Departmental Oral Examination (Thesis Title: “Fluctuations and Phase Transitions in Quantum Ising Systems”)

Event Date and Time: 
Thu, 2016-04-21 14:00 - 16:00
Henn 309
Local Contact: 
Physics and Astronomy, UBC
Intended Audience: 

The quantum Ising model is perhaps the simplest possible model of a quantum magnetic material. In an applied magnetic field transverse to the easy axis of the material, the Ising model will undergo a quantum phase transition between ferromagnetic and paramagnetic states. The magnetic insulating crystal LiHoF4 is a physical realization of the quantum Ising model, with the additional complications that the dominant coupling between spins is the long range dipolar interaction, and each electronic spin is strongly coupled to a nuclear degree of freedom. In this thesis, we present an effective model for LiHoF4 that fully incorporates the long range dipolar interaction and the nuclear degrees of freedom, and we analyze the effects of the nuclear spins on the quantum phase transition within the random phase approximation. We then present a general field theoretic formalism for incorporating the effects of fluctuations beyond the random phase approximation in quantum Ising systems. This formalism is used to calculate corrections to the magnetization of LiHoF4.

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