George Yumnam
Experimental Condensed Matter Physics

George Yumnam

Postdoctoral Fellow

Stewart Blusson Quantum Matter Institute

Department of Physics and Astronomy

The University of British Columbia, Vancouver

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Profile

About Me

I am an experimental condensed-matter physicist and a postdoctoral fellow at the Stewart Blusson Quantum Matter Institute (SBQMI) at the University of British Columbia, Vancouver. My research uses neutron and X-ray scattering to study how spin, lattice, and crystal-field degrees of freedom couple to one another, and how this coupling evolves when a material is tuned by disorder, magnetic field, pressure, or chemical substitution.

My work centers on collective excitations: how they emerge in ordered and unconventional magnets, why they hybridize, and how external tuning reshapes the magnetic spectrum. By constraining models directly with scattering data, I aim to identify the organizing principles that govern magnetic behavior in complex quantum materials.

George Yumnam at a neutron scattering beamline

At the NSE beamline for our Magnetic charge dynamics work (2019)

Career

Employment

Training

Education

Research

Current Research

Itinerant Magnets and Quantum Information Science

Itinerant Magnets & Quantum Information Science

At SBQMI, I study itinerant magnets that do not develop conventional long-range order. Their spin fluctuations extend over wide ranges of energy and wavevector, and the correlations they carry are difficult to quantify with standard probes. My approach is to extract the Quantum Fisher Information (QFI) directly from neutron scattering data. QFI provides a rigorous lower bound on multipartite entanglement and thereby connects a scattering measurement to quantities relevant for quantum sensing and computing. In parallel, I grow single crystals and characterize their bulk properties to identify the most promising candidate systems.

Itinerant Magnetism Quantum Fisher Information Quantum Entanglement
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Altermagnetism and Magnon-Phonon Coupling

Altermagnetism & Magnon-Phonon Coupling

Altermagnets are magnetically ordered materials with spin-split energy bands but no net magnetization, a combination found in neither ferromagnets nor conventional antiferromagnets. I study the spin dynamics of three such systems. In α-MnTe, I resolved the spin-split magnon dispersion and characterized how doping and pressure modify the magnetic order and its coupling to phonons. In hematite, I am probing the chiral magnon branches predicted by the altermagnetic symmetry. In RuO₂, where the magnetic ground state remains under debate, our inelastic neutron scattering and Mössbauer measurements place the tightest experimental bounds on the magnetism reported to date.

Altermagnetism Spin-Split Magnons Spin-Lattice Coupling
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Hybrid Magnon Excitations and Crystal Fields

Hybrid Magnon Excitations: Crystal Fields & High-Entropy Oxides

When non-magnetic atoms are substituted into an antiferromagnet, percolation theory predicts the dilution at which coherent spin waves should collapse. In Y-doped TbSb, the magnon branches remain well defined far beyond this threshold, and the additional stability appears to arise from hybridization between crystal-field levels and the collective spin-wave modes. Using HYSPEC, ARCS, and VERITAS at SNS, I am working to establish this mechanism quantitatively. In parallel, in rock-salt high-entropy oxides, we study how extreme chemical disorder shapes the coupled magnetic and lattice thermodynamics.

Crystal-Field Hybridization Diluted Antiferromagnets High-Entropy Oxides
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Archive

Past Research

My earlier work spans nanoengineered artificial honeycomb spin-ice lattices and first-principles studies of thermoelectric materials and thermal transport, including machine-learning approaches to lattice thermal conductivity.

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Papers

Selected Publications

Constraints on magnetism and correlations in RuO₂ from lattice dynamics and Mössbauer spectroscopy

George Yumnam, Parul R. Raghuvanshi, John D. Budai, Lars Bocklage, et al.

Cell Reports Physical Sciences, 2025

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Tuning the magnetic properties of the spin-split antiferromagnet MnTe through pressure

Edison P. Carlisle, George Yumnam, Stuart A. Calder, Bianca Haberl, Jia-Xin Xiong, et al.

Physical Review B, 112, 014450 (2025)

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Magnon gap tuning in lithium-doped MnTe

George Yumnam, Duncan H. Moseley, Joseph A. M. Paddison, Christiana Z. Suggs, Emma Zappala, et al.

Physical Review B, 109, 214434 (2024)

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Quantum disordered state of magnetic charges in nanoengineered honeycomb lattice

George Yumnam, Yiyao Chen, Jiasen Guo, Jong K. Keum, Valeria Lauter, Deepak K. Singh

Advanced Science, 8, 2004103 (2021)

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Magnetic charge and geometry confluence for ultra-low forward voltage diode in artificial honeycomb lattice

George Yumnam, Jiasen Guo, Yiyao Chen, Ashutosh Dahal, Pousali Ghosh, et al.

Materials Today Physics, 22, 100574 (2022)

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Magnetic charge's relaxation propelled electricity in two-dimensional magnetic honeycomb lattice

Yiyao Chen, George Yumnam, Jiasen Guo, Laura Stingaciu, Piotr Zolnierczuk, et al.

iScience, 24, 102206 (2021)

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Coupling the high-throughput property map to machine learning for predicting lattice thermal conductivity

Rinkle Juneja, George Yumnam, Swanti Satsangi, Abhishek K. Singh

Chemistry of Materials, 31, 5145-5151 (2019)

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Mentorship

Teaching & Mentoring

As a postdoctoral researcher, I typically join projects once a concrete materials or scattering question has been defined. I am not currently in a position to hire students directly, but I am glad to co-advise, to mentor students through neutron and X-ray scattering experiments, and to collaborate on joint proposals. In teaching physics at the college and graduate level, I follow a bottom-up approach that builds from fundamentals.

Co-advised Students

Joint projects on neutron and X-ray scattering studies of magnon dynamics and related quantum materials.

Visiting Researchers

Short research visits organized around a scattering experiment, with shared analysis notebooks and open data pipelines.

Collaborative Proposals

Joint beamtime proposals on magnetic and quantum materials, with scope and authorship planned from the outset.

Community

MitSna Foundation

MitSna Foundation is a non-governmental organization that helps students from underserved communities enter and complete higher education. I have been involved with MitSna since its formation in 2019, first as a founding member and later as an Advisor, and I remain an active member today.

Organizational Founding

Helped shape the organization's direction from its earliest stages, including drafting the founding bylaws under which it still operates.

Seminars & Workshops

Delivered seminars, training sessions, and workshops for students and members on academic pathways, research opportunities, and careers in STEM.

Human Resources & Advisory

Served in advisory and human-resources roles, recruiting and guiding volunteers and mentors and helping build the organizational culture that supports MitSna's educational mission.

Contact

Get In Touch

I welcome conversations about research, collaboration, and mentorship.

Email

georgeyumnam@gmail.com

george.yumnam@ubc.ca

Location

Stewart Blusson Quantum Matter Institute, UBC

Scholar Profile

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