January 16, 2018
Amorphous topological insulators constructed from random point sets.
Using a set of gyroscopes linked together, physicists explored the behavior of a material whose structure is arranged randomly, instead of an orderly lattice. They found they could set off one-way ripples around the edges, much like spectators in a sports arena—a “topological wave,” characteristic of a particularly unusual state of matter.
Published Jan. 15 in Nature Physics, the discovery offers new insight into the physics of collective motion and could one day have implications for electronics, optics or other technologies.
The team, led by Assoc. Prof. William Irvine, used gyroscopes—the top-like toys you played with as a kid—as a model system to explore physics. Because gyroscopes move in three dimensions, if you connect them with springs and spin them with motors, you can observe all kinds of things about the rules that govern how objects move together.
“Everything up to this point was engineered. We thought you had to build a particular lattice, and that determines where the wave goes,” said Irvine. “But when we asked what happened if you took away the spatial order, no crystal plane, no clear structure…the answer’s yes. It just works.”
January 12, 2018
Observe particles acting coherently as they undergo phase transitions.
A study published Dec. 18 in Nature Physics by University of Chicago scientists observed how particles behave as the change takes place in minute detail. In addition to shedding light on the fundamental rules that govern the universe, understanding such transitions could help design more useful technologies.
One of the questions was whether, as particles prepare to transition between quantum states, they can act as one coherent group that “knows” the states of the others, or whether different particles only act independently of one another, or incoherently.
Cheng Chin, Professor in the James Franck Institute and Department of Physics, and his team looked at an experimental setup of tens of thousands of atoms cooled down to near absolute zero. As the system crossed a quantum phase transition, they measured its behavior with an extremely sensitive imaging system.
The conventional wisdom was that the atoms should evolve incoherently after the transition--a hallmark of older “classic” rather than quantum models of physics. “In contrast, we found strong evidence for coherent dynamics,” said graduate student Lei Feng, the first author on the study. “In no moment do they become classical particles; they always behave as waves that evolve in synchrony with each other, which should give theorists a new ingredient to include in how they model such systems that are out of equilibrium.”
November 8, 2017
Demonstrates the power of modern computing for simulating viruses.
Computer modeling has helped a team of scientists, including several scholars from the the Voth group in the JFI, to decode previously unknown details about the process by which HIV forces cells to spread the virus to other cells. The findings, published Nov. 7 in Proceedings of the National Academy of Sciences, may offer a new avenue for drugs to combat the virus.
A key part of HIV’s success is a nasty little trick to propagate itself inside the body. Once HIV has infected a cell, it forces the cell to make a little capsule out of its own membrane, filled with the virus. The capsule pinches off—a process called “budding”—and floats away to infect more cells. Once inside another unsuspecting cell, the capsule coating falls apart, and the HIV RNA gets to work.
Scientists knew that budding involves an HIV protein complex called Gag protein, but the details of the molecular process were murky. “For a while now we have had an idea of what the final assembled structure looks like, but all the details in between remained largely unknown,” said Gregory Voth, the Haig P. Papazian Distinguished Service Professor of Chemistry and corresponding author on the paper.
Since it’s been difficult to get a good molecular-level snapshot of the protein complex with imaging techniques, Voth and his team built a computer model to simulate Gag in action. Simulations allowed them to tweak the model until they arrived at the most likely configurations for the molecular process, which was then validated by experiments in the laboratory of Jennifer Lippincott-Schwartz at the National Institutes of Health and the Howard Hughes Medical Institute Janelia Research Campus.
November 7, 2017
Reveals new form of spontaneous quantum scattering in a driven many-body system.
“This is a very fundamental behavior that we have never seen before; it was a great surprise to us,” said study author Cheng Chin, Professor of Physics and in the JFI. Published Nov. 6 in Nature, the research details a curious phenomenon — seen in what was thought to be a well-understood system — that may someday be useful in quantum technology applications.
Chin’s lab studies what happens to particles called bosons in a special state called a Bose-Einstein condensate. When cooled down to temperatures near absolute zero, bosons will all condense into the same quantum state. Researchers applied a magnetic field, jostling the atoms, and they began to collide—sending some flying out of the condensate. But rather than a uniform field of random ejections, they saw bright jets of atoms shooting together from the rim of the disk, like miniature fireworks.
The tiny jets may show up in other systems, researchers said and understanding them may help shed light on the underlying physics of other quantum systems.
October 25, 2017
Recognized by ETH Zürich at Materials Day 2017 meeting.
The ETH Materials Research Prize for Young Investigators recognizes outstanding contributions of young investigators that advance materials, from fundamental to applied research. These contributions could include, for example: the discovery of new classes of materials, the observation of novel phenomena leading to either fundamentally new applications and insights, and work that substantially impacts our understanding or applications of existing materials and phenomena.
Bozhi Tian, Assistant Professor at the University of Chicago, triumphed over stiff competition. Tian researches interactions between biological and electronic systems; for example, he examines how the behaviour of cells can be mimicked with semiconducting nanomaterials or how special nanomaterials can be used to measure the electrical conductivity of cells.
“Tian combines hard and soft materials in his research and connects the living with the lifeless,” explains Ralph Spolenak, Professor of Nanometallurgy and Head of the Department of Materials at ETH Zürich. “The bridge between these two poles is a major area in today’s materials science, one that is not only important for medicine, but also enables interesting applications in many other areas.”
October 24, 2017
Utilizing gas-surface collisions on patterned silicon.
In a paper published in Physical Review Letters, a team led by Prof. Steven J. Sibener describes a way to separate isotopes of neon using a beam of gas aimed at a precisely patterned silicon wafer, which reflects the different isotopes at slightly different angles. The method could one day be a less costly and more energy-efficient way to separate isotopes for medicine, electronics and other applications.
“One can think about it like separating the various colors of light into a rainbow using a prism,” said Sibener, the Carl William Eisendrath Distinguished Service Professor of Chemistry and the James Franck Institute. “This is a wonderful and very precise demonstration study, and we are very pleased with the results,” Sibener said. “It has been a delight to run down to the lab every day to see what’s happened. We’re very much looking forward to planning the next steps in this project to explore other atoms and molecules.”
October 18, 2017
For experiments and theory on the topological aspects of fluid dynamics and mechanical metamaterials.
William Irvine was recently elected a Fellow of the American Physical Society, nominated by the Topical Group on Soft Matter. The criterion for APS Fellow election is exceptional contributions to the physics enterprise; e.g., outstanding physics research, important applications of physics, leadership in or service to physics, or significant contributions to physics education. Fellowship is a distinct honor signifying recognition by one's professional peers.
Research for the Irvine group was recently featured on the cover of Physics Today. The Irvine Group at the University of Chicago has put a new twist on the smoke ring. Instead of blowing smoke into the air to create and visualize swirling flows known as vortex rings, they drove 3D-printed hydrofoils, lined with fluorescent dye, through water. Here, the wispy outer ring of white dye reveals a vortex ring; the orange and green trails are a tomographic reconstruction of the ring’s evolution over time. To learn how the group’s technique helped unveil hidden structure in fluid vortices, see the story.
October 11, 2017
Awarded for Study of Exciton Interactions in Semiconductor Nanostructures.
The Young Investigator Program is open to scientists and engineers at research institutions across the United States who received Ph.D. or equivalent degrees in the last five years and who show exceptional ability and promise for conducting basic research. The objective of this program is to foster creative basic research in science and engineering, enhance early career development of outstanding young investigators, and increase opportunities for the young investigators to recognize the Air Force mission and the related challenges in science and engineering.
September 20, 2017
Layer-by-layer assembly of two-dimensional materials into wafer-scale heterostructures.
In a study published Sept. 20 in Nature, UChicago and Cornell University researchers describe an innovative method to make stacks of semiconductors just a few atoms thick. The technique offers scientists and engineers a simple, cost-effective method to make thin, uniform layers of these materials, which could expand capabilities for devices from solar cells to cell phones.
“The scale of the problem we’re looking at is, imagine trying to lay down a flat sheet of plastic wrap the size of Chicago without getting any air bubbles in it,” said Jiwoong Park, a UChicago professor in the Department of Chemistry, the Institute for Molecular Engineering and the James Franck Institute, who led the study. “When the material itself is just atoms thick, every little stray atom is a problem. We expect this new method to accelerate the discovery of novel materials, as well as enabling large-scale manufacturing,” Park said.
September 6, 2017
Recognized at biennial conference on Bose-Einstein Condensation.
The 2017 Junior BEC Award is given to Cheng Chin for important contributions to the field of Bose-Einstein condensation, including the study of Feshbach resonances, scale invariance in 2D Bose gases, and universality near a quantum phase transition in 2D optical lattices.
August 23, 2017
Chemical & Engineering News identifies young rising stars.
Recognized as a "Bioelectronics Boss" who turns common reagents into unconventional materials, twists ordinary lab procedures into uncommon ones, and finds ways of using his creations in nontraditional applications.
“Bozhi is the real definition of an interdisciplinary scientist,” says fellow Chicago chemistry professor Andrei Tokmakoff. He adds that Tian is also fearless, thoughtful, and soft-spoken, which is unusual in the materials business, where there can be a lot of bluster.
August 16, 2017
Mathematical model helps explain animals’ decision-making process.
The C. elegans roundworm sees by eating, sucking in big gulps of bacteria to learn about its surrounding environment. As researchers watched, they noticed an odd pattern marked by “bursts” of eating.
JFI researchers including the Dinner group develeoped a mathematical model to explain such eating bursts. The findings, published Aug. 10 in Proceedings of the National Academy of Sciences, help inform a broader understanding of animals’ feeding behavior and the science of decision-making.
“It’s an interesting model for understanding the processes that underlie how animals decide where and when to eat,” said lead author Monika Scholz, a Howard Hughes Medical Institute international student research fellow with UChicago’s Biophysical Sciences program and now at Princeton University. “For these worms, it’s all about the balance between speed and accuracy.”
August 3, 2017
Clever experiment documents multi-scale fluid dynamics.
The new findings, published Aug. 3 in Science, are the first to show that helicity maintains a constant value during the flow of viscous fluids. Vortex dynamics have important applications in everyday life; meteorologists, for example, view helicity as a factor that contributes to the formation of supercell tornadoes.
“The fact that we have some measurements for the first time that show helicity can be preserved, especially in the presence of stretching, can translate directly to those efforts,” said William Irvine, an Associate Professor of Physics in the James Franck Institute, who published the findings along with four co-authors.
Simulating helicity in those flows has been difficult because of the widely separated yet interconnecting scales in which they operate. Previous work had been largely theoretical and involved hypothetical, simpler fluids totally lacking in viscosity. Calculations showed that helicity was conserved in these hypothetical fluids, but viscosity emerged as a significant factor in the flow of actual fluids.
“One of the core problems is that you need to sample or measure features of the flow that exist on very different length scales,” said Martin Scheeler, the study’s lead author, who recently completed his Doctorate in Physics in the JFI. The scales range from the diameter of a vortex (approximately 30 centimeters or one foot) to the diameter of its thin core (approximately one milllimeter or three hundredths of an inch).
“You need to measure the flow inside the core as well as the overall shape evolution of that vortex,” Irvine said. “That’s quite a separation.” Irvine characterized Scheeler’s work in overcoming the experimental challenges— simultaneously tracking the fine details of the flow while still measuring the critical larger-scale dynamics—as “a tour de force.”
July 27, 2017
New method promises easier nanoscale manufacturing.
The new research, published in Science, is expected to make such materials easily available for eventual use in everything from LED displays to cellular phones to photodetectors and solar cells. Though nanomaterials are promising for future devices, ways to build them into complex structures have been limited and small-scale.
“This is a step needed to move quantum dots and many other nanomaterials from proof-of-concept experiments to real technology we can use,” said co-author Dmitri Talapin, Professor of Chemistry in the James Franck Institute and Scientist with the Center for Nanoscale Materials at Argonne. “It really expands our horizons.”
The new technique, called DOLFIN, makes different nanomaterials directly into “ink” in a process that bypasses the need to lay down a polymer stencil. Talapin and his team carefully designed chemical coatings for individual particles. These coatings react with light, so if you shine light through a patterned mask, the light will transfer the pattern directly into the layer of nanoparticles below—wiring them into useful devices.
“We found the quality of the patterns was comparable to those made with state-of-the-art techniques,” said lead author Yuanyuan Wang, postdoctoral researcher in the Talapin group. “It can be used with a wide range of materials, including semiconductors, metals, oxides or magnetic materials—all commonly used in electronics manufacturing.”
The team is working toward commercializing the DOLFIN technology in partnership with UChicago’s Polsky Center for Entrepreneurship and Innovation.
June 27, 2017
Arriving in Autumn 2017.
The JFI is pleased to welcome the Vitelli group to campus in Autumn 2017.