusive quasiparticles in cuprate superconductors.

The spatial scale over which metal–insulator transitions happen is not known, despite the importance of this phenomenon in basic and applied research. The authors show that in chromium-doped V₂O₃, with decreasing temperature, microscopic metallic domains coexist with an insulating background.

1T-TaS2 possesses complex electronic phase behaviors in transition-metal di-chalcogenides, undergoing several charge-ordered phases before finally into an insulating state of unknown origin. Here, the authors determine its electronic and structural properties experimentally, revealing its origin.

During a photoinduced phase transition, electronic rearrangements are usually faster than lattice ones. Time-resolved measurements now show that the insulator-to-metal transition in a thin-film Mott insulator is preceded by lattice reconfiguration.

The authors image non-equilibrium exciton phase-transition dynamics in moiré superlattices, revealing how strong long-range dipolar repulsion freezes the motion of the Mott insulator over a timescale of tens of nanoseconds.

The concept of resonant valence bond phases has inspired many areas of condensed matter physics, but few realistic models have been identified. Now an analytical solution of such a phase has been found for pyrochlore and related lattices.

Metallic surface states on CoO₂ and Pd terminated surfaces due to electronic reconstruction have been observed in the CoO₂-based delafossites. In contrast, here the authors report an interesting insulating state on the CrO₂ terminated surface of PdCrO₂ due to charge-disproportionation.

Ca₂RuO₄ is a Mott insulator that becomes a metal when a current is passed through it. Now, the changes in its electronic structure are revealed as this transition takes place.

Magnetic excitations in infinite-layer cuprates have been intensively studied. Here the authors use resonant inelastic x-ray scattering and theoretical calculations to study magnons in thin films of SrCuO₂, finding distinct magnon dispersion attributed to renormalization due to quantum fluctuations.

Identifying external mechanisms to tune magnon properties has remained a major challenge. Here, the authors demonstrate that an interfacial metal-insulator transition offers an effective method for controlling the magnon dispersion of Sr₂IrO₄.

Electron or hole doping in a Mott insulator leads to superconductivity, with the mechanism obscured by multi-orbital Fermi surface reconstructions. Here, Kawasugi et al. report doping dependent Hall coefficients and resistivity anisotropy of an organic Mott insulator, revealing doping asymmetry of reconstructed Fermi surface of a single electronic orbital.

Spin liquids are states of matter in which the constituent spins of a magnet are highly correlated yet fluctuate strongly down to millikelvin temperatures. Here the authors report torque magnetometry measurements of the Mott insulator EtMe₃Sb[Pd(dmit)₂]₂and find it displays an ungapped quantum spin liquid state.

Transition metal dichalcogenide heterostructures with layers of localized and itinerant electrons are candidates for heavy fermion lattices. The authors report delocalization of Mott electrons in a monolayer of 1T-TaS₂ on a bulk metallic 2H-TaS₂ substrate, indicating the formation of a coherent Kondo lattice.

Interfaces between two dissimilar transition metal oxides can exhibit emergent strongly correlated electronic and magnetic states due to charge transfer and electronic reconfiguration. Here, the authors synthesize and investigate an exotic Mott ground state in LaTiO_3+δ/LaNiO₃heterostructures.

Chiral spin liquids, a topological phase in frustrated quantum spin systems, have been recently very sought-after. Here, Bauer et al.present a model for a Mott insulator on the Kagome lattice with broken time-reversal symmetry exhibiting such a topological phase.

Topological classification of interacting electronic states has emerged as an important topic recently. Wagner at al. show that the momentum structure of the zeros of the electron Green’s function can be used to identify a topological Mott insulator phase, similarly to the single-particle dispersion.

Doping a Mott insulator can lead to novel electronic states. Wildman et al. observe a novel quantum insulating state in electron-doped Mott insulator CeMnAsO and propose a tentative interpretation in terms of many-body localization, which has not been observed in a solid-state material.

Spin-orbit Mott materials such as Sr₃Ir₃O₇ and Sr₂IrO₄exhibit rich correlation-driven physics, which makes them promising candidates for novel electronic states. Here, the authors explore the effect of hole-doping within the spin-orbit Mott phase and show that the carriers localize within a phase-separated ground state.

The optimal condition for superconductivity is a long-sought issue but remains challenging. Here, Ivashko et al. demonstrate that the compressive strain to La₂CuO₄ films enhances the Coulomb and magnetic-exchange interactions relevant for superconductivity, providing a strategy to optimise the parent Mott state for superconductivity.

Surprising observations in the evolution of electronic states in electron-doped iridates provide fresh insight into the melting of the Mott state and might lead to a fuller understanding of corresponding processes in copper-oxide superconductors.

Superconductivity induced on a topological insulator’s surface may realize Majorana modes. Here, Herbrych et al. predict that a large Coulomb interaction helps develop a spiral spin order, which is a topological state at the edge of a canonical superconductor with orbital degrees of freedom.

Spin-charge interactions are at the core of electronic correlation phenomena in Mott insulators. Here, the authors observe a positive anomalous magnetoresistance in a SrIrO₃/SrTiO₃ superlattice, indicative of strong spin-charge fluctuations in this pseudospin-half square-lattice Mott insulator.

Strongly correlated insulating Mott and generalized Wigner phases are detected in WSe₂/WS₂ moiré superlattices, and their electrical properties and excited spin states are studied using an optical technique.

Knowing whether a quantum phase transition is first- or second-order is crucial for understanding any associated exotic phenomena, but direct experimental evidence has been scarce. Here, Frandsen et al. report first-order magnetic quantum phase transitions in archetypal Mott systems, providing insight into the underlying quantum fluctuations.

A major goal in the fields of ultracold quantum gases and quantum simulations is measuring the phase diagram of strongly interacting many-body systems. This has now been achieved in an optical-lattice-based quantum simulator. The simulation is validated through an ab initio comparison with large-scale numerical quantum Monte Carlo simulations.

Irradiation with a strong terahertz electric-field pulse is found to induce a Mott transition in an organic molecular compound. The metallization is attributed to an impulsive dielectric breakdown.

Scanning tunnelling microscopy images of the evolution of the pseudogap phase of a hole-doped cuprate superconductor suggest that it emerges in localized clusters that grow with increasing doping. Moreover, the eventual coalescence of these clusters coincides with the emergence of superconductivity.

The dynamics of the magnetic correlations after photo-doping Sr₂IrO₄ are studied through ultrafast time-resolved resonant inelastic X-ray spectroscopy. The timescales are found to depend on the dimensionality of the correlations.

Superconductivity and magnetic order are well known in C₆₀ compounds of the form A₃C₆₀ (where A = alkali metal). The spherical C₆₀ molecular ions in these crystals are almost always arranged in a face-centred cubic (f.c.c.) packing, except in Cs₃C₆₀, where the known superconducting phase has a body-centred cubic (b.c.c) packing. Now the f.c.c. polymorph for Cs₃C₆₀ has been isolated; it too is superconducting, although its magnetic properties are very different to those of its b.c.c counterpart.

A thorough analysis of the optical and transport properties of several two-dimensional organic conductors and insulators with varying on-site correlation strengths and bandwidths led to a quantitative phase diagram for pristine Mott insulators.