Unconventional electronic phase transition in SnBi2Te4: role of anomalous thermal expansion.

We propose SnBi2Te4to be a novel topological quantum material exhibiting temperature (T) mediated transitions between rich electronic phases. Our combined theoretical and experimental results suggest that SnBi2Te4goes from a low-Tsemimetallic phase to a high-T(room temperature) insulating phase via an intermediate metallic phase. Single crystals of SnBi2Te4are characterized by various experimental probes including synchrotron based x-ray diffraction, magnetoresistance, Hall effect, Seebeck coefficient and magnetization. X-ray diffraction data confirms an anomalous thermal expansion of the unit cell volume below ∼100 K, which significantly affects the bulk band structure and hence the transport properties. Simulated surface states are found to be topologically robust with varyingT. This indirectly supports the experimentally observed paramagnetic singularity in the entireT-range. The proposed coexistence of such rich phases is a rare occurrence, yet it facilitates a fertile ground to tune them in a material driven by structural changes.

Nature-based interventions for vulnerable youth: a scoping review.

Nature-based interventions hold promise for vulnerable youth experiencing mental, emotional, developmental, behavioral, or social difficulties. This scoping review examined wilderness therapy, animal assisted therapy, care farming, and gardening and horticultural therapy programs to raise awareness and guide future development of research and treatment options. Studies included in this review were identified through a systematic search of the literature informed by a scoping review framework. Studies were examined by design, sample, intervention, and key findings. The majority of studies were quantitative using repeated measures designs and were conducted primarily in the United States. Sample sizes were generally small. Interventions were residential and community based with varying degrees of duration. Outcomes were largely positive across a wide range of psychosocial and behavioral measures and often maintained post-treatment. We emphasize the importance of robust empirical designs, comprehensive description of the interventions and surrounding therapies, and identification of target groups.

Making the case for librarian expertise to support evidence synthesis for the sustainable development goals.

Evidence syntheses that engage librarians as co-authors produce higher-quality results than those that do not. Trained as teachers, researchers, and information managers, librarians possess expert knowledge on research methodologies and information retrieval approaches that are critical for evidence synthesis. Researchers are under increasing pressure to produce evidence syntheses to inform practice and policymaking. Many fields outside of health science and medicine, however, do not have established guidelines, processes, or methodologies. This article describes how librarians led the creation of an interdisciplinary toolkit for researchers new to evidence synthesis. The implementation of the tools, including a protocol, supported eight evidence syntheses focused on effective agricultural interventions published in a special collection in Nature Research in October 2020. This article is a step-by-step overview of the tools and process. We advocate that librarian collaboration in evidence synthesis must become the norm, not the exception. Evidence synthesis project leads without access to a qualified librarian may use this toolkit as a point of entry for production of transparent, reproducible reviews.

Reversible coordination-induced spin-state switching in complexes on metal surfaces.

Molecular spin switches are attractive candidates for controlling the spin polarization developing at the interface between molecules and magnetic metal surfaces1,2, which is relevant for molecular spintronics devices3-5. However, so far, intrinsic spin switches such as spin-crossover complexes have suffered from fragmentation or loss of functionality following adsorption on metal surfaces, with rare exceptions6-9. Robust metal-organic platforms, on the other hand, rely on external axial ligands to induce spin switching10-14. Here we integrate a spin switching functionality into robust complexes, relying on the mechanical movement of an axial ligand strapped to the porphyrin ring. Reversible interlocked switching of spin and coordination, induced by electron injection, is demonstrated on Ag(111) for this class of compounds. The stability of the two spin and coordination states of the molecules exceeds days at 4 K. The potential applications of this switching concept go beyond the spin functionality, and may turn out to be useful for controlling the catalytic activity of surfaces15.

Light-Induced Spin Crossover in an Fe(II) Low-Spin Complex Enabled by Surface Adsorption.

Understanding and controlling the spin-crossover properties of molecular complexes can be of particular interest for potential applications in molecular spintronics. Using near-edge X-ray absorption fine structure spectroscopy, we investigated these properties for a new vacuum-evaporable Fe(II) complex, namely [Fe(pypyr(CF3)2)2(phen)] (pypyr = 2-(2'-pyridyl)pyrrolide, phen = 1,10-phenanthroline). We find that the spin-transition temperature, well above room temperature for the bulk compound, is drastically lowered for molecules arranged in thin films. Furthermore, while within the experimentally accessible temperature range (2 K < T < 410 K) the bulk material shows indication of neither light-induced excited spin-state trapping nor soft X-ray-induced excited spin-state trapping, these effects are observed for molecules within thin films up to temperatures around 100 K. Thus, by arranging the molecules into thin films, a nominal low-spin complex is effectively transformed into a spin-crossover complex.