• Theoretical Condensed-Matter Physics
• Theoretical Elementary Particle Physics
• Astrophysics and General Relativity
• Experimental Elementary Particle Physics
• Accelerator Physics
• Experimental Condensed-Matter Physics
• Biological Physics
• Multidisciplinary Research
• Major Research Facilities
• Resources for Researchers

Selected Publications
LASSP Faculty page

B.S., 1986, Physics and Mathematics, Vanderbilt University. Ph.D., 1993, Physics, Cornell University. Postdoctoral Research Associate, Harvard University, 1993-96. Assistant Professor, Physics, Cornell University, 1996-2000. Associate Professor, Physics, Cornell University, 2000-2004, Professor, Physics, Cornell University, 2004-present. Alfred P. Sloan Fellow, 1996-99; David and Lucile Packard Foundation Fellow, 1997-2002; William L. McMillan Award, 1997; Research Corporation Research Innovation Award, 1997; ONR Young Investigators Award, 1997-2000. 

Research Areas
New nanofabrication techniques; electronic properties on molecular length scales; high-speed dynamics in magnetic devices; correlated-electron states in magnets and superconductors; quantum properties of defects and impurities

Current Research
Our group's research focuses on the electronic and magnetic properties of nm-scale samples. The work in the group consists of making nanometer-size devices using equipment at the Cornell NanoScale Science & Technology Facility (CNF), and then performing measurements in Clark Hall (usually) at low temperatures. Students and postdocs in the group are pursuing a wide variety of projects.

In collaboration with the groups of Bob Buhrman, Farhan Rana, and several groups outside Cornell, we are investigating the "spin-transfer torque effect."  This is a phenomenon by which the magnetic orientation of a small magnet can be manipulated by transferring angular momentum from a current of spin-polarized electrons, rather than by using magnetic fields.  We are using the spin torque as a tool for studying the fundamental physics of ferromagnetic and antiferromagnetic dynamics. This project is also progressing quickly toward applications for magnetic memory devices and high-speed signal processing.

We are probing the properties of the discrete spectra of "electrons-in-a-box" quantum-mechanical energy states inside nanometer-scale metal particles and carbon nanotubes.  These systems act as "quantum dots" within which the number of electrons can be controlled one-by-one and the individual electronic energy levels can be investigated in detail. We have used studies of these energy levels to probe the consequences of superconducting pairing interactions, spin-orbit interactions, and magnetic exchange interactions, and at present we are focusing on understanding spin-polarized electron tunneling via individual states.

In collaboration with the groups of Paul McEuen, Jiwoong Park, Garnet Chan, Will Dichtel, and Tito Abruna, we are measuring electron and spin transport through single molecules.  We are able to make single-molecule transistors, in which one molecule bridges between a source and a drain electrode, while the resistance of the molecule can be changed by applying a voltage to a third gate electrode and thereby shifting the energy levels in the molecule. We are working to develop new experimental techniques, such as ways in which a molecule can be stretched mechanically while we measure its electrical properties in a transistor geometry, and ways in which light can be used to manipulate the structure of the molecule being measured.  The primary challenges in this field now are to achieve reproducible behavior in different devices and to conduct controlled, systematic studies of the mechanisms that affect electron flow through molecules.

Graduate Students
Yongtao Cui, Ted Gudmundsen, Wan Li, Alex Mellnik, Josh Parks, Sufei Shi, Eugenia Tam, Kiran Thadani, Chen Wang and Lin Xue 

Postdocs
Saikat Ghosh and Takahiro Moriyama 

Spotlight

Jalina Keeling is an undergraduate student with the Itai Cohen Group on Complex Matter Physics (who is at Cornell as part of the NSF's Research Experiences for Undergraduates program). She is conducting experiments similar to the epitaxial growth of crystals, but using polymer beads. She uses a confocal microscope to scan a sample of these beads from bottom to top. Her research seeks to answer the questions "What structures form? How do we tune the concentration of polymers to change ...
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