Manuel Franco Sevilla Joins UMD Physics

Manuel Franco Sevilla installs ODMB modules into the CMS detector at CERN. (Photo: Jeff Richman)

Manuel Franco Sevilla has joined the Department of Physics as an assistant professor. He recently completed a postdoctoral appointment at the University of California at Santa Barbara.

Franco Sevilla received his Ph.D. in experimental particle physics at Stanford University, working on the BaBar experiment at the SLAC National Accelerator Laboratory. At SLAC he did seminal work on lepton universality, a fundamental assumption within the Standard Model (SM) of particle physics that states that the interactions of all charged leptons differ only because of their different masses. Franco Sevilla’s work challenges this assumption and helped launch a new area of studies in the experimental programs at the CERN Large Hadron Collider (LHC) and B factories, stimulating many possible interpretations based on physics beyond the SM.

As a postdoctoral researcher, Dr. Franco Sevilla moved to the Compact Muon Solenoid (CMS) experiment at the LHC, where he made major contributions both to the development of particle detector instruments as well as to the physics analysis of the data in the area of Supersymmetry. In 2014 he was recognized with a CMS Achievement Award for “outstanding design and construction of the 72 Optical Data MotherBoards (ODMB) that control and read out” the complex electronics needed in this part of the operation, and during 2016-2018 he was appointed Coordinator of the CMS Cathode Strip Chambers (CSCs) upgrade for the high luminosity LHC and Deputy Project Manager of the CSC group.

He now joins the LHCb experiment at CERN and looks forward to continuing his research on lepton universality violation and engaging students in the study of today’s open questions in fundamental physics. Additionally, he will contribute to the development of the electronics for a new tracker detector to be installed in LHCb in 2020.

 MFS CERN 2smManuel Franco Sevilla installs ODMB modules into the CMS detector at CERN. (Photo credit: Jeff Richman)

Juan Maldacena Awarded Prange Prize

Juan Maldacena of the Institute for Advanced Study has been named the 2018 recipient of the Richard E. Prange Prize and Lectureship in Condensed Matter Theory and Related Areas. Dr. Maldacena will receive a $10,000 honorarium. He delivered a public lecture entitled "Black Holes and the Structure of Spacetime” at the University of Maryland, College Park on October 2, 2018, and also gave a Condensed Matter Theory Center/Joint Quantum Institute seminar entitled “Wormholes and Entangled States” on Monday, October 1.

The Prange Prize, established by the UMD Department of Physics and Condensed Matter Theory Center (CMTC), honors the late Professor Richard E. Prange, whose distinguished professorial career at Maryland spanned four decades (1961-2000). The Prange Prize is made possible by a gift from Dr. Prange's wife, Dr. Madeleine Joullié, a professor of chemistry at the University of Pennsylvania.

Maldacena received his Ph.D. in 1996 at Princeton University, focusing on black holes in string theory. Just a few years later, he received a MacArthur Fellowship and tenure at Harvard University. He studies quantum gravity, string theory, quantum field theory and quantum entanglement. Among his honors are the Albert Einstein Medal, the Lorentz Medal, the Fundamental Physics Prize, the Dirac Prize and Medal, the Dannie Heineman Prize for Mathematical Physics, the Sackler Prize, a Packard Fellowship and a Sloan Fellowship. He is a member of the National Academy of Sciences.

Maldacena is most known for his 1997 solo theoretical discovery of a deep connection between gauge theories, which describe the world of particle physics at the microscopic scale, and quantum gravity, which describes the physics of gravitational forces holding the universe together. This famous Maldacena gauge-gravity (or AdS/CFT) duality, arguably the most important theoretical physics result of the last 30 years, has remained a topic of great fundamental interest in particle physics, string theory, gravity, nuclear physics, and condensed matter physics, and is one of the most actively-studied topics in theoretical physics. In particular, Maldacena conjectured that certain strongly-interacting quantum field theories are equivalent to certain weakly-interacting theories of gravity, leading to new insights in all of physics. This work of Maldacena, receiving in excess of 10,000 citations, is among the most cited papers in all of science over the last 20 years.

Maldacena’s Prange Prize lecture was given in Room 1412 of UMD’s John S. Toll Physics Building at 4:00 p.m. on Tuesday, October 2.

At the University of Chicago, Richard Prange received his Ph.D. under Nobelist Yoichiro Nambu and also worked with Murray Gell-Mann and Marvin Goldberger. At the University of Maryland, he edited a highly-respected book on the quantum Hall effect and made important theoretical contributions to the subject. His interests extended into all aspects of theoretical physics, and continued after his retirement. Dr. Prange was a member of the Maryland condensed matter theory group for more than 40 years and was an affiliate of CMTC since its inception in 2002.

"Richard enjoyed a fascinating and fulfilling career at the University of Maryland exploring condensed matter physics, and even after retirement was active in the department," said Dr. Joullié. "He spent the very last afternoon of his life in the lecture hall for a colloquium on graphene, followed by a vigorous discussion. And so I was happy to institute the Prange Prize, to generate its own robust discussions in condensed matter theory."

"The Prange Prize provides a unique opportunity to acknowledge transformative work in condensed matter theory, a field that has proven to be an inexhaustible source of insights and discoveries in both fundamental and applied physics,” said Dr. Sankar Das Sarma, who holds the Richard E. Prange Chair in Physics at UMD and is also a Distinguished University Professor and director of the CMTC.

Since its initiation in 2009, the Prange Prize has been awarded to Philip W. Anderson, Walter Kohn, Daniel Tsui, Andre Geim, David Gross, Klaus von Klitzing, and Frank Wilczek.

 

    

 

Modified Superconductor Synapse Reveals Exotic Electron Behavior

JQI researchers modified a Josephson junction to include a sliver of topological crystalline insulator (TCI). Using this circuit, they detected signs of exotic quantum states lurking on the TCI's surface. (Credit: E. Edwards/JQI)

Electrons tend to avoid one another as they go about their business carrying current. But certain devices, cooled to near zero temperature, can coax these loner particles out of their shells. In extreme cases, electrons will interact in unusual ways, causing strange quantum entities to emerge.

At the Joint Quantum Institute (JQI), a group, led by Jimmy Williams, is working to develop new circuitry that could host such exotic states. “In our lab, we want to combine materials in just the right way so that suddenly, the electrons don’t really act like electrons at all,” says Williams, a JQI Fellow and an assistant professor in the University of Maryland Department of Physics. “Instead the surface electrons move together to reveal interesting quantum states that collectively can behave like new particles.”

These states have a feature that may make them useful in future quantum computers: They appear to be inherently protected from the destructive but unavoidable imperfections found in fabricated circuits. As described recently in Physical Review Letters, Williams and his team have reconfigured one workhorse superconductor circuit—a Josephson junction—to include a material suspected of hosting quantum states with boosted immunity.

Josephson junctions are electrical synapses comprised of two superconductors separated by a thin strip of a second material. The electron movement across the strip, which is usually made from an insulator, is sensitive to the underlying material characteristics as well as the surroundings. Scientists can use this sensitivity to detect faint signals, such as tiny magnetic fields. In this new study, the researchers replaced the insulator with a sliver of topological crystalline insulator (TCI) and detected signs of exotic quantum states lurking on the circuit’s surface.

Physics graduate student Rodney Snyder, lead author on the new study, says this area of research is full of unanswered questions, down to the actual process for integrating these materials into circuits. In the case of this new device, the research team found that beyond the normal level of sophisticated material science, they needed a bit of luck.

“I'd make like 16 to 25 circuits at a time. Then, we checked a bunch of those and they would all fail, meaning they wouldn’t even act like a basic Josephson junction,” says Snyder. “We eventually found that the way to make them work was to heat the sample during the fabrication process. And we only discovered this critical heating step because one batch was accidentally heated on a fluke, basically when the system was broken.”

Once they overcame the technical challenges, the team went hunting for the strange quantum states. They examined the current through the TCI region and saw dramatic differences when compared to an ordinary insulator. In conventional junctions, the electrons are like cars haphazardly trying to cross a single lane bridge. The TCI appeared to organize the transit by opening up directional traffic lanes between the two locations. 

The experiments also indicated that the lanes were helical, meaning that the electron’s quantum spin, which can be oriented either up or down, sets its travel direction. So in the TCI strip, up and down spins move in opposite directions. This is analogous to a bridge that restricts traffic according to vehicle colors—blue cars drive east and red cars head west. These kinds of lanes, when present, are indicative of exotic electron behaviors.

Just as the careful design of a bridge ensures safe passage, the TCI structure played a crucial role in electron transit. Here, the material’s symmetry, a property that is determined by the underlying atom arrangement, guaranteed that the two-way traffic lanes stayed open. “The symmetry acts like a bodyguard for the surface states, meaning that the crystal can have imperfections and still the quantum states survive, as long as the overall symmetry doesn’t change,” says Williams.

Physicists at JQI and elsewhere have previously proposed that built-in bodyguards could shield delicate quantum information. According to Williams, implementing such protections would be a significant step forward for quantum circuits, which are susceptible to failure due to environmental interference.

In recent years, physicists have uncovered many promising materials with protected travel lanes, and researchers have begun to implement some of the theoretical proposals. TCIs are an appealing option because, unlike more conventional topological insulators where the travel lanes are often given by nature, these materials allow for some lane customization. Currently, Williams is working with materials scientists at the Army Research Laboratory to tailor the travel lanes during the manufacturing process. This may enable researchers to position and manipulate the quantum states, a step that would be necessary for building a quantum computer based on topological materials.

In addition to quantum computing, Williams is driven by the exploration of basic physics questions. “We really don't know yet what kind of quantum matter you get from collections of these more exotic states,” Williams says. “And I think, quantum computation aside, there is a lot of interesting physics happening when you are dealing with these oddball states.”

Written by E. Edwards and S. Elbeshbishi

RESEARCH CONTACT
Jimmy Williams  This email address is being protected from spambots. You need JavaScript enabled to view it.