arXiv subjects

S. M. A. Tabei

Publications and source records attributed to S. M. A. Tabei.

4 recordsLinked to original sources

arXiv2007

Effective Spin-1/2 Description of Transverse-Field-Induced Random Fields in Dipolar Spin Glasses with Strong Single-Ion Anisotropy

We present analytical and numerical evidence for the validity of an effective S=1/2 approach to the description of random field generation in S>=1, and especially in an S=1, dipolar spin glass models with strong uniaxial Ising anisotropy and subject to weak external magnetic field Bx transverse to the Ising direction. Explicitely Bx-dependent random fields are shown to naturally emerge in the effective low-energy description of a microscopic S=1 toy model. We discuss our results in relation to recent theoretical studies pertaining to the topic of Bx-induced random fields in the LiHo$_x$Y$_{1-x}$F$_4$ magnetic materials with the Ho$^{3+}$ Ising moments subject to a transverse field. We show that the S_{eff}=1/2 approach is able to capture both the qualitative and quantitative aspects of the physics at small Bx, giving results that agree with those obtained using conventional second order perturbation theory.

cond-mat.dis-nn↗

arXiv2006

Induced Random Fields in the LiHo$_x$Y$_{1-x}$F$_4$ Quantum Ising Magnet in a Transverse Magnetic Field

The LiHo$_x$Y$_{1-x}$F$_4$ magnetic material in a transverse magnetic field $B_{x}\hat x$ perpendicular to the Ising spin direction has long been used to study tunable quantum phase transitions in a random disordered system. We show that the $B_{x}-$induced magnetization along the $\hat x$ direction, combined with the local random dilution-induced destruction of crystalline symmetries, generates, via the predominant dipolar interactions between Ho$^{3+}$ ions, {\it random fields} along the Ising $\hat z$ direction. This identifies LiHo$_x$Y$_{1-x}$F$_4$ in $B_x$ as a new random field Ising system. The random fields explain the rapid decrease of the critical temperature in the diluted ferromagnetic regime and the smearing of the nonlinear susceptibility at the spin glass transition with increasing $B_{x}$, and render the $B_{x}-$induced quantum criticality in LiHo$_x$Y$_{1-x}$F$_4$ likely inaccessible.

cond-mat.dis-nn↗

arXiv2005

Zero tension Kardar-Parisi-Zhang equation in (d+1)- Dimensions

The joint probability distribution function (PDF) of the height and its gradients is derived for a zero tension $d+1$-dimensional Kardar-Parisi-Zhang (KPZ) equation. It is proved that the height`s PDF of zero tension KPZ equation shows lack of positivity after a finite time $t_{c}$. The properties of zero tension KPZ equation and its differences with the case that it possess an infinitesimal surface tension is discussed. Also potential relation between the time scale $t_{c}$ and the singularity time scale $t_{c, ν\to 0}$ of the KPZ equation with an infinitesimal surface tension is investigated.

nlin.CD↗

arXiv2005

Intermittency of Height Fluctuations and Velocity Increment of The Kardar-Parisi-Zhang and Burgers Equations with infinitesimal surface tension and Viscosity in 1+1 Dimensions

The Kardar-Parisi-Zhang (KPZ) equation with infinitesimal surface tension, dynamically develops sharply connected valley structures within which the height derivative is not continuous. We discuss the intermittency issue in the problem of stationary state forced KPZ equation in 1+1--dimensions. It is proved that the moments of height increments $C_a = < | h (x_1) - h (x_2) |^a > $ behave as $ |x_1 -x_2|^{ξ_a}$ with $ξ_a = a$ for length scales $|x_1-x_2| << σ$. The length scale $σ$ is the characteristic length of the forcing term. We have checked the analytical results by direct numerical simulation.

physics.flu-dyn↗