Neutral Larkin-Ovchinnikov-Fulde-Ferrell state and chromomagnetic instability in two-flavor dense QCD

In two-flavor dense quark matter, we describe the dynamics in the single plane wave Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) state satisfying the color and electric neutrality conditions. We find that because the neutral LOFF state itself suffers from a chromomagnetic instability in the whole region where it coexists with the (gapped or gapless) two-flavor superconducting phases, it cannot cure this instability in those phases. This is unlike the recently revealed gluonic phase which seems to be able to resolve this problem.     

Ceramic foam substrates for automotive catalyst applications: fluid mechanic analysis

Several properties of ceramic foams render them promising substrates for various industrial processes. For automotive applications, the foam properties that need to be further studied include the substrate impact on the exhaust gas flow, in terms of pressure drop and flow uniformity. In this paper, pressure drop measurements are performed with different honeycomb and ceramic foam substrates, and pressure drop correlations are discussed. The flow uniformity upstream and downstream of the substrates is evaluated using particle image velocimetry. The results show that ceramic foam substrates induce higher pressure drop, while increasing the uniformity of the flow. In contrast to honeycomb monoliths, the flow uniformity downstream of ceramic foams does not decrease with increasing flow velocity. The higher flow uniformity of ceramic foams is not only caused by their higher pressure drop, but also by flow homogenization that occurs inside the ceramic foam structure, as a result of the momentum exchange perpendicular to the main flow direction.     

Electronic Properties of Strained Double‐Weyl Systems

The effects of strains on the low‐energy electronic properties of double‐Weyl phases are studied in solids and cold‐atom optical lattices. The principal finding is that deformations do not couple, in general, to the low‐energy effective Hamiltonian as a pseudoelectromagnetic gauge potential. The response of an optical lattice to strains is simpler, but still only one of the several strain‐induced terms in the corresponding low‐energy Hamiltonian can be interpreted as a gauge potential. Most interestingly, the strains can induce a nematic order parameter that splits a double‐Weyl node into a pair of Weyl nodes with the unit topological charges. The effects of deformations on the motion of wavepackets in the double‐Weyl optical lattice model are studied. It is found that, even in the undeformed lattices, the wavepackets with opposite topological charges can be spatially split. Strains, however, modify their velocities in a very different way and lead to a spin polarization of the wavepackets.     

Spin-glass, antiferromagnetism and kondo behavior in Ce2Au1−x Co x Si3 alloys

Recently, the solid solution Ce₂Au_{1− x Co} xSi₃ has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce₂AuSi₃, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce₂AuSi₃ lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.     

Fermi Arcs and DC Transport in Nanowires of Dirac and Weyl Semimetals

The transport properties and electron states in cylinder nanowires of Dirac and Weyl semimetals are studied paying special attention to the structure and properties of the surface Fermi arcs. The latter make the electric charge and current density distributions in nanowires strongly nonuniform as the majority of the charge density is accumulated at the surface. It is found that a Weyl semimetal wire also supports a magnetization current localized mainly at the surface because of the Fermi arcs contribution. By using the Kubo linear response approach, the direct current (DC) conductivity is calculated and it is found that its spatial profile is nontrivial. By explicitly separating the contributions of the surface and bulk states, it is shown that when the electric chemical potential and/or the radius of the wire is small, the electron transport is determined primarily by the Fermi arcs and the electrical conductivity is much higher at the surface than in the bulk. Due to the rise of the surface-bulk transition rate, the relative contribution of the surface states to the total conductivity gradually diminishes as the chemical potential increases. In addition, the DC conductivity at the surface demonstrates noticeable peaks when the Fermi level crosses energies of the surface states.     

Energy gaps at neutrality point in bilayer graphene in a magnetic field

Utilizing the Baym-Kadanoff formalism with the polarization function calculated in the random phase approximation, the dynamics of the ν = 0 quantum Hall state in bilayer graphene is analyzed. Two phases with nonzero energy gap, the ferromagnetic and layer asymmetric ones, are found. The phase diagram in the plane ($ \bar \Delta _0 $ \bar \Delta _0 , B), where $ \bar \Delta _0 $ \bar \Delta _0 is a top-bottom gates voltage imbalance, is described. It is shown that the energy gap scales linearly, ΔE ∼ 14B [T] K, with magnetic field.     

The growth of a single crystal of Sr3CuIrO6 and its magnetic behavior compared to polycrystals

We have grown single crystals of the psuedo-one-dimensional compound Sr₃CuIrO₆, a K₄CdCl₆-derived monoclinic structure with Cu-Ir chains along the [101] direction. We present the ac and dc magnetization behavior of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence for at least two magnetic transitions, at 5 K (T ₁) and 19 K (T ₂), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of both the forms is found to be widely different, exhibiting unexpected time dependence.     

Statistical screening in aP,T-invariant model

It is shown that in theP, T-invariant model with the mixed Chern-Simons term the interaction of charge carriers leads to effective changing of their statistics, which depends on distance between them. In particular, in the limit of large distances fermions effectively turn into bosons.     

Gap generation for Dirac fermions on Lobachevsky plane in a magnetic field

We study symmetry breaking and gap generation for fermions in the 2D space of constant negative curvature (the Lobachevsky plane) in an external covariantly constant magnetic field in a four-fermion model. It is shown that due to the magnetic and negative curvature catalyses phenomena the critical coupling constant is zero and there is a symmetry breaking condensate in the chiral limit even in free theory. We analyze solutions of the gap equation in the cases of zero, weak, and strong magnetic fields. As a byproduct, we calculate the density of states and the Hall conductivity for noninteracting fermions that may be relevant for studies of graphene.