The identification of quantum spin-liquid phases in Kitaev candidate materials remains a major experimental challenge. Since most Kitaev candidates develop antiferromagnetic (AFM) order at low temperatures, currently there is great interest on the field-induced magnetic disordered phase in these compounds that are distinct from (partially) polarized states. Recently, a cobaltate ${\mathrm{Na}}_2{\mathrm{Co}}_2{\mathrm{TeO}}_6$ has emerged as a promising Kitaev candidate with high-spin $t_{2g}^5{e}_g^2$ configuration and spin-orbit-entangled $J_{\mathrm{eff}}=1/2$ honeycomb lattice system. There are intensive studies on field-induced magnetic states and phase transitions under in-plane magnetic fields. In this study, we propose an intermediate disordered phase induced by an out-of-plane field along the $c$-axis, through high-field magnetization and magnetocaloric effect measurements. To explain the high-field behavior of ${\mathrm{Na}}_2{\mathrm{Co}}_2{\mathrm{TeO}}_6$, we develop an effective $K\text{−}J\text{−}\mathrm{\Gamma }\text{−}{\mathrm{\Gamma }}^{\prime }$ spin model featuring a dominant AFM Kitaev interaction. This framework uncovers an intermediate quantum spin-liquid phase, establishing the material as a unique platform for exploring Kitaev physics and field-induced quantum-disordered states.

In this study, we experimentally explore the band structure of chirally twisted triple bilayer graphene, a moiré system consisting of three helically stacked Bernal bilayer graphene. We verify the existence of flat bands at the charge neutral point and accurately measure the gaps both between these flat bands and between the flat and the dispersive bands via capacitance measurements. Furthermore, we discover a finite gap even in the absence of an external perpendicular electric field, potentially driven by Coulomb interactions. Our comprehensive analysis offers robust evidence for the existence of flat bands and reveals intriguing physical phenomena.

The applicability of the one-parameter scaling hypothesis to nonreciprocal high-dimensional disordered systems, specifically, those in dimensions higher than the critical dimension $d_c=2$, as predicted by the standard one-parameter scaling theory of Anderson localization, remains unresolved. In this work, we propose that the size dependence of the reduced participation ratio $Y_L$ in nonreciprocal $d$-dimensional systems of size $L^d$ follows a universal one-parameter scaling form. This feature is encapsulated by the one-parameter $\beta$ function $\beta \left[Y_L\right]=dln\left[Y_L\right]/dln\left[L\right]$, which describes the critical properties of Anderson localization transitions, including the critical exponent $\nu$, the fractal dimension $D$, and the critical reduced participation ratio $Y_L^{*}$. We demonstrate the applicability of our one-parameter scaling theory across the AI, A, and AII classes of three-dimensional nonreciprocal systems under periodic boundary conditions and further extend our analysis to higher dimensions in the presence of nonreciprocity, specifically $d=4$, 5, and 6. Our one-parameter scaling theory also applies to nonreciprocal systems with open boundary conditions, where all states are non-Hermitian skin modes. The scaling analysis indicates that open nonreciprocal systems do not exhibit genuine extended states extending throughout the system in the thermodynamic limit.

We establish multiple interrelated, fundamental results in quantum many-body systems that can have long-range interactions. For a sufficiently long quantum spin chain, we first show that if the multispin interactions in the Hamiltonian decay fast enough as their ranges increase and the Hamiltonian is gapped, then the ground states satisfy the entanglement area law, even if there is a ground-state degeneracy due to a spontaneously broken discrete symmetry. This area law also holds for certain excited states. Second, if such a long-range interacting Hamiltonian has an anomalous symmetry, then the Lieb-Schultz-Mattis theorem applies, i.e., the Hamiltonian cannot have a unique gapped symmetric ground state. If the Hamiltonian contains only 2-spin interactions, then these results hold when the interactions decay faster than $1/r^2$, with $r$ the distance between the two interacting spins. Third, we show that pure states with an anomalous symmetry, which may not be a ground state of any natural Hamiltonian, must be long-range entangled. The symmetries we consider include on-site internal symmetries combined with lattice translation symmetries, and they can also extend to purely internal but non-on-site symmetries. Moreover, these internal symmetries can be discrete or continuous. We explore the applications of these results through various examples.

The manipulation of skyrmions by surface acoustic waves (SAWs) has garnered significant interest in the field of spintronic devices. Previous studies established that skyrmions can be generated and moved by strain pulses. In this study, we propose that sawtooth-SAWs can be used to drive a ratchet motion of magnetic skyrmions in the presence of pinning centers. This results in a net motion of the skyrmions orthogonal to the continuously applied SAW. The ratchet motion is fundamentally caused by nonvanishing pinning, so that a certain strain gradient magnitude is required to overcome pinning and start skyrmion motion. We demonstrate the feasibility of our concept by micromagnetic simulations and analytical model calculations.

Using total and resonant x-ray scattering coupled to large-scale computer modeling, we study the lattice modulations in the complex charge density wave (CDW) material ${\mathrm{Lu}}_2{\mathrm{Ir}}_3{\mathrm{Si}}_5$. We find that it is a unique quantum system where periodic lattice modulations related to emergent CDW order occur in three orthogonal atomic planes of the crystal lattice, leading to the emergence of an unusual three-dimensional (3D) pattern of short and long Ir-Ir and Lu-Lu bonds. The 3D character of observed lattice modulations explains the largely isotropic character of the changes in the electronic properties occurring when the CDW order sets in, demonstrating the strong electron-lattice coupling in ${\mathrm{Lu}}_2{\mathrm{Ir}}_3{\mathrm{Si}}_5$. The result is supported by DFT calculations based on the experimental structure data. Altogether, our work provides strong evidence for the presence of a relationship between the dimensionality of emergent lattice distortions and that of concurrent changes in the electronic properties of CDW materials. The relationship may need to be accounted for when these materials are explored for practical applications.

Three-dimensional kinetic Monte Carlo simulations are used to investigate the sensitivity to material parameters of the photoluminescence efficiency curves that are obtained from field-induced dissociation (FID) experiments of devices that are based on disordered small-molecule organic semiconductors. The study contains a comparison with the results of a simplified one-dimensional Master Equation model [O. Rubel et al., Phys. Rev. Lett. 100, 196602 (2008)] and with two-dimensional simulation results. The error-function-like efficiency curves show a field sensitivity that is strongly determined by the average exciton binding energy, $E_{\mathrm{exc},\mathrm{b}}$. However, the shape of the efficiency curves is also affected by other material properties, such as the energetic disorder, the hopping attempt rate, the relative permittivity, the radiative lifetime, and various other parameters. A sensitivity analysis shows that for materials with $E_{\mathrm{exc},\mathrm{b}}\approx$ 1.0 eV, the results of FID experiments are nevertheless expected to enable determining $E_{\mathrm{exc},\mathrm{b}}$ with an accuracy of 0.10–0.15 eV. Carrying out FID experiments is therefore expected to become a useful route to quite accurately obtain the electron affinity from the ionization energy, the optical gap, and this measured value of $E_{\mathrm{exc},\mathrm{b}}$.

Key quantities for designing new opto-electronic devices that are based on disordered organic semiconductors, such as organic light-emitting diodes (OLEDs), are the frontier orbital energies, exciton energies, and exciton binding energies. Obtaining these quantities spectroscopically with a high accuracy is complicated by the nonadiabaticity of such experiments. Here, we present, for two isomers of the blue-emitting prototypical OLED material 2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN), multiscale first-principles simulations of optical absorption spectra and of the electron affinity $E_{\mathrm{A}}$, a theoretical prediction and analysis of low-energy inverse photoemission spectroscopy (LEIPS) spectra that probe $E_{\mathrm{A}}$, and experimental LEIPS spectra. The simulations combine many-body Green's function theory, polarizable film embedding, and multimode electron-vibrational coupling. We show how the onset energy of LEIPS spectra, which is commonly used to estimate $E_{\mathrm{A}}$, can differ from the actual adiabatic value, depending on material parameters and the instrumental resolution. For the two isomers of MADN, the theoretical and experimental onset energies differ by about 0.20–0.25 eV, which is within the expected uncertainty margin. However, the experimental spectra are almost featureless, whereas the theoretical spectra show a clear peak structure. An extensive study is presented of the possible effects of thin-film charging on the spectra, including charging of deep trap states. The calculated optical absorption spectra agree excellently with experiment, with a peak energy difference of only about 0.05 eV. For the two isomers of MADN, the calculated adiabatic singlet exciton binding energies are 1.0–1.1 eV.

A method is developed for deducing the electron affinity of disordered organic semiconductors from spectroscopic thin-film studies of the ionization energy and the optical gap energy, combined with field-induced dissociation (FID) device experiments that are analyzed with kinetic Monte Carlo simulations using a methodology that has been presented by de Jong et al., Phys. Rev. B 112, 224202 (2025). The FID experiments are carried out for a set of eight organic semiconductor materials that are often used in organic light-emitting diodes. The analysis is focused on the $\alpha$ and $\beta$ isomers of the blue fluorescent emitter material 2-methyl-9,10-di-naphthyl-anthracene. For these two materials, the experimental ionization energy, the optical gap energy, the exciton binding energy, and the electron affinity are shown to be consistent with the results of quantum-chemical calculations, presented by G. Tirimbò et al., Phys. Rev. B 112, 224203 (2025). For all fluorescent emitter materials studied, the FID experiments reveal an exciton binding energy of approximately 1.0–1.2 eV, whereas for a thermally activated delayed fluorescence material, a slightly smaller value is obtained.

Understanding the lattice dynamical behavior responsible for anomalous lattice thermal conductivity is crucial for the discovery and design of materials with intrinsically low lattice thermal conductivity, thereby enabling high thermoelectric performance. In this work, we employ the harmonic approximation, self-consistent phonon theory, and the self-consistent phonon theory including bubble diagrams (SCPB) to correct phonon self-energy and renormalize phonon frequencies at various theoretical levels. Based on different theoretical foundations, phonon transport behaviors of eight half-Heusler (HH) compounds are systematically calculated within the Wigner transport framework. Multivalley conduction band minimum with varying effective masses lead to the coexistence of high Seebeck coefficients and electrical conductivity. However, moderate spin-orbit coupling (SOC) significantly narrows the band gap, reduces valence band degeneracy, and flattens dispersion, strongly affecting electronic transport. In this study, (i) the SCPB method captures lattice thermal conductivity with minimal deviation from experimental values by including both particle-like and wavelike phonon contributions, underscoring the necessity of bubble diagram corrections in strongly anharmonic materials; (ii) a multidimensional analysis reveals the physical origin of distinct rattling-like behavior observed only in KMgAs, KMgSb, and RbMgSb among the studied HH compounds; (iii) a correlation between phonon bandwidth, phonon band gap, and phonon-phonon scattering is established, offering an efficient approach to qualitatively infer phonon lifetimes from the phonon spectra; (iv) even relatively small wavelike phonon contributions significantly affect the temperature dependence of lattice thermal conductivity; and (v) SOC significantly influences the electronic properties of HH compounds (35.7–$50.0\%$), even without heavy elements, challenging the conventional belief that SOC can be ignored in materials lacking heavy atoms.

We investigate the magnetic property and charge-transport property for the kagome-frustrated antiferromagnet DyAgGe with the ZrNiAl-type crystal structure by measurements of magnetization, resistivity, and resonant x-ray scattering. The magnetization curve shows the 1/9, 1/3, 5/9, and 7/9 plateaus of saturated magnetization under the magnetic field along the $c$-axis before entering the forced ferromagnetic phase at 7.3 T and 2 K. Magnetic superlattice x-ray reflections with the modulation vector (1/3, 1/3, 0), resonantly enhanced at the Dy $L_3$ edge, are observed in these plateau phases. All of these phases, except for the 1/9-plateau phase, evolve into the paramagnetic phase around 12 to 15 K with strong competition among them in the field range of 4 to 6 T. Furthermore, we find the large negative magnetoresistivity and anomalous Hall resistivity not proportional to magnetic field or magnetization near and above the magnetic transition temperature around 3-7 T. For comparison, we also investigated the charge-transport for the isostructural magnet DyPtIn, which does not exhibit the field-induced multiple phase transitions. In contrast with the behavior of DyAgGe, DyPtIn does not show remarkable magnetoresistivity and anomalous Hall resistivity near and above the magnetic transition temperature. The anomalous Hall effect persisting above the magnetic transition temperature is likely caused by spin fluctuations enhanced by the competing multiple magnetic phases through the scalar spin chirality mechanism in DyAgGe.

We revise the temporal coupled mode theory to describe the resonant response of quasiguided modes under oblique incidence in periodic dielectric metasurfaces accounting for the constraints imposed by the symmetry of the unit cell. We derive a universal expression for the Fano resonance line shape in reflection and transmission for subwavelength period metasurfaces and reveal a fundamental link between the Fano parameters and unit cell symmetries, including robust reflection and transmission zeros, as well as spectral signatures of bound states in the continuum. To demonstrate the power of the developed theory, we provide a generalized framework for analyzing asymmetry in the coupling and decoupling coefficients. This allows us to reveal the dual nature of unidirectional guided resonances and counter-propagating modes characterized by single-sided coupling to incident waves, which have been actively discussed in recent years. These insights provide a powerful analytical tool for designing high-Q resonances in metasurfaces through symmetry exploitation.

The presence of carriers and van Hove singularities is essential for the emergence of intraband and interband plasmons, as evidenced by studies on small-angle twisted bilayer transition metal dichalcogenides and graphene, where van Hove singularities are induced by flat bands. In this work, we employ a tight-binding model in conjunction with the random phase approximation to investigate charge-neutral 2H-stacked bilayer ${\mathrm{MoS}}_2$ without flat bands. We demonstrate that both intraband and interband plasmons, along with their lifetimes, can be effectively modulated by electric fields. These phenomena are attributed to the semiconductor-to-semimetal transition and the electric field-induced van Hove singularities near the Fermi energy. Our results indicate that the interlayer electronic transition barely affects in-phase plasmon modes, while strongly modifying out-of-phase ones. Furthermore, plasmonic characteristics remain robust against twist angle for electric fields between 0.3 and 0.4 eV/Å. This insensitivity facilitates experimental realization of plasmon modulation without requiring precise twist angle control. Finally, the effects of the intrinsic electron doping and the screening using Keldysh potential on plasmons are discussed.

The propagation of transverse impact energy in a multilayer packing (in an array) of parallel single-walled carbon nanotubes has been simulated. It has been shown that such nanotube arrays are effective shock absorbers. The depreciation effect is most pronounced for packings of nanotubes with a diameter of 2.7 to 3.9 nm. Here, part of the impact energy is absorbed due to the transfer of the packing to a higher-energy stationary state in which part of the nanotubes is in a collapsed state. The impact impulse reaches the other edge of the packing most weakened and distributed over time. For nanotubes with a smaller diameter, the compression of the array occurs elastically without energy accumulation, and for nanotubes with a larger diameter with energy release.

It is commonly believed that light cannot couple to the collective excitations of the fractional quantum Hall effect (FQHE). This assumption relies on Kohn's theorem that states that electron-electron interactions decouple from homogeneous electromagnetic fields due to Galilean invariance. Here, we demonstrate that light-matter coupling beyond the dipole approximation circumvents Kohn's theorem, and enables the coupling of cavity photons to the plasmonic edge modes of the FQHE. We derive the coupling using the FQHE bulk-boundary correspondence and predict the formation of experimentally detectable plasmon polaritons. In conjunction with recent experiments, we find that a single cavity mode leaves the system's topological protection intact. Interestingly, however, a multimode cavity mediates plasmon backscattering and effectively transforms the edges of the two-dimensional (2D) FQHE into a 1D wire. Such cavity-meditated nonlocal backscattering bodes the breakdown of the topological protection in the regime of ultrastrong photon-plasmon coupling. Our analytical framework and findings pave the way for investigating the topological order of the FQHE via optical spectroscopic probes as well as provide opportunities to control FQHE edge excitations using light.

Although significant advancements have been made in wireless technologies and portable devices, it remains a challenge for high-frequency and nanowatt-level radiofrequency rectification. In this work, we report a pronounced radiofrequency rectification up to 37 GHz in nominally centrosymmetric $\mathrm{SrIr}{\mathrm{O}}_3$ epitaxial films, with the minimum detectable power as low as −15 dBm. Strikingly, the $\mathrm{SrIr}{\mathrm{O}}_3$ rectifier is highly field tunable and exhibits a strong in-plane field anisotropy, thus showing a unique advantage in broadband radiofrequency rectification. The rectification effect can persist up to at least 360 K and shows a sensitive temperature dependence including a sign inversion. By a systematic study of the nonlinear transport properties of $\mathrm{SrIr}{\mathrm{O}}_3$, it's further revealed that the radiofrequency rectification originates from the nonlinear Hall effect with the dominant contribution from field-induced Berry curvature dipole. Our work demonstrates the superior performance of the field-tunable $\mathrm{SrIr}{\mathrm{O}}_3$ rectifiers, unleashing the great application potential of centrosymmetric materials in harvesting and detecting ambient electromagnetic energy.