Research Interests

Jason Jeffries is a condensed matter physicist and group leader for the High Pressure Physics group in the Physics Division at Lawrence Livermore National Laboratory. During his graduate studies, Jason worked under Professor M. Brian Maple studying superconductivity and magnetism under pressure. At LLNL, he studies how magnetic, electrical, and structural degrees of freedom affect the physical properties of materials. His interests include a wide range of materials from f-electron-bearing materials (lanthanide and actinide materials) to “simple,” p-block compounds. However, the systems that he studies generally possess the common attribute that quantum effects (e.g., strong spin-orbit coupling and strong electronic correlations) dominate the emergent properties: these materials are often simply called quantum materials. He often employs high-pressure diamond anvil cell techniques and characterizations, including x-ray and neutron scattering, to explore a wide phase space of structural and quantum parameters.

Ph.D., Condensed Matter Physics, University of California, San Diego, 2007

B.S., Physics, Clemson University, 2000

• J. R. Jeffries, J. A. Hammons, T. M. Willey, M. A. Wall, D. Ruddle, J. Ilavsky, P. G. Allen, and T. van Buuren, “Probing He bubbles in naturally aged and annealed delta-Pu alloys using ultra-small-angle x-ray scattering,” J. Nucl. Mater. 498, 505 (2018).
• F. F. Tafti, M. S. Torikachvili, R. L. Stillwell, B. Baer, E. Stavrou, S. T. Weir, Y. K. Vohra, H.-Y. Yang, E. F. McDonnell, S. K. Kushwaha, Q. D. Gibson, R. J. Cava, and J. R. Jeffries, “Tuning the electronic and the crystalline structure of LaBi by pressure: from extreme magnetoresistance to superconductivity,” Phys. Rev. B 95, 014507 (2017).
• J. R. Jeffries, R. L. Stillwell, S. T. Weir, Y. K. Vohra, and N. P. Butch, “Emergent ferromagnetism and T-linear scattering in USb2 at high pressure,” Phys. Rev. B 93, 184406 (2016).
• N. P. Butch, J. Paglione, P. Chow, Y. Xiao, C. A. Marianetti, C. H. Booth, and J. R. Jeffries, “Pressure-resistant intermediate valence in the Kondo insulator SmB6,” Phys. Rev. Lett. 116, 156401 (2016).
• J. R. Jeffries, N. P. Butch, M. J. Lipp, J. A. Bradley, K. Kirshenbaum, S. R. Saha, J. Paglione, C. Kenney-Benson, Y. Xiao, P. Chow, and W. J. Evans, “Persistent Fe moments in the normal-state collapsed-tetragonal phase of the pressure-induced superconductor Ca0.67Sr0.33Fe2As2,” Phys. Rev. B 90, 144506 (2014).