The quantum-level interplay between geometry, topology and correlation is at the forefront of fundamental physics1-15. Kagome magnets are predicted to support intrinsic Chern quantum phases owing to ...their unusual lattice geometry and breaking of time-reversal symmetry14,15. However, quantum materials hosting ideal spinorbit-coupled kagome lattices with strong out-of-plane magnetization are lacking16-21. Here, using scanning tunnelling microscopy, we identify a new topological kagome magnet, TbMn6Sn6, that is close to satisfying these criteria. We visualize its effectively defect-free, purely manganese-based ferromagnetic kagome lattice with atomic resolution. Remarkably, its electronic state shows distinct Landau quantization on application of a magnetic field, and the quantized Landau fan structure features spin-polarized Dirac dispersion with a large Chern gap. We further demonstrate the bulk-boundary correspondence between the Chern gap and the topological edge state, as well as the Berry curvature field correspondence of Chern gapped Dirac fermions. Our results point to the realization of a quantum-limit Chern phase in TbMn6Sn6, and may enable the observation of topological quantum phenomena in the RMn6Sn6 (where R is a rare earth element) family with a variety of magnetic structures. Our visualization ofthe magnetic bulk-boundary-Berry correspondence covering real space and momentum space demonstrates a proof-of-principle method for revealing topological magnets.
Owing to the unusual geometry of kagome lattices-lattices made of corner-sharing triangles-their electrons are useful for studying the physics of frustrated, correlated and topological quantum ...electronic states
. In the presence of strong spin-orbit coupling, the magnetic and electronic structures of kagome lattices are further entangled, which can lead to hitherto unknown spin-orbit phenomena. Here we use a combination of vector-magnetic-field capability and scanning tunnelling microscopy to elucidate the spin-orbit nature of the kagome ferromagnet Fe
Sn
and explore the associated exotic correlated phenomena. We discover that a many-body electronic state from the kagome lattice couples strongly to the vector field with three-dimensional anisotropy, exhibiting a magnetization-driven giant nematic (two-fold-symmetric) energy shift. Probing the fermionic quasi-particle interference reveals consistent spontaneous nematicity-a clear indication of electron correlation-and vector magnetization is capable of altering this state, thus controlling the many-body electronic symmetry. These spin-driven giant electronic responses go well beyond Zeeman physics and point to the realization of an underlying correlated magnetic topological phase. The tunability of this kagome magnet reveals a strong interplay between an externally applied field, electronic excitations and nematicity, providing new ways of controlling spin-orbit properties and exploring emergent phenomena in topological or quantum materials
.
Lipids are ubiquitous and serve numerous biological functions; thus lipids have been shown to have great potential as candidates for elucidating biomarkers and pathway perturbations associated with ...disease. Methods expanding coverage of the lipidome increase the likelihood of biomarker discovery and could lead to more comprehensive understanding of disease etiology.
We introduce LipidMatch, an R-based tool for lipid identification for liquid chromatography tandem mass spectrometry workflows. LipidMatch currently has over 250,000 lipid species spanning 56 lipid types contained in in silico fragmentation libraries. Unique fragmentation libraries, compared to other open source software, include oxidized lipids, bile acids, sphingosines, and previously uncharacterized adducts, including ammoniated cardiolipins. LipidMatch uses rule-based identification. For each lipid type, the user can select which fragments must be observed for identification. Rule-based identification allows for correct annotation of lipids based on the fragments observed, unlike typical identification based solely on spectral similarity scores, where over-reporting structural details that are not conferred by fragmentation data is common. Another unique feature of LipidMatch is ranking lipid identifications for a given feature by the sum of fragment intensities. For each lipid candidate, the intensities of experimental fragments with exact mass matches to expected in silico fragments are summed. The lipid identifications with the greatest summed intensity using this ranking algorithm were comparable to other lipid identification software annotations, MS-DIAL and Greazy. For example, for features with identifications from all 3 software, 92% of LipidMatch identifications by fatty acyl constituents were corroborated by at least one other software in positive mode and 98% in negative ion mode.
LipidMatch allows users to annotate lipids across a wide range of high resolution tandem mass spectrometry experiments, including imaging experiments, direct infusion experiments, and experiments employing liquid chromatography. LipidMatch leverages the most extensive in silico fragmentation libraries of freely available software. When integrated into a larger lipidomics workflow, LipidMatch may increase the probability of finding lipid-based biomarkers and determining etiology of disease by covering a greater portion of the lipidome and using annotation which does not over-report biologically relevant structural details of identified lipid molecules.
Magnetic topological phases of quantum matter are an emerging frontier in physics and material science. Along these lines, several kagome magnets have appeared as the most promising platforms. Here, ...we explore magnetic correlations in the kagome magnet Co
Sn
S
. Using muon spin-rotation, we present evidence for competing magnetic orders in the kagome lattice of this compound. Our results show that while the sample exhibits an out-of-plane ferromagnetic ground state, an in-plane antiferromagnetic state appears at temperatures above 90 K, eventually attaining a volume fraction of 80% around 170 K, before reaching a non-magnetic state. Strikingly, the reduction of the anomalous Hall conductivity (AHC) above 90 K linearly follows the disappearance of the volume fraction of the ferromagnetic state. We further show that the competition of these magnetic phases is tunable through applying either an external magnetic field or hydrostatic pressure. Our results taken together suggest the thermal and quantum tuning of Berry curvature induced AHC via external tuning of magnetic order.
Researchers have a responsibility to cause no harm, but research has been a source of distress for indigenous people because of inappropriate methods and practices. The way researchers acquire ...knowledge in indigenous communities may be as critical for eliminating health disparities as the actual knowledge that is gained about a particular health problem. Researchers working with indigenous communities must continue to resolve conflict between the values of the academic setting and those of the community. It is important to consider the ways of knowing that exist in indigenous communities when developing research methods. Challenges to research partnerships include how to distribute the benefits of the research findings when academic or external needs contrast with the need to protect indigenous knowledge.
► We present spectroscopic data from McDonald Observatory covering almost 30years and 130 comets. ► We find that 9% of the comets are carbon-chain depleted by the strictest definition (25% by a more ...customary definition). ► Jupiter Family comets are more likely to be depleted than Long Period comets. ► On average, there are few compositional differences with increasing orbital semi-major axis.
We report on the results of a spectroscopic survey of 130 comets that was conducted at McDonald Observatory from 1980 through 2008. Some of the comets were observed on only one night, while others were observed repeatedly. For 20 of these comets, no molecules were detected. For the remaining 110 comets, some emission from CN, OH, NH, C3, C2, CH, and NH2 molecules were observed on at least one occasion. We converted the observed molecular column densities to production rates using a Haser (Haser, L. 1957. Liege Inst. Astrophysics Reprint No. 394) model. We defined a restricted data set of comets that had at least three nights of observations. The restricted data set consists of 59 comets. We used ratios of production rates to study the trends in the data. We find two classes of comets: typical and carbon-chain depleted comets. Using a very strict definition of depleted comets, requiring C2and C3 to both be depleted, we find 9% of our restricted data set comets to be depleted. Using a more relaxed definition that requires only C2 to be below a threshold (similar to other researchers), we find 25% of the comets are depleted. Two-thirds of the depleted comets are Jupiter Family comets, while one-third are Long Period comets. 37% of the Jupiter Family comets are depleted, while 18.5% of the Long Period comets are depleted. We compare our results with other studies and find good agreement.
Metal-oxide thin films are used extensively in electronic and energy applications. Solution processing offers a potentially scalable and inexpensive deposition method to expand the applications of ...metal-oxide films and to complement vacuum-deposition techniques. Among precursors for solution deposition, metal nitrates stand out for their ability to form high-quality metal-oxide thin films. This review focuses on unique aspects of metal-nitrate chemistry that have been exploited to advance the development of solution-processed thin films. We discuss the solid-state bulk, solution, and thin-film chemical reactions involving metal nitrates and illustrate how the resulting metal-oxide thin-film properties depend on the entire reaction pathway. To conclude, we offer perspective as to how understanding the chemistry of film formation from metal-nitrate precursors is useful for addressing the primary drivers for industrial manufacturing of solution-processed metal-oxide thin films.
Unique chemistries of metal-nitrate precursors that enable the preparation of high-quality, high-performance metal-oxide thin films by solution deposition are reviewed.
The absence of inversion symmetry in non-centrosymmetric materials has a fundamental role in the emergence of a vast number of fascinating phenomena, like ferroelectricity, second harmonic ...generation, and Weyl fermions. The removal of time-reversal symmetry in such systems further extends the variety of observable magneto-electric and topological effects. Here we report the striking topological properties in the non-centrosymmetric spin-orbit magnet PrAlGe by combining spectroscopy and transport measurements. By photoemission spectroscopy below the Curie temperature, we observe topological Fermi arcs that correspond to projected topological charges of ±1 in the surface Brillouin zone. In the bulk, we observe the linear energy-dispersion of the Weyl fermions. We further observe a large anomalous Hall response in our magneto-transport measurements, which is understood to arise from diverging bulk Berry curvature fields associated with the Weyl band structure. These results establish a novel Weyl semimetal phase in magnetic non-centrosymmetric PrAlGe.
The nonlinear optical responses from topological semimetals are crucial in both understanding the fundamental properties of quantum materials and designing next-generation light sensors or solar ...cells. However, previous work focused on the optical effects from bulk states only, disregarding the responses from topological surface states. In this Letter, we propose a new surface-only photocurrent response from chiral Fermi arcs. Using the ideal topological chiral semimetal RhSi as a representative, we quantitatively compute the photogalvanic currents from Fermi arcs on different surfaces. By rigorous crystal symmetry analysis, we demonstrate that Fermi arc photogalvanic currents can be perpendicular to the bulk injection currents regardless of the choice of materials surface. We then generalize this finding to other cubic chiral space groups and predict material candidates. Our theory reveals a powerful notion where common crystalline symmetry can be used to completely disentangle bulk and surface optical responses in many conducting material families.
Intraflagellar transport (IFT) moves IFT trains carrying cargoes from the cell body into the flagellum and from the flagellum back to the cell body. IFT trains are composed of complexes IFT-A and ...IFT-B and cargo adaptors such as the BBSome. The IFT-B core proteins IFT74 and IFT81 interact directly through central and C-terminal coiled-coil domains, and recently it was shown that the N termini of these proteins form a tubulin-binding module important for ciliogenesis. To investigate the function of IFT74 and its domains in vivo, we have utilized Chlamydomonas reinhardtii ift74 mutants. In a null mutant, lack of IFT74 destabilized IFT-B, leading to flagella assembly failure. In this null background, expression of IFT74 lacking 130 amino acids (aa) of the charged N terminus stabilized IFT-B and promoted slow assembly of nearly full-length flagella. A further truncation (lacking aa 1–196, including part of coiled-coil 1) also stabilized IFT-B, but failure in IFT-A/IFT-B interaction within the pool at the base of the flagellum prevented entry of IFT-A into the flagellum and led to severely decreased IFT injection frequency and flagellar-assembly defects. Decreased IFT-A in these short flagella resulted in aggregates of stalled IFT-B in the flagella. We conclude that IFT74 is required to stabilize IFT-B; aa 197–641 are sufficient for this function in vivo. The N terminus of IFT74 may be involved in, but is not required for, tubulin entry into flagella. It is required for association of IFT-A and IFT-B at the base of the flagellum and flagellar import of IFT-A.
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•IFT74 is required for IFT-B stability and flagella assembly•The N terminus of IFT74 coiled-coil 1 is required for recruitment of IFT-A to IFT-B•Impaired IFT-A/IFT-B interaction in the cell body reduces IFT injection frequency•IFT74 sequence prior to coiled-coil 1 is not required for tubulin to enter flagella
Intraflagellar transport (IFT) trains contain subcomplexes IFT-A and IFT-B and carry critical cargoes into cilia. Brown et al. show that the N terminus of the IFT-B subunit IFT74 is required to recruit IFT-A to IFT-B for assembly of IFT trains at the base of the cilium and for their subsequent injection into the cilium.
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