George Yumnam
Postdoctoral Fellow
Stewart Blusson Quantum Matter Institute
Department of Physics and Astronomy
The University of British Columbia, Vancouver
Postdoctoral Fellow
Stewart Blusson Quantum Matter Institute
Department of Physics and Astronomy
The University of British Columbia, Vancouver
I am a postdoctoral fellow at the Stewart Blusson Quantum Matter Institute (SBQMI) at the University of British Columbia, Vancouver. I am an experimental condensed-matter physicist specializing in neutron and X-ray scattering. My research centers on how spin, lattice, and crystal-field degrees of freedom hybridize and evolve under disorder, field, pressure, and chemical tuning.
I focus on understanding how collective excitations emerge and hybridize in ordered and unconventional magnets, and how external tuning reshapes magnetic spectra. By building experimentally grounded models of these coupled excitations, my work aims to uncover organizing principles that govern magnetic behavior in complex quantum materials.
At the neutron scattering beamline
Altermagnetism is a recently recognized type of magnetic order with spin-split energy bands but no net magnetization, making it fundamentally distinct from both ferromagnets and antiferromagnets. My work maps the spin dynamics across three material platforms. In α-MnTe, I resolved the spin-split magnon dispersion and tracked how chemical doping and applied pressure reshape the magnetic order and magnon-phonon hybridization. In hematite, I probe chiral magnon branches that reflect the underlying altermagnetic symmetry. In RuO₂, where the magnetic ground state is still actively debated, a combination of inelastic neutron scattering and Mössbauer spectroscopy places the tightest experimental bounds on its magnetism reported to date. This research is built on a PI-led neutron user program across SEQUOIA, ARCS, HYSPEC, and TAX at SNS and HFIR.
When non-magnetic atoms replace magnetic ones in an antiferromagnet, at some point the lattice becomes too diluted to sustain coherent spin waves. In Y-doped TbSb, I am studying exactly this regime. Substituting non-magnetic yttrium for magnetic terbium progressively dilutes the magnetic sublattice, yet the spin waves turn out to be far more robust than simple percolation theory predicts. Crystal-field interactions between the single-ion and collective degrees of freedom appear to stabilize magnon branches well past the expected breakdown point. Using HYSPEC, ARCS, and VERITAS at SNS, the goal is to pin down this mechanism and understand how local single-ion anisotropy protects collective magnetism from disorder more generally.
My PhD work centered on patterning thin-film permalloy and Nd into honeycomb geometries to study how magnetic charges behave when the lattice geometry is controlled at the nanoscale. In Nd-based honeycomb lattices, we found a quantum-disordered state of these charges, published as the Frontispiece in Advanced Science (2021). In permalloy networks, the same charge physics produces a rectifying effect: the lattice acts as a magnetic diode with a very low forward voltage, tunable by field history and temperature (Mater. Today Phys., 2022). The measurements relied on polarized neutron reflectometry and SANS with DWBA modeling, techniques I developed hands-on during my PhD in close collaboration with beamlines at ORNL.
At SBQMI, I am studying itinerant magnets that do not order in any conventional sense. These materials are interesting because their spin fluctuations span a wide range of energy and wavevector, encoding correlations that standard probes struggle to characterize. One approach I am developing is to extract the Quantum Fisher Information (QFI) directly from neutron scattering data. QFI gives a lower bound on multipartite entanglement, which connects the measurement to quantities relevant for quantum sensing and computing. Alongside this, I am growing single crystals and doing physical property characterization to identify the best candidate systems. The broader goal is to find materials where magnetic fluctuations are genuinely useful for quantum information applications.
Cell Reports Physical Sciences, 2025
View Publication →Physical Review B, 112, 014450 (2025)
View Publication →Advanced Science, 8, 2004103 (2021)
View Publication →Materials Today Physics, 22, 100574 (2022)
View Publication →iScience, 24, 102206 (2021)
View Publication →Chemistry of Materials, 31, 5145-5151 (2019)
View Publication →As a postdoctoral researcher, I typically join projects once a concrete materials or scattering question is on the table. I am not currently hiring students directly, but I am very happy to co-advise, mentor on neutron and X-ray scattering experiments, and collaborate on joint proposals. I follow a bottom-up approach in teaching physics at the college and graduate level.
Joint projects on neutron and X-ray scattering studies of magnon dynamics and related quantum materials.
Short-term visits to pair scattering experiments with shared analysis notebooks and open data pipelines.
Partners on neutron/X-ray scattering experiments on magnetic and quantum materials with shared authorship plans.
MitSna Foundation is a non-governmental organization dedicated to helping students from underserved communities access and navigate higher education. I have been involved with MitSna since its early formation in 2019, beginning as a founding member and served as Advisor, and have remained an active member ever since.
Contributed to shaping the strategic direction of the organization from its earliest stages, including drafting the founding bylaws that govern its structure and operations.
Delivered multiple seminars, training sessions, and workshops for students and members: covering topics ranging from academic pathways and research opportunities to professional development in STEM.
Served in advisory and human resources capacities, helping recruit and guide volunteers and mentors, and building the organizational culture that supports MitSna's educational mission.
I'm always open to collaboration, mentorship, and new research conversations.