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Band structures with Fermi arcs characteristic of Weyl semimetals are observed on NbP and TaP. By studying NbP, TaP and TaAs, the evolution of the Fermi surface with the spin–orbit coupling is reported. Topological Weyl semimetals (TWSs) represent a novel state of topological quantum matter 1 , 2 , 3 , 4 which not only possesses Weyl fermions (massless chiral particles that can be viewed as magnetic monopoles in momentum space) in the bulk and unique Fermi arcs generated by topological surface states, but also exhibits appealing physical properties such as extremely large magnetoresistance and ultra-high carrier mobility 5 , 6 , 7 , 8 . Here, by performing angle-resolved photoemission spectroscopy (ARPES) on NbP and TaP, we directly observed their band structures with characteristic Fermi arcs of TWSs. Furthermore, by systematically investigating NbP, TaP and TaAs from the same transition metal monopnictide family, we discovered their Fermiology evolution with spin–orbit coupling (SOC) strength. Our experimental findings not only reveal the mechanism to realize and fine-tune the electronic structures of TWSs, but also provide a rich material base for exploring many exotic physical phenomena (for example, chiral magnetic effects, negative magnetoresistance, and the quantum anomalous Hall effect) and novel future applications 3 , 4 , 9 , 10 , 11 .

We report an unusual pressure-induced superconducting state that coexists with an antiferromagnetic ordering of Eu 2+ moments and shows a large upper critical field comparable to the Pauli paramagnetic limit in EuTe 2 . In concomitant with the emergence of superconductivity with T c  ≈ 3–5 K above P c  ≈ 6 GPa, the antiferromagnetic transition temperature T N ( P ) experiences a quicker rise with the slope increased dramatically from d T N /d P  = 0.85(14) K/GPa for P  ≤  P c to 3.7(2) K/GPa for P  ≥  P c . Moreover, the superconducting state can survive in the spin-flop state with a net ferromagnetic component of the Eu 2+ sublattice under moderate magnetic fields μ 0 H  ≥ 2 T. Our findings establish the pressurized EuTe 2 as a rare magnetic superconductor possessing an intimated interplay between magnetism and superconductivity. Here, the authors report pressure-induced superconductivity with concomitant enhancement of antiferromagnetic transition in layered EuTe 2 . The superconductivity is distinctly characterized by the high upper critical fields exceeding the Pauli limit among binary tellurides, a prerequisite of the coexistence of ferromagnetism with superconductivity.

Vortices are topological defects of type-II superconductors in an external magnetic field. In a similar fashion to a quantum anomalous Hall insulator, quantum anomalous vortices (QAV) spontaneously nucleate due to orbital-and-spin exchange interaction between supercurrent and magnetic impurity moment without an external magnetic field. Here, we used scanning superconducting quantum interference device microscopy (sSQUID) to search for its signatures in iron-chalcogenide superconductor Fe(Se,Te). Under zero magnetic field, we found a stochastic distribution of isolated anomalous vortices and antivortices with flux quanta Φ0. By applying a small local magnetic field under the coil of the nano-SQUID device, we observed hysteretic flipping of the vortices reminiscent of the switching of ferromagnetic domains, suggesting locally broken time-reversal symmetry. We further observed vectorial rotation of a flux line linking a vortex-antivortex pair by manipulating the local field. These unique properties of the anomalous vortices satisfy the defining criteria of QAV. Our observation suggests an emergent quantum phase with spontaneously nucleated vortex-antivortex matter in an iron-based superconductor with nontrivial topological band structure.

We report \\(^195\\)Pt nuclear magnetic resonance (NMR) measurements on topological superconductor candidate YPtBi which has the broken inversion symmetry and topological non-trivial band structures due to the strong spin-orbit coupling(SOC). In the normal state, we find that Knight shift \\(K\\) is field- and temperature-independent, suggesting that the contribution from the topological bands is very small at low temperatures. However, the spin-lattice relaxation rate 1/\\(T_1\\) divided by temperature (\\(T\\)), 1/\\(T_1T\\), increases with decreasing \\(T\\), implying the existence of antiferromagnetic spin fluctuations. In the superconducting state, no Hebel-Slichter coherence peak is seen below \\(T_ c\\) and 1/\\(T_1\\) follows \\(T^3\\) variation, indicating the unconventional superconductivity. The finite spin susceptibility at zero-temperature limit and the anomalous increase of the NMR line width below \\(T_ c\\) point to a mixed state of spin-singlet and spin-triplet(or spin-septet) pairing.

We fabricate CrP 4 single crystal under high pressure and high temperature at 5 GPa and 1373 K. The comprehensive physical properties including electronic transport, magnetic properties, specific heat, Hall, thermal Seebeck and thermal conductivity are reported here. The resistivity shows a good metallic conductivity and T 2.7 law relation in the low temperature, which indicates a weak correlation of electrons. It is interesting to note that CrP 4 shows large magnetoresistance (MR) of 500% under T  = 2 K and B  = 9 T, and the MR does not reach saturation until 9 T. The mechanism of large MR in CrP 4 is interpreted as the Fermi surface anisotropy. The Hall measurement shows that there is only one single type of carriers in CrP 4 with holes. CrP 4 exhibits paramagnetic behavior observed from the magnetic susceptibility measurement. Though CrP 4 exhibits high electrical conductivity, unexpected low thermal conductivity is observed at low temperature, which is due to the zigzag chain of CrP 6 octahedra along the c -axis. Low thermal conductivity is useful to design thermoelectric materials or devices by properly doping in CrP 4 .

Solid-state spin sensors have the capacity to act as quantum microscopes for probing material properties and physical processes. However, so far, these tools have relied on quantum defects hosted in rigid, three-dimensional (3D) crystals such as diamond, limiting their ability to closely interface with the sample. Here we demonstrate a versatile quantum microscope using point defects embedded within a thin layer of the van der Waals material hexagonal boron nitride. To showcase the multi-modal capabilities of this platform, we assemble two different heterostructures of a van der Waals material in combination with a quantum-active boron nitride flake. We demonstrate time-resolved, simultaneous temperature and magnetic imaging near the Curie temperature of a van der Waals ferromagnet, as well as map out charge currents and Joule heating in an operating graphene device. The straightforward integration of the hexagonal boron nitride quantum sensor with other van der Waals materials will yield substantial practical benefits for the design and measurement of 2D devices.Hexagonal boron nitride is a common component of 2D heterostructures. Defects implanted in boron nitride crystals can be used to perform spatially resolved sensing of properties, including temperature, magnetism and current.

Experiments show that TaAs is a three-dimensional topological Weyl semimetal. Three-dimensional (3D) topologicalWeyl semimetals (TWSs) represent a state of quantum matter with unusual electronic structures that resemble both a ‘3D graphene’ and a topological insulator. Their electronic structure displays pairs of Weyl points (through which the electronic bands disperse linearly along all three momentum directions) connected by topological surface states, forming a unique arc-like Fermi surface (FS). Each Weyl point is chiral and contains half the degrees of freedom of a Dirac point, and can be viewed as a magnetic monopole in momentum space. By performing angle-resolved photoemission spectroscopy on the non-centrosymmetric compound TaAs, here we report its complete band structure, including the unique Fermi-arc FS and linear bulk band dispersion across the Weyl points, in agreement with the theoretical calculations 1 , 2 . This discovery not only confirms TaAs as a 3DTWS, but also provides an ideal platform for realizing exotic physical phenomena (for example, negative magnetoresistance, chiral magnetic effects and the quantum anomalous Hall effect) which may also lead to novel future applications.

The intrinsic magnetic topological insulatorMnBi2Te4exhibits rich topological effects such as quantum anomalous Hall effect and axion electrodynamics. Here, by combining the use of synchrotron and laser light sources, we carry out comprehensive and high-resolution angle-resolved photoemission spectroscopy studies onMnBi2Te4and clearly identify its topological electronic structure. In contrast to theoretical predictions and previous studies, we observe topological surface states with diminished gap forming a characteristic Dirac cone. We argue that the topological surface states are mediated by multidomains of different magnetization orientations. In addition, the temperature evolution of the energy bands clearly reveals their interplay with the magnetic phase transition by showing interesting differences between the bulk and surface states, respectively. The investigation of the detailed electronic structure ofMnBi2Te4and its temperature evolution provides important insight into not only the exotic properties ofMnBi2Te4, but also the generic understanding of the interplay between magnetism and topological electronic structure in magnetic topological quantum materials.

TaTe4, a metallic charge-density wave (CDW) material discovered decades ago, has attracted renewed attention due to its rich interesting properties, such as pressure-induced superconductivity and candidate nontrivial topological phase. Here, using high-resolution angle-resolved photoemission spectroscopy and ab initio calculation, we systematically investigate the electronic structure of TaTe4. At 26 K, we observe a CDW gap as large as 290 meV, which persists up to 500 K. The CDW-modulated band structure shows a complex reconstruction that closely correlates with the lattice distortion. Inside the CDW gap, there exist highly dispersive energy bands contributing to the remnant Fermi surface and metallic behavior in the CDW state. Interestingly, our ab initio calculation reveals that the large CDW gap mainly opens in the electronic states with out-of-plane orbital components, while the in-gap metallic states originate from in-plane orbitals, suggesting an orbital texture that couples with the CDW order. Our results shed light on the interplay between electron, lattice, and orbital in quasi-one-dimensional CDW materials.

Summary Osteoporosis is a major public health problem characterized by low bone mineral density (BMD). This replication study confirmed 38 single-nucleotide polymorphisms (SNPs) out of 139 SNPs previously reported in three recent genome-wide association studies (GWASs) in an independent US white sample. Ten SNPs achieved combined p < 3.6 × 10⁻⁴. Introduction BMD is under strong genetic control. This study aims to verify the potential associations between BMD and candidate genes/loci reported by GWAS of FHS100K, Icelandic deCODE, and UK-NL. Methods Eight promising (at the genome-wide significant level after Bonferroni correction) and 131 available sub-promising (at the most stringent p value, p < 5.5 × 10⁻⁵ in the three GWASs reports) SNPs were selected. By using genotypic information from Affymetrix 500 K SNP arrays, we tested their associations with BMD in 1,000 unrelated US whites. Fisher's combined probability method was used to quantify the overall evidence of association. BMD was measured by dual energy X-ray absorptiometry. Results Two promising SNPs, rs3762397 and rs3736228, were replicated in the current study with p < 0.05. Besides, 36 sub-promising SNPs were replicated at the same significant level. Ten SNPs achieved significant combined p < 3.6 × 10⁻⁴ (0.05/139 SNPs, corrected for multiple testing). Conclusions Osteoporosis susceptibility of 38 SNPs was replicated in 1,000 unrelated US whites. This study showed promise for replication of some initial genome-wide association signals.