Exotic Phenomena Emerging from Localized Multipolar Degrees of Freedom

The rich diversity of building blocks in condensed matter systems offers the opportunity for exotic macroscopic quantum phenomena. Multipolar moments, higher order generalizations of the familiar dipole, present a unique avenue for the discovery of a variety of exotic and novel phases of matter. These anisotropic charge and magnetization densities provide additional internal degrees of freedom for localized electrons, allowing an expansion of nature's microscopic toolbox.In this thesis, we examine the nature of emergent multipolar phases, and propose experimental protocols to detect their existence and properties. We first examine the multipolar Kondo effect, where conduction electrons equipped with spin and orbital degrees of freedom scatter off a quantum impurity that hosts electric quadrupolar and magnetic octupolar moments. Using renormalization group methods, we uncover a number of stable non-Fermi liquid ground states. We next examine the nature of these fixed points using boundary conformal field theory techniques, to provide a non-perturbative description of their transport and thermodynamic properties. We then consider the development of unconventional superconductivity mediated by multipolar Kondo interactions. Employing group theoretic methods, in partnership with mean-field theory, we characterize the higher-angular momentum nature of the superconducting pairing states with point nodal quasiparticle excitations. Finally, motivated by recent experiments on rare-earth metallic compounds and insulating pyrochlore oxides, we propose the implementation of lattice-based probes -- magnetostriction -- to unveil hidden multipolar orderings and multipolar-based quantum spin liquid states.

Department dc:contributor.department

Physics

Year dc:date.issued

2021

Author dc:creator

• Patri, Adarsh Seshachalam

Advisor dc:contributor.advisor

• Kim, Yong Baek

• Conformal field theory
• Hidden ordering
• Kondo effect
• Multipolar physics
• Quantum spin ice
• Unconventional superconductivity

Handle dc:identifier.uri

http://hdl.handle.net/1807/109231

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/109231