School of Physics Thesis Dissertation Defense

Presenter:       Sami Hakani

Title:                Dynamics and Transport in Strongly Correlated Quantum Magnets

Date:               Friday, March 29, 2024

Time:               11:00 AM

Location:         Howey N110

Committee members: 

Dr. Itamar Kimchi, School of Physics, Georgia Institute of Technology (advisor)

Dr. Martin Mourigal, School of Physics, Georgia Institute of Technology

Dr. Zhigang Jiang, School of Physics, Georgia Institute of Technology

Dr. Michael Pustilnik, School of Physics, Georgia Institute of Technology

Dr. Joshua Kretchmer, School of Chemistry & Biochemistry, Georgia Institute of Technology

Abstract:

A complete understanding of a physical phenomenon must include an understanding of its dynamics: how it changes in time. One burgeoning area of condensed matter physics where dynamics are actively studied is in the magnetic excitations of frustrated spin systems. Such spin systems can host exotic quantum liquid phenomena including fractional excitations, emergent gauge fields, and novel particle statistics. In addition to broadening basic scientific knowledge, understanding the dynamics of frustrated magnetic systems can further technological applications in quantum computing. 

This thesis discusses Raman dynamics and charge transport in strongly correlated quantum magnets. In candidate materials, inelastic Raman scattering is shown to provide signatures for fractional spinoff excitations, while charge transport is shown to be consistent with chiral orbital currents. Finally, a novel theoretical effect in Raman dynamics is explored in the presence of crystalline topological defects. Even when such defects do not couple to the low energy Hamiltonian, it is shown that they can produce qualitatively new effects by coupling to electric field probes. Such effects rely on an underlying spinon liquid state, and they are not observed for magnetically ordered or gapped phases. Potential applications include using crystalline topological defects to modify response-theory operators independently of the Hamiltonian and thereby generate new probes of quantum phases.