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Vengalattore group develop novel quantum resonators

Mukund Vengalattore's group has developed a novel method of manipulating mechanical resonators to be sensitive enough to work at the quantum scale.

Read more in the Chronicle and in The Times of India and the article in Physics Review Letters.

resonator

McEuen group twists and folds graphene like paper

Physicists in the McEuen research group use the principles of kirigami to manipulate graphene, laying the groundwork for future nano-machines. Both Co-Directors of KIC, Paul McEuen and David Muller, contributed to the July article in Nature. Read more and see videos of the graphene kirigami in action in the Cornell Chronicle.

Kirigami

Physics professor Chris Henley dies at 59

By Anne Ju
Reprinted from The Chronicle.

Christopher L. Henley, professor of physics in the College of Arts and Sciences, died June 29 after an illness. He was 59 years old.

Henley joined the Cornell faculty in 1989 as an assistant professor of physics, was promoted to associate professor in 1993, and became a full professor in 2001. Before that, he was an assistant professor at Boston University and also worked at AT&T Bell Laboratories.

At Cornell, Henley's research was in the theory of frustrated magnetism, both classical and quantum; interacting electron systems; quasicrystals; and biological physics.

In interacting electron systems, Henley's research group worked on the border of analytic theory and computation. They studied the ground states of a spinless fermion lattice model with supersymmetry. They also worked on phenomenology of scanning tunneling microscopy measurements in high-temperature superconductors.

In biological physics, Henley led projects in pattern formation and mechanics, specifically a large project about the physical bases of left/right symmetry breaking in various animals including snails; in plants; or in assemblies of single cells. He also was fascinated by the exterior shell geometry of viruses and worked to model the mechanics of plant roots.

Paul McEuen, the John A. Newman Professor of Physical Science, called Henley a “brilliant scientist.”

“He was interested in almost anything, unafraid of applying his careful and precise approach to wild and wooly problems in fields ranging from quantum physics to biology,” McEuen said.

“He was a productive colleague, dedicated mentor and deeply committed to intellectual and academic pursuits,” said Jeevak Parpia, professor of physics. “He will be missed by all of us.”

Last September, Henley's colleagues and friends came together to celebrate his 59th birthday and his contributions to the field of theoretical solid-state physics. The symposium included an international panel of speakers.

Henley was born Sept. 24, 1955, in Washington, D.C., to Norman F. and Nancy Henley. He received a bachelor's degree in physics and mathematics from the California Institute of Technology in 1977 and his doctorate in physics from Harvard University in 1983. He was a fellow of the American Physical Society and was the recipient of many professional honors, including an Alfred P. Sloan Research Fellowship and a Presidential Young Investigator Award.

When young, according to his mother, he had a strong interest in maps and was a precocious navigator for his family's trips. In adulthood, Henley ran, swam or bicycled every day, and enjoyed hiking, reading, contra dancing, classical music and Scrabble, among other things.

Henley was given a natural burial in Chesterfield, Massachusetts. He is survived by his mother, son, aunt and cousins.

Chris Henley

Eun-Ah Kim group finds new insights to entanglement entropy

Eun-Ah Kim's group reported in May 22 issue of Physical Review Letters that the poster child non-Fermi liquid state found at filling factor ν = ½ shows strongly enhanced quantum entanglement as a result of strong correlations in the system. The ν = ½ composite fermion non-Fermi liquid state occurs when extremely clean two dimensional electron gas is subject under magnetic field such that there are two flux quanta per electron. This state has long been viewed as a prototypical example of fermions coupled to emergent gauge field which mediates strong interaction. However the state does not show any broken symmetry and hence cannot be described using conventional order parameter formalism. Kim group and collaborators used state of art numerical scheme to calculate the bi-partite entanglement entropy which measures the quantum mechanical entanglement between a sub-region and the rest of the system. They report two unforeseen aspects: 1) there is no change in the scaling of the entaglement 2) the scaling factor which counts number of free channels for free fermions is greatly enhanced. The results can be found at:

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.206402

 Entanglement entropy scaling

Visualizing how radiation bombardment boosts superconductivity

A precision spectroscopic-imaging scanning tunneling microscope (SI-STM) developed by Davis is the first tool that can map out those three characteristics on the same material. Under Davis' guidance, Brookhaven Lab postdoctoral fellow Freek Massee (now at University Paris-Sud in France) and Cornell University graduate student Peter Sprau -- the two lead co-authors on the paper -- used the instrument's fine electron-tunneling tip to scan over the material's surface, imaging the atomic structure of the landscape below and the properties of its electrons, atom by atom. The precision allows the scientists to scan the same atoms repeatedly under different external conditions -- such as changes in temperature and ramped up magnetic fields -- to study the formation, movement, and effects of quantum vortices.

Their atomic-scale imaging studies reveal that vortex pinning -- the ability to keep those disruptive eddies in place -- depends on the shape of the high-energy ion damage tracks (specifically whether they are point-like or elongated), and also on a form of "collateral damage" discovered by the researchers far from the primary route traversed by each ion. Collaborating theorists at the University of Illinois are now using the experimental results to develop a descriptive framework the scientists can use to predict and test new approaches for materials design.

"These studies will really help us solve at which temperature which type of defects will be best for carrying a particular current," Kwok said. "The ability to achieve critical current by design is one of the ultimate goals of the Center for Emergent Superconductivity."

 

High-energy gold ions impact the crystal surface from above at the sites indicated schematically by dashed circles.

David Mermin Elected to American Philosophical Society

Congratulations to N. David Mermin for being elected to the American Philosophical Society! One of 25 Cornellians elected since 1865. Previous Cornell physicists in the APS were Hans Bethe, Michael Fisher, Bob Richardson, Ed Salpeter, and R. R. Wilson.

David Mermin