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New spin-wave microscopy highlighted by an Editors’ Suggestion and a featured story in Physics Magazine.  

December 20, 2024

Researchers at UNC (Zhang, Tsui group in Physics) and Cahoon group (Chemistry) recently developed a new method for imaging spin waves in magnetic materials uses flash-like intensity variations in a laser beam to capture the wave motion at specific moments in time. The work was published in the journal Physical Review Applied and was featured both by an Editors’ Suggestion and a FOCUS story in Physics Magazine. https://physics.aps.org/articles/v17/186

Unveiling a Lightweight Giant: JWST Reveals the True Nature of a Young Exoplanet

December 20, 2024
A recent study led by graduate student Pa Chia Thao has unveiled exciting new findings on a 17-million-year-old exoplanet, HIP 67522 b, using cutting-edge data from the James Webb Space Telescope (JWST). Originally classified as a “hot Jupiter” due to its size – about 10 times that of Earth – and its short orbital period of less than 7 days, the planet’s atmosphere tells a different story. Using transmission spectroscopy, a technique that analyzes how starlight filters through a planet’s atmosphere during transit, researchers can probe the atmosphere’s composition and structure by observing how transit depths vary across different wavelengths.
image credit: NASA/JPL-Caltech/R. Hurt (IPAC). 
Signatures of water and carbon dioxide were detected, with absorption features 30-50% deeper than expected. By analyzing the strength of these spectral features and the planet’s atmospheric scale height, they determined that HIP 67522 b has a mass less than 15 times that of Earth – reclassifying this planet as a precursor to the more common sub-Neptune planets. Despite being about the size of Jupiter, the planet’s density is comparable to that of cotton balls. This revised mass also confirms HIP 67522 b as one of the least dense planets ever discovered. The planet is likely undergoing significant mass loss – between 0.01 and 0.03 Earth masses per million years –potentially leading to the destruction of its envelope within a billion years. These findings highlight the rapid and dramatic evolution taking place within the first 100 million years of the planet’s existence.
The attached plot shows the transmission spectrum of HIP 67522 b, observed with SOAR and JWST, compared to three atmospheric models: a clear model (purple), a photochemical model (pink), and a cloudy model (red). The strength of the molecular features in the spectrum constrains the planet’s mass to an upper limit of 15 Earth masses – significantly lower than expected for a planet of Jovian size (R = 10 Earth radii).
The study was published in Astrophysical Journal (https://iopscience.iop.org/article/10.3847/1538-3881/ad81d7).

UNC Student Finds Newborn Planet in Warped System

November 20, 2024

Planet-forming disks are a natural outcome of angular momentum conservation as molecular clouds collapse to form stars. During this collapse, the clouds begin to spin faster, eventually flattening into a disk shape. These “protoplanetary disks” are thought to form planets over roughly 10 million years, after which the disk material dissipates, leaving behind a mature planetary system. It is generally expected that planets will align with the disk from which they formed. Indeed, the orderly, flat orientation of the planets in our Solar System was among the earliest clues that planets emerge from flattened protoplanetary disks.

A recent discovery, led by Madyson Barber and Andrew Mann, has unveiled a rare example of a young giant planet – IRAS 04125+2902b (also known as TIDYE-1b). This system resides in the Taurus-Auriga Molecular Cloud, a stellar nursery home to hundreds of newly formed stars. At just three million years old, this infant planet is the youngest transiting planet detected to date, roughly equivalent to a ten-day-old newborn on human timescales. The host star still retains its protoplanetary disk, further distinguishing it from other known planetary systems.

Previously, systems like TIDYE-1b were thought to be nearly impossible to detect. By three million years, it was uncertain if planets had developed to a detectable degree (for context, Earth took 10-20 million years to form). Additionally, if the disk and planet were aligned, the disk would obstruct our view. However, in this case, the inner portion of the disk is depleted, and the outer disk is tilted relative to both the planet and its host star.

The discovery of TIDYE-1b challenges current theories of planet formation timescales and the relationship between planets and their parent disks. It also offers a unique opportunity to study a planet shortly after its formation.

The results were published in the most recent edition of Nature. In addition to Madyson and Andrew, the paper is co-authored by four other members of UNC Physics and Astronomy; Andrew Boyle, Matthew Fields, Isabel Lopez-Murillo, and Pa Chia Thao, all members of the Young Worlds Lab


Madyson Barber, a graduate student in the department of Physics and Astronomy, discovered TIDYE-1b, is lead-author on the Nature paper, and is PI of the TIDYE survey. Prior to starting graduate school, she was an undergraduate and Chancellor’s Science Scholar at UNC [left].

An artistic interpretation of the TIDYE-1b system. Young stars like this are covered in starspots—regions cooler than the surrounding stellar surface. The inner disk is depleted, leaving an intact outer disk that forms a donut-like structure around the host star. The planet’s orbit aligns with the host star’s rotation, while the nearly face-on outer disk allows an unobstructed view of the system. If the disk were edge-on, it would block both the planet and the host. Image credit: NASA/JPL-Caltech/R. Hurt, K. Miller (Caltech/IPAC) [right]





Prof. Janssens’ Research on Chromium-62 Featured in Nature Physics

October 31, 2024

From https://frib.msu.edu/news/2024/chromium-62:

In a recent paper in Nature Physics, an international research collaboration, including Edward G. Bilpuch Distinguished Professor Robert Janssens as a co-PI for the experiment, used world-class instrumentation at the Facility for Rare Isotope Beams (FRIB) to study the rare isotope chromium-62. Researchers used a gamma-ray spectroscopy experiment in tandem with theoretical models to identify an unexpected variety of shapes in chromium-62. The finding provides more insight into islands of inversion. (Graphic courtesy of the Facility for Rare Isotope Beams)

More information can be found in From https://frib.msu.edu/news/2024/chromium-62

Communicating with Magnons — UNC’s Work in Hybrid Magnonics highlighted by a recent editorial

October 14, 2024

Increasing the bandwidth of existing optical fiber networks is vital as society’s appetite for information grows. Writing in npj Spintronics, an editorial article (titled ‘Communicating with magnons’: https://www.nature.com/articles/s44306-024-00060-1) highlighted a recent publication by Y. Xiong et al from Wei Zhang’s group (https://www.nature.com/articles/s44306-024-00012-9), where the team reported a new magnonic phenomena for further increasing the information capacity of a hybrid magnon-photon system, termed “opto-electro-magnonic oscillator”.

Prof. Barlow Receives NC Space Grant Funding to Search for Spider Binaries

September 16, 2024

Congratulations to Prof. Brad Barlow who was recently awarded a 2024-2025 Faculty Research Grant from the NC Space Grant! This funding will support Barlow and several undergraduate students as they use optical photometry from space- and ground-based observatories to search for and characterize new spider binaries.

From the NC Space Grant announcement:

“Spider binaries are a class of compact binaries that typically consist of a pulsar (a highly magnetized, rotating neutron star) and a low-mass companion. The intense, high-energy radiation and wind from the neutron star slowly heats up and ablates material from the companion. In time, the orbital period will shorten, and the companion will be consumed. Studies of spider binaries can provide valuable insights into various astrophysical processes, including mass transfer and evolution, the properties and behavior of neutron stars, and high–energy electromagnetic emissions. Such systems are rare, and most have been discovered through X-ray/gamma-ray detections or radio observations of their millisecond pulsars. Due to a series of serendipitous events, Barlow’s research group has discovered one of the closest (and thus brightest) spider binaries currently known using optical photometry instead of radio or high-energy observations. This discovery was made while investigating high signal-to-noise light curves of hot subdwarf binaries — an unrelated type of binary. As the highly irradiated hot spot on the companion rotates in and out of view, the optical flux can vary by up to a factor of ~10 with a light curve shape that mimics those of hot subdwarf reflection effect binaries. Here Barlow’s team proposes a series of optical search strategies to uncover and study new spider binaries using data from NASA’s TESS spacecraft, the 4.1-m SOAR telescope, and Skynet.

Barlow’s hope is that student participation in this project will foster enthusiasm, collaboration, and a deeper understanding of the subject matter in student researchers. Students will learn how to search and review the astronomical literature on spider binaries and related objects; write basic Python scripts for data analysis and visualization; use TOPCAT to inspect and manipulate tabular data; download TESS photometry from the Barbara A. Mikulski Archive for Space Telescopes; compute Lomb Scargle periodograms to search for periodic signals in time-series data; obtain, reduce, and analyze time-series photometry from the Skynet telescope network; obtain, reduce, and analyze time-series spectroscopy from SOAR/Goodman; write clear and concise reports summarizing research results and progress; and give engaging and effective scientific presentations to the public and scientific audiences.”

Otto Zhou and Jianping Lu win Carolina Creativity Hubs Award

September 13, 2024


Profs Otto Zhou and Jianping Lu, along with Prof. Yueh Lee, Radiology and Adjunct Prof of Physics and colleagues from computer sciences and data sciences and school of medicine, won one of the five Carolina Creativity Hubs award. The title of the project is:

“Advanced Medical Screening in Underserved Populations Using a Transportable Nanotube-Enabled Imaging System”
The project is based on the nanotube x-ray technology invented in our department.

More information can be found in the CAS announcement.

A new study quantifies how dark is the Universe

September 13, 2024

A new study, co-authored by Prof. Mike Shull, quantifies the true darkness of the cosmic sky. It was recently published in the Astrophysical Journal (Vol 972, 95) and was featured on a NASA press release.

The study is based on observations seen from the distant
vantage point of New Horizons, the spacecraft that flew past Pluto in 2015. At a distance of 59 astronomical units from the Sun (59 times the Sun’s orbit) the
cameras aboard the mission are not confused by radiation from gas and dust in
the inner solar system. They can see the light from the outer portions of our Galaxy
and the radiation emitted by galaxies billions of light years away.

The group finds that the diffuse optical light in the universe is consistent with the integrated
radiation from distant galaxies down to 30th magnitude, as seen in the Hubble Space
Telescope deep fields. That emission is 25 magnitudes fainter than the dimmest stars
visible to the human eye; ten billion times fainter than the dim stars seen in the sky.

Other key points from the study:

– New Horizons is 59 times farther out in the solar system than Earth’s orbit.
(that’s 5.5 billion miles, or light-travel travel time of 8 hrs 10 min)

– The faraway galaxies that contribute to the cosmic optical background emitted
their light many billions of years in the past.

Image: Map revealing the regions in space, marked by circles and triangles, where New Horizons measured the cosmic optical background. The team pointed the spacecraft’s LORRI instrument above and below the plane of the Milky Way Galaxy, along the map’s equator, to avoid light from the galaxy. (Credit: Postman et al., 2024, The Astrophysical Journal)

Wei Zhang joins forces in uplifting quantum sciences research and education across NC Triangle and Triad (NCAT)

September 13, 2024

Prof. Wei Zhang joins forces in uplifting quantum sciences research and education across NC Triangle and Triad (NCAT).

A recent NSF grant under the NSF QISE interdisciplinary program may help build quantum connections across the NC Triangle (UNC) and Triad (NCAT) regime. The project aims to engineer tailored modes in hybrid magnonics for quantum signal transduction and communication. The research activities will be also complemented by rich outreach activities to engage with students from local high schools and community colleges, and dissemination plans to share the research findings with the public research community.
For more information regarding “magnonics”: please find “The 2024 magnonics roadmap”, J. Phys.: Condens. Matter 36 363501

Figure Caption: A microwave photon-magnon chip operating at cryogenic temperatures. (Zhang lab at UNC)

Graduate student Joseph Moscoso and Professor Amy Nicholson have recently published a paper in Physical Review Letters and Physical Review D, both being selected as editors’ suggestion

February 12, 2024
The paper “Two-Pole Nature of the Λ(1405) Resonance from Lattice QCD” published by the Baryon Scattering (BaSc) collaboration was recently accepted as editors’ suggestion in the Physical Review Letters.  The accompanying paper “Lattice QCD study of πΣ−KN scattering and the Λ(1405) resonance” was also accepted as editors’ suggestion in the Physical Review D.
The role of the fundamental theory of the strong nuclear force, Quantum Chromodynamics (QCD), in the formation of the observed hadron spectrum is an outstanding issue for the standard model of particle physics. The use of QCD to describe the binding of quarks and gluons into hadrons, such as protons and neutrons, is a low-energy phenomenon that requires a nonperturbative calculation that is difficult to apply. The nonperturbative technique we utilize is lattice QCD, where the theory is formulated on a spacetime lattice that allows statistical calculations on computers through Monte Carlo methods. States observed in experiments can be explained using scattering formalism, with theoretical methods necessary to compare calculations on Euclidean spacetime lattices to continuous Minkowski amplitudes. However, the study of nuclear systems using LQCD has been hampered because of a signal-to-noise problem that is heightened when extracting correlation functions. Recent advances in stochastic algorithms have allowed multi-hadron computations and the determination of meson-baryon scattering amplitudes, allowing studies of resonances and excited states in the hadron spectrum.
Lambda Poles Image
Lambda Pols Image
The work of the BaSc collaboration is the first lattice QCD study of a coupled-channel scattering system containing meson-baryon scattering amplitudes. This work is concerned with explaining the Lambda (1405) resonance which is a spin-1/2, negative parity state first identified experimentally in 1959. Explaining the nature of the Lambda (1405) has been a challenge to nuclear theorists as its relatively low mass and quantum numbers are difficult to explain in the three-quark model of low-energy QCD, leading to exotic explanations of the particle such as the meson-baryon molecular structure. The lattice study in this work utilizes quarks that are slightly heavier than physical and can identify two poles in the complex scattering amplitude with the resonance near the kaon-nucleon threshold and a virtual bound state as the lower pole below the pion-sigma threshold. These results provide a model-independent determination of the scattering amplitude and support the two-pole picture with qualitative results predicted by chiral symmetry and unitarity. This work also opens the use of lattice QCD toward other baryon resonances that can explain the nature of some of the shortest-lived particles observed in experimental physics.
Papers:

MAJORANA DEMONSTRATOR final result published in Physical Review Letters was the journal’s most downloaded Nuclear Physics paper in 2023

February 7, 2024

The “Final Result of the Majorana Demonstrator’s Search for Neutrinoless Double-β Decay in 76Ge,” caught the eye of the scientific community becoming the most downloaded Nuclear Physics related paper that was published in Physical Review Letters in 2023.

From 2015 until 2021, the Majorana Demonstrator, tucked nearly a mile underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, searched for an elusive decay that might be the key to solving one of the universe’s biggest puzzles: why matter abounds rather than nothingness.  The postulated decay, known as neutrinoless double beta decay, if observed would reveal the quantum nature of neutrinos and prove that neutrinos are their own antiparticles.

The experiment’s final results, while not observing the decay, set a limit on the half-life of the decay of greater than 8 x 1025 years (a timescale more than 1015 times longer than the age of the universe).  The experiment has helped pave the way for a next generation experiment known as LEGEND that aims to eventually have a hundred times the sensitivity of the Demonstrator.

UNC Physics and Astronomy faculty Julieta Gruszko, Reyco Henning, and John Wilkerson together with Matthew Busch from Duke, faculty member Matthew Green from NCSU, and UNC and NCSU graduate students and postdoctoral scholars made essential contributions to the  Majorana efforts.  UNC Postdoctoral fellow Ian Guinn (now at Oak Ridge National Laboratory) served as the paper’s corresponding author.  This collaborative research was supported and facilitated by the Triangle Universities Nuclear Laboratory(TUNL), a DOE Center of Excellence that is a consortium of UNC, Duke, NCSU, and NCCU nuclear physics researchers.

The Demonstrator was enabled by support from the  U.S. Department of Energy Office of Nuclear Physics and the National Science Foundation.

 

The cover of the article The Majorana Demonstrator project article has the most downloads under Nuclear Physics section

(Left: the Cover of the Article; Right: The Article has the most downloads under the Nuclear Physics section in 2023)