Ward Beyermann, Assistant Professor of Physics, specializes in the transport and thermodynamic properties of highly correlated electronic condensed matter systems. These include materials where the strong interactions between the electrons lead to unusual properties at low temperatures. Specific heat and resisitivity are measured down to millikelvin temperatures and in high magnetic fields. Some of the systems investigated include lanthanide and actinide intermetallic compounds, lanthanide intermetallic borocarbides, and carbon-fullerene materials.

Thermodynamic and Transport of Highly-Correlated Systems

Strong many-body correlations play an important role in certain intermetallic compounds that contain 4f and 5f moments. The interactions between the localized f electrons and the conduction electrons renormalize the relevant energy scales and modify the thermodynamic and transport properties at low temperatures. Depending on the magnitude of the interactions, these compounds are referred to as either "heavy-fermion" or "mixed-valent" systems. The strong correlations are also responsible for unusual superconducting and magnetic ground states in some materials. Studying properties like the specific heat and transport in prototypical and recently discovered materials is the main trust of this research. These properties are measured at temperatures as low as ~50 mK, and some experiments are performed in magnetic fields as high as 50 T at the National High Magnetic Field Laboratory. Neutron scattering is also used to investigate magnetic e xcitations in these systems in collaboration with the Los Alamos Neutron Scattering Center. Rare-earth and intermetallic atomic substitutions help us investigate the interplay between magnetic, superconducting, and normal state interactions.

Finally, the properties of the new carbon fullerene compounds (e.g. C 60, K3C60 and nanotubes) are being investigated. Specific-heat experiments are being performed to study the intra-vibrational, inter-vibrational, and rotational modes which are unique to these systems.

(Photo: Transfer of liquid helium to superconducting magnet.)

Recent Publications

W.P. Beyermann, M.F. Hundley, J.D. Thompson, F.N. Diederich, and G. Gruner, "Low-Temperature Specific Heat of C60 ," Phys. Rev. Lett. 68, 2046 (1992).

A. Yatskar, W.P. Beyermann, R. Movshovich, and P.C. Canfield, "Possible Correlated-Electron Behavior from Quadrupolar Fluctuations in PrInAg2 ," Phys. Rev. Lett. 77, 3637 (1996).

A. Yatskar, N.K. Budraa, W.P. Beyermann, P.C. Canfield, and S.L. Bud'ko, "Heavy-Electron Behavior in Single-Crystal YbNi2B2C," Phys. Rev. B54, R3772 (1996).