Materials World Network: Spin Effects in Quasi-1D Systems of Narrow Gap Semiconductors

The possibility of developing new paradigms for electronics and information technology has motivated world-wide interest in spintronics, which is based on manipulating the intrinsic spin of charge carriers in solids to develop new, efficient functionalities for high-speed, low-power devices and circuits. The goals of the present research effort, involving close collaboration between groups at the University at Buffalo (UB) and the Ruhr Universitaet, Bochum (RUB), are: to develop a full understanding of the basic physics of the spin-orbit (SO) interaction in quasi-one-dimensional systems in InAs-based heterostructures; to discover new spin-related phenomena; and to explore opportunities for developing novel spintronic devices. Strong SO coupling effects originate in the lack of inversion symmetry in the structures, which can be controlled by growth or by application of an external electric field. The narrow fundamental gap and large spin-orbit splitting of InAs also play a strong role. The two main research activities are: 1) photoresponse and absorption studies of electric-dipole spin resonance in Quantum Hall edge channels in InAs quantum wells; and 2) electrical transport, magnetotransport and electric-dipole spin resonance studies of lithographically fabricated quantum wires in similar InAs-based heterostructures. Results from the two systems will be compared and similarities and differences will provide deeper insight into the fundamental spin physics of these systems. Terahertz and low frequency experiments as a function of electric and magnetic fields will provide essential information on the interplay of the fields and the SO interaction in these structures. The detailed understanding derived from this coordinated effort should allow tailoring complex one-dimensional structures, for example, combining short quantum wires with quantum Hall edge channels in a Mach-Zehnder interferometer for spin-dependent coherence measurements. The MWN funding will support a closely coupled experimental research and education program, between the US and German groups. Collaborative theoretical and materials growth (molecular beam epitaxy) efforts also support this work. The two groups have common interests in the physics of these structures and complementary expertise. The advancement of fundamental knowledge through this program will impact the fields of spintronics and quantum information processing. Graduate students directly involved in these studies will receive a unique broad, multidisciplinary education in basic physics, materials science, and nanofabrication, as well as cultural education through the regular exchanges of students and the PIs. Undergraduate students will be provided with a research experience abroad via training and independent study at UB, and a one month early summer visit to our partner's laboratory at RUB.