Happy New Year from everyone at the Materials Processing Center!
Faculty Highlight: Keith A. Nelson Spectroscopy techniques demonstrate ballistic heat transport at micron length scales.
Chemistry Professor Keith A. Nelson
Advanced spectroscopy techniques developed by MIT Chemistry Professor Keith A. Nelson are yielding insights into heat transfer in crystalline materials that overturn long held assumptions.
Nelson and colleagues have developed time-resolved optical spectroscopy methods for measuring the acoustic phonons associated with heat transfer.
His team demonstrated experimentally that in silicon at room temperature, the long-held diffusive model of heat transfer was invalid for distances from 1 to 5 microns, where ballistic movement, rather than diffusion, seems to be the driving force.
"When we build devices, we worry about how transport works. In materials like thermoelectrics, we care about motion on length scales like that. So we can't model it as diffusion, the thermal conductivity that we would get is really way off if we try to do that," Nelson says. Read more.
A Collaborative Effort Breaks Fourier's Law Laser spectroscopy challenges entrenched barriers in understanding thermal transport.
Alexei Maznev and Jeff Eliason in time resolved spectroscopy lab at MIT.
Time resolved optical spectroscopy experiments showing that heat carrying acoustic phonons in silicon travel much longer distances at room temperature than previously thought grew partly out of theory and partly out of serendipity, according to MIT researchers who participated in the work.
"I think this study resulted partially from accidental discovery, but also from our collaboration with (MIT Professor) Gang Chen and others developing an advanced understanding of the thermal transport. A number of things came together that resulted in this work," explains Alexei A. Maznev, staff scientist in the lab of Professor Keith A. Nelson. Maznev developed the model and planned the experiment.Read more.
Introducing High School Students to Laser Spectroscopy
Jill Sewell shepherding Lambda Project in MIT Professor Keith A. Nelson's lab.
High school science teacher Jill Sewell, far right, with students, from left, Andrew James, Kenny Li, Alexa Beatrice and Noah Gopen in the spectroscopy lab at MIT. Photo: Jeffrey K. Eliason.
Swampscott High School Chemistry and Physics teacher Jill Sewell turned a summer learning opportunity at MIT into a second job as a lab manager for Professor Keith Nelson's Lambda Project for high school students.
"I feel blessed to have this come my way," Sewell says. It started from her participation in the Center for Materials Science and Engineering at MIT summer Research Experience for Teachers (RET) program. Sewell joined Nelson's lab for the RET, and he asked her to take on the Lambda Project.
Over two years, Sewell shepherded three groups of students from Swampscott and Saugus through the program, which lasts for three days on campus during April and summer vacations. Read more.
Exotic Quantum Electronic States at Graphene Edges
On a piece of graphene (hexagonal pattern of carbon atoms), in a strong magnetic field, electrons can move only along the edges, and are blocked from the interior. In addition, only electrons with one direction of spin can move in only one direction along the edges (indicated by the blue arrows), while electrons with the opposite spin are blocked (as shown by the red arrows). Photo Courtesy of the Researchers
David L. Chandler, MIT News Office
Graphene has become an all-purpose wonder material, spurring armies of researchers to explore new possibilities for this two-dimensional lattice of pure carbon. But new research at MIT has found additional potential for the material by uncovering unexpected features that show up under some extreme conditions - features that could render graphene suitable for exotic uses such as quantum computing.
The research is published in the journal Nature, in a paper by professors Pablo Jarillo-Herrero and Ray Ashoori, postdocs Andrea Young and Ben Hunt, graduate student Javier Sanchez-Yamaguchi, and three others. Under an extremely powerful magnetic field and at extremely low temperature, the researchers found, graphene can effectively filter electrons according to the direction of their spin, something that cannot be done by any conventional electronic system. Read more.
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