Public Lecture on Quantum Mechanics

August 12, 2026

Finding Chiral Superconductivity’s Fingerprint

April 23, 2026

With a carefully-designed experiment and a handful of tin atoms, UT’s physicists have found a long-sought form of superconductivity, taking one more step toward creating custom quantum materials.

Twists and Turns

Scientists have known about superconductivity for more than a century. At low temperatures, resistance in certain materials vanishes and they carry electrical current without losing any energy. Superconductors are part of particle accelerators and magnetic resonance imaging machines. While they need extremely cool environments to work, the mechanism that drives them is quite well-understood: electrons, which normally repel each other, form pairs and carry the current.

Chiral superconductivity is another story. Here, electron pairs reject the typical symmetry and twist into a signature left or right “handedness.” Scientists have searched for this phase for decades because it has promise for quantum technologies.

In 2023 Chancellor’s Professor Hanno Weitering and Bains Professor Steve Johnston published findings in Nature Physics reporting that strategically scattering tin atoms across a silicon base could give rise to a superconductor. They proposed the system could also be a potential chiral superconductor. This latest work, outlined in Physical Review X, provides the evidence.

The research team carefully deposited one-third layer of tin atoms on a silicon substrate, then used sophisticated imaging to pick up distinctive chiral superconductivity patterns.

Simply Beautiful Interference

Weitering said the structural and electronic simplicity of the tin-silicon material is the key to seeing chirality. More complex materials have overlapping states and multiple interactions that can mask the telltale patterns.

In this system, one-third layer of tin means a controlled deposition of atoms placed relatively far apart on a silicon layer. Those atoms spontaneously organize into a nicely ordered triangular lattice. The geometry is important.

“Chirality is non-existent in high-temperature cuprate superconductors because they have a square lattice,” Weitering said, which gives you a different phase. “But in the tin layer, it exists because the lattice isn’t square. It’s a triangle.”

To see chiral superconductivity’s distinctive fingerprint he and his colleagues turned to quasiparticle interference imaging, or QPI.

“In condensed matter these particles always are moving in a surrounding that effects their behavior, so they’re not really a single entity anymore,” Weitering said. “They’re all under the influence of their surroundings. That’s why we call them quasiparticles.”

If you picture electrons behaving like waves, he explained, and think about throwing stones in a pond, one after another in different spots, you’ll see waves start to run into each other.

“We call those interference patterns, he said. “This is where the interference comes from: quasiparticle interference. With the scanning tunneling microscope (STM) we can see those waves. Quasiparticles interfere and give these beautiful patterns.”

The calling card for chirality is encoded in these patterns surrounding a point defect; a single atom defect to be precise.

“That could be a missing tin atom; it could a tin atom that has been replaced by a silicon atom because there’s a big reservoir of silicon underneath and sometimes atoms do that,” Weitering said. “You can never get a crystal perfect. There are always some defects in there. One crucial point in this system is that with the STM we can see each and every point defect in the tin layer.”

This research could serve as a template for using QPI to find other forms of unconventional superconductivity.

“Most superconductors are discovered through serendipity,” Weitering said. “This was all by design.”

Customizing materials is an important step on the long journey to possible applications.

“Quantum materials are usually not very useful unless you can make devices out of them,” he explained. “To make devices you usually need to make thin films and interfaces.”

He said that chiral superconductors are topological, and “people are excited about topological systems because we could use topological superconductors to build, for instance, qubits for quantum computing.”

Qubits store or process information that’s highly sensitive to outside influences like temperature, everyday radiation, etc.

“Topological systems are interesting in a sense that topological property is not something that’s local,” Weitering said. “It’s global. By making it global it’s much less sensitive to perturbations.”

Showing Off for Friends

Though the tin-silicon system was designed with intention, recognizing the chirality pattern actually did involve a little bit of serendipity.

Weitering’s former postdoctoral research associate, Fangfei Ming, is now a professor in China. He sent QPI images of the material taken by his group, showing how the detail has improved over time—specifically patterns that resemble flowers.

Weitering was impressed and showed the results to Assistant Professor Ruixing Zhang.

“Ruixing looked at this pattern and saw something very striking that was at the center of the page,” he said.

Zhang went back to his office and had his graduate students (Zhuo Chen and Yuchang Cai) do some numerical and analytical calculations, proving that only chiral superconductivity will result in the flower-like QPI pattern with an atomic-size hole at the center—chiral fingerprints.

“Ruixing saw that and his intuition was right,” Weitering said, admitting that, at first, he was more focused on the sharpness of the images when he shared them with Zhang.

“I was just showing off,” he joked.

Having friends to work with (and impress) is a critical element to moving fundamental research forward.

“If you do science by yourself, you’re never going to get there,” Weitering said.

He, Zhang, Johnston, Chen, and Cai all contributed to the PRX research, along with colleagues from China. He and Zhang are also reviewing patterns from QPI images and plan to create a database. They hope to train a machine learning program to recognize the intricate details of those patterns.

“It’s really part of the MRSEC (the university’s Materials Research Science and Engineering Center, funded by the National Science Foundation),” Weitering said. “It’s using AI to analyze data. It’s curating data. You need to train AI with data. It’s not just theory; it’s also experimental data. Then there’s the validation component of theory predictions.”

Verifying where the theory leads next is a big part of his work. First there was the Nature Physics research; now the PRX findings.

“We found superconductivity,” Weitering said. “Then we found chiral superconductivity. Every time we get a step further.”

Hanno Weitering Named 2026 Macebearer

April 8, 2026

Chancellor’s Professor and Professor of Physics Hanno Weitering is the University of Tennessee, Knoxville, 2026 Macebearer. The honor is the highest bestowed on UT faculty members and recognizes outstanding service to the university, its students, and the greater society.

Keeping with tradition, the new Macebearer was surprised by an entourage, this year comprising Vice Chancellor for Research Deb Crawford, College of Arts and Sciences (CAS) Divisional Dean Kate Jones and Associate Dean Todd Moore, and Weitering’s wife Carol, who had been following his location on her phone to make sure he made it to the physics colloquium in time for the announcement.

Weitering said he was running a bit late and didn’t think much of the texts and calls checking that he was on his way.

“Then the deans and the vice chancellor suddenly came in with Carol, which felt completely bizarre,” he said. “Everything happened very quickly.”

As Professor and Head Adrian Del Maestro shared later in a departmental message: “For those of you who joined us for Colloquium today, you witnessed a truly surprised Hanno accepting the award from Vice Chancellor Crawford! Congratulations to a member of our faculty who truly embodies the volunteer spirit!”

Robert Hinde, Executive Dean and Herbert Family Dean’s Chair for the College of Arts and Sciences, added praise for Weitering’s selection.

“Hanno’s record of teaching, research, and service, combined with his personal dedication to the physics and university community, make him an ideal choice for Macebearer,” said Hinde.

On what being Macebearer means to him, Weitering said he “can only reflect with deep gratitude on the tremendous support I’ve had throughout my career. I’m fortunate to be part of a strong physics department with wonderful colleagues, and to have benefited from the guidance and support of mentors, colleagues, and department heads. As head, I had the privilege of serving under an inspirational dean during a period of significant progress for the university. It gave me the opportunity to give back by helping position the department for new challenges and opportunities. Now, I’m glad to be back focused on teaching and research—being an academic truly is a privilege.”

Small Systems with Big Potential

Weitering joined the university in 1993 as part of the physics department’s condensed matter research program. His work explores materials at the microscopic level, focusing on their structure and the behavior of conduction electrons, particularly at surfaces and interfaces. By scattering small numbers of tin atoms across a silicon substrate, he has created idealized material systems that revealed a novel form of superconductivity—the long-sought chiral superconducting state.

While many superconductors have historically been discovered through serendipity, Weitering takes a deliberate, theory-driven approach. Because theoretical models often simplify the complex physics of real materials, he creates precisely engineered material systems that faithfully represent those models. These nanoscale realizations allow him to directly test and validate their predictions. Each step in uncovering the subtle physics of these atomic-scale designs brings researchers closer to identifying and controlling phases with potential applications in quantum technologies.

Weitering has published more than 100 original research papers that have been cited nearly 7,800 times, and was recognized by the College of Arts and Sciences with the 2023 Distinguished Research Career Award.

A True Volunteer Family

Weitering’s contributions to the university go far beyond atomic creativity. In 2012 he began a decade of leadership as head of the physics department, a position that for several years overlapped with a 10-year position as deputy director of UT’s Joint Institute for Advanced Materials (JIAM) (now the Institute for Advanced Materials and Manufacturing, or IAMM). Among his proudest accomplishments is the number of scientists involved in quantum science who joined the university during that time (including Del Maestro). He has also supervised or co-supervised 15 PhD students (including four new PhD alumni in the past four years) and 13 postdocs. He’s taught courses including Thermal Physics, Structure of Matter, and Introduction to Quantum Mechanics, as well as a capstone course for physics majors. He and Carol are also parents of two UT CAS alumni: Bart, who graduated in 2013 with a double major in geological sciences and physics; and Hanneke, who graduated in 2014 with a physics degree.

Carrying the Mace, and a Legacy

Weitering earned both master’s and doctoral degrees in chemistry at the University of Groningen in his native Netherlands. He moved to physics when he accepted a Benjamin Franklin Postdoctoral Fellowship at the University of Pennsylvania. From there he joined the UT faculty. The Macebearer is one of many honors he’s won during his tenure. In addition to selection as a Chancellor’s Professor and the CAS Distinguished Research Career Award, he has been recognized with the JIAM Chair of Excellence, election as a Fellow of the American Physical Society, and election as a Fellow of the American Association for the Advancement of Science.

Weitering will be formally recognized as Macebearer at the Chancellor’s Honors Banquet later this month. He will carry the symbolic mace during the spring 2026 commencement ceremonies, following in the footsteps of former physics professors chosen for the honor: Alvin Nielsen, Bill Bugg, Lee Riedinger, and Soren Sorensen.

With ORNL, UT Works Toward a Quantum Future

November 11, 2025

The University of Tennessee, Knoxville, expects to receive $2.3 million to play a key role in the nation’s quantum future, thanks to renewed funding for the Quantum Science Center (QSC) at Oak Ridge National Laboratory (ORNL).

The U.S. Department of Energy is investing $125 million in QSC over the next five years to pioneer quantum-accelerated high-performance computing (QHPC), developing open-source software for quantum-classical workflows that accelerate scientific advancements across multiple disciplines. Since its founding in 2018 as part of the National Quantum Initiative Act, the QSC has pooled the unique strengths of national laboratories, industry partners, and academia to build a combined research program in quantum science. UT is part of that collaboration and will receive $2.3 million to lead work in materials and models and to train early-career scientists.

With its commitment to innovation gateways in Advanced Materials and Manufacturing and Artificial Intelligence, the university is well-positioned for this assignment. In 2023, UT launched the Center for Advanced Materials and Manufacturing (CAMM), a premier Materials Research Science and Engineering Center funded by the National Science Foundation. Through experiment, synthesis, and modeling, CAMM is dedicated to discovering advanced materials for new quantum technologies and giving students the opportunity to learn in a world-class environment.

UT is a world leader in quantum spin systems and brings its unique expertise to the validation of quantum-classical computations, which are beyond the reach of conventional computation.

Physics Professor Alan Tennant is the CAMM Director.

“UT is a key part in this,” he said of QSC research. He explained that “machine learning to extract models from quantum magnets has been an important innovation from UT and CAMM, allowing parameters to be determined from materials with neutron scattering which are essential for validating quantum computations. QSC will continue to strengthen its collaboration with CAMM.”

He added that this new funding will also support UT students who will make materials, conduct neutron experiments, and undertake quantum computations.

Tennant said the QSC is building the country’s foundation for a new quantum age and that the university’s involvement puts UT at the center of that work.

“This is actually right in the heart of where tech starts connecting,” he said. “We are integral to the American road map.”

The QSC is headquartered at the Department of Energy’s Oak Ridge National Laboratory, which is managed by UT-Battelle for the DOE Office of Science. By uniting national laboratories, academic institutions and industry partners, the QSC endeavors to advance American innovation and global leadership by enhancing the computational robustness, algorithmic scalability and simulation accuracy of quantum computing systems. For more information, visit qscience.org.

NSF CAREER Award for Joon Sue Lee

October 14, 2025

TRAINING THE NEXT GENERATION

Enhancing Thermoelectric Effects

September 29, 2025

UT’s physicists have helped develop a new approach to enhancing thermoelectric materials, energy converters that can turn waste heat into electricity or electricity into cooling and heating.

Thermoelectric materials use heat to create electricity by one of two avenues. The Seebeck effect moves current from the hot side to the cold side of a material. The temperature difference generates electricity. The lesser-studied Nernst effect creates voltage in a transverse direction but requires an external magnetic field. While this complicates its possible uses, this effect intrigues researchers because its geometry provides greater efficiency.

In this study, Dongliang Gong, Junyi Yang, Shashi Pandey, Dapeng Cui, Yang Zhang, and Jian Liu* were part of the team that synthesized an antiferromagnetic oxide material that could generate transverse voltage without the need for an external magnetic field. This anomalous Nernst effect (ANE) is the largest among the known magnetic oxides because of the magnetically broken symmetry. This opens a path to looking at other materials with similar symmetry configuration as candidates for greater thermoelectric efficiency.

Read the full research highlight from Argonne National Laboratory, or the original paper in Nature Communications.

*Dongliang Gong is a former postdoctoral research associate.

Junyi Yang completed his PhD in 2022 and is now working at Argonne National Laboratory.

Shashi Pandey graduated with a PhD in 2024 and is currently a postdoc at the University of Michigan.

Dapeng Cui is a postdoctoral research associate.

Yang Zhang is an assistant professor of physics. Jian Liu is a professor of physics.

Research Overview: The Power of RIXS

August 28, 2025

Courtesy of Bains Professor Steven Johnston and students Jinu Thomas and Debshikha Banerjee

Quantum materials—systems whose properties are dominated by quantum mechanical many-body effects—represent one of the most exciting frontiers of condensed matter physics. They also have the potential to revolutionize technology with applications in superconductors, magnets, and sensors.

In these systems, it is common for different degrees of freedom like spin, charge, orbital, and lattice vibrations to become intricately entangled, making it difficult to identify which is the driver of a given phenomenon. This entanglement makes quantum materials hard to model, but it also produces a wide range of exotic phenomena, including high-temperature superconductivity, various types of density waves, topological states, and more. Notably, the Bains Professor Steven Johnston’s research group has long been interested in how electrons couple to atomic vibrations and how this interaction can influence the properties of these materials.

Advanced experimental and numerical techniques are required to unravel the complex behavior present in quantum materials. Among them, resonant inelastic x-ray scattering (RIXS) has emerged as a powerful spectroscopic tool due to its ability to simultaneously probe spin, charge, orbital, and lattice excitations in a single experiment. A recent perspective piece published in Physical Review X by Johnston and Adjunct Professor Mark Dean, along with their colleagues, sheds light on applications of RIXS in quantum materials. More recently, members of Johnston’s group have published a study in Physical Review Letters, presenting state-of-the-art calculations for RIXS response for a correlated quantum material with strong interactions to phonon modes via a novel kinetic energy coupling mechanism.

First author and PhD student Debshikha Banerjee, together with Jinu Thomas, Alberto Nocera (University of British Columbia), and Johnston, used the density matrix renormalization group (DMRG) to predict the RIXS spectra for a one-dimensional Hubbard chain coupled with Su-Schrieffer-Heeger (SSH)-like electron-phonon coupling. This model has established itself for studying chain systems like Sr₂CuO₃, which has long served as a platform for studying quantum magnetism in low-dimensional systems.

Most studies of electron-phonon coupling have focused on simplified models (e.g., Holstein or Fröhlich), where coupling is between electron density and lattice displacements. In contrast, the SSH model captures lattice vibrations that alter atomic bond lengths, an interaction present in all materials. SSH electron-phonon interactions have gained widespread interest in recent years following predictions that SSH interactions can contribute to high-temperature superconductivity. SSH interactions have also been tied to topological edge states, a topic of interest in recent years. To test these theoretical claims, the community needs experimental protocols to identify the existence of SSH interaction in materials. Banerjee et al.’s work demonstrates how RIXS can be exploited to identify and quantify SSH interactions in quantum materials.

This study builds on a recent work led by PhD student Jinu Thomas and the same team, published in Physical Review X, which has adv­­anced the state-of-the-art modeling of lattice excitations in RIXS.