STROBE in the News

Quantum materials, a fascinating class of materials that harness the power of quantum mechanics, are revolutionizing modern science and technology. Quantum materials often possess exotic states of matter, such as superconductivity or magnetic ordering, that defy conventional understanding and can be manipulated for various technological applications. To further enhance and manipulate the intriguing characteristics of quantum materials, researchers leverage nanostructuring—the ability to precisely control the geometry on the atomic scale. Specifically, nanostructuring provides the ability to manipulate and fine-tune the electrical and thermal properties of quantum and other materials. This can result, for example, in designer structures that conduct current very well, but impede heat transport. These structures can help recapture and utilize waste heat in electronics, buildings, and vehicles—enhancing their efficiency and, thereby, reducing power consumption. A related critical challenge for a broad range of nanotechnologies is the need for more efficient cooling, so that the nano devices do not overheat during operation. To better understand heat transport at the nanoscale, JILA Fellows Margaret Murnane, Henry Kapteyn, and their research groups within the STROBE NSF Center, JILA and the University of Colorado Boulder, created the first general analytical theory of nanoscale-confined heat transport, that can be used to engineer heat transport in 3D nanosystems—such as nanowires and nanomeshes—that are of great interest for next-generation energy-efficient devices. This discovery was published in NanoLetters. 

For a new study, a team of physicists recruited roughly 1,000 undergraduate students at CU Boulder to help answer one of the most enduring questions about the sun: How does the star’s outermost atmosphere, or “corona,” get so hot? The research represents a nearly-unprecedented feat of data analysis: From 2020 to 2022, the small army of mostly first- and second-year students examined the physics of more than 600 real solar flares—gigantic eruptions of energy from the sun’s roiling corona…

Researchers created topologically stable magnetic monopoles and imaged them in 3D with unprecedented spatial resolution using a technique developed at the Advanced Light Source (ALS). The work enables the study of magnetic monopole behavior for both fundamental interest and potential use in information storage and transport applications. A bar magnet cut in half will always have a north and south pole, ad infinitum. Thus, magnetic monopoles—particles with a single magnetic “charge”—have never been observed in isolation. Yet the idea continues to intrigue: How would magnetic monopoles behave? What could you do with the magnetic equivalent of electric charge or current? Remarkably, scientists might be able to explore such questions via quasiparticles—particle-like phenomena emerging from collective interactions in condensed matter. However, it has been difficult to directly measure these quasiparticles and probe their behavior at the nanoscale…

Surrounded by some of the world’s most advanced lasers, computers, and microscopes sits Brendan McBennett, a graduate student at JILA. McBennett has been working in the laboratories of JILA Fellows Margaret Murnane and Henry Kapteyn, as part of the KM group since 2019, excited to see his research advance significantly over that time. “We use ultraviolet and extreme ultraviolet (EUV) lasers to study heat flow in nanostructured materials,” McBennett states. “EUV photons have a higher photon energy that makes them insensitive to electron dynamics in most materials, combined with nanometer wavelengths. This allows them to very precisely probe surface deformations induced by heat – or thermal phonons – to capture new materials behaviors.”

In the 17th Century, a Dutch merchant named Antony van Leeuwenhoek began experimenting with making new microscope lenses and, in the process, plunged humanity into a new world—this one teeming with previously-undiscovered life, from small bacteria to single-celled algae and more.

More than 400 years later, scientists are in the midst of an equally-important revolution. They’re diving into a previously-hidden realm—far wilder than anything van Leeuwenhoek, known as the “father of microbiology,” could have imagined. Some researchers, like physicists Margaret Murnane and Henry Kapteyn, are exploring this world of even tinier things with microscopes that are many times more precise than the Dutch scientist’s. Others, like Jun Ye, are using lasers to cool clouds of atoms to just a millionth of a degree above absolute zero with the goal of collecting better measurements of natural phenomena.

Functional materials—like molecular electronics, biomaterials, light-emitting diodes, or new photovoltaic materials—gain their electronic or photonic properties from complex and multifaceted interactions occurring at the elementary scales of their atomic or molecular constituents. In addition, the ability to control the functions of these materials through external stimuli , e.g., in the form of strong optical excitations, enables new properties in the materials, making them appealing for new technological applications. However, a major obstacle to overcome is the combination of the very fast time (billionths of a second) scales and the very small spatial (nanometer) scales which define the many-body interactions of the elementary excitations in the material which define its function. The extremely high time and spatial resolutions needed have been extremely difficult to achieve simultaneously. Many physicists have, therefore, struggled to visualize the interactions within these materials. In a paper recently published in Nature Communications, JILA Fellow Markus Raschke and his team report on a new ultrafast imaging technique that could solve this issue.

In a new paper published in the Journal of Physical Chemistry Letters, Jimenez and his team report a new experimental setup to search for the cause of a mysterious fluorescent signal that appears to be from entangled photon excitation. According to Jimenez: “We built a setup where you could use either a classical laser or entangled photons to look for fluorescence. And the reason we built it is to ask: ‘What is it that other people were seeing when they were claiming to see entangled photon-excited fluorescence?’ We saw no signal in our previous work published a year ago, headed by Kristen Parzuchowski. So now, we’re wondering, people are seeing something, what could it possibly be? That was the detective work here.” The results of their new experiments suggested that hot-band absorption (HBA) by the subject molecules, could be the potential culprit for this mysterious fluorescent signal, making it the prime suspect.

Many substances around us, from table salt and sugar to most metals, are arranged into crystals. Because their molecules are laid out in an orderly, repetitive pattern, much is understood about their structure.

However, a far greater number of substances — including rubber, glass and most liquids — lack that fundamental order throughout, making it difficult to determine their molecular structure. To date, understanding of these amorphous substances has been based almost entirely on theoretical models and indirect experiments.

A UCLA-led research team is changing that. Using a method they developed to map atomic structure in three dimensions, the scientists have directly observed how atoms are packed in samples of amorphous materials. The findings, published today in Nature Materials, may force a rewrite of the conventional model and inform the design of future materials and devices using these substances.

Understanding the chemical and physical properties of surfaces at the molecular level has become increasingly relevant in the fields of medicine, semiconductors, rechargeable batteries, etc. For example, when developing new medications, determining the chemical properties of a pill’s coating can help to better control how the pill is digested or dissolved. In semiconductors, precise atomic level control of interfaces determines performance of computer chips. And in batteries, capacity and lifetime is often limited by electrode surface degradation.  These are just three examples of the many applications in which the understanding of surface coatings and molecular interactions are important.

The imaging of molecular surfaces has long been a complicated process within the field of physics. The images are often fuzzy, with limited spatial resolution, and researchers may not be able to distinguish different types of molecules, let alone how the molecules interact with each other. But it is precisely this–molecular interactions–which control the function and performance of molecular materials and surfaces.  In a new paper published in Nano Letters, JILA Fellow Markus Raschke and graduate student Thomas Gray describe how they developed a way to image and visualize how surface molecules couple and interact with quantum precision. The team believes that their nanospectroscopy method could be used for molecular engineering to develop better molecular surfaces, with controlled properties for molecular electronic, photonic, or biomedical applications.