Author: Richard Jones

Professor Munirul Islam: Celebrating His Life and His Legacy

Dear Colleagues:

I would like to share some thoughts on Munir Islam who recently passed away. Prof. Islam came to UConn in 1967 from a faculty position at Brown University. In the late 1970s there were two particle theorists at UConn, Profs. Kurt Haller and Munir Islam. They set about building an elementary-particle theory program here and garnered the support of then Physics Head Joe Budnick and CLAS Dean Julius Elias. They soon obtained funding for a new Department of Energy initiative to support particle theory in the Department. In 1979 they
were able to bring me in as an Associate Professor and Mark Swanson as an Assistant Professor. So eager were Kurt and Munir to bring us in, they chose to forego the summer salary that they had been awarded on the DOE grant.  The impact of the DOE grant on the UConn administration was quite far reaching and led to further internal support. Within a few years I had been tenured and promoted to Full and Mark had been tenured and appointed to Associate at our Stamford branch, where he later became an administrator.

After that, Kurt and Munir were able to secure a bridge position with the DOE that would provide five years of support, provided the UConn administration would create a tenure track position for the recipient. This they agreed to do, and so we brought in Daniel Caldi at the Assistant level, who subsequently was appointed Associate with tenure. Dan eventually opted to leave us for SUNY Buffalo, but our particle group was then able to convince the UConn administration to let us keep the position, and we then hired Gerald Dunne. Gerald went up the ladder very quickly to tenured Full professor. The success of our program enabled us subsequently to bring in Alex
Kovner, followed by Tom Blum (both now tenured Full) and current Assistant Luchang Jin. The success and endurance of the particle group for more than forty years now is a testament to the foresight and the unwavering and unabating commitment of Kurt and Munir to it, and it serves as permanent memorial to both of them.

Munir Islam always retained an enthusiasm for research, an enthusiasm which did not diminish at all after he retired. He focused on fundamental problems in particle physics, with particular emphasis on the theory of the structure of the proton as revealed by high-energy proton-proton scattering. This is perhaps best evidenced in what essentially became a lifelong collaboration with his former graduate student Richard Luddy (at the right, with Prof Islam at the left in the above photograph) as the two of them grappled with Munir’s deep ideas on proton scattering during many of Munir’s later years as a Professor and then as an Emeritus. Munir had a gift for simple pictorial explanations of his research, which he was able to explain lucidly in a lecture for visiting high-school teachers and students during an open house. Munir was urbane, worldly, and wise, and it was a great joy to have him not just as a colleague but also as a friend. He will be sorely missed by all of those that knew him and especially by me as my career owes so much to him. In appreciation, Philip Mannheim.In appreciation,

Philip Mannheim.

A Signal from Beyond

Looking for ripples in the fabric of spacetime.

UConn astrophysicist Chiara Mingarelli is part of a team of researchers who recently published data on a hint of a signal that sent ripples of excitement through the physics community. These monumental findings are the culmination of twelve and a half years of data gathered from NANOGrav — a network of pulsars across the galaxy — all in the hopes of detecting gravitational waves.

Gravitational waves are generated when galaxies merge and supermassive black holes at their centers collide and send low-frequency gravitational waves out into the universe. The team thinks the source of the signal could be gravitational waves, but it will take about 2 more years of data to be sure.

The findings sparked the interest of other physicists with their own speculations about the signal, such as cosmic strings or primordial black holes. Though still a couple of years away, Mingarelli says the final results could also help test General Relativity or even open the door to entirely new physics.

This article first appeared on UConn Today, February 15, 2021

Jonathan Trump wins NSF Early Career Award

Jonathan Trump, Assistant Professor of Physics, will receive $738,090 over five years to compile a census of supermassive black holes in the universe. This will give insights into how supermassive black holes and galaxies evolve across cosmic time. Trump will also develop a bridge program for underrepresented undergraduate physics majors at UConn to increase their participation in STEM fields.
The NSF Faculty Early Career Development (CAREER) Program supports early-career faculty who have the potential to serve as academic role models in research and education, and to lead advances in the mission of their department or organization. Activities pursued by early-career faculty build a firm foundation for a lifetime of leadership in integrating education and research.
Trump was one of 7 junior faculty at the University of Connecticut to receive the prestigious Early Career awards from NSF in 2020. For a description of all 7 awards, see this recent article published in UConn Today.

Radiation Damage Spreads

Radiation Damage Spreads Among Close Neighbors

X-ray absorption cascade
Direct hit. A soft x-ray (white) hits a holmium atom (green). A photo-electron zooms off the holmium atom, which releases energy (purple) that jumps to the 80-carbon fullerene cage surrounding the holmium. The cage then also loses an electron. (Courtesy of Razib Obaid)

 – Kim Krieger – UConn Communications

A single x-ray can unravel an enormous molecule, physicists report in the March 17 issue of Physical Review Letters. Their findings could lead to safer medical imaging and a more nuanced understanding of the electronics of heavy metals.

Medical imaging techniques such as MRIs use heavy metals from the bottom of the periodic table as “dyes” to make certain tissues easier to see. But these metals, called lanthanides, are toxic. To protect the person getting the MRI, some chemists wrap the lanthanide inside a cage of carbon atoms.

Molecular physicist Razib Obaid and his mentor, Prof. Nora Berrah in the physics department, wanted to know more about how the lanthanides interact with the carbon cages they’re wrapped in. The cages, 80 carbon atoms strong, are called fullerenes and are shaped like soccer balls. They don’t actually bond to the lanthanide; the metal floats inside the cage. There are many similar situations in nature. Proteins, for example, often have a metal hanging out close to a giant organic (that is, mostly made of carbon) molecule.

So Obaid and his team of collaborators from Kansas State University, Pulse Institute at Stanford, Max Planck Institute at Heidelberg, and the University of Heidelberg studied how three atoms of the lanthanide element holmium inside of an 80-carbon fullerene reacted to x-rays. Their initial guess was that when an x-ray first hit one of the holmium atoms, it would get absorbed by an electron. But that electron would be so energized by the absorbed x-ray that  it would fly right out of the atom, leaving a vacant spot. That spot would than get taken by another of the holmium’s electrons, which would have to jump down from the outer edge of the atom to fill it. That electron had formerly been partnered with another electron on the outskirts of the atom. When it jumped down, its lonely ex, called an Auger electron, would zoom away from the whole molecule and get detected by the scientists.  Its distinctive energy would give it away. 

It sounds complicated, but that would have been the simplest (and thus most likely) scenario, the physicists thought. But it’s not what they saw.

When Obaid and his colleagues zapped the holmium-fullerene molecule with a soft x-ray (about 160 electron-volts), the number of the Auger electrons detected was too low. And too many of the electrons had energies much less than the Auger electrons should have. 

After some calculating, the team figured out there was more going on than they’d guessed.

First, the x-ray would hit the holmium, which would lose an electron. The vacant spot would then be filled by the outer edge electron from the holmium atom. That much was correct. But the energy released by the jumping electron (when it jumps ‘down’ from the outskirts of the atom to the interior, it also jumps ‘down’ in energy) would then be absorbed by the carbon fullerene cage or another of the neighboring holmium atoms. In either case, the energy would cause an additional electron to zoom away from whatever absorbed it, the fullerene cage or the holmium atom.

Losing these multiple electrons destabilized the whole molecule, which would then fall apart entirely.

The end result?

“You can induce radiation damage just by striking one atom out of 84,” says Obaid. That is, a single x-ray strike is  enough to destroy the entire molecule complex through this energy transfer process involving neighboring atoms. It gives some insight into how radiation damage occurs in living systems, Obaid says. It was always thought that radiation damaged tissue by stripping away electrons directly. This experiment shows that interactions between an ionized atom or molecule and its neighbors can cause even more damage and decay than the original irradiation.

The work also gives medical physicists an idea of how to limit patient’s exposure to heavy metals used as dyes in medical imaging. Shielding all parts of the body from the radiation except for those to be imaged with heavy metal dyes can potentially restrict the heavy metal exposure as well as the radiation damage, the researchers say. The next step of this work would be to understand exactly how fast this interaction with the neighbors occurs. The researchers expect it to take place in just a few femtoseconds (10-15 s). 

The work was funded by Department of Energy, Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences, and Biosciences, under Grant No. DE-SC0012376.

UConn seismometer detects Puerto Rico event

 

The Geophysics research group (Prof. Vernon Cormier and students) operate a seismic wave station that continuously monitors vibrations in the earth’s crust, many of which arise from seismic events that happen far away. These waves travel through the deep earth, and eventually make their way to the surface where they are detected. The above figures show high frequency and low frequency filtered seismograms recorded at UConn’s seismic station for the vertical component of ground motion from the earthquakes in Puerto Rico on January 7, 2020.  The 3 bursts of energy are P and S elastic waves, followed by a T wave, which propagates as an acoustic wave in the ocean.  In the high frequency seismogram (first figure), the large red trace is the main shock and the black trace below it is an aftershock. In the low frequency filtered seismogram (second figure), the largest energy propagates as a surface wave trapped in Earth’s crust and upper most mantle, with energy exponentially decaying into the mantle. Amplitude scale for ground particle velocity is shown by a bar in the upper left corner.

Insight from APS: Careers in Physics

What is a Bachelors of Science degree in Physics good for? What kinds of jobs are available to graduates who complete a 4-year degree in physics, but decide not to pursue an advanced degree? How does a physics degree stack up against other STEM fields in terms of employment options in today's highly competitive job market? Each year the American Physical Society gathers data to help answer questions like these, which they post on their physics careers web site and summarize in their Insight Slideshow. Scroll inside the window below to browse the latest edition of Insight.

Ron Mallett Featured on NBC Connecticut

Could traveling into the past be part of our future? Quite possibly, says Ron Mallett, a UConn emeritus professor of physics who has studied the concept of time travel for decades. Earlier this month, he spoke with NBC Connecticut reporter Kevin Nathan about his life and work as a theoretical physicist, and discussed how time travel may be possible someday.

View the video on nbc.com

Astronomer Jonathan Trump interviewed on UConn 360

UConn Astrophysicist and observational astronomer Jonathan Trump was a recent guest on UConn 360, a podcast from the Storrs campus of the University of Connecticut. In this conversation, Jonathan tells about how attending a lecture as an undergraduate at Penn State captured his interest and changed the course of his professional career. Now Jonathan offers similar career-changing opportunities to UConn students, who just this year have applied for and obtained dedicated time for observations by the Hubble space telescope.

Breaking Up is Hard To Do (for Electrons in High Temperature Superconductors)

Physics researcher Ilya Sochnikov next to a dilution refrigerator in the Gant Complex on July 16, 2019. (Sean Flynn/UConn Photo)

Physicists used to think that superconductivity – electricity flowing without resistance or loss – was an all or nothing phenomenon. But new evidence suggests that, at least in copper oxide superconductors, it’s not so clear cut.

Superconductors have amazing properties, and in principle could be used to build loss-free transmission lines and magnetic trains that levitate above superconducting tracks. But most superconductors only work at temperatures close to absolute zero. This temperature, called the critical temperature, is often only a few degrees Kelvin and requires liquid helium to stay that cold, making such superconductors too expensive for most commercial uses. A few superconductors, however, have a much warmer critical temperature, closer to the temperature of liquid nitrogen (77K), which is much more affordable. 

Many of these higher-temperature superconductors are based on a two-dimensional form of copper oxide. 

“If we understood why copper oxide is a superconductor at such high temperatures, we might be able to synthesize a better one” that works closer to room temperature (293K), says UConn physicist Ilya Sochnikov.

Sochnikov and his colleagues at Rice University, Brookhaven National Lab and Yale recently figured out part of that puzzle, and they report their results in the latest issue of Nature.

Their discovery was about how electrons behave in copper oxide superconductors. Electrons are the particles that carry electric charge through our everyday electronics. When a bunch of electrons flow in the same direction, we call that an electric current. In a normal electric circuit, say the wiring in your house, electrons bump and jostle each other and the surrounding atoms as they flow. That wastes some energy, which leaves the circuit as heat. Over long distances, that wasted energy can really add up: long-distance transmission lines in the U.S. lose on average 5% of their electricity before reaching a consumer, according to the Energy Information Administration. 

But in a superconductor below its critical temperature, electrons behave totally differently. Instead of bumping and jostling, they pair up and move in sync with the other electrons in a kind of wave. If electrons in a normal current are a rushing, uncoordinated mob, electrons in a superconductor are like dancing couples, gliding across the floor like people in a ballroom. It’s this friction-free dance – coherent motion – of paired electrons that makes a superconductor what it is.

The electrons are so happy in pairs in a superconductor that it takes a certain amount of energy to pull them apart. Physicists can measure this energy with an experiment that measures how big a voltage is needed to tear an electron away from its partner. They call it the ‘gap energy’. The gap energy disappears when the temperature rises above the critical temperature and the superconductor changes into an ordinary material. Physicists assumed this is because the electron pairs have broken up. And in classic, low-temperature superconductors, it’s pretty clear that that’s what’s happening.

But Sochnikov and his colleagues wanted to know whether this was really true for copper oxides. Copper oxides behave a little differently than classic superconductors. Even when the temperature rises well above the critical level, the energy gap persists for a while, diminishing gradually. It could be a clue as to what makes them different.

The researchers set up a version of the gap energy experiment to test this. They made a precise sandwich of two slices of copper oxide superconductor separated by a thin filling of electrical insulator. Each slice was just a few nanometers thick. The researchers then applied a voltage between them. Electrons began to tunnel from one slice of copper oxide to the other, creating a current.

By measuring the noise in that current, the researchers found that a significant number of the electrons seemed to be tunneling in pairs instead of singly, even above the critical temperature. Only about half the electrons tunneled in pairs, and this number dropped as the temperature rose, but it tapered off only gradually.

“Somehow they survive,” Sochnikov says, “they don’t break fully.” He and his colleagues are still not sure whether the paired states are the origin of the high-temperature superconductivity, or whether it’s a competing state that the superconductor has to win out over as the temperature falls. But either way, their discovery puts a constraint on how high temperature superconductors happen.

“Our results have profound implications for basic condensed matter physics theory,” says co-author Ivan Bozovic, group leader of the Oxide Molecular Beam Epitaxy Group in the Condensed Matter Physics and Materials Science Division at the U.S. Department of Energy’s Brookhaven National Laboratory and professor of applied physics at Yale University. Sochnikov agrees.

“There’s a thousand theories about copper oxide superconductors. This work allows us to narrow it down to a much smaller pool. Essentially, our results say that any theory has to pass a qualifying exam of explaining the existence of the observed electron pairs,” Sochnikov says. He and his collaborators at UConn, Rice University, and Brookhaven National Laboratory plan to tackle the remaining open questions by designing even more precise materials and experiments. 

The research work at UConn was funded by the State of Connecticut through laboratory startup funds.

This article first appeared on UConn Today, August 21, 2019.

Daniel McCarron wins NSF Early Career Award

Daniel McCarron, assistant professor of physics, the College of Liberal Arts and Sciences, will receive $645,000 over five years for his work on the development of techniques to trap large groups of molecules and cool them to temperatures near absolute zero. The possible control of molecules at this low temperature provides access to new research applications, such as quantum computers that can leverage the laws of quantum mechanics to outperform classical computers.

The NSF Faculty Early Career Development (CAREER) Program supports early-career faculty who have the potential to serve as academic role models in research and education, and to lead advances in the mission of their department or organization. Activities pursued by early-career faculty build a firm foundation for a lifetime of leadership in integrating education and research.

McCarron was one of 8 junior faculty at the University of Connecticut to receive the prestigious Early Career awards from NSF in 2019. For a description of all 8 awards, see this recent article published in UConn Today.