paper

Random Transverse Field Ising Model in dimension : scaling analysis in the disordered phase from the Directed Polymer model

arXiv:1110.3145 · doi:10.1088/1751-8113/45/9/095002

Abstract

For the quantum Ising model with ferromagnetic random couplings and random transverse fields at zero temperature in finite dimensions , we consider the lowest-order contributions in perturbation theory in to obtain some information on the statistics of various observables in the disordered phase. We find that the two-point correlation scales as : , where is the typical correlation length, is a random variable, and coincides with the droplet exponent of the Directed Polymer with transverse directions. Our main conclusions are (i) whenever , the quantum model is governed by an Infinite-Disorder fixed point : there are two distinct correlation length exponents related by ; the distribution of the local susceptibility presents the power-law tail where vanishes as , so that the averaged local susceptibility diverges in a finite neighborhood before criticality (Griffiths phase) ; the dynamical exponent diverges near criticality as (ii) in dimensions , any infinitesimal disorder flows towards this Infinite-Disorder fixed point with (for instance and ) (iii) in finite dimensions , a finite disorder strength is necessary to flow towards the Infinite-Disorder fixed point with (for instance ), whereas a Finite-Disorder fixed point remains possible for a small enough disorder strength. For the Cayley tree of effective dimension where , we discuss the similarities and differences with the case of finite dimensions.

22 pages, v2=final version

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