Effects of aperiodicity on the quantum transitions in XY chains

Author(s)

Fleury Jose de Oliveira Filho

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2011-04-08

Examining board members

Andre de Pinho Vieira; José Abel Hoyos Neto; Silvio Roberto de Azevedo Salinas

• Advisor: Andre de Pinho Vieira

Abstract

We employ an adaptation of the Ma, Dasgupta, Hu method in order to analyze the quantum phase transition, induced by a transversal magnetic eld, at spin-1/2 aperiodic XY chains, in analogy to the corresponding adaptation for XXZ chains. We derive analytical expressions for some cri tical exponents related with the ferro-paramagnetic transitions, and shed light onto the nature of the ground state structures. The main results obtained by this approach were tested by the free-fermion method, nite-size scaling analyses and, at the Ising limit of the model, by using results derived from a mapping to a random-walk problem. (AU)