The recent discovery of superconductivity with a transition temperature of 26K in the LaO_1-xF_xFeAs system has generated tremendous interest in the scientific community. More recently, superconductors LnO_1-xF_xFeAs with rare-earth substitution (Ln=Ce, Pr, Sm, Nd etc.) were realized and superconducting transition temperature was raised to above 50K. One of the crucial issues to understanding the underlying superconducting mechanism in such transition metal-based systems is the pairing interaction, i.e., the symmetry of the superconducting order parameter and the nature of the low energy excitations. I am involved in the specific heat and other transport measurements for this new system. Specific heat measurement is one of the powerful tools to measure the density of states at the Fermi level, which is an effective way to detect the gap symmetry of superconductors.

 

The other projects I am involved in include the experimental study of heavy fermion 115 compounds and the study of filled skutterudite compounds. The filled skutterudite compounds have recently attracted much attention due to their large potential as thermoelectric materials for the next generation, and to significant scientific interest in their unusual properties, exhibited particularly by Pr-based filled skutterudites.

 

In addition to experimental measurements and sample growth mentioned above, I plan to develop a more efficient calorimeter probe for specific heat measurements.

L. Shu, D. E. MacLaughlin, R. H. Heffner, F. D. Callaghan, J. E. Sonier, G. D. Morris, O. O. Bernal, A. Bosse, J. E. Anderson, W. M. Yuhasz, N. A. Frederick, and M. B. Maple, “Penetration depth study in the heavy-fermion superconductor in PrOs₄Sb₁₂,” Physica B 374-375, 247 (2006).

 

L. Shu, W. Higemoto, Y. Aoki, N. A. Frederick, W. M. Yuhasz, R. H. Heffner, K. Ohishi, T. U. Ito, K. Ishida, R. Kadono, A. Koda, D. Kikuchi, H. Sato, H. Sugawara, S. Sanada, Y. Tunashima, Y. Yonezawa, M. B. Maple, and D. E. MacLaughlin, “Time reversal symmetry breaking in superconducting (Pr, La)Os₄Sb₁₂ and Pr(Os,Ru)₄Sb₁₂,” J. Magn. Magn. Mat., 310, 551-553 (2007).

 

L. Shu, D. E. MacLaughlin, Y. Aoki, Y. Tunashima, Y. Yonezawa, S. Sanada, D. Kikuchi, H. Sato, R. H. Heffner, W. Higemoto, K. Ohishi, T. U. Ito, O. O. Bernal, A. D. Hillier, R. Kadono, A. Koda, K. Ishida, H. Sugawara, N. A. Frederick, W. M. Yuhasz, T. A. Sayles, T. Yangisawa, and M. B. Maple, “Muon spin relaxation and hyperfine-enhanced ¹⁴¹Pr nuclear spin dynamics in Pr(Os,Ru)₄Sb₁₂ and (Pr, La)Os₄Sb₁₂,” Phys. Rev. B 76, 014527 (2007).

 

R. H. Heffner, G. D. Morris, M. J. Fluss, B. Chung, S. McCall, D. E. MacLaughlin, L. Shu, K. Ohishi, E. D. Bauer, J. L. Sarrao, W. Higemoto, and T. U. Ito, “Limits for ordered magnetism in Pu from muon spin rotation spectroscopy,” Phys. Rev. B 73, 094453-1-5 (2006).

 

L. Shu, C. Yu-Guang, and C. Hong, “Ground state properties of the two-dimensional spin-Peierls model with Dzyaloshinskii-Moriya interaction”, Acta Physica Sinica 51, 902 (2002).