2,788 research outputs found
Relativistic dissipative hydrodynamics with spontaneous symmetry breaking
In this paper we consider dissipative hydrodynamic equations for systems with
continuous broken symmetries. We first present the case of superfluidity, in
which the symmetry U(1) is broken and then generalize to the chiral symmetry
. The corresponding new transport coefficients are
introduced.Comment: 5 pages, RevTeX Minor changes, version accepted for publicatio
Three-sublattice Skyrmion crystal in the antiferromagnetic triangular lattice
The frustrated classical antiferromagnetic Heisenberg model with
Dzyaloshinskii-Moriya (DM) interactions on the triangular lattice is studied
under a magnetic field by means of semiclassical calculations and large-scale
Monte Carlo simulations. We show that even a small DM interaction induces the
formation of an Antiferromagnetic Skyrmion crystal (AF-SkX) state. Unlike what
is observed in ferromagnetic materials, we show that the AF-SkX state consists
of three interpenetrating Skyrmion crystals (one by sublattice), and most
importantly, the AF-SkX state seems to survive in the limit of zero
temperature. To characterize the phase diagram we compute the average of the
topological order parameter which can be associated to the number of
topological charges or Skyrmions. As the magnetic field increases this
parameter presents a clear jump, indicating a discontinuous transition from a
spiral phase into the AF-SkX phase, where multiple Bragg peaks coexist in the
spin structure factor. For higher fields, a second (probably continuous)
transition occurs into a featureless paramagnetic phase.Comment: 8 pages, 8 figure
Ground states of quantum kagome antiferromagnets in a magnetic field
We study the ground state properties of a quantum antiferromagnet in the
kagome lattice in the presence of a magnetic field, paying particular attention
to the stability of the plateau at magnetization 1/3 of saturation. While the
plateau is reinforced by certain deformations of the lattice, like the
introduction of structural defect lines and against an Ising anisotropy, ground
state correlations are seen to be quite different and the undistorted SU(2)
case appears to be rather special.Comment: 3 pages, 3 figures, contribution to the Japanese-French symposium on
"Quantum magnetism in spin, charge and orbital systems", Paris 1-4 October
200
Hydrodynamics with spontaneous symmetry breaking: application to relativistic heavy ion collisions
In this paper we apply hydrodynamics for systems with continuous broken
symmetries to heavy ion collisions in the framework of (1+1) dimensional
Bjorken model. The temperature profile with respect to proper time determined
in that context exhibits no differences with the ideal fluid. On the contrary,
it is shown that the profile obtained when M\"{u}ller-Israel-Stewart second
order theory of dissipation is included on top of standard hydrodynamics
indicates a slower cooling of the system.Comment: 5 pages, 2 figures, version accepted for publication as a Brief
Report in Physical Review
Quantum phase transitions in three-leg spin tubes
We investigate the properties of a three-leg quantum spin tube using several
techniques such as the density matrix renormalization group method, strong
coupling approaches and the non linear sigma model. For integer spins S, the
model proves to exhibit a particularly rich phase diagram consisting of an
ensemble of 2S phase transitions. They can be accurately identified by the
behavior of a non local string order parameter associated to the breaking of a
hidden symmetry in the Hamiltonian. The nature of these transitions are further
elucidated within the different approaches. We carry a detailed DMRG analysis
in the specific cases S = 1. The numerical data confirm the existence of two
Haldane phases with broken hidden symmetry separated by a trivial singlet
state. The study of the gap and of the von Neumann entropy suggest a first
order phase transition but at the close proximity of a tricritical point
separating a gapless and a first order transition line in the phase diagram of
the quantum spin tube.Comment: 20 pages, 18 figure
Bosonization and density-matrix renormalization group studies of Fulde-Ferrell-Larkin-Ovchinnikov phase and irrational magnetization plateaus in coupled chains
We review the properties of two coupled fermionic chains, or ladders, under a
magnetic field parallel to the lattice plane. Results are computed by
complementary analytical (bosonization) and numerical (density-matrix
renormalization group) methods which allows a systematic comparison. Limiting
cases such as coupled bands and coupled chains regimes are discussed. We
particularly focus on the evolution of the superconducting correlations under
increasing field and on the presence of irrational magnetization plateaus. We
found the existence of large doping-dependent magnetization plateaus in the
weakly-interacting and strong-coupling limits and in the non-trivial case of
isotropic couplings. We report on the existence of extended
Fulde-Ferrell-Larkin-Ovchinnikov phases within the isotropic t-J and Hubbard
models, deduced from the evolution of different observables under magnetic
field. Emphasis is put on the variety of superconducting order parameters
present at high magnetic field. We have also computed the evolution of the
Luttinger exponent corresponding to the ungaped spin mode appearing at finite
magnetization. In the coupled chain regime, the possibility of having polarized
triplet pairing under high field is predicted by bosonization.Comment: 18 pages, 19 figure
Statistical transmutation in doped quantum dimer models
We prove a "statistical transmutation" symmetry of doped quantum dimer models
on the square, triangular and kagome lattices: the energy spectrum is invariant
under a simultaneous change of statistics (i.e. bosonic into fermionic or
vice-versa) of the holes and of the signs of all the dimer resonance loops.
This exact transformation enables to define duality equivalence between doped
quantum dimer Hamiltonians, and provides the analytic framework to analyze
dynamical statistical transmutations. We investigate numerically the doping of
the triangular quantum dimer model, with special focus on the topological Z2
dimer liquid. Doping leads to four (instead of two for the square lattice)
inequivalent families of Hamiltonians. Competition between phase separation,
superfluidity, supersolidity and fermionic phases is investigated in the four
families.Comment: 3 figure
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