The curves show how the conductivity , at a fixed temperature, changes with time t after a temporary change of the electron concentration during the time tw. Obviously, tw has a dramatic effect on the relaxations, both qualitatively and quantitatively. At very long times, conductivity approaches its equilibrium value 0 (zero on the vertical axis).

log t(s)

Far-from-equilibrium behavior, where system properties change with time, is poorly understood although some of the most striking phenomena in nature, such as life itself, occur out of equilibrium. The nonequilibrium dynamics is also believed to underlie complex behavior of many new electronic materials. This group has already demonstrated that, at very low temperatures, electrons in silicon transistors, the basic building blocks of the electronics industry, represent excellent model systems for studying nonequilibrium phenomena.

New work shows that this system also exhibits “aging”, i.e. that its electrical conductivity σ depends not only on time t but also on the measurement history (“age”). σ(t) was measured after the temporary change of the electron density during time tw. The history was varied by changing tw and temperature. The observed complex dynamics of the electronic transport is strikingly similar to that of other out-of-equilibrium systems. This is important for the development of proper theories.

Physical Review Letters 99, 046405 (2007)

Far-From-Equilibrium Behavior of Electrons in Si Transistors Dragana Popović, Florida State University, DMR 0403491

Education:

• 1 undergraduate (Kelly McKirahan), 2 graduate students (Ivana Raičević and Xiaoyan Shi), 1 postdoc (Marko Dragosavac), and 1 senior researcher (Jan Jaroszyński) worked on research supported by this Award.• The 2 graduate students are continuing their research efforts towards Ph.D. I. Raičević received several travel awards, including one from I2CAM, to present her results at an international conference in Italy.

Far-From-Equilibrium Behavior of Electrons in Si TransistorsDragana Popović, Florida State University, DMR 0403491

Broader Impacts:• PI gave a lecture to a large group of REU and RET (Research Experiences for Teachers) participants at NHMFL/Tallahassee.• PI served as Science Fair Judge at local schools.• PI served as Science Judge for The Best & Brightest Awards for high school seniors in Leon County, Florida.• As Chair of the NHMFL Diversity Committee for more than 3 years, the PI has been involved on a daily basis in organizing various activities and programs to increase the participation of the members of underrepresented groups in the fields of STEM at all levels.• Understanding of nonequilibrium behavior is of fundamental importance for many scientific disciplines, since the majority of phenomena in nature, including physical, chemical, and biological systems, are examples of nonequilibrium states. This is one of the most challenging problems in science. Our electronic devices are particularly appealing model systems for studying this problem.Graduate students: Ivana Raičević (left) and

Xiaoyan Shi (right).