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Gregory Stewart



PhD Stanford University (1975)

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Office: 2132 NPB

Lab: B-40/44/48

Research Group

Condensed Matter Experiment

Research Interests

Binary and ternary compounds for possible high-pressure-induced superconductivity (including hydrides); highly correlated superconductors with an emphasis on those containing Beryllium; Iron pnictide superconductors (new materials as well as known compounds).  Once prepared, these samples are investigated using specific heat, susceptibility, and resistivity down to 3He temperatures and in fields up to 16 T (in-house) / 45 T (NHMFL Tallahassee) / 60 T (Los Alamos long pulse NHMFL facility). Advances in our understanding of the unusual magnetic and superconducting properties of these materials are carried out with a collaboration with the high pressure group of Prof. James Hamlin, U of F Physics, the theory group of Prof. Peter Hirschfeld, U of F Physics, and the theory group of Prof. Richard Hennig, U of F Materials Science.

Selected Publications

J. Lim, A. C. Hire, Y. Quan, J. S. Kim, S. R. Xie, R. S. Kumar, D. Popov, C. Park, R. J. Hemley, J. J. Hamlin, R. G. Hennig, P. J. Hirschfeld, and G. R. Stewart, “Creating superconductivity in WB2 through pressure-induced metastable planar defects,” in submission to Nature Communications, arXiv:2109.11521.

Jinhyuk Lim, J. S. Kim, Ajinkya C. Hire, Yundi Quan, R. G. Hennig, P. J. Hirschfeld, J. J. Hamlin, G. R. Stewart and Bart Olinger, “A15 Nb3Si: A ‘high’ Tc superconductor synthesized at a pressure of one megabar and metastable at ambient conditions,” Journal of Physics: Condensed Matter 33, 285705 (2021).

J. Lim, A. C. Hire, Y. Quan, J. Kim, L. Fanfarillo, S. R. Xie, R. S. Kumar, C. Park, R. J. Hemley, Y. K. Vohra, R. G. Hennig, P. J. Hirschfeld, G. R. Stewart, and J. J. Hamlin “High pressure study of low-Z superconductor Be22Re,” Phys. Rev. B 104, 064505 (2021). G. N. Tam, H. Maruyama, J. C. Nino, and G. R. Stewart, “22 K Superconductivity in BaFe2As2 exposed to F2 and Cl2,” Phys. Rev. B 102, 134507 (2020).

Q. Niu, W. Zhang, Y. T. Chan, E. C. T. O’Farrell, R. Doganov, K. Y.Yip, K. T. Lai, W. C. Yu, G. R. Stewart, J. S. Kim, and Swee K. Goh, “Stabilization of antiferromagnetism in 1T-Fe0.05TaS2”, Phys. Rev. Research 2, 023297 (2020).