Topological stripelike coreless textures with inner incommensurability in two-dimensional Heisenberg antiferromagnet

For two-dimensional Heisenberg antiferromagnet we present an analysis of topological coreless excitations having a stripe form. These textures are characterized by singularities at boundaries. A detailed classification of the stripe textures results in a certain analogy with the coreless excitations in $^3He-A$ phase: Mermin-Ho and Anderson-Toulouse coreless vortices. The excitations of the last type may have a low bulk energy. The stripe textures may be observed as an occurrence of short-range incommensurate order in the antiferromagnetic environment

Bose-Einstein condensation of semi-hard bosons in S=1 dimerized organic compound F2PNNNO

An analysis of the energy spectrum and the magnetization curve of two-dimensional organic antiferromagnet F2PNNNO with a spin-one dimerized structure shows that a behavior of the compound in an external magnetic field can be explained within a lattice boson model with an extended Pauli's exclusion principle, i.e. no more than two bosons per a dimer. The unusual magnetization curve observed experimentally in the compound reflects a sequence of phase transitions intrinsic for a lattice boson system with strong on-site and inter-site repulsions due to a tuning of magnon density by the applied magnetic field

Theory of magnetoelastic resonance in a mono-axial chiral helimagnet

We study magnetoelastic resonance phenomena in a mono-axial chiral helimagnet belonging to hexagonal crystal class. By computing the spectrum of coupled elastic wave and spin wave, it is demonstrated how hybridization occurs depending on their chirality. Specific features of the magnetoelastic resonance are discussed for the conical phase and the soliton lattice phase stabilized in the mono-axial chiral helimagnet. The former phase exhibits appreciable non-reciprocity of the spectrum, the latter is characterized by a multi-resonance behavior. We propose that the non-reciprocal spin wave around the forced-ferromagnetic state has potential capability to convert the linearly polarized elastic wave to circularly polarized one with the chirality opposite to the spin wave chirality.Comment: 12 pages, 5 figures, Accepted in Phys. Rev.

The Fermi surface and the role of electronic correlations in Sm2−x_{2-x}Cex_{x}CuO4_4

Using LDA+GTB (local density approximation+generalized tight-binding) hybrid scheme we investigate the band structure of the electron-doped high-$T_c$ material Sm$_{2-x}$Ce$_{x}$CuO$_4$. Parameters of the minimal tight-binding model for this system (the so-called 3-band Emery model) were obtained within the NMTO ($N$-th order Muffin-Tin orbital) method. Doping evolution of the dispersion and Fermi surface in the presence of electronic correlations was investigated in two regimes of magnetic order: short-range (spin-liquid) and long-range (antiferromagnetic metal). Each regime is characterized by the specific topologies of the Fermi surfaces and we discuss their relation to recent experimental data.Comment: 10 pages, 4 figures, 1 table, Published versio

On the theory of Josephson effect in a diffusive tunnel junction

Specific features of the equilibrium current-carrying state of a Josephson tunnel junction between diffusive superconductors are studied theoretically in the 1D geometry. It is found that the Josephson current induces localized states of electron excitations in the vicinity of the tunnel barrier, which are a continuous analog of Andreev levels in a ballistic junction. The depth of the corresponding ``potential well'' is much greater than the separation between an Andreev level and the continuous energy spectrum boundary for the same transmissivity of the barrier. In contrast to a ballistic junction in which the Josephson current is transported completely by localized excitations, the contribution to current in a diffusive junction comes from whole spectral region near the energy gap boundary, where the density of states differs considerably from its unperturbed value. The correction to the Josephson current in the second order of the barrier transmissivity, which contains the second harmonic of the phase jump, is calculated and it is found that the true expansion parameter of the perturbation theory for a diffusive junction is not the tunneling probability $\Gamma$ itself, but a much larger parameter $W = (3\xi_0/4l)\Gamma$.Comment: 8 pages, 5 Postscript figures, submitted to Low Temp. Phy

Surface Electronic Structures and Field Emission Currents at Sodium Overlayers on Low-Index Tungsten Surfaces

The total energy distributions (TEDs) of the emission currents in field emission and surface photofield emission and the overlayer-induced modifications in the surface electronic structures from the technologically important W surfaces with the commensurate W(100)/Na c(2x2), W(110)/Na (2x2) and W(111)/Na (1x1) overlayers are calculated. The TEDs obtained by our recent numerical method that extends the full-potential linear augmented plane wave method for the electronic structures to the study of field and photofield emission are used to interpret the shifts of the peaks in the experimental TEDs in field emission and photofield emission from the W(100) and W(110) surfaces at sub-monolayer and monolayer Na coverage. Hybridization of the 3s Na states with the pairs of dz2-like surface states of the strong Swanson hump in clean W(100) and surface resonances in clean W(111) below the Fermi energy shifts these W states by about -1.2 eV and -1.0 eV, thus stabilizing these states, to yield new strong peaks in the TEDs in field emission and photofield emission from W(100)/Na c(2x2) and W(111)/Na (1x1) respectively. The effect of Na intralayer interactions are discussed and are shown to shift the strong s- and p-like peaks in the surface density of states of W(110) below and above the Fermi energy respectively to lower energy with increased Na coverage, in agreement with experiments.Comment: 12 page