We study the violation of the fluctuation-dissipation theorem in the three and four dimensional Gaussian Ising spin glasses using on and off equilibrium simulations. We have characterized numerically the function X(C) that determine the violation and we have studied its scaling properties. Moreover we have computed the function x(C) which characterize the breaking of the replica symmetry direct...

We compare the normal-state resistivities ρ and the critical temperatures Tc for superconducting dx2−y2 pairing due to antiferromagnetic (AF) spin fluctuation exchange in the context of the two phenomenological dynamical spin susceptibility models, recently proposed by Millis, Monien, and Pines (MMP) and Monthoux and Pines (MP) and, respectively, by Radtke, Ullah, Levin, and Norman (RULN), for ...

In this article we discuss several aspects of the stochastic dynamics of spin models. The paper has two independent parts. Firstly, we explore a few properties of the multi-point correlations and responses of generic systems evolving in equilibrium with a thermal bath. We propose a fluctuation principle that allows us to derive fluctuation-dissipation relations for many-time correlations and li...

We test the quasiequilibrium picture of the aging dynamics--strictly valid in the asymptotic dynamical regime of aging systems--in the preasymptotic aging regime of the two-dimensional Edwards-Anderson spin glass model. We compare the fluctuation-dissipation characteristic for spin autocorrelation function and response with a corresponding one obtained for a suitably defined correlation functio...

Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constants, and for the [110] Dresselhauss model, a new type of SU(2) spin rotation symmetry is discovered. This symmetry is robust against spin-independent disorder and interactions and is generated by operators whose wave vector depends on the coupling strengt...

The dielectric susceptibility and dielectric tunability of the temperature-graded BaTiO3 thin films are investigated by using a modified transverse Ising model, taking the four-spin interaction and quantum fluctuation into account. There is a broad and smooth peak of the dielectric susceptibility at low temperature except for the sharp dielectric peak corresponding to the phase-transition tempe...

We report the NQR study on the pressure-induced paramagnetic state in the antiferromagnetic (AF) intermetallic compound YMn2 with the Néel temperature TN=100 K at ambient pressure. From the T variation of the nuclear spin-lattice relaxation rate, (1/T1) of Mn above the critical pressure of 4 kbar, the spin fluctuation feature is found to change below a temperature Tsf. At higher temperature tha...

We analyse the dynamical density fluctuation spectra for cuprates starting from the t− J model in a slave-boson 1/N representation. The results obtained are consistent with diagonalization studies and show novel low-energy structure on the energy scale J + δt due to the correlated motion of holes in a RVB spin liquid. The low-energy response implies an anomalous renormalization of several phono...

The superconducting state of a two-dimensional d-p model is studied from the spin fluctuation point of view by using a strong coupling theory. The fluctuation exchange (FLEX) approximatoin is employed to calculate the spin fluctuations and the superconducting gap functions self-consistently in the optimaland over-doped regions of hole concentration. The gap function has a symmetry of dx2−y2 typ...