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Penn State researchers unveil an electrical method to modify electron flow in quantum materials, paving the way for advanced electronics and quantum computers.

For the first time, researchers demonstrated how to electronically alter the direction of electron flow in promising materials for quantum computing.

A new electrical method to conveniently change the direction of electron flow in some quantum materials could have implications for the development of next-generation electronic devices and quantum computers. A team of researchers from Penn State developed and demonstrated the method in materials that exhibit the quantum anomalous Hall (QAH) effect a phenomenon in which the flow of electrons along the edge of a material does not lose energy. The team described the work in a paper that was published on October 19 in the journal Nature Materials.

As electronic devices get smaller and computational demands get larger, it is increasingly important to find ways to improve the efficiency of information transfer, which includes the control of electron flow, said Cui-Zu Chang, Henry W. Knerr Early Career Professor and associate professor of physics at Penn State and co-corresponding author of the paper. The QAH effect is promising because there is no energy loss as electrons flow along the edges of materials.

In 2013, Chang was the first to experimentally demonstrate this quantum phenomenon. Materials exhibiting this effect are referred to as QAH insulators, which are a type of topological insulator a thin layer of film only a couple dozen atoms thick that have been made magnetic so that they only conduct current on their edges. Because the electrons travel cleanly in one direction, the effect is referred to as dissipationless, meaning no energy is lost in the form of heat.

A new method by Penn State researchers conveniently changes the direction of electron flow in materials that exhibit the quantum anomalous Hall (QAH) effect a phenomenon in which the flow of electrons along the edge of a material does not lose energy. The method takes advantage of a physical mechanism called spin-orbit torque, which is related to the materials internal magnetism. Applying a 5-millisecond current pulse to the material impacts the internal magnetism and changes the discretion of electron flow (e.g. from right-handed to left-handed). Credit: Chang Lab/Penn State

In a QAH insulator, electrons on one side of the material travel in one direction, while those on the other side travel in the opposite direction, like a two-lane highway, Chang said. Our earlier work demonstrated how to scale up the QAH effect, essentially creating a multilane highway for faster electron transport. In this study, we develop a new electrical method to control the transport direction of the electron highway and provide a way for those electrons to make an immediate U-turn.

The researchers fabricated a QAH insulator with specific, optimized properties. They found that applying a 5-millisecond current pulse to the QAH insulator impacts the internal magnetism of the material and causes the electrons to change directions. The ability to change direction is critical for optimizing information transfer, storage, and retrieval in quantum technologies. Unlike current electronics, where data is stored in a binary state as on or off as one or zero quantum data can be stored simultaneously in a range of possible states. Changing the flow of electrons is an important step in writing and reading these quantum states.

The previous method to switch the direction of electron flow relied on an external magnet to alter the materials magnetism, but using magnets in electronic devices is not ideal, said Chao-Xing Liu, professor of physics at Penn State and co-corresponding author of the paper. Bulky magnets are not practical for small devices like smartphones, and an electronic switch is typically much faster than a magnetic switch. In this work, we found a convenient electronic method to change the direction of electron flow.

The researchers previously optimized the QAH insulator so that they could take advantage of a physical mechanism in the system to control its internal magnetism.

To make this method effective, we needed to increase the density of the applied current, Liu said. By narrowing the QAH insulator devices, the current pulse resulted in very high current density that switched the magnetization direction, as well as the direction of the electron transport route.

This shift from magnetic to electronic control in quantum materials, according to the researchers, is similar to a shift that has occurred in traditional memory storage: While the storage of information on original hard drives and floppy disks involved the use of magnets to create a magnetic field and write data, newer flash memory such as that used in USB drives, solid state hard drives, and smartphones is written electronically. Promising new technologies to scale up memory, such as MRAM, similarly rely on physical mechanisms related to internal magnetism.

Theoretical Interpretation and Future Endeavors

Beyond the experimental demonstration, the research team also provided a theoretical interpretation of their methodology.

The team is currently exploring how to pause electrons on their route to essentially turn the system on and off. They are also pursuing how to demonstrate the QAH effect at higher temperatures.

This effect, as well as current requirements for quantum computers and superconductors, require very low temperatures near absolute zero, Chang said. Our long-term goal is to replicate the QAH effect at more technologically relevant temperatures.

Reference: Electrical switching of the edge current chirality in quantum anomalous Hall insulators by Wei Yuan, Ling-Jie Zhou, Kaijie Yang, Yi-Fan Zhao, Ruoxi Zhang, Zijie Yan, Deyi Zhuo, Ruobing Mei, Yang Wang, Hemian Yi, Moses H. W. Chan, Morteza Kayyalha, Chao-Xing Liu and Cui-Zu Chang, 19 October 2023, Nature Materials.DOI: 10.1038/s41563-023-01694-y

In addition to Chang and Liu, the research team at Penn State at the time of the research includes postdoctoral researchers Wei Yuan, Yang Wang, and Hemian Yi; graduate students Ling-Jie Zhou, Kaijie Yang, Yi-Fan Zhao, Ruoxi Zhang, Zijie Yan, Deyi Zhuo, and Ruobing Mei; Morteza Kayyalha, assistant professor of electrical engineering; and Moses Chan, Evan Pugh University Professor Emeritus of Physics.

The Army Research Office, the Air Force Office of Scientific Research, and the National Science Foundation (NSF) funded this research. The NSF-funded Materials Research Science and Engineering Center for Nanoscale Science at Penn State and the Gordon and Betty Moore Foundations EPiQS Initiative provided additional support.

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Quantum Control Breakthrough a Game Changer for Next-Gen Electronics and Computers - SciTechDaily

Four University of Michigan physics researchers and one biophysicist were elected to the American Physical Society, each from a different field within physics.

The APS Fellowship Program was created to recognize members who may have made advances in physics through original research and publication, or made significant innovative contributions in the application of physics to science and technology. They may also have significantly contributed to the teaching of physics or through service and participation in the activities of the society.

APS elects approximately 150-160 fellows per yearless than half of 1% of its membership. Fellows are elected by their peers across a broad set of disciplines within physics.

These five new fellows from five different divisions speak to both the excellence and the breadth of our faculty, said David Gerdes, chair of the U-M Department of Physics. I am so proud of all of their accomplishments in research and in the classroom.

Kai Sun, professor of physics, was elected for his groundbreaking and long-standing contributions to the theory of topological insulators and superconductors, and for applications to soft matter systems. Topological states of matter is a fast-growing area of physics research that involves extensions of geometrical concepts to classical and quantum mechanics. Sun is well known for his foundational contributions to this new program, and for work on many-body physics generally, including collaborations with experimentalists at U-M and elsewhere.

Im thrilled to receive this honor, he said. What brings me even greater joy is receiving this fellowship alongside my exceptional colleagues who have also been recognized this year.

Christine Aidala, professor of physics, was elected for a series of experiments aimed at elucidating the flavor and spin structure of the proton in terms of the quarks and gluons of quantum chromodynamics. Quantum chromodynamics is the theory that describes the action of the strong nuclear force, one of the fundamental forces in physics. Her experiments were conducted at high-energy facilities in both the United States and Europe.

I am honored to have my contributions to advancing our knowledge of quantum chromodynamics recognized by being named as an APS Fellow, she said.

Sarah Veatch, associate director of U-Ms biophysics program, was elected for her foundational work in understanding the miscibility phase transition and associated phenomena in membranes. These types of transitions occur when membranes convert between well mixed and phase-separated states.

Think oil and water in a salad dressing bottle, she said. The same type of phase transition can happen in the membranes that make up the surface of our cells, and we study how this phase transition helps cells sense their local environments.

Veatch also was recognized for rigorously applying these concepts to biological processes.

This recognition is especially meaningful because it comes from a scientific community that knows my work well, she said. It is also exciting to be a member of a growing cohort of fellows working at the interface of physics and biology, demonstrating the societys commitment to interdisciplinary physics.

Tim McKay, professor of physics, astronomy and education, was recognized for his tireless efforts to catalyze systemic change and make STEM learning environments equitable and inclusive, as well as for using data and technology to inform and improve STEM learning.

Its a great honor to be selected as an APS fellow by my fellow physicists, he said. Training the next generation of scientists is an essential part of our discipline, and this recognition is a sign of our communitys commitment to equity and inclusion in physics teaching.

Marcelle Soares-Santos, associate professor of physics, was recognized for organizing and leading a team that co-discovered the optical kilonova counterpart to the first binary neutron star gravitational wave event from LIGO-Virgo.

Receiving the APS fellowship is a wonderful recognition, and it is even more special to share it with five of my esteemed colleagues at the University of Michigan, she said. I am honored to be elected and proud to be in such a great company.

Gerdes says, including faculty affiliates and faculty, this years inductees increase the departments total number of APS fellows to 27.

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5 U-M researchers named American Physical Society fellows - University of Michigan News

Imagine being able to measure tiny changes in the flow of time caused by Earths gravity with atomic clocks atop one of Colorados iconic peaks above 14,000 feet.

That could soon be a reality thanks to a $1.9 million grant from the National Science Foundation that will advance geodesy the study of accurately measuring Earths geometric shape, orientation in space and gravity field through the use of quantum sensors, some of the most precise in the world.

Scott Diddams, professor in CU Boulders Department of Electrical, Computer and Energy Engineering(ECEE), is collaborating on this four-year, multi-agency effort with physicists from the National Institute of Standards and Technology (NIST) and the National Oceanic and Atmospheric Administration (NOAA). To further get students involved, Diddams aims to bring undergraduate and graduate researchers in on the endeavor.

Our vision is to take the best quantum science from the lab and translate it out to the world, said Diddams. Its going to be an important activity for the university and field to show how optical clocks can impact the field of geodesy.

Albert Einsteins theory of general relativity states that time evolves more slowly under the influence of gravity known as the gravitational redshift. Essentially, a clock at higher elevations will tick at a faster rate than ones closer to the Earth.

Diddams and the research group are developing a portable hyper-accurate optical atomic clock, which will be the most advanced quantum sensor of time to operate at such a high elevation.

Andrew Ludlow, an adjoint professor with ECEE and the NIST physicist building the ytterbium optical clocks used in the project, noted, if you can measure time extremely well with these atomic clocks, you can look for tiny signals that are signatures of interesting new phenomena in physics.

We're also constantly improving our time standards to support the measurement of evolving technologies in industry and science, he added.

While there have been other efforts around the world to replicate similar aspects of this project, this one will take place at one of the most elevated locations in the United States - an exciting feat for the research community.

Mount Blue Sky, nestled in the Rocky Mountains of Colorado,is home to the highest paved road in North Americapeaking at 14,264 feet. This will allow the team to transport an optical atomic clock up the summit to measure geopotential differences corresponding to one centimeter changes in elevation.

If successful, these measurements could open up new realms of how we use quantum and atomic physics for areas in hydrology, seismology, coastal mapping and geodetic surveying.

The research team will first test these clocks at lower elevations before taking them ultimately up 14,000 feet in summer 2025.

We sat down with Professor Scott Diddams for a deep dive into the ambitious project.

What does your project entail with this new NSF grant?

Our project is really focused on using the best optical clocks the most precise measurement tools ever made to measure gravity. We think of the Earth as being just a sphere, but theres actually significant variation in the Earths shape on large and small scales. Our plan is to use our clocks to measure those gravitational changes very precisely due to those features at different elevations.

How will you achieve this?

We're going to take one clock to the top of Mount Blue Sky and compare it to a local atomic clock in Boulder, Colo. This will be done via a laser link that transmits the clocks rate over a laser beam through the air from Mount Blue Sky down to the Denver metro area. A challenge is that you dont have a clear light of sight to Boulder, so well have to go to a location about 10 miles away near the Broomfield area for that. Well use an optical fiber to connect from that location back to the reference clock at NIST.

This perspective provides how the mobile optical clock atop Mt. Blue Sky will communicate with the transfer node in Broomfield, Colo. and connect with a reference optical clock in Boulder.

What do you hope these atomic optical clocks will prove?

When we compare their rates with the two clocks, we should see the one on the top of Mount Blue Sky ticking faster. By measuring the difference in the tick rates, we hope to make the most accurate test Einstein's predictions of general relativity.

How can we relate this to everyday life?

One thing that absolutely knows gravity is water, and water will flow to the lowest gravitational potential. And so in large coastal areas, determining elevation and the flow of water at the centimeter or a few centimeters level is quite important, particularly with climate change and rising sea levels. So our project will build a connection from very fundamental quantum science to a whole new area in geodesy and surveying as we know it. This is not a topic that you would initially think is connected to quantum physics.

What makes Colorados Rocky Mountains uniquely fitting for this project?

We have this tremendous difference in elevation or relief, in topographic terms over a relatively short distance. There is around 9,000 feet of relief from Denver to Mount Blue Sky over a span of less than 50 miles, which we can use as leverage in the relative precision of our measurement. If we can measure the effect of that difference at the centimeter level, we stand to make the most precise measurement of the gravitational redshift. So that's pretty unique to Colorado.

What excites you about the collaboration with NIST & NOAA?

This is a very unique team, and even more so that we are all here in Boulder. We have world experts in all the areas that are needed to make the project successful like being able to develop portable atomic optical clocks (Andrew Ludlow) and synchronize these clocks from the top of mountains down to the city (Laura Sinclair). Well also have a leading expert in geodesy (Derek van Westrum) who has actually already surveyed benchmarks in our labswith millimeter-level precision.

Would you say this will be the highest altitude experiment youve ever conducted so far?

This probably will be the highest altitude experiment of its kind in the world. I have done short-term experiments with frequency combs on Mauna Kea in Hawaii, but that's 13,800 feet above sea level. I've never had an experiment at 14,000 feet yet, which makes this pretty unique. We're going to have to learn to efficiently work and operate the clock over extended periods in that high-altitude environment, as well.

Atomic Optical Clock Image Credit: Jesse Petersen

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Researchers to test Einstein's predictions of general relativity atop ... - University of Colorado Boulder

Article by Beth Miller Photo by Kathy F. Atkinson November 02, 2023

More than 200 physicists, researchers and students will converge on the University of Delaware campus this weekend as UD hosts the annual meeting of the American Physical Societys 2023 Mid-Atlantic Section.

A wide range of topics is on the agenda, including studies in astrophysics, astroparticle physics, atomic and molecular and optical physics, biophysics, machine learning, solid-state physics, magnetism, quantum and 2D materials, physics education and much more.

UD researchers faculty and students will participate in scores of presentations during the three-day event and several are invited speakers, including Associate Professor Federica Bianco (machine learning), Assistant Professor Chitraleema Chakraborty (two-dimensional and quantum materials), Associate Professor Anderson Janotti (quantum materials), Professor Chaoying Ni (magnetism and spintronics) and postdoctoral researcher Quang To (magnetization dynamics and spin-transport phenomena).

The opening plenary session at 3 p.m. Friday in 120 Smith Hall is open to all. Prior registration was required for the rest of the meeting. Speakers at that plenary session are Professor Peter N. Armitage of Johns Hopkins University on Isings Model of Ferromagnetism and Professor Eun-Suk Seo of the University of Maryland on Recent Progress in Direct Measurements of Cosmic Rays.

The meeting was organized locally by Associate Professor Frank Schroeder of UDs Bartol Research Institute and by Associate Professor Benjamin Jungfleisch, his colleague in the Department of Physics and Astronomy. Schroeder is chair-elect of the APS Mid-Atlantic Section and Jungfleisch also serves on the sections executive committee. Other colleagues, students and department and college staff assisted as well.

The APS Mid-Atlantic Section, which marks its 10th anniversary this year, includes Delaware, New Jersey, Maryland, Pennsylvania, Washington, D.C., and West Virginia. It is the first time UD has hosted the annual event since 2016.

The Mid-Atlantic Section was established in 2013 to engage and strengthen the physics community in the Mid-Atlantic region of the United States, as well as to aid APS in its mission to advance and diffuse the knowledge of physics at the regional level, according to its website.

The American Physical Society has about 50,000 members, including physicists in academia, national laboratories and industry throughout the world.

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Hundreds of physicists to converge on UD campus | UDaily - UDaily

Scientists may have just caught their first glimpse of an ultra-rare version of nitrogen containing five more protons than it can stably hold.

Scientists discovered hints of the new isotope, called nitrogen-9, by smashing beams of oxygen isotopes into beryllium atoms in the U.S. National Superconducting Cyclotron Laboratory.

If follow-up experiments can confirm its existence, the isotope will set a new record for an atomic nucleus with the highest number of extra protons moving the number from four to five. The researchers described the strange new isotope Oct. 27 in the journal Physical Review Letters.

Related: Scientists discover 1st 'neutron-rich' isotope of uranium since 1979

The ultra-unstable version of nitrogen decays like a Russian nesting doll, sequentially emitting one or two protons while revealing the next set, Robert Charity, a nuclear scientist at Washington University in St. Louis, said in a statement.

Protons and neutrons are held together inside atomic nuclei by the strong force, a glue which in stable atoms overpowers the repulsive force of positively-charged protons pushing against each other. But add more protons and this balance eventually tips moving atoms beyond the so-called "drip line."

Beyond the drip line atoms become unstable, and decay by chucking out protons or neutrons. Because they exist on the furthest edge of possible atomic nuclei, semi-stable atoms beyond the drip line (which come in the form of rare isotopes) have long fascinated nuclear scientists.

"The existence of such an exotic system is a good test of the quantum mechanics of open or unbound many-body systems," Charity said.

The researchers found the first hints of nitrogen-9s presence in data from a years-old experiment conducted by the National Superconducting Cyclotron Laboratory. Originally, the scientists smashed oxygen-13 atoms into beryllium in a bid to create another isotope called oxygen-11.

But lurking among the millions of interactions was another decay signature that pointed to something else. Right on the borderline of statistical significance, the researchers spotted rare atoms of nitrogen-9 popping into existence for just 10^-21 seconds.

To get partial confirmation they had found the weird isotope, the scientists modeled the isotopes structure, finding that it consisted of a helium nucleus with two protons and two neutrons surrounded by five loosely held protons. After the briefest slice of time the protons decayed, successively escaping the nucleus through a quantum tunnel.

Further experiments will be needed to confirm the discovery. They remain hopeful that, when they do, the isotope will help them to piece together the decay paths more common isotopes take to come into existence.

"The elements we have around us are made via a set of mechanisms that work through intermediates that we do not have around us," Lee Sobotka, a professor of chemistry and physics at Washington University, said in the statement. "These intermediates are unstable and often have highly unusual neutron-to-proton ratios. Our work involves both reconstructing the structure of, and reactions producing, such nuclei."

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Scientists get rare glimpse of 'nesting doll' isotope nitrogen-9 - Livescience.com