80 research outputs found
Dynamical Condensation in a Holographic Superconductor Model with Anisotropy
We study dynamical condensation process in a holographic superconductor model
with anisotropy. The time-dependent numerical solution is constructed for the
Einstein-Maxwell-dilaton theory with complex scalar in asymptotic AdS
spacetime. The introduction of dilaton field generates the anisotropy in
boundary spatial directions. In analogy of isotropic case, we have two black
hole solutions below certain critical temperature , the anisotropic
charged black hole with and without scalar hair, corresponding respectively to
the supercooled normal phase and superconducting phase in the boundary theory.
We observe a nonlinear evolution from a supercooled anisotropic black hole
without scalar hair to a anisotropic hairy black hole. Via AdS/CFT
correspondence, we extract time evolution of the condensate operator, which
shows an exponential growth and subsequent saturation, similar to the isotropic
case. Furthermore, we obtain a nontrivial time evolution of the boundary
pressure, while in isotropic case it remains a constant. We also generalize
quasinormal modes calculation to anisotropic black holes and shows scalar
quasinormal modes match with relaxation time scale of the condensate operator.
In addition, we present the final temperature and anisotropic pressure as
functions of initial temperature and background anisotropy.Comment: 18 pages, 12 figures. v2: minor revision and references adde
Correlation function of dyonic strings
We investigate the two- and three-point correlation functions of the dyonic
magnon and spike, which correspond to the solitonic string moving in the
Poincare AdS and three-dimensional sphere. We show that the coupling between
two dyonic magnons or spikes together with a marginal scalar operator in the
string theory is exactly the same as one obtained by the RG analysis in the
gauge theory.Comment: 15 pages, no figur
Quarter Magnetization Plateau of Triplet Spin Dimers in the Shastry-Sutherland Lattice
The Shastry-Sutherland lattice, 2-dimensional orthogonal arrangement of the
spin dimers, has been realized in the magnetic semiconductor, BaNd2ZnS5. A
signature feature of Shastry-Sutherland lattice materials is fractional
magnetization plateaus, which often indicate novel quantum phases. Here we
report the quarter magnetization plateau from a single crystal of BaNd2ZnS5 by
neutron diffraction. A 2-Q antiferromagnetic order of the triplet spin dimers
was determined at zero-field, which can be understood by the local Ising
magnetic anisotropy of Nd spins that was revealed by local magnetic
susceptibility method through polarized neutron diffraction. The quantized
magnetization plateau was measured under field along (1-10). The two magnetic
sublattices connected to each propagation vector of 2-Q respond to the field
differently, the stripe phase with q1 = (0.5, 0.5, 0) disappears at ~1.7 T
entering the quarter magnetization plateau. The other stripe phase with q2=
(-0.5, 0.5, 0) remains nearly intact up to 6 T. Furthermore, microscopic
magnetic model was used to provide insight into the formation of quarter
magnetization plateau, that is unexpected in gapless dimer triplet system,
contrast to the well-known dimer-singlet Shastry-Sutherland lattice.Comment: 15 pages, 4 figure
Geometric integration of classical spin dynamics via a mean-field Schr\"odinger equation
The Landau-Lifshitz equation describes the time-evolution of magnetic
dipoles, and can be derived by taking the classical limit of a quantum
mechanical spin Hamiltonian. To take this limit, one constrains the many-body
quantum state to a tensor product of coherent states, thereby neglecting
entanglement between sites. Expectation values of the quantum spin operators
produce the usual classical spin dipoles. One may also consider expectation
values of polynomials of the spin operators, leading to quadrupole and
higher-order spin moments, which satisfy a dynamical equation of motion that
generalizes the Landau-Lifshitz dynamics [Zhang and Batista, Phys. Rev. B 104,
104409 (2021)]. Here, we reformulate the dynamics of these generalized
spin components as a mean-field Schr\"odinger equation on the -dimensional
coherent state. This viewpoint suggests efficient integration methods that
respect the local symplectic structure of the classical spin dynamics
Time Evolution of Entanglement Entropy in Quenched Holographic Superconductors
We investigate the dynamical evolution of entanglement entropy in a
holographic superconductor model by quenching the source term of the dual
charged scalar operator. By access to the full background geometry, the
holographic entanglement entropy is calculated for a strip geometry at the AdS
boundary. It is found that the entanglement entropy exhibits a robust
non-monotonic behaviour in time, independent of the strength of Gaussian quench
and the size of the strip: it first displays a small dip, then grows linearly,
and finally saturates. In particular, the linear growth velocity of the
entanglement entropy has an upper bound for strip with large width; The
equilibrium value of the non-local probe at late time shows a power law scaling
behaviour with respect to the quench strength; Moreover, the entanglement
entropy can uncover the dynamical transition at certain critical quench
strength which happens to coincide with the one obtained form the dynamical
evolution of scalar order parameter.Comment: 19 pages; 7 figures; compatible with JHEP versio
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