Ph.D., 1978, California Institute of Technology
William Barton Rogers Professor of Physics
Experimental Condensed Matter Physics
My research group currently focuses on three projects: (i) Experimental and computational study of thermoelectric properties of narrow-gap semiconductors and semimetals. The narrow-bandgap semiconductors studied are often in the proximity of topological semimetals that show unusual thermo-magnetic and electrical transport properties. (ii) Synthesis of thin films and computational study of ferrimagnetic and antiferromagnetic heterostructures that show skyrmionic state and anomalous Hall effect. The unique magnetic spin texture and fast dynamics are ideal for low-power and ultrafast spintronics. (iii) In our third project, we employ data science and experiment to study high-entropy alloys (HEAs) with specific properties in the complex high-dimensional composition space. The enormous flexibility of HEAs offers nearly unlimited possibilities for realizing superior physical and functional properties.
1. “Tunable Magnetic Skyrmions in Ferrimagnetic Mn4N”, Chung T. Ma, Timothy Q. Hartnett, Wei Zhou, Prasanna V. Balachandran, and S. Joseph Poon, Appl. Phys. Lett. 119, 192406 (2021).
2. “Skyrmionics - Computing and Memory Technologies Based on Topological Excitations in Magnets”, Hamed Vakili, Wei Zhou, Chung T. Ma, S. J. Poon, M. G. Morshed, Mohammad Nazmus Sakib, Samiran Ganguly, Mircea Stan, Timothy Q. Hartnett, Prasanna Balachandran, Jun-Wen Xu, Yassine Quessab, Andrew D. Kent, Kai Litzius, Geoffrey S. D. Beach, and Avik W. Ghosh. J. Appl. Phys. 130, 070908 (2021); doi: 10.1063/5.0046950
3. “Harnessing the High-Dimensional Compositional Space of High-Entropy Alloys”, S. J. Poon, J. Qi, and A. M. Cheung, book chapter in “High-Entropy Materials: Theory, Experiments, and Applications”, ISBN-978-3-030-77640-4 (Springer Nature, 2021), p. 63-113.4. “Tuning Interfacial Dzyaloshinskii-Moriya Interactions in Thin Amorphous Ferrimagnetic Alloys”, Y. Quessab, J.-W. Xu, C. T. Ma, W. Zhou, G. A. Riley, J. M. Shaw, H. T. Nembach, S. J. Poon, and A. D. Kent, Scientific Reports, 10:7447 (2020).
5. “Robust Formation of Ultrasmall Room-Temperature Neél Skyrmions in Amorphous Ferrimagnets from Atomistic Simulations", Chung Ting Ma, Yunkun Xie, Howard Sheng, Avik W. Ghosh, and S. Joseph Poon, Scientific Reports, 9:9964 (2019).
6. “Half Heusler Compounds: Promising Materials for Mid-to-High Temperature Thermoelectric Conversion”, S Joseph Poon, J. Physics D: Appl. Phys. 52, 493001 (2019).
7. “Enhanced Figure of Merit in Bismuth-Antimony Fine-Grained Alloys at Cryogenic Temperatures”, Sheng Gao, John Gaskins, Xixiao Hu, Kathleen Tomko, Patrick Hopkins, and S. Joseph Poon, Scientific Reports, 9:14892 (2019).