Professor Nadya Mason has been elected a Fellow of the American Physical Society (APS) "for seminal contributions to the understanding of electronic transport in low dimensional conductors, mesoscopic superconducting systems, and topological quantum materials."
Mason is an experimental condensed matter physicist who has earned a reputation for her deep-sighted and thorough lines of attack on the most pressing problems in strongly correlated nanoscale physics.
Recently, a team of scientists led by Pablo Jarillo-Herrero at the Massachusetts Institute of Technology (MIT) created a huge stir in the field of condensed matter physics when they showed that two sheets of graphene twisted at specific angles—dubbed “magic-angle” graphene—display two emergent phases of matter not observed in single sheets of graphene. Graphene is a honeycomb lattice of carbon atoms—it’s essentially a one-atom-thick layer of graphite, the dark, flaky material in pencils.
Researchers at the University of Illinois at Urbana-Champaign have recently shown that the insulating behavior reported by the MIT team has been misattributed. Professor Philip Phillips, a noted expert in the physics of Mott insulators, says a careful review of the MIT experimental data by his team revealed that the insulating behavior of the “magic-angle” graphene is not Mott insulation, but something even more profound—a Wigner crystal.
Now, a novel sample-growing technique developed at the U. of I. has overcome these obstacles. Developed by physics professor James Eckstein in collaboration with physics professor Tai-Chang Chiang, the new “flip-chip” TI/SC sample-growing technique allowed the scientists to produce layered thin-films of the well-studied TI bismuth selenide on top of the prototypical SC niobium—despite their incompatible crystalline lattice structures and the highly reactive nature of niobium.
These two materials taken together are ideal for probing fundamental aspects of the TI/SC physics, according to Chiang: “This is arguably the simplest example of a TI/SC in terms of the electronic and chemical structures. And the SC we used has the highest transition temperature among all elements in the periodic table, which makes the physics more accessible. This is really ideal; it provides a simpler, more accessible basis for exploring the basics of topological superconductivity,” Chiang comments.
Researchers have produced a “human scale” demonstration of a new phase of matter called quadrupole topological insulators that was recently predicted using theoretical physics. These are the first experimental findings to validate this theory.
The researchers report their findings in the journal Nature.
The team’s work with QTIs was born out of the decade-old understanding of the properties of a class of materials called topological insulators. “TIs are electrical insulators on the inside and conductors along their boundaries, and may hold great potential for helping build low-power, robust computers and devices, all defined at the atomic scale,” said mechanical science and engineering professor and senior investigator Gaurav Bahl.
The uncommon properties of TIs make them a special form of electronic matter. “Collections of electrons can form their own phases within materials. These can be familiar solid, liquid and gas phases like water, but they can also sometimes form more unusual phases like a TI,” said co-author and physics professor Taylor Hughes.
On Thursdays throughout the semester, staff writer Adalberto Toledo will book an appointment with a UI professor. Today: physics professor NADYA MASON, director of the new Materials Research Science and Engineering Center.
Theorists have discovered topological insulators that are insulating in their interior and on their surfaces but have conducting channels at corners or along edges.
Excitonium has a team of researchers at the University of Illinois at Urbana-Champaign… well… excited! Professor of Physics Peter Abbamonte and graduate students Anshul Kogar and Mindy Rak, with input from colleagues at Illinois, University of California, Berkeley, and University of Amsterdam, have proven the existence of this enigmatic new form of matter, which has perplexed scientists since it was first theorized almost 50 years ago.
The team studied non-doped crystals of the oft-analyzed transition metal dichalcogenide titanium diselenide (1T-TiSe2) and reproduced their surprising results five times on different cleaved crystals. University of Amsterdam Professor of Physics Jasper van Wezel provided crucial theoretical interpretation of the experimental results.
The American Chemical Society (ACS), through its Division of History of Chemistry, has an award that acknowledges these greatest of strides: the Chemical Breakthrough Awards are presented annually in recognition of “seminal chemistry publications, books, and patents that have been revolutionary in concept, broad in scope, and long-term in impact.” These awards are made to the department where the breakthrough occurred, not to the individual scientists or inventors.
This year, the ACS honored the discovery of “J-coupling” (also known as spin-spin coupling) in liquids, a breakthrough that enabled scientists to use Nuclear Magnetic Resonance (NMR) spectroscopy to identify atoms that are joined by a chemical bond and so to determine the structure of molecules.
Innovative materials are the foundation of countless breakthrough technologies, and the Illinois Materials Research Science and Engineering Center will develop them. The new center is supported by a six-year, $15.6 million award from the National Science Foundation’s Materials Research Science and Engineering Centers program. It is led by U of I Professor of Physics Nadya Mason and will be situated in the Frederick Seitz Materials Research Laboratory, part of the Department of Physics complex.
The Illinois Materials Research Science and Engineering Center will build highly interdisciplinary teams of researchers and students to study two types of materials. One research group will study new magnetic materials, where ultra-fast magnetic switching could form the basis of smaller, more robust magnetic memory storage. The second group will design materials that can withstand bending and crumpling that typically destroys the properties of those materials—and will even create materials where crumpling enhances performance. This would enable materials in better contact with our bodies, because our limbs, skin, and even cells bend and move dynamically at both the macro- and microscale. In this way, such materials can form the basis of wearable electronics or medical devices that interface with, conform to, and move with our bodies.
Quanta Magazine recently spoke with Goldenfeld about collective phenomena, expanding the Modern Synthesis model of evolution, and using quantitative and theoretical tools from physics to gain insights into mysteries surrounding early life on Earth and the interactions between cyanobacteria and predatory viruses. A condensed and edited version of that conversation follows.
Researchers at the University of Illinois at Urbana-Champaign and Princeton University have theoretically predicted a new class of insulating phases of matter in crystalline materials, pinpointed where they might be found in nature, and in the process generalized the fundamental quantum theory of Berry phases in solid state systems. What’s more, these insulators generate electric quadrupole or octupole moments—which can be thought of roughly as very specific electric fields—that are quantized. Quantized observables are a gold standard in condensed matter research, because experimental results that measure these observables have to, in principle, exactly match theoretical predictions—leaving no wiggle room for doubt, even in highly complex systems.
The research, which is the combined effort of graduate student Wladimir Benalcazar and Associate Professor of Physics Taylor Hughes of the Institute for Condensed Matter Theory at the U. of I., and Professor of Physics B. Andrei Bernevig of Princeton, is published in the July 7, 2017 issue of the journal Science.
Since the discovery two decades ago of the unconventional topological superconductor Sr2RuO4, scientists have extensively investigated its properties at temperatures below its 1 K critical temperature (Tc), at which a phase transition from a metal to a superconducting state occurs. Now experiments done at the University of Illinois at Urbana-Champaign in the Madhavan and Abbamonte laboratories, in collaboration with researchers at six institutions in the U.S., Canada, United Kingdom, and Japan, have shed new light on the electronic properties of this material at temperatures 4 K above Tc. The team’s findings may elucidate yet-unresolved questions about Sr2RuO4’s emergent properties in the superconducting state.
In a surprising new discovery, alpha-tin, commonly called gray tin, exhibits a novel electronic phase when its crystal structure is strained, putting it in a rare new class of 3D materials called topological Dirac semimetals (TDSs). Only two other TDS materials are known to exist, discovered as recently as 2013. Alpha-tin now joins this class as its only simple-element member.
This discovery holds promise for novel physics and many potential applications in technology. The findings are the work of Caizhi Xu, a physics graduate student at the University of Illinois at Urbana-Champaign, working under U. of I. Professor Tai-Chang Chiang and in collaboration with scientists at the Advanced Light Source at the Lawrence Berkeley National Laboratory and six other institutions internationally.
Topological insulators, an exciting, relatively new class of materials, are capable of carrying electricity along the edge of the surface, while the bulk of the material acts as an electrical insulator. Practical applications for these materials are still mostly a matter of theory, as scientists probe their microscopic properties to better understand the fundamental physics that govern their peculiar behavior.
Using atomic quantum-simulation, an experimental technique involving finely tuned lasers and ultracold atoms about a billion times colder than room temperature, to replicate the properties of a topological insulator, a team of researchers at the University of Illinois at Urbana-Champaign has directly observed for the first time the protected boundary state (the topological soliton state) of the topological insulator trans-polyacetylene. The transport properties of this organic polymer are typical of topological insulators and of the Su-Schrieffer-Heeger (SSH) model.
Physics graduate students Eric Meier and Fangzhao Alex An, working with Professor Bryce Gadway, developed a new experimental method, an engineered approach that allows the team to probe quantum transport phenomena.
The other half of the Nobel prize, awarded for “topological phase transitions,” also unites topology and physics, but “topology enters in a somewhat different way,” says Eduardo Fradkin, a physicist at the University of Illinois Urbana-Champaign.
Relevant here is the fact that topological properties often cannot be determined locally. An ant sitting on a pastry can’t tell by looking around whether the perch is a bun, bagel, or pretzel.
Physics professor Taylor Hughes and mechanical science and engineering professor Gaurav Bahl of the University of Illinois at Urbana-Champaign are part of an interdisciplinary team that will study non-reversible sound wave propagation over the next four years, with a range of promising potential applications.
The National Science Foundation has announced a $2-million research award to the team, which includes University of Oregon physics professor Hailin Wang and Duke University electrical and computer engineering professor Steven Cummer. The grant is part of a broader $18-million NSF-funded initiative, the Emerging Frontiers in Research and Innovation (EFRI) program, supporting nine teams—a total of 37 researchers at 17 institutions—to pursue fundamental research in the area of new light and acoustic wave propagation, known as NewLAW.