Search

A Dirac operator on the plane with constant (positive) mass is a Chern insulator, sitting in class D of the Kitaev table. Despite its simplicity, this system is topologically ill-behaved: the non-compact Brillouin zone prevents definition of a bulk invariant, and naively placing the model on a manifold with boundary results in violations of the bulk-edge correspondence (BEC). We overcome both issues by letting the mass spatially vary in the vertical direction, interpolating between the original model and its negative-mass counterpart. Proper bulk and edge indices can now be defined. They are shown to coincide, thereby embodying BEC. The shallow-water model exhibits the same illnesses as the 2D massive Dirac. Identical problems suggest identical solutions, and indeed extending the approach above to this setting yields proper indices and another instance of BEC. [ABSTRACT FROM AUTHOR]

Electrical resistivity experiments show superconductivity atTc=1.1K in a high-quality single crystal of trigonal γ -PtBi 2 , with an enhanced critical magnetic fieldμ0Hc2(0)≳1.5Tesla and a low critical current-densityJc(0)≈40 A cm -2 at H  = 0. Both T c andHc2(0)are the highest reported values for stoichiometric bulk samples at ambient pressure. We found a weakHc2anisotropy withΓ=Hc2ab/Hc2c<1, which is unusual among superconductors. Under a magnetic field, the superconducting transition becomes broader and asymmetric. Along with the low critical currents, this observation suggests an inhomogeneous superconducting state. In fact, no trace of superconductivity is observed through field-cooling-zero-field-cooling magnetization experiments., (© 2024 IOP Publishing Ltd.)

The emerging field of orbitronics aims to generate and control orbital angular momentum for information processing. Chiral crystals are promising orbitronic materials because they have been predicted to host monopole-like orbital textures, where the orbital angular momentum aligns isotropically with the electron's crystal momentum. However, such monopoles have not yet been directly observed in chiral crystals. Here, we use circular dichroism in angle-resolved photoelectron spectroscopy to image orbital angular momentum monopoles in the chiral topological semimetals PtGa and PdGa. The spectra show a robust polar texture that rotates around the monopole as a function of photon energy. This is a direct consequence of the underlying magnetic orbital texture and can be understood from the interference of local atomic contributions. Moreover, we also demonstrate that the polarity of the monopoles can be controlled through the structural handedness of the host crystal by imaging orbital angular moment monopoles and antimonopoles in the two enantiomers of PdGa, respectively. Our results highlight the potential of chiral crystals for orbitronic device applications, and our methodology could enable the discovery of even more complicated nodal orbital angular momentum textures that could be exploited for orbitronics., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2024.)

Uranium ditelluride (UTe 2 ) is the strongest contender to date for a p -wave superconductor in bulk form. Here we perform a spectroscopic study of the ambient pressure superconducting phase of UTe 2 , measuring conductance through point-contact junctions formed by metallic contacts on different crystalline facets down to 250 mK and up to 18 T. Fitting a range of qualitatively varying spectra with a Blonder-Tinkham-Klapwijk (BTK) model for p -wave pairing, we can extract gap amplitude and interface barrier strength for each junction. We find good agreement with the data for a dominant p y -wave gap function with amplitude 0.26 ± 0.06 meV. Our work provides spectroscopic evidence for a gap structure consistent with the proposed spin-triplet pairing in the superconducting state of UTe 2 ., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2024.)