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Guoqing Wu
Assistant Professor Ph.D. in Physics, Florida Atlantic University B.S. in Physics, Hubei University (China) |
Phone: (850) 474-2271
Office Location: Bldg 4, Room 444
Email: gwu@uwf.edu
Website: TBA
Courses taught
PHY 2053 – General Physics I
PHY 2054 – General Physics II
PHY 2048 – University Physics I
PHY 3424 – Optics
PHY 4513 – Thermodynamics and Kinetic Theory
Research Interests
Physical properties and design of novel electronic/magnetic materials in experimental condensed matter/materials physics. Example materials include high temperature superconductors (Cu-based and non-Cu based), low-dimensional materials, and transition metal oxides which exhibit charge/spin density waves (CDW/SDW), ferro-/antiferro-magnetism, structural/thermal phase transition, colossal magnetoresistance, charge ordering, spin frustration, and/or non—Fermi liquid behavior. The design of the materials can be made based on specific or potential applications in structure, thermal, electrical, magnetic, and/or optical aspects.
The form of the bulk materials is usually made in polycrystalline, single-crystal or thin film.
Besides the growth and characterization of the materials, many of our experiments focus on the study of phase transitions, the connection between/among structure, electrical, magnetic, and/or thermal properties, and the potential mechanism for the understanding of these properties.
Specific topics include
(a) spin-spin, spin-orbital and hyperfine interactions (in highly correlated electron systems); (b) spin gap, driven vortex motion, pinning, nucleation and magnetic fluctuations (in high-Tc superconductors); (c) spin statics and dynamics for spin–phonon interactions of charge/spin density waves (CDW/SDW) and multi-phase transitions (in low dimensional organic and non-organic conductors); (d) high hydrostatic pressure and high magnetic field effects to the structural, electrical, magnetic and thermal properties of transition-metal oxides; (e) growth, characterization and structure determination (including structure phase transitions) of bulk materials for experimental and/or potential application purposes, and (f) development of novel experimental probes and devices for materials research and science education.
Through out the study, the parameters of high pressure (P), low temperatures (T) and high magnetic field (B0) are widely applied since the materials properties are often tunable by their applications that are helpful to the understanding of their mechanisms.
The high techniques & apparatus in our experiments mainly include
(1) magnetic resonance (MR) and spin resonance (NMR/ESR), (2) SQUID DC/AC magnetometry, (3) four-probe electrical transport, (4) high pressure cells, (5) materials growth furnaces, (6) X-ray diffraction & Rietveld refinement, (7) neutron scattering & GSAS, (8) heat capacity, (9) thermal expansion, (10) iodometric titrations in materials chemistry, (11) high magnetic field in NHMFL at Tallahassee, and (12) vacuum and low temperature techniques (He-3 refrigerator and dilution refrigerator), etc..
Among these, the high pressure cells are combined for use for most of our experiments, such as high pressure MR, high pressure electrical transport, high pressure X-ray diffraction, and high pressure magnetic susceptibility.
Selected publications
1. “Measurements of the anisotropic irreversibility field in electron-doped high-Tc superconductor Pr2-xCexCuO4-y’’, Guoqing Wu, W. G. Clark, S. E. Brown, H. Balci, R. L. Green, P. L. Kuhns, A. P. Reyes, and W. G. Moulton, submitted to Physical Review Letters and reviewed in 2008, to be resubmitted to Physical Review B. (4 pages)
2. “77Se-NMR measurements of the pi-d exchange field in the organic superconductor lambda-(BETS)2FeCl4 ”, Guoqing Wu, W. G. Clark, S. E. Brown, J. S. Brooks, A. Kobayashi, and H. Kobayashi, Physical Review B 76, 132510 (2007). (4 pages)
3. “1H-NMR spin-echo measurements of the spin dynamic properties in lambda-(BETS)2FeCl4”, Guoqing Wu, P. Ranin, G. Gaidos, W. G. Clark, S. E. Brown, L. Balicas, and L. K. Montgomery, Physical Review B 75, 174416 (2007). (8 pages)
4. “Proton NMR measurements of the local magnetic field in the paramagnetic metal and antiferromagnetic insulator phases of lambda-(BETS)2FeCl4”, Guoqing Wu, P. Ranin, W. G. Clark, S. E. Brown, L. Balicas, and L. K. Montgomery, Physical Review B 74, 064428 (2006). (10 pages)
5. “Inhomogeneous electronic structure probed by spin-echo experiments in the electron doped high-Tc superconductor Pr1.85Ce0.15CuO4-y”, F. Zamborszky, Guoqing Wu, J. Shinagawa, W. Yu, H. Balci, R. L. Greene, W. G. Clark, and S. E. Brown, Physical Review Letters 92, 047003 (2004). (4 pages)
6. “NMR Investigation of the organic conductor lambda-(BETS)2FeCl4”, W. G. Clark, Guoqing Wu, P. Ranin, L. K. Montgomery, and L. Balicas, Applied Magnetic Resonance 27, 279 (2004). (9 pages)
7. “Small polaron transport and pressure dependence of the electrical resistivity of La2-xSrxNiO4 (0 £ x £ 1.2)”, Guoqing Wu and J. J. Neumeier, Physical Review B 67, 125116 (2003). (8 pages).
8. “Temperature evolution of the crystal structure of La2-xSrxNiO4 (x = 0.25 and 1/3) as revealed through neutron powder diffraction”, Guoqing Wu, J. J. Neumeier, C. D. Ling, and D. N. Argyriou, Physical Review B 65, 174113 (2002). (8 pages)
9. “Magnetic susceptibility, heat capacity, and pressure dependence of the electrical resistivity of La3Ni2O7 and La4Ni3O10”, Guoqing Wu, J. J. Neumeier, and M. F. Hundley, Physical Review B 63, 245120 (2001). (5 pages)
10. “Neutron diffraction study of La3Ni2O7: structural relationships among n = 1, 2, and 3 phases Lan+1NinO3n+1”, Christopher D. Ling, Dimitri N. Argyriou, Guoqing Wu and J. J. Neumeier, J. Solid Stat. Chem. 152, 517 (1999). (9 pages)