Keywords and Phrases
Monte Carlo simulation; Phase transition; Quantum phase transition; Quenched disorder effects; Renormalization group theory; Superfluid-insulator transition
"Disorder can have a wide variety of consequences for the physics of phase transitions. Some transitions remain unchanged in the presence of disorder while others are completely destroyed. In this thesis we study the effects of disorder on several classical and quantum phase transitions in condensed matter systems. After a brief introduction, we study the ferromagnetic phase transition in a randomly layered Heisenberg magnet using large-scale Monte-Carlo simulations. Our results provide numerical evidence for the exotic infinite-randomness scenario. We study classical and quantum smeared phase transitions in substitutional alloys A₁₋ₓBₓ. Our results show that the disorder completely destroys the phase transition with a pronounced tail of the ordered phase developing for all compositions x < 1. In addition, we find that short-ranged disorder correlations can have a dramatic effect on the transition. Moreover, we show an experimental realization of the composition-tuned ferromagnetic-to-paramagnetic quantum phase transition in Sr₁₋ₓCaₓRuO₃. We investigate the effects of disorder on first-order quantum phase transitions on the example of the N-color quantum Ashkin-Teller model. By means of a strong disorder renormalization group, we demonstrate that disorder rounds the first-order transition to a continuous one for both weak and strong coupling between the colors. Finally, we investigate the superfluid-insulator quantum phase transition of one-dimensional bosons with off-diagonal disorder by means of large-scale Monte-Carlo simulations. Beyond a critical disorder strength, we find nonuniversal, disorder-dependent critical behavior"--Abstract, page iv.
Parris, Paul Ernest, 1954-
Medvedeva, Julia E.
Ph. D. in Physics
Missouri University of Science and Technology
xii, 146 pages
© 2013 Fawaz Y. Hrahsheh, All rights reserved.
Dissertation - Open Access
Phase transformations (Statistical physics)
Quantum theory -- Mathematical models
Ferromagnetism -- Computer simulation
Electronic OCLC #
Hrahsheh, Fawaz Y., "Phase transitions in disordered systems" (2013). Doctoral Dissertations. 2235.