With an advanced technology known as angle-resolved photoemission spectroscopy (ARPES), scientists are able to map out a material’s electron energy-momentum relationship, which encodes the material’s electrical, optical, magnetic and thermal properties like an electronic DNA. But the technology has its limitations; it doesn’t work well under a magnetic field. This is a major drawback for scientists who want to study materials that are deployed under or even actuated by magnetic fields. Inspired by refrigerator magnets, a team of Yale researchers may have found a solution. Their study was featured recently on the cover of the Journal of Physical Chemistry Letters.
Why you should care:
Quantum materials - such as unconventional superconductors or topological materials - are considered critical to advancing quantum computing, high-efficiency electronics, nuclear fusion, and other fields. But many of them need to be used in the presence of a magnetic field, or even only become activated by magnetic fields. Being able to directly study the electronic structure of these materials in magnetic fields would be a huge help in better understanding how they work.
The problem:
Typically, ARPES technology can’t measure electronic structures in a magnetic field because the magnetic field throws the photoelectrons off their natural trajectory and causes them to move in circles.
“So it becomes almost impossible to reconstruct the electron behavior in the solid based on what our detector sees,” said Yu He, assistant professor of applied physics and of physics.” It has been a long-standing challenge to directly measure electronic structures under a magnetic field. Without it, we’re essentially blind to how the electronic states evolve under a magnetic field.”
The solution:
Typically, ARPES technology can’t measure electronic structures in a magnetic field because the magnetic field throws the photoelectrons off their natural trajectory and causes them to move in circles.
“So it becomes almost impossible to reconstruct the electron behavior in the solid based on what our detector sees,” said Yu He, assistant professor of applied physics and of physics.” It has been a long-standing challenge to directly measure electronic structures under a magnetic field. Without it, we’re essentially blind to how the electronic states evolve under a magnetic field.”
This magnetic structure is akin to an industrial mainstay known as the Halbach array, and He said its introduction to quantum materials study is a serendipitous interdisciplinary adventure with many brilliant collaborators.
“We asked ourselves, how could one make nano-scale Halbach-like arrays? Well, we had a neighbor in Becton center - the Schiffer group - that is a world leader in this. We asked ourselves, how can we figure out the actual surface magnetic field and put quantum materials onto such an array? Our colleagues at Boston College and Georgia Tech - the Ma group and the Du group - came to our rescue,” said He. “Then of course, our long-term collaborators at Rice university are indispensable to help ascertain the photoelectron trajectory through elegant analytical derivations.”
The researchers noted that this collaborative approach was key to the breakthrough.
“One should definitely keep an open mind in interdisciplinary research - a stone from another mountain may become your jade!” He said.
Going forward, the researchers say their method could significantly open up research possibilities in their field.
“Understanding the electron behavior under a magnetic field in the past has been almost impossible with ARPES,” He said. “With this development, we’re really hoping that this opens the door to direct electronic investigations of many field-induced electronic phenomena such as flatband superconductivity and magnetic vortices.”
One should definitely keep an open mind in interdisciplinary research - a stone from another mountain may become your jade!
Yu He
Assistant Professor of Applied Physics and Physics
This story is modified from the Yale Engineering News Story of January 29, 2026. Please see below for a link to the original article and other related links.