Zhenyu Zhang

Topological magnetic excitations represent an active frontier of research in condensed matter physics. The introduction of various types of antiferromagnetism can further enrich the degrees of freedom and expand the topological phase space. Here we propose a generic strategy to properly characterize the topological magnetic excitations on a honeycomb lattice with zigzag-type antiferromagnetic correlations, featured by ferromagnetism along the chains and antiferromagnetism between neighboring chains. The enabling step is to map the honeycomb lattice onto a quartet lattice whose irreducible unit cell contains four inequivalent spin sites, from which all the emergent magnetic excitations can be derived and properly described. In the presence of easy in-plane or out-of-plane anisotropy, we can readily disentangle the intricate magnetic textures from atomistic magnetics simulations, leading to the identification of meronic or skyrmionic excitations due to creation of vortex-antivortex pairs or Dzyaloshinskii-Moriya interaction, respectively. Such topological magnetic excitations can emerge in some or all of the four sublattices, thus underpinning the critical need to generalize the well-studied scalar topological charge to an effective four-component vectorial form.

Nowadays, the full‐spectrum artificial lighting technology that approaches the solar spectrum has become an important issue in the field of lighting. Yet, to date, the development of full‐spectrum white‐light‐emitting diodes (WLEDs) remains hindered by the fixed band gaps of conventional semiconductors and the synthetic challenges of certain specific‐color phosphors, resulting in poor spectral tenability and far deviation from the solar spectrum. Herein, based on first‐principles calculations, we propose a new conceptual scheme to potentially achieve full‐spectrum white light emission via two‐dimensional (2D) amorphous heterojunction (a‐SiC/a‐MoS ₂ ), which intrinsically emits broadband white light closely matching the D65 standard source. We further reveal that the underlying mechanism of full‐spectrum emission stems from two aspects: firstly, the quantum confinement effects in 2D amorphous heterojunctions lead to the formation of a series of discrete and strongly localized Anderson tail states in their bandgaps; secondly, the disordered structure breaks the orbital symmetry, which fully enables transitions of these states that maybe forbidden in crystalline counterparts. Thus, the combined effect of the two not only allows for sufficient transition energy levels, but also modulates the spectral distribution. Our work opens a new approach for full‐spectrum artificial lighting, with promising implications for the advancement of high‐quality lighting.

Chiral phonons have recently been established to emerge in systems containing intrinsically chiral atomic structures or magnetic systems. Here we show that such intriguing chiral phonons can also be induced in nonmagnetic Kagome lattices that lack atomic structural chirality but harbor electronic chirality rooted in the presence of loop current order. This central finding is demonstrated using two types of loop current order, the restricted chiral flux phase characterized by a pure imaginary charge bond order and the more generalized chiral flux phase characterized by a complex charge bond order, as typified in layered AV_{3}Sb_{5} (A=Cs, Rb, K). At a mechanistic level, the time-reversal symmetry breaking caused by the electronic chirality is shown to pronouncedly influence their vibrational properties through electron-phonon coupling. The electronic chirality in either chiral flux phase is accompanied by a nonzero molecular Berry curvature, which in turn manifests as a nonlocal effective magnetic field of vectorial nature acting on the phonons. Consequently, the double degeneracy at each Brillouin zone corner is lifted, empowering chirality to the phonon modes. This Letter provides an indispensable component toward a more complete understanding of various chiral collective electronic phenomena in such structurally achiral systems.

Recent experiments have observed superconductivity up to 48 K in La3Ni2O7-derived films under compressive strain imposed by the SrLaAlO4 substrate, while such films on the SrTiO3 substrate with tensile strain have failed to reach the superconducting state. Here we propose to broadly expand the choices of materials platforms to achieve high-Tc superconducting La3Ni2O7 films by proposing designer substrates of Ba1-xSrxO (x = 0 - 1) that allow to continuously tune the strain in the films from being tensile to compressive. Our systematic study of the structural and electronic reconstructions of the strained La3Ni2O7 bilayer film leads to the central finding that at the optimal tensile strain of ~2% (x ~0.25), the spectral weight of the Ni dz2 orbital is peaked right at the Fermi level, and its hybridization with the Ni dx2-y2 orbital is substantially enhanced. Consequently, the expected Tc should be unprecedentedly high, at least substantially higher than those achieved in the compressive regime. Furthermore, our detailed thickness-dependent energetic analyses show that such films can be stably grown for thicknesses equal to or beyond the bilayer regime, and predict that the SrO-terminated SrTiO3 should also be able to stabilize the films with optimal tensile strain and higher Tc's.