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 $T_c$, 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 $N^2-1$ generalized spin components as a mean-field Schr\"odinger equation on the $N$-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