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dc.contributor.advisor Si, Qimiao
dc.creatorWu, Jianda
dc.date.accessioned 2016-02-05T22:07:43Z
dc.date.available 2016-02-05T22:07:43Z
dc.date.created 2014-12
dc.date.issued 2014-08-15
dc.date.submitted December 2014
dc.identifier.citation Wu, Jianda. "Research on Dynamics and Thermodynamics near Quantum Critical Points." (2014) Diss., Rice University. https://hdl.handle.net/1911/88431.
dc.identifier.urihttps://hdl.handle.net/1911/88431
dc.description.abstract Quantum phase transition arises in general as second order phase transition at zero temperature, tuned by a non-thermal parameter such as pressure, doping or a magnetic field. The point in the phase diagram of the material in which different phases meet is called a quantum critical point (QCP). Physics around QCPs are of extensive current interest because the critical quantum fluctuations influence the physical properties in a wide temperature range (quantum criticality), and are believed to be responsible for many emergent physical properties such as non-Fermi liquids and unconventional superconductivity. In this research we explore dynamics and thermodynamics near QCPs via investigating three classes of models, which all have real material correspondence. Specifically first, we study local dynamics in a perturbed quantum critical Ising chain with E8 symmetry, where we show the local dynamical spin susceptibility has a singular dependence on frequency, but differs from the diffusion form. The nuclear magnetic resonance (NMR) relaxation rate at low temperatures depends exponentially on the inverse temperature, whose prefactor we also determine. We propose NMR experiments as a means to further test the applicability of the E8 description for CoNb2O6. Second, we investigate the thermodynamic properties of itinerant ferromagnets near quantum critical points, described by the quantum Landau-Ginzburg theory. We provide a regularized perturbative renormalization group procedure to calculate the free energy. We further carry out numerical calculations on thermodynamic quantities, capturing not only the leading critical behaviors, but also the subleading and nonsingular contributions. We demonstrate various thermodynamic signatures of quantum criticality, including the entropy accumulation effect and the divergence of the specific heat coefficient. A detailed comparison to the recent experimental results on an itinerant ferromagnet Sr3Ru2O7 is also presented. Third, we explore Ising-nematic and magnetic phases and their transitions in iso-electronically doped iron pnictides by carrying out a large-N study of an effective low-energy Ginzburg-Landau model for these systems. We demonstrate that the magnetic and Ising orders transitions are concurrent at zero temperature, and both transitions are weakly first-order, which is consistent with RG-based prediction and experimental observations.
dc.format.mimetype application/pdf
dc.language.iso eng
dc.subjectQuantum phase transition
Quantum criticality
E8 model
Itinerant spin-density-wave transition
Perturbative renormalization group
Iron pnictides
Large-N approach
dc.title Research on Dynamics and Thermodynamics near Quantum Critical Points
dc.contributor.committeeMember Nevidomskyy, Andriy
dc.contributor.committeeMember Deem, Michael
dc.date.updated 2016-02-05T22:07:43Z
dc.type.genre Thesis
dc.type.material Text
thesis.degree.department Physics and Astronomy
thesis.degree.discipline Natural Sciences
thesis.degree.grantor Rice University
thesis.degree.level Doctoral
thesis.degree.name Doctor of Philosophy


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