2022 KU Physics and Astronomy Newsletter

UNIVERSITY OF KANSAS

Momentum

MOMENTUM SUMMER 2022 2022

Department of Physics & Astronomy

Spotlight on KU’s Newest Astronomers!

Shining New Light on the Centers of Galaxies Professor Elisabeth Mills joined the Physics and Astronomy Department in January 2020, after moving to Lawrence from Boston, Massachusetts.

At KU she leads the Nearby Galaxies Lab, which focuses on looking at the centers of the Milky Way and its neighbors with unique wavelengths of light, from infrared to radio, allowing us see deeply into the activity at their hearts.

Despite the unexpected challenge of a global pandemic beginning just three months after she arrived at KU, her research program is off to a fast start. Since coming to KU she has been awarded more than a thousand hours of observing time as a Principal Investigator on some of the premier international facilities for astronomy, including the Atacama Large Millimeter Array (ALMA) and the Very Large Array. This also includes some of the final data to be taken with NASA’s SOFIA observatory, a telescope mounted on a modified Boeing 747 that makes observations from Earth’s stratosphere. She is additionally part of several teams making some of the first observations of massive stars and nearby galaxies with the newlylaunched JWST.

(Continued on page 8.)

Big Plans, New Planets, and a Planetarium!

Professor Ian Crossfield was hired away from MIT to start at KU in January 2020­—just months before the pandemic hit. Despite this challenging start, he has been steadily building his astronomy-focused research group— the KU ExoLab—and has become involved in a growing number of department activities. What follows is a conversation with Prof. Crossfield...

Momentum: How would you describe your work to our readers?

Crossfield: As an astronomer, my research relies primarily on observations that we make using optical and infrared telescopes around the world, and in outer space. Our efforts mainly aim at two areas: extrasolar planets and stellar astrophysics. On the stellar side of things, we’re conducting cutting-edge measurements of the abundances of trace elements and isotopes that trace the formation of the stars, their planets, and of the Milky Way Galaxy. The arena of exoplanets is a particularly hot subfield: it was the topic of the 2019 Nobel Prize in Physics, and one of the key science goals highlighted in the recent Astro2020 Decadal Report.

In this area, our team works both on discovering new exoplanets orbiting other stars, and on the first detailed characterization of those planets’ sizes, masses, orbits, and atmospheric compositions.

M: Tell us about the ExoLab. C: We’re a growing group of researchers here at KU focusing on the exoplanetary and stellar topics I just mentioned. Three graduate students are working with us so far: third-year Alex Polanski is working on a catalog of over a dozen stellar abundances for several thousand nearby stars; secondyear David Coria is making the first measurements of carbon and oxygen isotopic abundances in nearby “solar twin” stars; and second-year Yoni Brande is completing his analysis of the atmospheric composition of a hot, Neptune-mass planet orbiting a

(Continued on page 8.)

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KU PHYSICS AND ASTRONOMY

A Letter from the Chair The past two and a half years have been particularly challenging for KU, our department, and the lives of all of us in the age of COVID. We have tried to continue on our mission as best we can under sub-optimal circumstances, facing the difficulties and obstacles and keeping our eyes on the important issues.

Reflecting on the recent past and the myriads of ways COVID has affected our lives is not easy nor always cheerful.

Like most people, the denizens of our department, as well as our alumni, friends, and hangers-on went through challenging times that do not seem to be ending soon. However, through all the difficulties we continued to engage in excellent, cutting-edge research, innovative and inclusive teaching, service to our students, the larger community, and have taken an active role in helping to improve the lives and to support the less fortunate among us, in the department, at KU, in Lawrence and Kansas, and in the nation as a whole. It has been quite a ride.

Faculty: Since 2013 we have lost nine faculty from retirements and other transitions and brought in ten new tenured track faculty (and we currently have an active search in Theoretical CMP modeling that will bring onboard one more tenure track faculty by August 2023) as well as three teaching faculty, increasing the strength of our instructional mission while keeping our research mission vibrant and extremely productive.

We have put our astronomy program on the map with the addition of three world renown young faculty, expanding our reach deep into the heart of galaxies and the supermassive black holes that inhabit them (Allison Kirkpatrick), the past and future of Active Galactic Nuclei (Betsy Mills), and the discovery and characterization of exoplanets (Ian Crossfield). This has led our astronomy

major count to increase by more than a factor of two in the past three years.

We have added a CMP theorist (Hartwin Peelaers) who develops stateof-the-art computational first-principles methods to describe and explain the physics of materials, with the goal of improving and designing the materials for the next generation nanoscale and energy devices.

We have concluded a successful search for an astroparticle physicist whose research is focused on radiobased detection techniques for highenergy particles, such as cosmic rays and neutrinos, at the South pole (our very own alumni Steven Prohira from The Ohio State University), Steven joined the department in June 2022.

We have also successfully concluded a search for a Quantum Information Science experimental position and have recruited Dmitry Ovchinnikov from the University of Washington. Dmitry will join our faculty in November 2022.

We also hired an Assistant Teaching Faculty, Jessy Changstrom, from K-State University. Jessy joined the faculty in August 2022 and is teaching this Fall 2023 semester.

Graduate Program: We have steadily increased our graduate enrollments as well as the diversity and quality of our graduate student body. Currently we have international students from over fifteen countries.

We have become an American Physical Society Bridge Program Partnership Site (APS-BP), a program designed to increase the number of physics PhDs awarded to underrepresented minority (URM) students, identified as Black, Latinx, and Indigenous, by creating sustainable transition programs and a national network of doctoral-granting institutions.

Teaching: Our teaching mission has clearly been affected by the restrictions

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the epidemic has imposed on us.

During the Spring 2020 semester we had to move all our classes from inperson to entirely online with a week’s notice. That was quite challenging, but the faculty, staff, and students stepped up and made it happen. We remained entirely virtual for the rest of 2020, but started moving back to in-person instructions in 2021. As we all experienced the topsy-turvy nature of the last two and a half years, it was quite remarkable to see that despite the hardship and difficulties, people were there to help each other, to go out of their way to support one another; in many ways we saw the beauty and commitment we have to one another (though, unfortunately, we also saw the opposite, both nationally and locally).

Research: For a while, especially during 2020, we saw our research mission curtailed. Our labs had to close, and then reopened slowly, tentatively, and sometimes not fully. Our ability to discuss and conduct research was impacted by the restrictions imposed by the virulent nature of the pandemic. Our travel to conferences, collaborations, and work at national and international centers was severely limited. However, as with the rest of the world, we have learned how to adapt, how to attend meetings and communicate with collaborators virtually and in small

MOMENTUM 2022 socially distanced groups. We learned that there are alternatives to the ways we have always done things, and some of those are actually quite efficient and sometimes even more effective than what we imagined or have done in the past.

Endowment: Our endowment has continued to grow. We recently received two large estate funds. One is the J. D. Stranathan Professorship of Experimental Physics. This fund provides a junior faculty position that covers five years of salary and provides some research funds for an experimental physicist. Chris Rogan joined our faculty thanks to this fund.

Chris has now been promoted to an associate professor with tenure, so we expect this fund will enable us to hire another faculty member in the coming year. The other estate fund is the Gene R. Feaster Physics Scholars fund, which provides a full ride for up to two UG students every year.

Other endowment funds provide us with support for both graduate and undergraduate students for various activities such as travel, research, outreach, etc. Our alumni board has helped us create an emergency fund for students that were impacted adversely by the pandemic. The dedication and commitment of our alumni and friends has made it possible for us to support our people and our missions in ways unimaginable without this assistance.

Our trusted Physics & Astronomy Development fund has remained our main workhorse, supplementing our other funds, and providing support for the various miscellaneous expenses that arise during the year.

Outreach: We continue and enhance our commitment to outreach and service in and out of KU. We have created a Diversity, Equity, and Inclusion (DEI) committee to oversee and support our efforts and improve the climate in the department and beyond. We are increasing our outreach efforts to area community colleges, HBCU, and other minority serving institutions. We also

KC Kong Awarded Keeler Intra-University Professorship The Keeler Family Intra-University Professorship program provides faculty members an opportunity to “strengthen their knowledge of an academic specialty, to broaden or achieve greater depth in a defined field of scholarship, or to achieve competence in a new area of scholarly endeavor.” The program is supported through a gift of the Keeler family in memory of W.W. Keeler, former president of the KU Alumni Association, the chief executive officer of Phillips Petroleum Company, and principal chief of the Cherokees.

Prof. Kong will be collaborating with members of the School of Engineering (in particular, Prof. Taejoon Kim in EECS) on a research project in quantum information science—a field at the intersection of engineering and physics.

The goal is to explore how quantum algorithms can help in problems related to quantum information science, quantum communication, and entanglement. As part of this collaboration, KC is preparing materials for a future class “Introduction to Quantum Computation.” participate in various outreach efforts to high schools. Our goal is to increase the number, diversity, and academic level of our incoming classes at both the undergraduate and graduate levels.

We have partnered with the American Association of Physics Teachers (AAPT) to develop the STEMTeach KU program—an educator preparation program focused on STEM majors who can pursue a teaching license alongside earning a degree in one of several STEM fields. We have created a new Graduate Student Organization (GSO).

Additional student led organizations include a Diversity in Physics group (Empowered Voices) and a Learning

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Professor Kyoungchul (KC) Kong is a theoretical particle physicist with a research focus on new physics beyond the standard model. His research is supported by the US Department of Energy. He has been a member of the Department since 2010.

Machine Learning group. All of these activities compliment and enhance the work of our Society of Physics Students (SPS/ΣΠΣ) group.

In short, the past few years have been interesting, taxing, joyful, and stressful. I am proud to report that the challenges we have faced have made us more resilient and more aware of what we must do, what we can do, and what we should do to excel in the future.

Hume Feldman Chair

KU PHYSICS AND ASTRONOMY

KU Physics and Astronomy Beyond Academia For the past several years, the Department has been hosting events where alumni who have found success in non-academic jobs have been invited back to describe their experiences. This year, Alumni Board Member Rebecca Chaky will discuss patents: Forty years after receiving her Ph.D. in Physics from KU, Rebecca Chaky has concluded that KU physics students need to know about patents.

Rebecca was one of four inventors on a spacecraft solar array patent issued in 1989. As an independent inventor,

she is the inventor of the Mobius bow tie (patent pending) and a smart shower (patents issued in USA, Australia, Canada, and Japan).

Although math and science (specifically physics) are discovered, not invented, and therefore are not patentable subject matter, there are opportunities in patent-related careers that are only open to people with a technical background. And, therein lies the connection of Physics (indeed, science and math) to patents and related careers.

Rebecca hopes to expand KU Physics students’ horizons beyond future employment restricted to academia or industry. If interest is shown in the Patent and Entrepreneurship breakout session of the upcoming KU Physics Industry Workshop on 17 September 2022, plans are to present at undergraduate and graduate physics student organizations in the 2022-2023 school year.

Test your memory!

How many past (and present) occupants of Malott Hall can you recognize?

1977

(key on p. 14)

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MOMENTUM 2022

Department Banquet 2022

A chance to honor the achievements of our students, staff, and faculty and to recognize and express gratitude to those who otherwise support the Department!

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KU PHYSICS AND ASTRONOMY

REU at KU

Prof. Allison Kirkpatrick 2022 REU Faculty and Participants Front: Prof. Allison Kirkpatrick, Maurissa Higgins (Iowa State), Julian Sewell (Texas Tech, non-REU student working with Prof.

Alice Bean), Derek Sikorski (Indiana), Mari Beltran (EmbryRiddle) Back: Prof. Hartwin Peelaers, Sasha Mintz (Virginia Tech), Reese Conti (UC Boulder), Zach Opoka (UMKC), Matthew Bruenning (Missouri State) Not shown: Gavin Holbrook (UConn) This year, the department was proud to host our first ever NSF Research Experience for Undergraduates program, chaired by Dr. Hartwin Peelaers and Dr. Allison Kirkpatrick.

We welcomed eight students from schools such as Virginia Tech and the University of Connecticut to perform cutting edge research in our department over the summer. Students arrived on May 30 and were housed in Stouffer Apartments. At the department, students worked on research projects ranging from measuring the atmospheres of extrasolar planets to understanding the properties of novel battery cathodes. Research projects culminated in student presentations at the department’s annual Undergraduate Research Symposium on August 4. In

Profs. Kirkpatrick (Astronomy) and Peelaers (Condensed Matter Physics) both joined the Department in 2018.

They share credit in promoting the Department’s first NSF REU program.

the coming year, students will present their research at a national conference.

Students were also introduced to all Lawrence had to offer. They spent their free time exploring downtown, hanging out at the public pool, or bowling. The social highlight of the summer was a trip to the Cosmosphere in Hutchinson, KS. Program participants found the REU significantly aided their development as scientists. “This REU has been an amazing experience for me. Coming in after my sophomore year meant that I had a lot of things to learn, but applying my knowledge from classes and labs to a real research project has helped my skills grow immensely. I have so much more confidence in my abilities

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Prof. Hartwin Peelaers

both as a researcher and as a student and have never been more excited to learn more about my field,” said Sasha Mintz. Maurissa Higgins noted, “KU’s REU has helped me grow technical soft skills as well as improve my interpersonal skills. I’ve discovered my interests for work in the future and created a network of people ready to help me get there.”

This REU program is supported by the NSF and will continue in 2023 and 2024.

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The Odderon – DISCOVERED! In 2021, a team of physicists from the D0 and TOTEM collaborations at Fermilab, USA and CERN, Switzerland, convened by Foundation Distinguished Professor Christophe Royon from the University of Kansas, announced the discovery of a three gluon compound in the proton, the odderon. D0 and TOTEM were both looking at patterns from a type of interaction called elastic scattering, in which fast-moving hadrons meet and exchange particles without breaking apart. In the past, scattering data had already revealed that gluons can group in even numbers, but it was not clear if the same principle would apply to groups made of an odd number of gluons. Fifty years ago, the existence of the odderon was predicted, but its observation has been elusive and, until now, it has not been experimentally verified. The cleanest way to observe the odderon is to look for differences between proton-proton and proton-antiproton interactions.

Where do we have the highest energetic collisions between protons and protonantiproton? This is respectively at the Large Hadron Collider (LHC) at CERN, Switzerland, and Fermilab,

USA, at the Tevatron!

When we first compared the Tevatron and LHC data on a piece of paper, we already saw some differences and this was the starting point. If the odderon did not exist, D0 and TOTEM data should have shown the same patterns.

But this was definitely not the case and the process was to quantify the discrepancy between both data sets. The discrepancy showed that these hadrons were sensitive to a new exchange, the odderon. When combined with previous data from TOTEM, the significance was high enough to claim the discovery, the odderon was finally discovered after 50 years, and the result was published in one of the best journal in the field, Physics Review Letters.

In order to obtain this fundamental discovery, an international team of scientists originating from across the globe worked on the research. The US contribution was funded by the US Department of Energy and the National Science Foundation. The next project is to look at the LHC for the existence of so-called glueballs,

Christophe Royon joined the KU Physics and Astronomy department in 2016 as a Foundation Distinguished Professor. He has been a principal researcher on the discovery of the odderon, for which he was awarded the Humbolt Prize. Professor Royon is the recipient of a NASA grant to design and build a particle telescope to launch into orbit. He is also funded by the Department of Energy for his work in nuclear physics. or balls of gluons, inside the proton.

This would be another fundamental discovery if found.

Water Fight!

(What better way to spend a hot late Summer day outside of Malott Hall!)

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KU PHYSICS AND ASTRONOMY (Shining, cont. from page 1) In 2022, she became a co-Investigator of a team designing a far-infrared space telescope (the PRobe far-Infrared Mission for Astrophysics or PRIMA) in response to NASA’s plan to launch a new class of $1 billion probe missions over the next decade. PRIMA will compete with other far-infrared and X-ray telescope concepts for a planned launch date in the coming decade.

In her first two and a half years at KU she has already brought in more than half a million dollars in grant funding from NSF, NASA, and NRAO, which she is using to support an active team of graduate and undergraduate students, and to build the computing infrastructure needed to manage the hundreds of terabytes of “big data” that her observing programs are producing.

Prof. Elisabeth Mills

(Big Plans, cont. from page 1) nearby cool star. And a bunch of KU undergrads have worked on various projects, including Sharon Gary, Ethen Schmidt, Jenny Zhang, Kate Wienke, and more. My colleague Prof. Jennifer Delgado also frequently joins us, and we’re in the process of hiring the ExoLab’s first postdoctoral researcher.

You can read a bit more about our work and our team at https://crossfield.ku.edu/team.shtml .

M: You mentioned the Astro2020 Decadal Report; what was that?

C: Starting in the 1960s, every ten years the entire U.S. astronomy community gets together to strategize and set the field’s top research priorities for the next ten years. The reports take several years to write and are a key reference for NASA, the NSF, and for Congress for directing research funding. Past reports were responsible for pushing many of NASA’s key space telescopes across the finish line. I was invited to work on the process this year (along

ExoLab student Ethen Schmidt (BS ‘21) made this model of the “hot Neptune” LTT9779b orbiting its host star.

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MOMENTUM 2022 with my colleague KU Prof. Dave Besson), which was a really exciting process that involved evaluating and synthesizing the collective views of thousands of astronomers. The final report, released in November, sets as its top priorities a “super-Hubble” space telescope operating in the optical and ultraviolet, and a next generation of giant ground-based telescopes that would be ten times more powerful than any current facilities. These will be big, challenging goals but we think they’re essential to maintain U.S. astronomy’s leadership in the world.

M: Are those the sort of telescopes that could search for life beyond the Solar System?

C: That’s right! One of the science topics that most catches the public’s imagination is the search for life. On exoplanets, that will mainly come from measurements of atmospheric gases— think oxygen, carbon dioxide, methane, and so forth. These next generation of telescopes should have the precision to make these measurements for at least a small number of Earth-size, Earthtemperature planets.

M: Is that what your work focuses on: looking for life?

C: That’s the biggest long-term goal of the field, but it’s still a ways off. In the meantime, we’ve discovered thousands of exoplanets that (while they probably don’t host life) are still utterly unlike anything in our Solar System. Many of these are bigger, hotter, and so are accessible to study today rather than a decade from now. So we use these systems as ‘training wheels’ to make sure we can properly interpret the measurements we make. The one thing we want to be sure we avoid is making a false claim about life elsewhere in the universe!

and to purchase a portable planetarium system. This won’t be a permanent structure like the Kansas City’s Gottlieb Planetarium—ours will be a smaller, portable system. We already have a room reserved where it will be set up at KU for teaching and public science shows, and we’ll also be able to take it around to schools throughout western Kansas—particularly schools that can’t afford to bus their kids to KU for a planetarium field trip. The system is installed and we gave a full day of shows this August for Hawk Week.

M: Any final thoughts? What are your long-term goals?

C: Astrophysics at KU is growing at a rapid clip, and it needs two things to really take it to the next level.

First, to keep attracting the top level of astronomy students I think that we need to offer an Astronomy PhD in addition to the current Physics PhD. I’ve straddled both worlds—I have a BS in Physics and a PhD in Astronomy —and each field attracts its own group of students. By offering both, we would appeal to a larger group of applicants and keep building on our current momentum. Second, to take KU astronomy to the next level we need shared access to an observatory substantially larger than the current one-meter telescope. That costs money, but I’m confident that we’ll find a way to make it happen—and thereby keep KU on the cutting edge of the field for many years to come.

M: Thanks for taking the time to talk.

C: It was my pleasure!

M: We heard a rumor that you’re bringing a planetarium to K.U.?

C: That’s right—we’re really excited about this. I was awarded a modest NSF grant early this year, which included funds both to hire a postdoc

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Prof. Ian Crossfield (In addition to his research, Prof.

Crossfield enjoys hiking, biking, and spending lots of time with his young toddler.)

KU PHYSICS AND ASTRONOMY

Physics Education Research at KU

Kayla Wegley applying energy concepts.

Several factors can influence the ability of a student to achieve proficiency in introductory physics, including prior experience with mathematics and physics, stereotype threat, overall stress and mental load, etc. There are also additional external pressures that can affect a student’s path to proficiency with course content.

For example, an ever larger number of college and university students have significant demands on their time and attention outside of academics, such as working (full- or part-time), managing child- or adult-care, coping with mental illness or feelings of isolation, or struggling with food insecurity. These pressures and responsibilities can overwhelm students and prevent them from maintaining a consistent schedule for studying, completing homework assignments on time, or even attending class regularly. When taken together, these factors can result in a distribution of pathways and associated rates taken by students to achieve proficiency in the different content areas of their courses.

In an attempt to accommodate better

this diversity of rates and pathways by which students develop proficiency with course content, the department’s Physics Education Research (PER) group, consisting of Associate Teaching Professor Jennifer Delgado, Assistant Teaching Professor Sarah Rush, and Professor Christopher Fischer, has developed a new grading system that assesses student proficiency in different content areas of the course conditional on two criteria. First, students must demonstrate proficiency with content on more than one assessment. This stipulation is motivated by a desire to evaluate retention of knowledge and/ or skills. Second, students who fail an initial assessment have sufficient subsequent opportunities to demonstrate their proficiency. This requirement seeks to impart the flexibility necessary to accommodate the varying schedules of our students. This grading method combines elements of mastery learning and competency-based grading and has been shown to improve the performance of all students in introductory physics, with women and first generation students displaying the largest gains.

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In a separate project, we developed a new curriculum for the first semester of calculus-based introductory physics that shifts the initial focus of instruction away from forces and associated vector mathematics, which are known to be problematic for students, to the scalar quantity energy, which is more closely aligned with their previously established intuition, and associated differential and integral calculus.

This curriculum tasks students with differentiating and integrating equations for energy to describe the mechanics of systems. Later in the course, students similarly differentiate and integrate equations for entropy to determine the equilibrium conditions of systems. The introduction of forces and Newton’s Laws in this curriculum is delayed until after students have gained proficiency with the concepts of classical mechanics using energy conservation.

The implementation of this calculusenhanced “energy-first” curriculum resulted in higher normalized gains on standardized assessments of knowledge of force concepts for all students and

MOMENTUM 2022 improved performance in downstream engineering courses for students with lower ACT math scores. In other words, the downstream benefits were largest for students with lower math abilities who also pose a larger retention risk. This new curriculum thus has the potential to help improve student retention by specifically helping the students who need help

the most, including traditionally underserved populations who often have weaker mathematics preparation. This curriculum may therefore also have the potential to well documented mathematics transference barrier to learning in introductory physics.

Professor Jennifer Delgado received her Ph.D. in Astrophysics from the University of Minnesota – Twin Cities in 2013. She joined the department in 2013 as a long term lecturer before being promoted to laboratory director in 2015. In 2019 she was promoted to her current position as associate teacher professor. In addition to organizing the curricula for the introductory laboratory courses and managing the GTAs teaching those courses, Professor Delgado has taught courses in introductory physics and introductory astronomy. Professor Delgado also leads our department’s monthly telescope night outreach program which brings together graduate students, undergraduates, and members of the KU and Lawrence community. Outside of her work at KU, Professor Delgado enjoys reading, especially science fiction, and spending time with her family.

Professor Sarah Rush received her Ph.D. in Physics from the University of Kansas in 2017. That same year she started her current position as an Assistant Teaching Professor in the department. She has taught a variety of introductory physics courses at both the calculus-based and algebra-based level. Professor Rush is also a leader on the department’s effort to improve the university’s STEM teacher preparation program with a goal of graduating more physics teachers.

Professor Rush enjoys spending time outdoors with her family, especially hiking and canoeing in state and national parks, both in Kansas, and across the country.

Professor Fischer received his Ph.D. in Applied Physics from the University of Michigan in 2000. After a postdoc at the Washington University School of Medicine, he joined the department in 2004. Professor Fischer serves as the department’s associate chair and the director of the undergraduate engineering physics program. He is also the co-director of the STEMTeach KU program, which is responsible for the preparation of high school STEM teachers. Professor Fischer also helps manage the department’s Twitter account where he can also engage with his interests in linguistics, poetry, and, recently, British politics.

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KU PHYSICS AND ASTRONOMY

Ultrafast Laser Laboratory

Graduate students Lalani Werake (PhD 2011) and Brian Ruzicka (PhD 2012, Honors) working in the Ultra-Fast Laser Laboratory. Both students have been working for Intel since their graduations.

In the condensed matter group, Professor Hui Zhao’s Ultrafast Laser Lab focuses on electronic and optical properties of van der Waals heterostructures formed by 2D materials.

produced in 2004 and was the topic of Nobel Prize in Physics in 2010. Since then, about 100 other 2D materials have been produced, including metals, insulators, semiconductors, semimetals, and superconductors.

Of the 100,000 or so materials that mankind has mastered so far, about 5,000 are the so-called van der Waals materials, which are stacks of atomic layers held by the van der Waals force.

Because this force is weak, one can produce single-layer materials by simply exfoliating such crystals with an adhesive tape. Since the electron motion is confined in two-dimensions, these materials can be drastically different from their 3D counterparts. The most well-known 2D material, graphene (a single layer of carbon atoms), was

Besides their fascinating properties as individual materials, these 2D materials can be used as building blocks to make new artificial materials, with “on-demand” properties, by simply stacking them together. Such a so-called “atomic Lego” approach was impossible with traditional 3D crystals, where only materials of similar lattice structures can be combined.

Considering the countless combinations of the thousands of 2D materials, this approach could deliver many new materials for varies applications such

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as photovoltaics, transistors, sensors, batteries, etc.

Zhao’s group, currently having 4 PhD students, focuses on understanding and controlling electron transfer between different atomic layers in the van der Waals heterostructures. This process plays a key role in harnessing emergent properties of these materials, allowing charge, energy, and information exchange between different layers.

The group makes its samples having desired structures by peeling off monolayer flakes from various crystals using (literally) Scotch tape, and then stacking them on top of each other under a microscope. In their laser measurements, they use an ultrashort laser pulse (100 fs duration) to excite electrons in one of the layers, using the

MOMENTUM 2022 fact that different layers have different resonant frequencies. They then use another laser pulse to monitor the population of electrons in another layer, and therefore time-resolve the electron interlayer transfer process. They are one of the first groups to discover ultrafast electron transfer between different atomic layers in 2014. So far, they have observed ultrafast electron transfer in several new materials, found ways to design certain potential landscapes to achieve desired electron transfer directions, and used laser pulses to control the electron transfer processes.

They have been one of the most productive groups, with about 40 publications, on this topic. The group has been closely collaborating with Prof. Wai-Lun Chan’s group (organic 2D semiconductors) and Prof. Hartwin Peelaers’ group (computational condensed matter physics). The research was funded by several awards from National Science Foundation and Department of Energy.

Prof. Hui Zhao grew up in a mid-sized town in north part of China.

He received his PhD from Beijing Jiaotong University in 2000 and joined KU in 2007 as an assistant professor, after postdoctoral stays at Karlsruhe Institute of Technology (Germany) and University of Iowa.

He received a CAREER Award from the National Science Foundation in 2010. He and his wife (an actuary but with a physics degree) live in Overland Park, with 3 lovely children. Besides researching and teaching physics, he is a big fan of Jayhawk basketball and Chiefs football.

What better way to celebrate the end of the Fall ‘21 term!

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KU PHYSICS AND ASTRONOMY

Department Picnic 2022

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MOMENTUM 2022

Malott Hall

Integrated Science Building (Gray-Little Hall) (New location for the condensed matter physics program as well as all large enrollment introductory physics classes.)

Looking Back – 41 Years Ago (1981) In August the department took delivery of a VAX 11/750 Super-minicomputer. This machine, housed in the basement of Malott Hall, is to be dedicated to Department of Physics and Astronomy research, and will be operated by faculty and graduate students.

With one megabyte of semiconductor memory and access to 120 megabytes of virtual memory through the VAX/VMS multi-user, multi-tasking operating system, the computer has a wide range of advanced software, both for number crunching and for driving such peripheral devices as the Tektronix color graphics terminal.

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Prof. Thomas Armstrong analyzing data from Voyager II using the VAX 11/750 Superminicomputer.

KU PHYSICS AND ASTRONOMY

The University of Kansas Department of Physics and Astronomy Malott Hall 1251 Wescoe Hall Dr, Room 1082 Lawrence, KS 66045-7582

Physics, astronomy and engineering physics alumni of the University of Kansas, both graduate and undergraduate, are invited to network and communicate in the LinkedIn group, KU Physics & Astronomy Alumni. Professor Dr. Daniel Tapa Takaki is administrator for the group. https://www.linkedin.com/groups/6783933/

PLEASE HELP US DO MORE! Your tax-deductible contribution to the Department of Physics and Astronomy will help us do things that would not otherwise be possible. The Department’s Giving Web Site is at https://physics.ku.edu/giving . Here you will find a list of Endowment Funds that allow donors an opportunity to direct their contributions to specific needs.

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