As one of paradigmatic phenomena in condensed matter physics, the quantum anomalous Hall effect (QAHE) in stoichiometric Chern insulators has drawn great interest for years. By using model Hamiltonian analysis and first-principle calculations, we establish a topological phase diagram and map on it with different two-dimensional configurations, which is taken from the recently-grown magnetic topological insulators MnBi4Te7 and MnBi6Te10 with superlattice-like stacking patterns. These configurations manifest various topological phases, including quantum spin Hall effect with and without time-reversal symmetry, as well as QAHE. We then provide design principles to trigger QAHE by tuning experimentally accessible knobs, such as slab thickness and magnetization. Our work reveals that superlattice-like magnetic topological insulators with tunable exchange interaction serve as an ideal platform to realize the long-sought QAHE in pristine compounds, paving a new avenue within the area of topological materials.

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With no requirements for lattice matching, van der Waals (vdW) ferromagnetic materials are rapidly establishing themselves as effective building blocks for next-generation spintronic devices. We report a hitherto rarely seen antisymmetric magnetoresistance (MR) effect in vdW heterostructured Fe3GeTe2 (FGT)/graphite/FGT devices. Unlike conventional giant MR (GMR), which is characterized by two resistance states, the MR in these vdW heterostructures features distinct high-, intermediate-, and low-resistance states. This unique characteristic is suggestive of underlying physical mechanisms that differ from those observed before. After theoretical calculations, the three-resistance behavior was attributed to a spin momentum locking induced spin-polarized current at the graphite/FGT interface. Our work reveals that ferromagnetic heterostructures assembled from vdW materials can exhibit substantially different properties to those exhibited by similar heterostructures grown in vacuum. Hence, it highlights the potential for new physics and new spintronic applications to be discovered using vdW heterostructures.

Nontrivial low-energy excitations of crystalline solids have insightfully strengthened understanding of elementary particles in quantum field theory. Usually, topological quasiparticles are mainly focused on fermions in topological semimetals. In this work, we alternatively show by first-principles calculations and symmetry analysis that ideal type-II Weyl phonons are present in zinc-blende cadmium telluride (CdTe), a well-known II-VI semiconductor. Importantly, these type-II Weyl phonons originate from the inversion between the longitudinal acoustic and transverse optical branches. Symmetry guarantees the type-II Weyl points to lie along the high-symmetry lines at the boundaries of Brillouin zone even with breaking the inversion symmetry, exhibiting the robustness of protected phonon features. The nontrivial phonon surface states and surface arcs projected on the semi-finite (001) and (111) surfaces are investigated. The phonon surface arcs connecting the Weyl points with opposite chirality, guaranteed to be very long, are clearly visible. This work not only offers a promising candidate for studying type-II Weyl phonons, but also provides a route to realize symmetry-protected nontrivial phonons and related applications in realistic materials.

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Buildings consume large amounts of materials and energy, making them one of the highest environmental impactors. Quantifying the impact of building materials can be critical to developing an effective greenhouse gas mitigation strategy. Using Athena Impact Estimator for Buildings (IE4B), this paper compares cradle-to-grave life-cycle assessment (LCA) results for a 12-story building constructed from cross-laminated timber (CLT) and a functionally equivalent reinforced concrete (RC) building. Following EN 15978 framework, environmental impacts for stages A1–A5 (product to construction), B2, B4, and B6 (use), C1–C4 (end of life), and D (beyond the building life) were evaluated in detail along resource efficiency. For material resource efficiency, total mass of the CLT building was 33.2% less than the alternative RC building. For modules A to C and not considering operational energy use (B6), LCA results show a 20.6% reduction in embodied carbon achieved for the CLT building, compared to the RC building. For modules A to D and not considering B6, the embodied carbon assessment revealed that for the CLT building, 6.57 × 105 kg CO2 eq was emitted, whereas for the equivalent RC building, 2.16 × 106 kg CO2 eq was emitted, and emissions from CLT building was 70% lower than that from RC building. Additionally, 1.84 × 106 kg of CO2 eq was stored in the wood material used in the CLT building during its lifetime. Building material selection should be considered for the urgent need to reduce global climate change impacts.