PhD Oral Exam - Mojdeh Saleh, Physics

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Spin-orbit coupling (SOC) arising in systems with broken inversion symmetry plays a central role in modern condensed-matter physics, linking charge, sin, valley, and orbital degrees of freedom and enabling a wide range of spintronic and optoelectronic phenomena. Understanding how SOC manifests itself in experimentally accessible response functions is therefore essential for both fundamental studies and practical applications. This thesis investigates two complementary manifestations of SOC in low-dimensional electronic systems: dynamical charge-spin response functions and electronic Raman scattering. The first part develops a kinetic-equation theory of the dynamical electromagnetic response of spin-orbit-coupled Fermi liquids, with particular emphasis on the Edelstein and inverse Edelstein effects. These cross-response functions are shown to provide sensitive probes of collective spin dynamics and chiral-spin modes, while electron-electron interactions strongly modify the response spectrum and, in multivalley systems, split the original resonance into multiple collective modes associated with coupled spin and spin-valley fluctuations. The second part develops a theory of non-resonant electronic Raman scattering in spin-orbit-coupled two-dimensional systems and applies it to graphene-based materials with proximity-induced Rashba and valley-Zeeman SOC. Distinct Raman fingerprints of different SOC mechanisms are identified, and the analysis is extended to bilayer graphene, where additional orbital and layer degrees of freedom enrich the Raman response and give rise to tunable spin-dependent Raman features. Taken together, the results establish dynamical response functions and electronic Raman scattering as complementary probes of spin-orbit-coupled systems and demonstrate how SOC modifies both electromagnetic and photon-scattering responses in low-dimensional quantum materials.