Department of Physics & Astronomony
- Experimental Condensed Matter Physics
A central theme of our research is to understand the behavior of electron spin in nanoscale structures and its relation to magnetic and opto-electronic properties. At the nanometer length scale quantum effects and interfacial phenomena dominate, leading to behavior not seen in bulk materials. Our work focuses on synthesizing novel heterostructures and devices consisting of magnetic, semiconducting, and organic materials, and exploring the new physics which emerge in these systems. The development of electronic devices that utilize the electron spin has come to be known as "spintronics," and there is a strong potential for applications in magnetic information storage, reconfigurable logic, magnetic field sensors, and their integration with display and communication technologies. The new heterostructures and materials developed in our laboratory might also become important for spin-based quantum information systems.
Molecular beam epitaxy (MBE) provides a means for synthesizing thin film heterostructures in an atom-by-atom manner (or molecule-by-molecule) for the best possible control over the material and interface structure. In situ scanning tunneling microscopy (STM) provides atomic-scale structural characterization, while in situ optics (including ultrafast optics and magneto-optics) investigates the dynamics of spin, magnetism, and light emission in these heterostructures. Combining these techniques with lithographically-defined templates enables electronic devices to be fabricated under the same high-quality MBE growth conditions, and specially-made sample holders allow the devices to be tested in situ; this avoids the potentially damaging effects of air. This new approach to fabricating and testing devices is being used to develop spintronic devices as well as charge-based optoelectronic devices.
Specific materials of interest include ferromagnetic metals, ferromagnetic semiconductors, organic semiconductors, and carbon nanotubes. Combinations of these materials are expected to yield new physical phenomena that do not exist in the individual materials and thus form a major part of our research. In addition, the development of half-metallic ferromagnets with high spin polarization at room temperature is recognized as one of the most important challenges for spintronic technologies and is part of our long term objectives.
Ph.D. 1999, University of California Berkeley
NSF CAREER Award (2005)
- R. K. Kawakami, Y. Kato, M. Hanson, I. Malajovich, J. M. Stephens, E. Johnston-Halperin, G. Salis, A. C. Gossard, and D. D. Awschalom, "Ferromagnetic Imprinting of Nuclear Spins in Semiconductors," Science, 294, 131 (2001).
- R. K. Kawakami, E. Johnston-Halperin, L. F. Chen, M. Hanson, N. Gübels, J. S. Speck, A. C. Gossard, and D. D. Awschalom, "(Ga,Mn)As as a Digital Ferromagnetic Heterostructure," Appl. Phys. Lett. 77, 2379 (2000).
- R. K. Kawakami, E. Rotenberg, Hyuk J. Choi, Ernesto J. Escorcia-Aparicio, M. O. Bowen, J. H. Wolfe, E. Arenholz, Z. Zhang, N. V. Smith, and Z. Q. Qiu, "Quantum Well States of Cu Thin Films," Nature 398, 132 (1999).
- R. K. Kawakami, E. Rotenberg, Ernesto J. Escorcia-Aparicio, Hyuk J. Choi, T. R. Cummins, J. G. Tobin, N. V. Smith, and Z. Q. Qiu, "Observation of the Quantum Well Interference in Magnetic Nanostructures by Photoemission," Phys. Rev. Lett. 80, 1754 (1998).
- R. K. Kawakami, Ernesto J. Escorcia-Aparicio and Z. Q. Qiu, "Symmetry-Induced Magnetic Anisotropy in Fe Films Grown on Stepped Ag(001)," Phys. Rev. Lett. 77, 2570 (1996).