11 research outputs found
Fermion-Higgs model with strong Wilson-Yukawa coupling in two dimensions
The fermion mass spectrum is studied in the quenched approximation in the
strong coupling vortex phase (VXS) of a globally U(1)U(1)
symmetric scalar-fermion model in two dimensions. In this phase fermion
doublers can be completely removed from the physical spectrum by means of a
strong Wilson-Yukawa coupling. The lowest lying fermion spectrum in this phase
consists most probably only of a massive Dirac fermion which has charge zero
with respect to the group. We give evidence that the fermion which is
charged with respect to that subgroup is absent in the VXS phase. When the
gauge fields are turned on, the neutral fermion may couple chirally to
the massive vector boson state in the confinement phase. The outcome is very
similar to our findings in the strong coupling symmetric phase (PMS) of
fermion-Higgs models with Wilson-Yukawa coupling in four dimensions, with the
exception that in four dimensions the neutral fermion does most probably
decouple from the bosonic bound states.Comment: 21 pages, 6 postscript figures (appended), Amsterdam ITFA 92-21, HLRZ
J\"ulich 92-5
Z2-vortex order of frustrated Heisenberg antiferromagnets in two dimensions
We discuss the recent experimental data on various frustrated
quasi-two-dimensional Heisenberg antiferromagnets from the viewpoint of the
Z2-vortex order, which include S=3/2 triangular-lattice antiferromagnet NaCrO2,
S=1 triangular-lattice antiferromagnet NiGa2S4, S=1/2 organic
triangular-lattice antiferromagnets \kappa-(BEDT-TTF)2Cu2(CN)3 and
EtMe3Sb[Pd(dmit)2]2, and S=1/2 kagome-lattice antiferromagnet volborthite
Cu3V2O7(OH)22H2O, etc.Comment: Proceedings of the International Conference on Frustration in
Condensed Matter (ICFCM
Stability of Unconventional Superconductivity on Surfaces of Topological Insulators
Superconductivity on the surface of topological insulators is known to be
anisotropic and unconventional in that the symmetry is the mixture of s-wave
and nodeless p-wave component. In contrast to Anderson's theorem for the
insensitivity of the s-wave superconducting critical temperature to the
nonmagnetic (time-reversal symmetric (TRS)) impurities, anisotropic
superconductors including nodeless p-wave one are in general fragile even with
small concentration of the TRS impurities. By employing the Abrikosov-Gor'kov
theory, we clarify that this type of unconventional superconductivity emergent
on the surface state of the strong topological insulators robustly survive
against TRS impurities
Staggered dimer order in S=1/2 quantum spin ladder system with four spin exchange
We study the S=1/2 quantum spin ladder system with the four-spin exchange,
using density matrix renormalization group method and an exact diagonalization
method. Recently, the phase transition in this system and its universality
class are studied. But there remain controversies whether the phase transition
is second order type or the other type and the nature of order parameter. There
are arguments that the massless phase appears. But this does not agree with our
previous result. Analyzing DMRG data, we try a new approach in order to
determine a phase which appears after the phase transition. We find that the
edge state appears in the open boundary condition, investigating excitation
energies of states with higher magnetizations.Comment: Submitted to Phys. Rev. B, (REVTeX4
Switching between different vortex states in 2-dimensional easy-plane magnets due to an ac magnetic field
Using a discrete model of 2-dimensional easy-plane classical ferromagnets, we
propose that a rotating magnetic field in the easy plane can switch a vortex
from one polarization to the opposite one if the amplitude exceeds a threshold
value, but the backward process does not occur. Such switches are indeed
observed in computer simulations.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let