Quantum criticality of strongly correlated systems
| dc.contributor.advisor | Si, Qimiao | en_US |
| dc.creator | Liu, Chia-Chuan | en_US |
| dc.date.accessioned | 2020-04-23T16:48:01Z | en_US |
| dc.date.available | 2020-04-23T16:48:01Z | en_US |
| dc.date.created | 2020-05 | en_US |
| dc.date.issued | 2020-04-22 | en_US |
| dc.date.submitted | May 2020 | en_US |
| dc.date.updated | 2020-04-23T16:48:01Z | en_US |
| dc.description.abstract | Quantum criticality has been an active research topic in condensed matter physics, with major efforts being devoted to the heavy fermion material in which local moments are coupled with itinerant electrons through Kondo coupling. The competition between Kondo coupling and the antiferromagnetic RKKY coupling between local moments leads to a rich global phase diagram for these systems. It is a fundamentally important but challenging problem to develop a unified scheme to understand such global phase diagram. We approach this issue from the magnetically ordered side by using a quantum non-linear sigma model (QNLS M) to represent the local moments. We firstly study the consequence of skyrmion defects of antiferromagnetism on a honeycomb lattice. We solve the low energy effective Dirac Hamiltonian in the skyrmion background, and then identify the singlet orders through an enhanced correlations in the corresponding channels. In addition, we perform a renormalization group (RG) analysis of the QNLS M with a Kondo coupling by treating both bosonic and fermionic degrees of freedom on an equal footing. These results shed new insight into the global phase diagram of the heavy fermion systems. Recent evidence of two consecutive Kondo destruction quantum critical points(QCPs) in Ce3Pd20Si6 also provides an interesting extension of the global phase diagram. Motivated by this development, we study a spin-orbital coupled Bose-Fermi Kondo model. By performing a Coulomb-gas based RG calculation of this model with Ising anisotropy, we show that a generic trajectory in the parameter space contains two QCPs associated with the destruction of the orbital and spin Kondo effects, respectively. Not only the heavy fermion systems, iron pnictides also provide a platform to study quantum criticality. The new ingredient here is that the quantum critical singularties in the nematic and magnetic channels are concurrent, and their relationship has yet to be clarified. Here we study this problem within an effective Ginzburg-Landau theory for both channels in the presence of a small external uniaxial potential that breaks the lattice C4 symmetry. We establish an identity that connects the spin excitation anisotropy, which is the difference of the dynamical spin susceptibilities at two ordering wave vectors Q1 = ( pi, 0) and Q2 = (0,pi ), with the dynamical magnetic susceptibility and static nematic susceptibility. Using this identity, we introduce a scaling procedure to determine the dynamical nematic susceptibility in the quantum critical regime, and illustrate the procedure in the case of the optimally Ni-doped BaFe2As2. | en_US |
| dc.format.mimetype | application/pdf | en_US |
| dc.identifier.citation | Liu, Chia-Chuan. "Quantum criticality of strongly correlated systems." (2020) Diss., Rice University. <a href="https://hdl.handle.net/1911/108364">https://hdl.handle.net/1911/108364</a>. | en_US |
| dc.identifier.uri | https://hdl.handle.net/1911/108364 | en_US |
| dc.language.iso | eng | en_US |
| dc.rights | Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder. | en_US |
| dc.subject | Quantum criticality | en_US |
| dc.subject | heavy fermion | en_US |
| dc.subject | iron pnictides | en_US |
| dc.title | Quantum criticality of strongly correlated systems | en_US |
| dc.type | Thesis | en_US |
| dc.type.material | Text | en_US |
| thesis.degree.department | Physics and Astronomy | en_US |
| thesis.degree.discipline | Natural Sciences | en_US |
| thesis.degree.grantor | Rice University | en_US |
| thesis.degree.level | Doctoral | en_US |
| thesis.degree.name | Doctor of Philosophy | en_US |
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