A possible propagating Majorana: Majorana states in solid-state systems may one day form a basis for topological quantum computing. Most of the candidates identified so far have been Majorana bound states, but theorists have predicted that propagating Majorana states may exist as well. Wang et al. looked for such a state on the surface of the material FeSe _0.45 Te _0.55 (see the Perspective by Tewari and Stanescu). Using scanning tunneling spectroscopy, the researchers measured a flat, bias-independent density of states along a particular type of domain wall, which was consistent with a theoretical prediction for a propagating Majorana state in this material. Although topologically trivial origins of this finding are difficult to completely rule out, the work is likely to stimulate interest in iron-based superconductors as hosts of Majorana states. Science , this issue p. 104 ; see also p. 23

Co ₃ Sn ₂ S ₂ hosts Co atom–derived surface states at the Kagome lattice, favoring the electron transfer process in oxygen evolution.

Conventional, thermally driven continuous phase transitions are described by universal critical behavior that is independent of the specific microscopic details of a material. However, many current studies focus on materials that exhibit quantum-driven continuous phase transitions (quantum critical points, or QCPs) at absolute zero temperature. The classification of such QCPs and the question of whether they show universal behavior remain open issues. Here we report measurements of heat capacity and de Haas–van Alphen (dHvA) oscillations at low temperatures across a field-induced antiferromagnetic QCP (B_c0 ≈ 50 T) in the heavy-fermion metal CeRhIn₅. A sharp, magnetic-field-induced change in Fermi surface is detected both in the dHvA effect and Hall resistivity at <mml:math><mml:mrow><mml:msubsup><mml:mi>B</mml:mi><mml:mn>0</mml:mn><mml:mo>*</mml:mo></mml:msubsup></mml:mrow></mml:math>B0* ≈ 30 T, well inside the antiferromagnetic phase. Comparisons with band-structure calculations and properties of isostructural CeCoIn₅ suggest that the Fermi-surface change at <mml:math><mml:mrow><mml:msubsup><mml:mi>B</mml:mi><mml:mn>0</mml:mn><mml:mo>*</mml:mo></mml:msubsup></mml:mrow></mml:math>B0* is associated with a localized-to-itinerant transition of the Ce-4f electrons in CeRhIn₅. Taken in conjunction with pressure experiments, our results demonstrate that at least two distinct classes of QCP are observable in CeRhIn₅, a significant step toward the derivation of a universal phase diagram for QCPs.