Intertwined orders appear when multiple orders are strongly interacting, and kagome metals have emerged as new platforms to explore exotic phases. FeGe has been found to develop a charge density wave (CDW) order within magnetic phase, suggesting an intricate interplay of the lattice, charge, and spin degrees of freedom. Recently, postgrowth annealing has been proposed to tune the CDW order from long-range to complete suppression, offering a tuning knob for the CDW order. Here, by comparing the electronic structures of FeGe subjected to different annealing conditions and distinct CDW properties, we report spectral evolution associated with the lattice and spin degrees of freedom. We find band evolution linked to a spin density wave (SDW) order present in both samples with and without CDW order, and another evolution connected to the lattice distortions that onset with the long-range CDW order and revert with the SDW order. Our results reveal a rare competitive cooperation of the lattice, spin, and charge in FeGe.

In the iron-based superconductors, unconventional superconductivity emerges in proximity to intertwined electronic orders consisting of an electronic nematic order and a spin density wave (SDW). Recently, ${\mathrm{BaNi}}_2{\mathrm{As}}_2$, like its well-known iron-based analog ${\mathrm{BaFe}}_2{\mathrm{As}}_2$, has been discovered to host a symmetry-breaking structural transition but coupled to a unidirectional charge density wave (CDW) instead of SDW, providing a novel platform to study intertwined orders. Here, through a systematic angle-resolved photoemission spectroscopy study combined with a detwinning $B_{1}g$ uniaxial strain, we identify distinct spectral evidence of band evolution due to the structural transition as well as CDW-induced band folding. In contrast to the nematicity and spin density wave in ${\mathrm{BaFe}}_2{\mathrm{As}}_2$, the structural and CDW order parameters in ${\mathrm{BaNi}}_2{\mathrm{As}}_2$ are observed to be strongly coupled and do not separate in the presence of uniaxial strain. Furthermore, no nematic band splitting is resolved above the structural transition. Our measurements point to a likely lattice origin of the CDW order in ${\mathrm{BaNi}}_2{\mathrm{As}}_2$.

In the search for unconventional magnetism, exotic quantum states are characterized by a lack of order and a broad spin excitation continuum approaching zero temperature. We study the two-dimensional triangular-lattice effective spin- 1 2 system CeMgAl ₁₁ O ₁₉ , which shows slight disorder but no magnetic ordering down to 100 millikelvin. Spin-wave analysis in the magnetic-field–polarized state determines the spin Hamiltonian featuring a mixed ferromagnetic-antiferromagnetic nearest-neighbor exchange interaction [ J z = −0.024(5) milli–electron volts, J ⊥ = 0.056(3) milli–electron volts]. This places the system near an exactly solvable point of the spin- 1 2 triangular-lattice XXZ model ( J z = − 1 2 J ⊥ ) with extensive ground-state degeneracy. In zero field, neutron spectroscopy reveals a prominent continuum; we show that this arises from an ensemble average of spin-wave spectra across the degenerate ground-state manifold. This demonstrates that the role of weak quenched disorder can be quantitatively constrained: It inhibits unique ground-state selection and stabilizes a local distribution within the degenerate manifold, yielding continuum-like spectra that necessitate a critical reevaluation of the experimental signatures of exotic quantum states.

Decarbonization of agriculture is critical to reshaping the U.S. economy as climate-resilient and less carbon-intensive. Decarbonizing nitrogen fertilizers specifically is increasingly important for the U.S. to achieve its climate targets while feeding a growing population in a changing climate, as around 5% of global greenhouse gas emissions result from nitrogen fertilizers alone. Carbon dioxide equivalent emissions from fertilizer come from non-renewable energy use, chemical processes, transportation, and on-farm applications. These emissions typically take the form of carbon dioxide or nitrous oxide, potent greenhouse gasses. To reduce emissions from nitrogen fertilizers, the United States Department of Agriculture (USDA), Environmental Protection Agency (EPA), and Department of Energy (DOE) should 1) create federal regulations for nitrogen fertilizer use, 2) provide financial incentives for farmers transitioning to less-intensive nitrogen fertilizer use, and 3) create a research grant solicitation focused on regional methods for reducing nitrogen fertilizer use and the creation of green hydrogen.