Low-frequency quantum oscillations in LaRhIn5_5: Dirac point or nodal line?

In the recent paper [1], a new method based on measuring a temperature correction to a quantum-oscillation frequency was proposed to study an energy-band dispersion of charge carriers in small Fermi surface (FS) pockets of crystals. To illustrate their approach, Guo et al. [1] applied it to a number of materials and, in particular, to the multiband metal LaRhIn$_5$ which, apart from high-frequency oscillations associated with a large FS, also exhibits the oscillations with the low frequency $F\approx 7$ T. Although the method of Ref. [1] really detects charge carriers with a linear dispersion, it does not distinguish between the carriers near a Dirac point and near a nodal line, since all such quasiparticles disperse linearly. Here we ask what is the nature of the carriers associated with the frequency $F$ in LaRhIn$_5$ and call attention to the puzzling origin of this frequency.Comment: This is matters arising from C. Guo et al. Nature Communications 12, 6213 (2021); 6 pages, 2 figure

The Berry phase and the phase of the Shubnikov-de Haas oscillations in three-dimensional topological insulators

Within the semiclassical approach, we calculate contributions of the Berry phase and of the Zeeman coupling of the electron moment with the magnetic field to the phase of the Shubnikov - de Haas oscillations for the surface electrons in the Bi$_2$X$_3$ family of three-dimensional topological insulators (X stands for Te or Se). We also discuss a relation of the obtained results with published experimental data on the Shubnikov-de Haas oscillations for this family of topological insulators.Comment: 4 pages, submitted to Phys. Rev.

Origin of the peaks in the Nernst coefficient of bismuth in strong magnetic fields

We explain the origin of most of the peaks in the Nernst coefficient that were recently observed at magnetic fields directed along the trigonal axis and the bisectrix direction in bismuth. Additional experiments are discussed that enable one to verify our explanation.Comment: Submitted to Physical Review B. 4 pages, 5 figure

Electron energy spectrum and the Berry phase in graphite bilayer

We emphasize that there exist four Dirac-type points in the electron-energy spectrum of a graphite bilayer near the point K of its Brillouin zone. One of the Dirac points is at the point K, and three Dirac points lie nearby. Each of these three points generates the Berry phase $\pi$, while the Dirac point at K gives the phase $-\pi$. It is these four points that determine the Berry phase in the bilayer. If an electron orbit surrounds all these points, the Berry phase is equal to $2\pi$.Comment: 4 pages, 2 figures, submitted to Phys. Rev. B ; expande