Yuya Ominato

Quantum transport in a three-dimensional Weyl electron system

Quantum transport in three-dimensional massless Dirac electron system with long-range Gaussian impurities is studied theoretically using a self-consistent Born approximation (SCBA). We find that the conductivity significantly changes the behavior at a certain scattering strength which separates the weak and strong disorder regimes. In the weak disorder regime, the SCBA conductivity mostly agrees with the Boltzmann conductivity, while the agreement fails near the Dirac point where the SCBA conductivity drops to zero linearly to the Fermi energy. In the strong disorder regime, the conductivity is smooth and finite near the Dirac point, and the minimum conductivity becomes larger in increasing the disorder potential, contrary to the usual metallic behavior. The theory applies to three dimensional gapless band structures, including Weyl semimetals.

Orbital magnetism of graphene flakes

Orbital magnetism is studied for graphene flakes with various shapes and edge configurations using the tight-binding approximation. In the low-temperature regime where the thermal energy is much smaller than to the energy level spacing, the susceptibility rapidly changes between diamagnetism and paramagnetism as a function of Fermi energy, in accordance with the energy level structure. The susceptibility at charge neutral point is generally larger in armchair flake than in zigzag flake, and larger in hexagonal flake than in triangular flake. As the temperature increases, the discrete structures due to the quantum confinement are all gone, and the susceptibility approximates the bulk limit independently of the atomic configuration. The diamagnetic current circulates entirely on the graphene flake at zero temperature, while in increasing temperature it is localized near the edge with the characteristic depth proportional to 1/T. We predict that the diamagnetism of graphene can be observed using the alignment of graphene flakes in a feasible range of magnetic field.

Orbital magnetic susceptibility of finite-sized graphene

We study the orbital magnetism of graphene ribbon in the effective-mass approximation, to figure out the finite-size effect on the singular susceptibility known in the bulk limit. We find that the susceptibility at

Magnetotransport in the Weyl semimetal in the quantum limit - the role of the topological surface states

T=0

Anisotropic magnetotransport in Dirac-Weyl magnetic junctions

oscillates between diamagnetism and paramagnetism as a function of

Orbital magnetism of graphene nanostructures

{\ensuremath{\varepsilon}}_{F}

Quantum transport in three-dimensional Weyl electron system -- in the presence of charged impurity scattering

, in accordance with the subband structure formed by quantum confinement. In increasing

Spin-orbit crossed susceptibility in topological Dirac semimetals.

T

Spin susceptibility of three-dimensional Dirac-Weyl semimetals

, the oscillation rapidly disappears once the thermal broadening energy exceeds the subband spacing, and the susceptibility

Magnetic response in topological Dirac semimetals

\ensuremath{\chi}({\ensuremath{\varepsilon}}_{F})