Volume 15 Issue 11, November 2016

Physicists have discovered a new topological phase of matter, the Weyl semimetal, whose surface features a non-closed Fermi surface whereas the low-energy quasiparticles in the bulk emerge as Weyl fermions. A brief review of these developments and perspectives on the next steps forward are presented.

Topological semimetals and metals have emerged as a new frontier in the field of quantum materials. Novel macroscopic quantum phenomena they exhibit are not only of fundamental interest, but may hold some potential for technological applications.

The half-Heusler GdPtBi is found to show transport and calorimetric signatures of the existence of Weyl fermions under the application of a magnetic field. The half-Heusler alloys form a big family of tunable compounds that may substantially enlarge the number of Weyl semimetals known.

Scaling of the phonon damping with the wavevector in glasses is found to be different from the traditionally assumed Rayleigh scattering, and related to surprising, long-range correlations in the local elasticity matrix.

Confocal microscopy and computational analysis, now used for measuring microscale stresses in colloidal crystals, could be developed for investigation of amorphous materials, crystal melting, and mechanical properties of tissues.

Graphene is used as a capping sheet to synthesize 2D gallium nitride by means of migration-enhanced encapsulation growth. This technique may allow the stabilization of 2D materials that are not amenable to synthesis by traditional methods.

MoTe₂ is reported to host type II topological Weyl semimetal states. Two sets of Weyl points exist at different energies above the Fermi energy. Fermi arcs that form closed loops and are unique to type II Weyl semimetals are also found.

The half-Heusler GdPtBi is reported to exhibit negative longitudinal magnetoresistance. This is attributed to the chiral anomaly due to the formation of Weyl nodes with an applied magnetic field. The anomaly is also found to suppress the thermopower.

A method to synthesize 2D layers of gallium nitride on SiC is reported. Epitaxial graphene preliminarily grown on SiC allows intercalation of gallium atoms on the SiC substrate and stabilizes the 2D gallium nitride islands formed by ammonolysis.

Nonlinear stresses surrounding defect cores in three-dimensional colloidal crystals are experimentally determined at the single-particle level.

Studies of the phonon damping mechanism in glasses reveal scaling with the wavevector k which is different from the traditionally assumed Rayleigh scattering. These findings are related to long-range correlations in the local stress.

Electrochemically induced stresses in battery electrodes leading to performance degradation are still poorly understood. In situ measurements show that stress scales proportionally with lithium intercalation rate and strain with capacity.

Anisotropic phase segregation and migration of Pt in nanocrystals is important in designing enhanced catalysts. Insight into the mechanism of Pt–Ni rhombic dodecahedra growth may provide a way to produce nanocatalysts with improved performance.

Nanomechanical experiments on samples of the ordered and disordered phases of trabecular bone show a transition from plastic deformation to brittle failure.

Nanostructured plasmonic substrates are used for in situ, label-free detection, by surface-enhanced resonance Raman scattering spectroscopy, of quorum sensing in growing Pseudomonas aeruginosa biofilms.

The blood clearance mechanism, by the liver, of administered hard nanomaterials is reported in relation to blood flow dynamics, organ microarchitecture and cellular phenotype.