Russell W Giannetta

Professor

Ph.D., Physics, Cornell University, 1980

Professor Giannetta received his PhD from Cornell University in 1980. He was a postdoc at Bell Telephone Laboratories from 1980-1982. He served on the faculty of Princeton University as an assistant professor from 1982-1988, and as an associate professor at the City College of New York from 1989-1992. He joined the Department of Physics at the University of Illinois in 1993. Professor Giannetta's lab has developed high precision techniques to measure the London penetration depth, a fundamental parameter of the superconducting state, in a wide variety of strongly correlated superconducting materials. He collaborated with Professor I. Adesida's group in Electrical and Computer Engineering to measure the transmission of heat and electricity through nanoscale semiconducting devices. More recently, in collaboration with Prof. C.P. Slichter he has begun using nuclear magnetic resonance (NMR) to explore many of the unusual magnetic properties shared by the high temperature and organic superconductors.

Other Activities

Since the initial discovery of high temperature superconductivity in 1986, a large number of new superconducting compounds have been discovered. These include electron doped copper oxides, heavy fermions, ruthenates, magnesium diboride and many new carbon-based organic superconductors. For many of these compounds, superconductivity coexists or competes with some form of magnetism.

To understand these complex materials, a window into the microscopic quantum mechanical state is needed. One feature common to all superconductors is the ability to screen out an applied magnetic field, a property known as the Meissner effect. The degree to which any superconductor performs this task is determined by a quantity known as the London penetration depth. Giannetta's lab employs high sensitivity electronic oscillator techniques to measure penetration depth in a variety of different superconductors, as a function of temperature, magnetic field and chemical composition.

Recent accomplishments include (1) the discovery that magnetism can actually enhance the Meissner effect in SmCeCuO₄, a copper oxide superconductor; (2) the demonstration that electron-doped copper oxide superconductors also possess a "d-wave" order parameter, similar to the more familiar hole-doped copper oxides; (3) the demonstration that penetration depth is sensitive to the phase of the order parameter, through the observation of surface Andreev bound states; (4) the observation of complex, multiple energy gap structure in 2H-NbSe₂ and (5) the observation of electronic phase separation in deuterated organic superconductors.

Giannetta and Professor C.P. Slichter are collaborating to perform NMR experiments in organic and copper oxide superconductors. Nuclear magnetic resonance is an extremely powerful probe that yields information about the local electronic environment. An overall goal is to use NMR to understand the magnetic manifestations of pseudogap behavior that are common to different classes of strongly correlated electronic materials, organic and otherwise.

Giannetta's group has also pursued research in nanoscience. In a collaboration with Professor I. Adesida's group in Electrical and Computer Engineering, they have measured the quantum mechanical transmission of heat and electricity through very small semiconducting devices. These structures contain a very high mobility two-dimensional gas of electrons. Using modern nanofabrication techniques, this electron gas can be patterned into wires, electron waveguides and tunneling structures. Measurements must be carried out at temperatures down to 50 mK to fully capture the quantum mechanical behavior in these devices. One recent accomplishment was the observation of a "zero bias peak" in which the electrical conductance through a quantum wire is enhanced, at very low temperatures, by a many-electron effect.

A second nanoscale project involved the use of a scanning tunneling microscope to initiate chemical reactions at the atomic scale with the intent of growing a superconducting "molecular" wire. By using the STM as both an electrochemical device and and an atomic scale probe of electrical conductance, one can study the nature of the superconductivity in an atomic-scale wire.

Honors and awards:

• American Physical Society Fellow
• Xerox Faculty Research Award, 2003

Selected Publications:

• R. W. Giannetta, T. A. Olheiser, M. Hannan, I. Adesida, and M. R. Melloch. Conductance quantization and zero bias peak in a gated quantum wire. Physica E: Low-Dimensional Systems and Nanostructures 27, 270-277 (2005).
• R. Prozorov, D. D. Lawrie, I. Hetel, P. Fournier, and R. W. Giannetta. Field-dependent diamagnetic transition in magnetic superconductor Sm_1.85Ce_0.15CuO_4-y. Phys. Rev. Lett. 93, 147001-1-4 (2004).
• A. Snezhko, et al. Nodal order parameter in electron-doped Pr_2-xCe_xCuO_4-δ superconducting films. Phys. Rev. Lett. 92, 157005-1-4 (2004).
• D. Guan, et al. Nonequilibrium Green's function method for a quantum Hall device in a magnetic field. Phys. Rev. B 67, 205328-1-9 (2003).
• R. Prozorov, et al. Campbell penetration depth of a superconductor in the critical state. Phys. Rev. B 67, 184501-1-4 (2003). also in Virtual J. of Applications of Superconductivity, Vol. 4:10, (2003)