"A quantum phase transition is a phase transition at absolute zero occurring under variations in an external non-thermal parameter such as magnetic field or pressure. Quantum phase transitions are one among the important topics currently investigated in condensed matter physics. They are observed in various systems, e.g., in the ferromagnetic-paramagnetic phase transition in LiHoF₄ or in the superconductor-metal phase transition in nanowires.
A particular class of quantum phase transitions, which is phase transitions in the presence of disorder and dissipation, is investigated here. An example of this class is the ferromagnetic-paramagnetic phase transition in Ni₁₋ₓVₓ or CePd1-xRhₓ caused by variations in chemical composition. In these system, disorder is due to random positions of doping element and the dynamics of order-parameter fluctuations is dissipative due to conduction electrons.
These quantum phase transitions are explained using the following approach: The Landau-Ginzberg-Wilson functional, which is derived from a microscopic Hamiltonian, is treated by the strong-disorder renormalization group method. For ohmic damping, phase transitions are strongly influenced by disorder and the critical point is an infinite-randomness fixed point, which is in the universality class same as that of the random transverse-field Ising model. The scaling form of observable quantities is activated type rather than conventional power-law type. For superohmic damping, the strong-disorder renormalization group method yields one of the recursion relationships different from ohmic damping. This difference indicates a more conventional transition for superohmic damping"--Abstract, pagef iii.
Medvedeva, Julia E.
Parris, Paul Ernest, 1954-
Ph. D. in Physics
National Science Foundation (U.S.)
Missouri University of Science and Technology. Research Board
University of Missouri Research Board
Missouri University of Science and Technology
viii, 98 pages
© 2011 Chetan Kotabage, All rights reserved.
Dissertation - Restricted Access
Phase transformations (Statistical physics)
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Kotabage, Chetan, "Quantum phase transitions in the presence of disorder and dissipation" (2011). Doctoral Dissertations. 68.
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