UCONN TODAY — Superconductors, which are materials that allow perfect, lossless flow of electrons through them, have intrigued physicists for decades. But most superconductors only exhibit this quantum-mechanical peculiarity at temperatures so low – a few degrees above absolute zero –as to render them impractical. Moreover, exotic forms of superconductivity, some of which have yet to be realized experimentally, may form the building blocks of future quantum technologies.

A research team led by Harvard Professor of Physics and Applied Physics Philip Kim has demonstrated a new strategy for making and manipulating a widely studied class of high-temperature superconductors, called cuprates, clearing a path to engineering new, unusual forms of superconductivity in previously unattainable materials.

The team worked with colleagues at the University of British Columbia led by Marcel Franz and Rutgers University led by Jed Pixley, whose teams previously performed theoretical calculations that accurately predicted the behavior of the cuprate superconductor in a wide range of twist angles. Reconciling the experimental observations with theoretical expectations also required new theory developments reported in the work, performed by Quantum Initiative physicist Pavel A. Volkov.

“Cuprates are complex materials that to this day host some of the most intriguing open puzzles in condensed matter physics,” says Volkov. “Taking some of this complexity into account is crucial for understanding the behavior of cuprate-based devices. Constructing models to analyze the experimental data, we could show that outcomes from completely different types of experiments all point to the existence of an exotic form of superconductivity in these devices – time-reversal breaking superconductivity.”

Using a uniquely low-temperature device fabrication method, the researchers report in the journal Science a promising candidate for the world’s first high-temperature, superconducting diode – essentially, a switch that makes current flow in one direction – made out of thin cuprate crystals. Such a device could theoretically fuel fledging industries like quantum computing, which rely on fleeting quantum mechanical phenomena that are difficult to sustain in any meaningful way.

“Our work shows that high-temperature superconducting diodes are, in fact, possible, without application of magnetic fields, and opens new doors of inquiry toward exotic materials study,” says Kim.

Cuprates are copper oxides that, decades ago, upended the physics world by showing they become superconducting at much higher temperatures than theorists had thought possible, “higher” being relative: the current record for a cuprate superconductor is -225 Fahrenheit (130 Kelvin, or -142 Celsius). However, handling these materials without destroying their superconducting phases is extremely complex due to their intricate electronic and structural features.

The team’s experiments were led by S. Y. Frank Zhao, a postdoctoral researcher at MIT. Using an air-free, cryogenic crystal manipulation method in ultrapure argon, Zhao engineered a clean interface between two extremely thin layers of the cuprate bismuth strontium calcium copper oxide, nicknamed BSCCO (“bisco”) by insiders. BSCCO is considered a “high-temperature” superconductor because it starts superconducting at about -288 Fahrenheit (95 Kelvin, or -177 Celsius) – very cold by practical standards, but astonishingly high among superconductors, which typically must be cooled to below -400 Fahrenheit.

Zhao first split the BSCCO into two layers, each one-thousandth the width of a human hair. Then, at -130 Fahrenheit, he stacked the two layers at a 45-degree twist, like an ice cream sandwich with askew wafers, retaining superconductivity at the fragile interface.

The team discovered that the maximum supercurrent that can be passed without resistance through the interface is different depending on the current’s direction. Crucially, the team also demonstrated electronic control over the interfacial quantum state by reversing this polarity. This control was what effectively allowed them to make a switchable, high-temperature superconducting diode – a demonstration of foundational physics that could one day be incorporated into a piece of computing technology, such as a quantum bit.

“These results open a new chapter in the cuprate story – the one where new forms of superconductivity can be realized on demand. Miniaturizing these devices can make them new ingredients in existing quantum computing platforms. Another exciting future prospect is the realization of the elusive topological superconductivity, predicted theoretically in twisted superconductors, a coveted ingredient for fault-tolerant quantum technologies,” says Volkov.

Read the original article on UConn Today.

S. Y. Frank Zhao et al., “Time-reversal symmetry breaking superconductivity between twisted cuprate superconductors.” Science 382, 1422 (2023).
DOI:10.1126/science.abl8371

UCONN TODAY — Quantum Initiative professor Baikun Li has recently published a paper on applying groundbreaking techniques to convert carbon dioxide emissions into renewable energy sources.

The researchers’ findings were recently published the Royal Society of Chemistry’s esteemed Energy and Environmental Science Journal.

Environmental engineering professor Baikun Li led a 12-person interdisciplinary team exploring the process of electrochemical CO2 reduction. In addition to supporting UConn’s priority research goal of climate change mitigation, it also achieved an interdisciplinary collaboration comprised of several schools and colleges. The effort featured faculty and grad students from environmental engineering, materials science and engineering, electrical and computer engineering, chemistry, and more.

“Climate change is one of the world’s most pressing challenges,” says Pamir Alpay, UConn’s Vice President for Research, Innovation, and Entrepreneurship and a co-author on the manuscript whose group worked on the atomistic modeling of the surface reactions of catalytic processes. “This study works to reduce our carbon footprint through carefully designed experimental work with sophisticated multi-scale modeling. “The resulting reduction in carbon dioxide benefits our planet and exemplifies UConn’s research priorities.”

Each year, the extraction and burning of fossil fuels like coal, oil, and natural gas releases more carbon dioxide into the atmosphere than natural processes can remove. The carbon dioxide can remain for thousands of years, trapping heat and warming the Earth’s surface.

In 2019, Li and the team set out to understand the fundamental mechanisms of CO2 reduction. Electrochemical CO2 reduction is the conversion of carbon dioxide into a hydrocarbon fuel through a chemical reaction. It represents a future possibility where humans could generate gasoline, aviation fuel, and other useful substances using carbon dioxide captured from the air — reducing greenhouse gas emissions while providing a sustainable energy source.

“What we really want to achieve in the future is the complete cycle of carbon,” says Xingyu Wang, an environmental engineering Ph.D. student who worked on the team. “One of the biggest questions we aim to explore is, ‘How can we utilize the carbon dioxide that already exists in the atmosphere without exploiting existing resources here on Earth?’”

It’s a question that many research studies aim to answer. But few break down electrochemical CO2 reduction to the most fundamental level: the reaction.

The chemical reaction that converts CO2 gas into other chemical feedstocks happens under the action of a metal catalyst. Polymers bonded to the surface of the catalyst help stabilize and promote the reaction by keeping metal nanoparticles in place.

For example, Li says that copper is a well-known catalyst for CO2 reduction, but it does not absorb CO2 easily. By coating the surface of the copper with a polymer called polytetrafluoroethylene (PTFE), the team was able to change the polarity of the surface and improve CO2 gas absorption.

“In our study, we laid the foundation for the exploration of other polymers,” says Li. “Later on, other researchers can use the fundamental modeling in our work to study other molecule polymers based on what we have discovered so far.”

Another value of this study is its cost effectiveness. CO2 reduction can be achieved through expensive manufacturing pathways or relatively simple methods like this one, says Wang.

“Our study shows that we do not need to rely on the most expensive methods. We can achieve the same goal through this mixture of organic and inorganic material,” Wang says.

The team is one of many interdisciplinary collaborations across UConn that addess climate change mitigation and seek sustainable fuel sources. Li and her team have won a Convergence Award for Research in Interdisciplinary Centers (CARIC) for their work across quantum technology and climate change. The team is working with the Physics Department to develop an animation of the process for educational purposes within the industry.

“The broad impact of this methodology doesn’t only apply to CO2 reduction,” Li says. “It has countless applications, but we used CO2 reduction as an example of how we can use quantum level modeling for potential future research.”

Read the original article by Christie Wang on UConn Today.

THE DAILY CAMPUS — The research co-op Quantum CT hosted its first “Quantum Consortium” at the University of Connecticut’s Innovation Partnership Building on Tuesday, Oct. 3.

The meeting is the first to “bring the hundred plus (quantum) faculty under one roof,” said Jit Banerjee, UConn’s associate vice president for research innovation and entrepreneurship.

The conference was attended by experts from a vast array of fields, each sharing their unique perspectives during roundtable discussions.

“We are a team,” stated quantum technologies program specialist Sanjeev Nayak, who emphasized that the “overarching goal is more important than one individual’s perspective of Quantum.”

The goal, as defined by UConn’s vice president for research, Pamir Alpay, is to “build up a regional innovation engine,” through the consolidated effort of the Quantum CT program.

Quantum CT, a partnership between UConn, Yale and a host of other research institutions, businesses and local governments, seeks to “greatly expedite the advancement of quantum technologies, leading to substantial long-term economic benefits for the state,” according to the project’s website.

The program commenced in May of this year, supported by a million-dollar grant from the National Science Foundation for the purpose of researching the potential applications of emergent quantum technologies. The team is now tasked with “putting together a winning proposal,” stated Alpay, who leads the interdisciplinary researchers as they compete for a $160 million NSF implementation grant.

“We want to have projects that we aggressively succeed at,” said business development manager Mike DiDonato, imploring the audience of researchers to organize their efforts as they face off against over 40 other teams nationwide.

The present successes of the team in quantum sensing, cryptography, materials and more have not gone unnoticed, however; the program boasts partnerships with a growing list of high-profile industry leaders including Microsoft, Raytheon Technologies and Boehringer Ingelheim.

Among the many challenges faced by the task force, perhaps the most difficult is demonstrating to business interests how the little-understood realm of quantum technologies will disrupt the current market – for better or worse.

A critical point expressed by participants of the consortium is the transformative effect quantum technologies will have on businesses: Those who can leverage its capabilities will experience growth, while those who neglect its potential will be outcompeted.

The current stage of quantum interest is limited in scope, and scientists must now confront the task of “unraveling information for companies” to integrate into real-world applications, said Banerjee.

In one discussion regarding workforce development and education in the quantum age, experts inspectors ranging from fine arts to physics evaluated the best methods for creating a quantum-literate population.

Group chairs Caroline Dealy, Jason Hancock, and Morgaen Donaldson were joined by many in advocating for quantum awareness. Talks about educating the future and current workforce with courses ranging from the high school to postgraduate level, alongside a general education effort such as the upcoming Quantum Awareness Day on Dec. 14, lay the groundwork for advancing quantum technology’s exposure beyond the lab.

“Our workforce in Connecticut is the best educated and most talented in the nation, trained with the modern skills needed to make the United States an international leader in the research an development of the emerging field of quantum technology,” said Governor Ned Lamont

The current status of quantum research is worryingly underrepresented in the United States, with many indications of foreign labs, including those in China, outperforming the U.S. To this end, the minds behind Quantum CT are tirelessly dedicated to their mission, and, in the words of Yale’s vice provost for research Michael Crair, creating a “quantum corridor in Connecticut.”

Reproduced from the original article in The Daily Campus by Gabriel Duffany.

In two new papers in Physical Review Letters and Physical Review B, UConn Physicist Pavel Volkov and his colleagues propose how to experimentally manipulate quantum quasiparticles in very thin layers of ordinary superconductors to create topological superconductors by slightly twisting the stacked layers.

These materials hold promise for improving materials we use in everyday life, says Volkov. Things already in use that take advantage of the topological states include devices used to set resistance standards with high accuracy. Topological superconductors are also potentially useful in quantum computing, as they serve as a necessary ingredient for proposals of fault-tolerant qubits, the units of information in quantum computing. Volkov also emphasizes the promise topological materials hold for precision physics,

“Topological states are useful because they allow us to do precision measurements with materials. A topological superconductor may allow us to perform such measurements with unprecedented precision for spin (magnetic moment of electron) or thermal properties.”

Read the full press release here.